Electronic supplementary material Groundwater arsenic removal using granular TiO 2 : Integrated laboratory and field study Jinli Cui a · Jingjing Du a · Siwu Yu b · Chuanyong Jing a, * · Tingshan Chan c, * a State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing, 100085, P. R. China b Guizhou Electric Power Testing & Research Institute, Guiyang, 550002, P. R. China c National Synchrotron Radiation Research Center, HsinChu, 1 1 2 3 4 5 6 7 8 9 10 11 12 13
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Electronic supplementary material
Groundwater arsenic removal using granular TiO2 Integrated laboratory and
Iron-Mn binary 15 40 145 176 321 22 253 347 754 (Maiti et al 2010a)
13
oxides
aUnit for ion concentration is mgL except as notedbestimated from bed volume breakthrough curves and influent As concentration if not explicitly expressed in the reference cThe species is As(V) if only one concentration is given
d
The groundwater As concentration was 385-440 μgL and additional ~600 μgL (As(III)As(V)=11) arsenic was added
14
222324252627
Fig S1 Boxplot of groundwater As levels in columns and filters in the literature in Table S1 Individual samples are shown as diamonds The range of each box represents the 25th
and 75th
percentile whereas the whiskers represent the 10th
and 90th
percentile
Synthesis of granular TiO2
Granular TiO2 (GTiO2) was prepared by hydrolysis of titanyl sulfate (TiOSO4)
Generally 300 g TiOSO4 was mixed with 1800 mL DI water in a 10 L jar reactor in an
ice bath at 4 oC Then 10 M NaOH was slowly added to adjust the pH to 6 The
precursor of TiO2 was obtained by washing the suspension with DI water several
times till the conductivity of the supernatant was less than 100 μScm Then 800 g
TiO2 precursor was mixed with 40 mL polyvinyl alcohol solution at 80 oC in a water
bath The product was crushed into 60-80 mesh and dried in an oven at 60 oC for 12 h
15
282930313233343536373839404142434445464748
49
50
51
52
53
54
55
56
57585960
Fig S2 Characterization of GTiO2 SEM (a) and XRD pattern with crystal face for each peak (b)
Fig S1 SEM images for GTiO2 in this study
Table S2 Average concentrations of As coexisting ions (mgL) and water chemistry for groundwater 1 and 2 from two wells
Table S3 Water parameters in the synthetic water used in the studyParameters Ca2+ Mg2+ HCO3
- Na+ Cl- pHConc (mgL) 401 1043 388 2460 3928 82
Table S4 PHREEQC input for a representative column with EBCT=054 min SOLUTION 0
This keyword is to define the influent groundwater chemistry parameters which are included in the adsorption reactions like ldquoArseniterdquo and ldquoArsenaterdquo and the experimental conditions including ldquopHrdquo The information defined in SOLUTION is available for subsequent transport and adsorptive reaction calculations
temp 23 pH 82 pe 4 redox pe units mgL density 1 Al 006 Arsenite 0374 Arsenate 0291 CO4
2-
4401 Ca 194 Cl 1456 F 115 Fe 047 K 137 Mg 395 Mn 012 NO3
-
34 Na 16872
17
79
80
8182
83
84858687888990919293949596979899
100101102103104105106107108109110111112
SO42-
1176 Si 89 -water 1 kg
SOLUTION 1-4 The small column was divided into four cells SOLUTION 1-4
are the groundwater chemistry parameters for the four cells temp 23 pH 83 pe 4 redox pe units ppm density 1 Al 006 C(4) 4401 Ca 194 Cl 1456 F 115 Fe 047 K 137 Mg 395 Mn 012 N(3) 34 Na 16872 S(6) 1176 Si 89 -water 1 kg
SOLUTION_SPECIES This keyword is to define the dissociation constant logK
and diffusion constant (dw) in solution for arsenite and arsenate
Arsenite adsorption equation on GTiO2 surface H3ArseniteO3 is the primary species of As(III) at the groundwater pH 82 (Surf_sO)2ArseniteOH-066 is the adsorptive bidentate binuclear structure of As(III) on GTiO2
log_k 1635 The adsorptive reaction constant for As(III) on GTiO2 in
the current condition which could be changed with different experimental conditions
-cd_music -2 -1 0 066 3 CD-MUSIC model is integrated in the PHREEQC
modeling The numbers represent -2 the change in charge at the plane of Surf_sOH due to loss of two hydrogens -1 the change in charge at 1 plane due to gain of one hydrogen and one oxygen on Arsenite 0 the change in charge at the 2 plane usually caused by the outer sphere adsorption 066 the fraction of the central ion (As) charge that is associated with plane 0 which reflecting the charge distribution 3 the charge on the central ion (As)
Table S54 Parameters of Weber-Morris intraparticle model for As(IIIV) adsorption kinetics on GTiO2 using synthetic water Initial As concentration = 800 μgL adsorbent dose = 02 gL pH = 82 in synthetic groundwater
External film diffusion
Intraparticle diffusion
aRex2 bkp1
cb1aRin
2 bkp2cb 2
As(V) 0984 0497 0022 0976 01331878
As(III) 0970 0583
-0088 0981 0218
1105
aRex is WM external proportion fitting parameter while Rin is WM intraparticle proportion fitting parameterbk The unit of kp is mggh05 cb The unit of b is mgg
Table S6 Comparison of the adsorption capacities of As(III) and As(V) on GTiO2 and the representative granular adsorbents in similar experimental condition from the literature
AdsorbentParticle size (mm) As
qm
(mgg)Dose (gL) Experimental conditions Literature
GTiO2 018~025 As(III) 980 1 0~500 mgL at pH 82 01 M NaCl This studyGTiO2 018~025 As(V) 358 1 0~500 mgL at pH 82 01 M NaCl This study
Granular TiO2 015~06 As(III) 392 10~60 mgL As at pH 70 in simulated groundwater (100 mgL Ca 20 mgL Mg 50 mgL Na 200 mgL Cl-
)(Bang et al 2005)
Granular TiO2 015~06 As(V) 400 10~60 mgL As at pH 70 in simulated groundwater (100 mgL Ca 20 mgL Mg 50 mgL Na 200 mgL Cl-
)(Bang et al 2005)
E33 (FeOOH)0044~0075 As(V) 202 1 0~15 mgL at pH 70 in 001 M NaCl
(Kanematsu et al 2010)
E33 (FeOOH) 05~2 As(V) 180 1 0~50 mgL at pH 70 in 004 M NaClO4 (Jing et al 2012)
GFH 02~06 As(V) 650 10 0~2000 mgL at pH 8 in 01 M NaNO3
(Guan et al 2008)
GFH0009~0125 As(V) 23 025 0~07 μgL at pH 65 in DI water
(Banerjee et al 2008)
GFH0009~0125 As(V) 200 - 0~01 μgL at pH 70 in DI water
(Badruzzaman et al 2004)
GFH 050~065 As(V) 155 - 0~06 μgL at pH 70 in DI water (Saha et al 2005)
GHFO-NN 015~030 As(V) 330 0001 0~225 mgL at pH 8 in DI water(Streat et al 2008)
GHFO-VL 015~030 As(V) 360 0001 0~225 mgL at pH 8 in DI water(Streat et al 2008)
25
374375
Spherical schwertmannite 1~15 As(V) 36 05 0~5 mgL at pH 70 in DI water (Dou et al 2013)Cylindrical schwertmannite 1~25 As(V) 223 05
0~5 mgL at pH 70 in DI water(Dou et al 2013)
Irregular schwertmannite 10~16 As(V) 317 05 0~5 mgL at pH 70 in DI water (Dou et al 2013)Fe impregnated chitosan beads (MICB) 25 As(III) 117 1 0~05 mgL at pH 60 in DI water
(Wang et al 2014)
MICB 25 As(V) 191 1 0~1 mgL at pH 60 in DI water(Wang et al 2014)
MICB 25 As(III) 353 1 0~15 mgL at pH 60 in DI water(Wang et al 2014)
MICB 25 As(V) 357 1 0~16 mgL at pH 60 in DI water(Wang et al 2014)
Iron hydroxide granules (GIH) 3~4 As(V) 23 4
5~100 mgL at pH 70 in 10 mgL SO42-
14 mgL NH4Cl buffer solution (Daus et al 2004)
Activated Al2O3
0074~0149 As(V) 159 - 285~115 mgL at pH 52 in DI water
(Lin and Wu 2001)
Activated Al2O3
0074~0149 As(III) 35 - 079~490 mgL at pH 70 in DI water
(Lin and Wu 2001)
Activated Al2O3 ~20 As(V) 73 at pH 70 in 004 M NaClO4 (Jing et al 2012)
Activated natural siderite 05~10 As(V) 22 10 0 1~20 mgL at pH 7 in DI water(Zhao and Guo 2014)
Polyaluminum Granulate 1~3 As(III) 705 10 0~150 mgL at pH 51-56 in DI water(Mertens et al 2012)
Polyaluminum Granulate 1~3 As(V) 180 10 0~150 mgL at pH 51-56 in DI water (Mertens et al
26
2012)
Acidified laterite 1~12 As(III) 19 1 025~5 mgL at pH 7 in 100 mgL NaHCO3
(Glocheux et al 2013)
Acidified laterite 1~12 As(V) 13 1 025~5 mgL at pH 7 in 100 mgL NaHCO3
(Glocheux et al 2013)
Laterite 1~12 As(III) 07 1025~5 mgL at pH 7 in 100 mgL NaHCO3 (Glocheux et al
2013)
Laterite 1~12 As(V) 04 1025~5 mgL at pH 7 in 100 mgL NaHCO3 (Glocheux et al
2013)
Treated laterite 03-05 As(V) 216 05 02-20 mgL at pH 70 in DI water(Maiti et al 2012)
Treated laterite 03-05 As(III) 94 05 02-20 mgL at pH 70 in DI water(Maiti et al 2012)
Treated laterite03-05
As(V) 241 05 02-20 mgL at pH 70 in DI water(Maiti et al 2010a)
Treated laterite03-05
As(III) 81 05 02-20 mgL at pH 70 in DI water(Maiti et al 2010a)
Acid-activated laterite-103-07
As(III) 0633 50 02-10 mgL at pH 66-70 in DI water(Maiti et al 2010b)
Acid-activated laterite-203-07
As(III) 087650 02-10 mgL at pH 66-70 in DI water (Maiti et al
2010b)
Acid-activated laterite-303-07
As(III) 063450 02-10 mgL at pH 66-70 in DI water (Maiti et al
2010b)
Acid-activated laterite-103-07
As(V) 059850 02-10 mgL at pH 66-70 in DI water (Maiti et al
2010b)
27
Acid-activated laterite-203-07
As(V) 07550 02-10 mgL at pH 66-70 in DI water (Maiti et al
2010b)
Acid-activated laterite-303-07
As(V) 07550 02-10 mgL at pH 66-70 in DI water (Maiti et al
2010b)
Treated laterite-1 03-06 As(V) 019 20 0-20 mgL As at pH 72 in DI water(Maiti et al 2013b)
Treated laterite-1 03-06 As(III) 018 20 0-20 mgL As at pH 72 in DI water(Maiti et al 2013b)
Treated laterite-2 03-06 As(V) 004 20 0-20 mgL As at pH 72 in DI water(Maiti et al 2013b)
Treated laterite-2 03-06 As(III) 003 20 0-20 mgL As at pH 72 in DI water(Maiti et al 2013b)
Treated laterite-3 03-06 As(V) 007 20 0-20 mgL As at pH 72 in DI water(Maiti et al 2013b)
Treated laterite-3 03-06 As(III) 004 20 0-20 mgL As at pH 72 in DI water(Maiti et al 2013b)
28
376377
Charge distribution multi-site surface complexation (CD-MUSIC) modeling
The CD-MUSIC model with the 2-pK TPM adsorption option was used to
describe adsorption behaviors of As cations and anions on GTiO2 The CD-MUSIC
model incorporates the structural information of surfaces adsorbed species and the
double layers by distributing the charge of an adsorbate between the surface and
interfacial water (Hiemstra and Van Riemsdijk 2006) The CD-MUSIC model has
been successfully used in describing As adsorption in batch experiments (Pena et al
2006 Stachowicz et al 2008)
The adsorption constants of counter ions were set to -1 and the proton affinity
constant was set to the PZC of 58 for TiOH-13 (Luo et al 2010) The charge
distribution (CD) value shows the fraction (f) of the charge of the central As ion
attributed to the surface plane and the remaining part (1-f) was attributed to the other
ligands of the complex which were positioned toward the diffuse layer The CD value
for As surface complexes was obtained by fitting the experimental data The
calculation was performed using the chemical equilibrium program MINTEQ to
simulate the adsorption and the aqueous reactions
29
378379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
Fig S32 Adsorption of silicate (a) calcium and magnesium (b) as a function of GTiO2
dose in groundwater 1 The solid lines represent the CD-MUSIC modeling result
30
400
401
402
403
404
405
406
407
408409410
Table S75 Surface parameters and species used in the CD-MUSIC modeling in As(IIIV) removal under different GTiO2 dose in 01 M NaCl and groundwater 1 in Fig 2 and Fig S32
= exp(-FΨ1RT) P2 = exp(-FΨ2RT) F the Faraday constant (C mol-1) R the gas constant (J mol-1 K-1) T the absolute temperature (K)
Ψ0 Ψ1 Ψ2 the electrostatic potential (V) of 0- 1- and 2-plane respectively alogK for 01 M NaCl at 6 hours blogK for 01 M NaCl at 6 days clogK for groundwater 1 at 6 days
31
411412
413414415
32
416
Table S86 The charge distribution (f) of central As atom to TiO2 surface in simulating the effect of cations and anions on As adsorption in 01 M NaCl at pH 82 in Fig 4 BK Si HCO3 All
As(V) 022 017 012 016As(III) 040 020 058 056
Fig S43 Molar percentage () of As Ca Mg and Si on pristine and spent GTiO2
surfaces using EDX analysis The spent GTiO2 samples after field column experiments using groundwater 1 were identified with EBCT in min under x-axis The value of molar percentage of each element was averaged from randomly-chosen positions on the adsorbent surface
33
417
418
419420
421422
423
424
425
426
427
428
429
430
431
432
433434435436437438
439
440
441
As speciation analysis on spent GTiO2 using XANES
The spent GTiO2 samples were ground using a mortar and pestle and then the
ground powder was spread on Scotch tape The As k-edge XANES spectra were
collected at beamline 01C1 at the National Synchrotron Radiation Research Center
(NSRRC) Taiwan Spectra were acquired from -150 to 300 eV relative to the As K-
edge of 11867 eV at cryogenic temperature (77 K) using a cryostat to prevent the
oxidation of As(III) by X-rays The fluorescence signals were collected using a Lytle
detector Two to four scans were collected for each sample and averaged to improve
the signalnoise ratio The XANES analysis was performed with the Athena program
in the IFEFFIT computer package for linear combination fit (LCF) (Cui et al 2013
Ravel and Newville 2005)
34
442
443
444
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447
448
449
450
451
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453
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461
462
463
PHREEQC modeling for As breakthrough curves in field column experiments
PHREEQC a geochemical model integrates macroscopic mass transfer
processes with a microscopic surface complexation model (Parkhurst and Appelo
2013) It can be applied in calculating solution complex speciation batch-reaction
and one-dimensional reactive-transport and inverse modeling In our study the one-
dimensional column was defined by four cells with the same length The cell length
was calculated to be one-fourth of the actual column length Time step (s) was
calculated according to equation Time step = Lcell(Q60A) where Lcell is the cell
length (cm) Q is flow velocity (mLmin) A is the effective column cross section area
(cm2) which is the column cross-sectional area multiplied by porosity (060) Total
shift number was calculated by dividing actual column operation time by the time
step The transport block was modeled by shifting the solute content from one cell to
the next one In each cell the aqueous solute was mixed and adsorbed on GTiO2
according to the equations In each cell the aqueous solute was mixed and assumed to
be in equilibration with GTiO2 The sequence of shifting mixing and equilibrium
adsorption was repeated for each cell until the total number of shifts was completed
The diffusion coefficient Dw in PHREEQC accounting for retardation was
calculated as Dw=x2
(36t) where x stands for the diffusion length (estimated as the
radius of the particle size) and t represents equilibrium time adopted from the batch
kinetic data (Mertens et al 2012)
For CD-MUSIC modeling in the PHREEQC take As(III) as an example to
explain the adsorption equation The As(III) adsorption is considered as a ligand
35
464
465
466
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473
474
475
476
477
478
479
480
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482
483
484
485
exchange reaction with the hydroxide group on GTiO2 (Surf_sOH-033) forming a
H3ArseniteO3 is the master species in groundwater at pH 82
(Surf_sO)2ArseniteOH-066 is the common adsorbed bidentate binuclear complex
evidenced by our previous reports(Pena et al 2006 Yan et al 2015) LogK is the
adsorption equilibrium constants Generally every adsorption equation under certain
experimental condition has a unique value of logK In the adsorption equation ldquo-2rdquo
represents the lost two hydrogens by Surf_sOH-033 after it adsorbs H3ArseniteO3 ldquo-
1rdquo represents the change in charge on Arsenite at 1 plane due to gaining one hydrogen
(+1) and one oxygen (-2) ldquo0rdquo represents no change in charge at the 2 plane ldquo066rdquo is
the fraction of the central ion (As) on GTiO2 surface that is associated with plane 0
ldquo3rdquo is the charge on the central ion As(III) Following this equation and the relevant
parameters As(III) adsorbed on GTiO2
The diffusion coefficient Dw in PHREEQC accounting for retardation was
calculated as Dw=x2(36t) where x stands for the diffusion length (estimated as the
radius of the particle size) and t represents equilibrium time adopted from the batch
kinetic data (Mertens et al 2012)
To well simulate the As breakthrough curve in columns four As(V) adsorption
reactions (Table 1) were employed Adsorption site density of 60 mmolg was
36
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
adopted from our previous study (Pena et al 2006) and the total adsorption sites were
calculated to be 1844 sitesnm2 The final optimized ratio of strong to weak sites was
51 The surface complexation constants were reasonably adjusted according to the
batch modeling results as the column reaction may not reach equilibrium in local
micro-interfacial areas due to much less contact time between As and GTiO2 than that
in batch experiments (Appelo and Postma 1999) In the modeling a stepwise
procedure was adopted to achieve a viable result An estimation of two thirds of the
surface site density being accessible for EBCT=011 min with large flow rate of 265
mLmin was optimized which could probably result from unavailable adsorption sites
due to fast transport through the column
The adsorbed As on GTiO2 in the column was calculated by mass balance
between the influent and effluent
where Asadsorbed is the adsorbed As on GTiO2 (mgg) n is the number of collected
samples Cin and Cout are influent and effluent As concentrations (mgL) respectively
Vi is volume (L) of groundwater passed through the column between sample i-1 and i
and m is the mass of GTiO2 (g)
Even though the oxidation of adsorbed As(III) occurred during filtration as
analyzed from XANES and mass balance analysis (Fig 7) no As(III) oxidation
reactions were considered in PHREEQC modeling which would not impact the
breakthrough of As(IIIV)
37
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510
511
512
513
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517
518
519
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Fig S54 Effect of EBCT on Si Ca and Mg breakthrough curves using groundwater 1 The sample notation in panel c indicates field column experiments with EBCT in minutes
References
Appelo CAJ Postma D 1999 A consistent model for surface complexation on birnessite (MnO2) and its application to a column experiment Geochim Cosmochim Ac 63 (19-20) 3039-3048Badruzzaman M Westerhoff P Knappe DRU 2004 Intraparticle diffusion and adsorption of arsenate onto granular ferric hydroxide (GFH) Water Res 38 (18) 4002-4012Banerjee K Amy GL Prevost M Nour S Jekel M Gallagher PM Blumenschein CD 2008 Kinetic and thermodynamic aspects of adsorption of arsenic onto granular ferric hydroxide (GFH) Water Res 42 (13) 3371-3378Bang S Patel M Lippincott L Meng XG 2005 Removal of arsenic from groundwater by granular titanium dioxide adsorbent Chemosphere 60 (3) 389-397Bang S Pena ME Patel M Lippincott L Meng X Kim KW 2011 Removal of arsenate from water by adsorbents a comparative case study Environ Geochem Hlth 33 133-141Cui JL Shi JB Jiang GB Jing CY 2013 Arsenic levels and speciation from ingestion exposures to biomarkers in Shanxi China Implications for human health Environ Sci Technol 47 (10) 5419-5424Daus B Wennrich R Weiss H 2004 Sorption materials for arsenic removal from water A comparative study Water Res 38 (12) 2948-2954Dou XM Mohan D Pittman CU 2013 Arsenate adsorption on three types of granular schwertmannite Water Res 47 (9) 2938-2948Dou XM Zhang Y Yang M Pei YS Huang X Takayama T Kato S 2006 Occurrence of arsenic in groundwater in the suburbs of Beijing and its removal using an iron-cerium bimetal oxide adsorbent Water Qual Res J Can 41 (2) 140-146Gibbons MK Gagnon GA 2010 Adsorption of arsenic from a Nova Scotia groundwater onto water treatment residual solids Water Res 44 (19) 5740-5749Glocheux Y Mendez Pasarin M Albadarin AB Allen SJ Walker GM 2013 Removal of arsenic from groundwater by adsorption onto an acidified laterite by-product Chem Eng J 228 565-574Guan XH Wang JM Chusuei CC 2008 Removal of arsenic from water using granular ferric hydroxide Macroscopic and microscopic studies J Hazard Mater 156 (1-3) 178-185Gupta K Maity A Ghosh UC 2010 Manganese associated nanoparticles agglomerate of iron(III) oxide Synthesis characterization and arsenic(III) sorption behavior with mechanism J Hazard Mater 184 (1-3) 832-842Hao JM Han MJ Wang C Meng XG 2009 Enhanced removal of arsenite from water by a mesoporous hybrid material - Thiol-functionalized silica coated activated alumina Micropor Mesopor
Mat 124 (1-3) 1-7Hiemstra T Van Riemsdijk WH 2006 On the relationship between charge distribution surface hydration and the structure of the interface of metal hydroxides J Colloid Interf Sci 301 (1) 1-18Hristovski K Baumgardner A Westerhoff P 2007 Selecting metal oxide nanomaterials for arsenic removal in fixed bed columns From nanopowders to aggregated nanoparticle media J Hazard Mater 147 (1-2) 265-274Jang M Chen WF Cannon FS 2008 Preloading hydrous ferric oxide into granular activated carbon for arsenic removal Environ Sci Technol 42 (9) 3369-3374Jing CY Cui JL Huang YY Li AG 2012 Fabrication characterization and application of a composite adsorbent for simultaneous removal of arsenic and fluoride ACS Appl Mater Interfaces 4 (2) 714-720Kanematsu M Young TM Fukushi K Green PG Darby JL 2010 Extended triple layer modeling of arsenate and phosphate adsorption on a goethite-based granular porous adsorbent Environ Sci Technol 44 (9) 3388-3394Kong S Wang Y Zhan H Yuan S Liu M Zhou C 2013 Arsenite and Arsenate Removal from Contaminated Groundwater by Nanoscale Iron-Manganese Binary Oxides Column Studies Environmental Engineering Science 30 (11) 689-696Li Y Liu JR Jia SY Guo JW Zhuo J Na P 2012 TiO2 pillared montmorillonite as a photoactive adsorbent of arsenic under UV irradiation Chem Eng J 191 66-74Lin TF Wu JK 2001 Adsorption of arsenite and arsenate within activated alumina grains Equilibrium and kinetics Water Res 35 (8) 2049-2057Luo T Cui JL Hu S Huang YY Jing CY 2010 Arsenic removal and recovery from copper smelting wastewater using TiO2 Environ Sci Technol 44 (23) 9094-9098Maiti A Basu JK De S 2010a Development of a Treated Laterite for Arsenic Adsorption Effects of Treatment Parameters Industrial amp Engineering Chemistry Research 49 (10) 4873-4886Maiti A Basu JK De S 2010b Removal of Arsenic from Synthetic and Natural Groundwater Using Acid-Activated Laterite Environmental Progress amp Sustainable Energy 29 (4) 457-470Maiti A Basu JK De S 2012 Experimental and kinetic modeling of As(V) and As(III) adsorption on treated laterite using synthetic and contaminated groundwater Effects of phosphate silicate and carbonate ions Chem Eng J 191 1-12Maiti A Thakur BK Basu JK De S 2013a Comparison of treated laterite as arsenic adsorbent from different locations and performance of best filter under field conditions J Hazard Mater 262 1176-1186Maiti A Thakur BK Basu JK De S 2013b Comparison of treated laterite as arsenic adsorbent from different locations and performance of best filter under field conditions J Hazard Mater 262 (0) 1176-1186Maji SK Pal A Pal T 2008 Arsenic removal from real-life groundwater by adsorption on laterite soil J Hazard Mater 151 (2-3) 811-820Maji SK Kao YH Wang CJ Lu GS Wu JJ Liu CW 2012 Fixed bed adsorption of As(III) on iron-oxide-coated natural rock (IOCNR) and application to real arsenic-bearing groundwater Chem Eng J 203 285-293Mertens J Rose J Kagi R Chaurand P Plotze M Wehrli B Furrer G 2012 Adsorption of arsenic on polyaluminum granulate Environ Sci Technol 46 (13) 7310-7317Nguyen TV Vigneswaran S Ngo HH Pokhre D Viraraghavan T 2006 Iron-coated sponge as
effective media to remove arsenic from drinking water Water Qual Res J Can 41 (2) 164-170Parkhurst DL Appelo CAJ 2013 Description of input and examples for PHREEQC version 3-A computer program for speciation batch-reaction one-dimensional transport and inverse geochemical calculations US Geological SurveyPena M Meng XG Korfiatis GP Jing CY 2006 Adsorption mechanism of arsenic on nanocrystalline titanium dioxide Environ Sci Technol 40 (4) 1257-1262Ravel B Newville M 2005 ATHENA ARTEMIS HEPHAESTUS Data analysis for X-ray absorption spectroscopy using IFEFFIT J Synchrotron Radiat 12 537-541Saha B Bains R Greenwood F 2005 Physicochemical characterization of granular ferric hydroxide (GFH) for arsenic(V) sorption from water Separation Science and Technology 40 (14) 2909-2932Shan H Ma T Wang Y Zhao J Han H Deng Y He X Dong Y 2013 A cost-effective system for in-situ geological arsenic adsorption from groundwater J Contam Hydrol 154 1-9Stachowicz M Hiemstra T van Riemsdijk WH 2008 Multi-competitive interaction of As(III) and As(V) oxyanions with Ca2+ Mg2+ PO4
3- and CO32- ions on goethite J Colloid Interf Sci 320 (2) 400-
414Streat M Hellgardt K Newton NLR 2008 Hydrous ferric oxide as an adsorbent in water treatment - Part 3 Batch and mini-column adsorption of arsenic phosphorus fluorine and cadmium ions Process Safety and Environmental Protection 86 (B1) 21-30Thirunavukkarasu OS Viraraghavan T Subramanian KS 2003 Arsenic removal from drinking water using iron oxide-coated sand Water Air Soil Poll 142 (1-4) 95-111USEPA 2008 Assessing arsenic removal by metal (hydr)oxide adsorptive media using rapid small scale column tests Govenrnment Printing Office Washington DCWang J Xu W Chen L Huang X Liu J 2014 Preparation and evaluation of magnetic nanoparticles impregnated chitosan beads for arsenic removal from water Chem Eng J 251 25-34Westerhoff P Highfield D Badruzzaman M Yoon Y 2005 Rapid small-scale column tests for arsenate removal in iron oxide packed bed columns J Environ Eng-Asce 131 (2) 262-271Westerhoff P De Haan M Martindale A Badruzzaman M 2006 Arsenic adsorptive media technology selection strategies Water Qual Res J Can 41 (2) 171-184Yan L Huang Y Cui J Jing C 2015 Simultaneous As(III) and Cd removal from copper smelting wastewater using granular TiO2 columns Water Res 68 (0) 572-579Zhao K Guo HM 2014 Behavior and mechanism of arsenate adsorption on activated natural siderite Evidences from FTIR and XANES analysis Environ Sci Pollut Res 21 (3) 1944-1953Zhao K Guo H Zhou X 2014 Adsorption and heterogeneous oxidation of arsenite on modified granular natural siderite Characterization and behaviors Appl Geochem 48 184-192
Iron-Mn binary 15 40 145 176 321 22 253 347 754 (Maiti et al 2010a)
13
oxides
aUnit for ion concentration is mgL except as notedbestimated from bed volume breakthrough curves and influent As concentration if not explicitly expressed in the reference cThe species is As(V) if only one concentration is given
d
The groundwater As concentration was 385-440 μgL and additional ~600 μgL (As(III)As(V)=11) arsenic was added
14
222324252627
Fig S1 Boxplot of groundwater As levels in columns and filters in the literature in Table S1 Individual samples are shown as diamonds The range of each box represents the 25th
and 75th
percentile whereas the whiskers represent the 10th
and 90th
percentile
Synthesis of granular TiO2
Granular TiO2 (GTiO2) was prepared by hydrolysis of titanyl sulfate (TiOSO4)
Generally 300 g TiOSO4 was mixed with 1800 mL DI water in a 10 L jar reactor in an
ice bath at 4 oC Then 10 M NaOH was slowly added to adjust the pH to 6 The
precursor of TiO2 was obtained by washing the suspension with DI water several
times till the conductivity of the supernatant was less than 100 μScm Then 800 g
TiO2 precursor was mixed with 40 mL polyvinyl alcohol solution at 80 oC in a water
bath The product was crushed into 60-80 mesh and dried in an oven at 60 oC for 12 h
15
282930313233343536373839404142434445464748
49
50
51
52
53
54
55
56
57585960
Fig S2 Characterization of GTiO2 SEM (a) and XRD pattern with crystal face for each peak (b)
Fig S1 SEM images for GTiO2 in this study
Table S2 Average concentrations of As coexisting ions (mgL) and water chemistry for groundwater 1 and 2 from two wells
Table S3 Water parameters in the synthetic water used in the studyParameters Ca2+ Mg2+ HCO3
- Na+ Cl- pHConc (mgL) 401 1043 388 2460 3928 82
Table S4 PHREEQC input for a representative column with EBCT=054 min SOLUTION 0
This keyword is to define the influent groundwater chemistry parameters which are included in the adsorption reactions like ldquoArseniterdquo and ldquoArsenaterdquo and the experimental conditions including ldquopHrdquo The information defined in SOLUTION is available for subsequent transport and adsorptive reaction calculations
temp 23 pH 82 pe 4 redox pe units mgL density 1 Al 006 Arsenite 0374 Arsenate 0291 CO4
2-
4401 Ca 194 Cl 1456 F 115 Fe 047 K 137 Mg 395 Mn 012 NO3
-
34 Na 16872
17
79
80
8182
83
84858687888990919293949596979899
100101102103104105106107108109110111112
SO42-
1176 Si 89 -water 1 kg
SOLUTION 1-4 The small column was divided into four cells SOLUTION 1-4
are the groundwater chemistry parameters for the four cells temp 23 pH 83 pe 4 redox pe units ppm density 1 Al 006 C(4) 4401 Ca 194 Cl 1456 F 115 Fe 047 K 137 Mg 395 Mn 012 N(3) 34 Na 16872 S(6) 1176 Si 89 -water 1 kg
SOLUTION_SPECIES This keyword is to define the dissociation constant logK
and diffusion constant (dw) in solution for arsenite and arsenate
Arsenite adsorption equation on GTiO2 surface H3ArseniteO3 is the primary species of As(III) at the groundwater pH 82 (Surf_sO)2ArseniteOH-066 is the adsorptive bidentate binuclear structure of As(III) on GTiO2
log_k 1635 The adsorptive reaction constant for As(III) on GTiO2 in
the current condition which could be changed with different experimental conditions
-cd_music -2 -1 0 066 3 CD-MUSIC model is integrated in the PHREEQC
modeling The numbers represent -2 the change in charge at the plane of Surf_sOH due to loss of two hydrogens -1 the change in charge at 1 plane due to gain of one hydrogen and one oxygen on Arsenite 0 the change in charge at the 2 plane usually caused by the outer sphere adsorption 066 the fraction of the central ion (As) charge that is associated with plane 0 which reflecting the charge distribution 3 the charge on the central ion (As)
Table S54 Parameters of Weber-Morris intraparticle model for As(IIIV) adsorption kinetics on GTiO2 using synthetic water Initial As concentration = 800 μgL adsorbent dose = 02 gL pH = 82 in synthetic groundwater
External film diffusion
Intraparticle diffusion
aRex2 bkp1
cb1aRin
2 bkp2cb 2
As(V) 0984 0497 0022 0976 01331878
As(III) 0970 0583
-0088 0981 0218
1105
aRex is WM external proportion fitting parameter while Rin is WM intraparticle proportion fitting parameterbk The unit of kp is mggh05 cb The unit of b is mgg
Table S6 Comparison of the adsorption capacities of As(III) and As(V) on GTiO2 and the representative granular adsorbents in similar experimental condition from the literature
AdsorbentParticle size (mm) As
qm
(mgg)Dose (gL) Experimental conditions Literature
GTiO2 018~025 As(III) 980 1 0~500 mgL at pH 82 01 M NaCl This studyGTiO2 018~025 As(V) 358 1 0~500 mgL at pH 82 01 M NaCl This study
Granular TiO2 015~06 As(III) 392 10~60 mgL As at pH 70 in simulated groundwater (100 mgL Ca 20 mgL Mg 50 mgL Na 200 mgL Cl-
)(Bang et al 2005)
Granular TiO2 015~06 As(V) 400 10~60 mgL As at pH 70 in simulated groundwater (100 mgL Ca 20 mgL Mg 50 mgL Na 200 mgL Cl-
)(Bang et al 2005)
E33 (FeOOH)0044~0075 As(V) 202 1 0~15 mgL at pH 70 in 001 M NaCl
(Kanematsu et al 2010)
E33 (FeOOH) 05~2 As(V) 180 1 0~50 mgL at pH 70 in 004 M NaClO4 (Jing et al 2012)
GFH 02~06 As(V) 650 10 0~2000 mgL at pH 8 in 01 M NaNO3
(Guan et al 2008)
GFH0009~0125 As(V) 23 025 0~07 μgL at pH 65 in DI water
(Banerjee et al 2008)
GFH0009~0125 As(V) 200 - 0~01 μgL at pH 70 in DI water
(Badruzzaman et al 2004)
GFH 050~065 As(V) 155 - 0~06 μgL at pH 70 in DI water (Saha et al 2005)
GHFO-NN 015~030 As(V) 330 0001 0~225 mgL at pH 8 in DI water(Streat et al 2008)
GHFO-VL 015~030 As(V) 360 0001 0~225 mgL at pH 8 in DI water(Streat et al 2008)
25
374375
Spherical schwertmannite 1~15 As(V) 36 05 0~5 mgL at pH 70 in DI water (Dou et al 2013)Cylindrical schwertmannite 1~25 As(V) 223 05
0~5 mgL at pH 70 in DI water(Dou et al 2013)
Irregular schwertmannite 10~16 As(V) 317 05 0~5 mgL at pH 70 in DI water (Dou et al 2013)Fe impregnated chitosan beads (MICB) 25 As(III) 117 1 0~05 mgL at pH 60 in DI water
(Wang et al 2014)
MICB 25 As(V) 191 1 0~1 mgL at pH 60 in DI water(Wang et al 2014)
MICB 25 As(III) 353 1 0~15 mgL at pH 60 in DI water(Wang et al 2014)
MICB 25 As(V) 357 1 0~16 mgL at pH 60 in DI water(Wang et al 2014)
Iron hydroxide granules (GIH) 3~4 As(V) 23 4
5~100 mgL at pH 70 in 10 mgL SO42-
14 mgL NH4Cl buffer solution (Daus et al 2004)
Activated Al2O3
0074~0149 As(V) 159 - 285~115 mgL at pH 52 in DI water
(Lin and Wu 2001)
Activated Al2O3
0074~0149 As(III) 35 - 079~490 mgL at pH 70 in DI water
(Lin and Wu 2001)
Activated Al2O3 ~20 As(V) 73 at pH 70 in 004 M NaClO4 (Jing et al 2012)
Activated natural siderite 05~10 As(V) 22 10 0 1~20 mgL at pH 7 in DI water(Zhao and Guo 2014)
Polyaluminum Granulate 1~3 As(III) 705 10 0~150 mgL at pH 51-56 in DI water(Mertens et al 2012)
Polyaluminum Granulate 1~3 As(V) 180 10 0~150 mgL at pH 51-56 in DI water (Mertens et al
26
2012)
Acidified laterite 1~12 As(III) 19 1 025~5 mgL at pH 7 in 100 mgL NaHCO3
(Glocheux et al 2013)
Acidified laterite 1~12 As(V) 13 1 025~5 mgL at pH 7 in 100 mgL NaHCO3
(Glocheux et al 2013)
Laterite 1~12 As(III) 07 1025~5 mgL at pH 7 in 100 mgL NaHCO3 (Glocheux et al
2013)
Laterite 1~12 As(V) 04 1025~5 mgL at pH 7 in 100 mgL NaHCO3 (Glocheux et al
2013)
Treated laterite 03-05 As(V) 216 05 02-20 mgL at pH 70 in DI water(Maiti et al 2012)
Treated laterite 03-05 As(III) 94 05 02-20 mgL at pH 70 in DI water(Maiti et al 2012)
Treated laterite03-05
As(V) 241 05 02-20 mgL at pH 70 in DI water(Maiti et al 2010a)
Treated laterite03-05
As(III) 81 05 02-20 mgL at pH 70 in DI water(Maiti et al 2010a)
Acid-activated laterite-103-07
As(III) 0633 50 02-10 mgL at pH 66-70 in DI water(Maiti et al 2010b)
Acid-activated laterite-203-07
As(III) 087650 02-10 mgL at pH 66-70 in DI water (Maiti et al
2010b)
Acid-activated laterite-303-07
As(III) 063450 02-10 mgL at pH 66-70 in DI water (Maiti et al
2010b)
Acid-activated laterite-103-07
As(V) 059850 02-10 mgL at pH 66-70 in DI water (Maiti et al
2010b)
27
Acid-activated laterite-203-07
As(V) 07550 02-10 mgL at pH 66-70 in DI water (Maiti et al
2010b)
Acid-activated laterite-303-07
As(V) 07550 02-10 mgL at pH 66-70 in DI water (Maiti et al
2010b)
Treated laterite-1 03-06 As(V) 019 20 0-20 mgL As at pH 72 in DI water(Maiti et al 2013b)
Treated laterite-1 03-06 As(III) 018 20 0-20 mgL As at pH 72 in DI water(Maiti et al 2013b)
Treated laterite-2 03-06 As(V) 004 20 0-20 mgL As at pH 72 in DI water(Maiti et al 2013b)
Treated laterite-2 03-06 As(III) 003 20 0-20 mgL As at pH 72 in DI water(Maiti et al 2013b)
Treated laterite-3 03-06 As(V) 007 20 0-20 mgL As at pH 72 in DI water(Maiti et al 2013b)
Treated laterite-3 03-06 As(III) 004 20 0-20 mgL As at pH 72 in DI water(Maiti et al 2013b)
28
376377
Charge distribution multi-site surface complexation (CD-MUSIC) modeling
The CD-MUSIC model with the 2-pK TPM adsorption option was used to
describe adsorption behaviors of As cations and anions on GTiO2 The CD-MUSIC
model incorporates the structural information of surfaces adsorbed species and the
double layers by distributing the charge of an adsorbate between the surface and
interfacial water (Hiemstra and Van Riemsdijk 2006) The CD-MUSIC model has
been successfully used in describing As adsorption in batch experiments (Pena et al
2006 Stachowicz et al 2008)
The adsorption constants of counter ions were set to -1 and the proton affinity
constant was set to the PZC of 58 for TiOH-13 (Luo et al 2010) The charge
distribution (CD) value shows the fraction (f) of the charge of the central As ion
attributed to the surface plane and the remaining part (1-f) was attributed to the other
ligands of the complex which were positioned toward the diffuse layer The CD value
for As surface complexes was obtained by fitting the experimental data The
calculation was performed using the chemical equilibrium program MINTEQ to
simulate the adsorption and the aqueous reactions
29
378379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
Fig S32 Adsorption of silicate (a) calcium and magnesium (b) as a function of GTiO2
dose in groundwater 1 The solid lines represent the CD-MUSIC modeling result
30
400
401
402
403
404
405
406
407
408409410
Table S75 Surface parameters and species used in the CD-MUSIC modeling in As(IIIV) removal under different GTiO2 dose in 01 M NaCl and groundwater 1 in Fig 2 and Fig S32
= exp(-FΨ1RT) P2 = exp(-FΨ2RT) F the Faraday constant (C mol-1) R the gas constant (J mol-1 K-1) T the absolute temperature (K)
Ψ0 Ψ1 Ψ2 the electrostatic potential (V) of 0- 1- and 2-plane respectively alogK for 01 M NaCl at 6 hours blogK for 01 M NaCl at 6 days clogK for groundwater 1 at 6 days
31
411412
413414415
32
416
Table S86 The charge distribution (f) of central As atom to TiO2 surface in simulating the effect of cations and anions on As adsorption in 01 M NaCl at pH 82 in Fig 4 BK Si HCO3 All
As(V) 022 017 012 016As(III) 040 020 058 056
Fig S43 Molar percentage () of As Ca Mg and Si on pristine and spent GTiO2
surfaces using EDX analysis The spent GTiO2 samples after field column experiments using groundwater 1 were identified with EBCT in min under x-axis The value of molar percentage of each element was averaged from randomly-chosen positions on the adsorbent surface
33
417
418
419420
421422
423
424
425
426
427
428
429
430
431
432
433434435436437438
439
440
441
As speciation analysis on spent GTiO2 using XANES
The spent GTiO2 samples were ground using a mortar and pestle and then the
ground powder was spread on Scotch tape The As k-edge XANES spectra were
collected at beamline 01C1 at the National Synchrotron Radiation Research Center
(NSRRC) Taiwan Spectra were acquired from -150 to 300 eV relative to the As K-
edge of 11867 eV at cryogenic temperature (77 K) using a cryostat to prevent the
oxidation of As(III) by X-rays The fluorescence signals were collected using a Lytle
detector Two to four scans were collected for each sample and averaged to improve
the signalnoise ratio The XANES analysis was performed with the Athena program
in the IFEFFIT computer package for linear combination fit (LCF) (Cui et al 2013
Ravel and Newville 2005)
34
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
PHREEQC modeling for As breakthrough curves in field column experiments
PHREEQC a geochemical model integrates macroscopic mass transfer
processes with a microscopic surface complexation model (Parkhurst and Appelo
2013) It can be applied in calculating solution complex speciation batch-reaction
and one-dimensional reactive-transport and inverse modeling In our study the one-
dimensional column was defined by four cells with the same length The cell length
was calculated to be one-fourth of the actual column length Time step (s) was
calculated according to equation Time step = Lcell(Q60A) where Lcell is the cell
length (cm) Q is flow velocity (mLmin) A is the effective column cross section area
(cm2) which is the column cross-sectional area multiplied by porosity (060) Total
shift number was calculated by dividing actual column operation time by the time
step The transport block was modeled by shifting the solute content from one cell to
the next one In each cell the aqueous solute was mixed and adsorbed on GTiO2
according to the equations In each cell the aqueous solute was mixed and assumed to
be in equilibration with GTiO2 The sequence of shifting mixing and equilibrium
adsorption was repeated for each cell until the total number of shifts was completed
The diffusion coefficient Dw in PHREEQC accounting for retardation was
calculated as Dw=x2
(36t) where x stands for the diffusion length (estimated as the
radius of the particle size) and t represents equilibrium time adopted from the batch
kinetic data (Mertens et al 2012)
For CD-MUSIC modeling in the PHREEQC take As(III) as an example to
explain the adsorption equation The As(III) adsorption is considered as a ligand
35
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
exchange reaction with the hydroxide group on GTiO2 (Surf_sOH-033) forming a
H3ArseniteO3 is the master species in groundwater at pH 82
(Surf_sO)2ArseniteOH-066 is the common adsorbed bidentate binuclear complex
evidenced by our previous reports(Pena et al 2006 Yan et al 2015) LogK is the
adsorption equilibrium constants Generally every adsorption equation under certain
experimental condition has a unique value of logK In the adsorption equation ldquo-2rdquo
represents the lost two hydrogens by Surf_sOH-033 after it adsorbs H3ArseniteO3 ldquo-
1rdquo represents the change in charge on Arsenite at 1 plane due to gaining one hydrogen
(+1) and one oxygen (-2) ldquo0rdquo represents no change in charge at the 2 plane ldquo066rdquo is
the fraction of the central ion (As) on GTiO2 surface that is associated with plane 0
ldquo3rdquo is the charge on the central ion As(III) Following this equation and the relevant
parameters As(III) adsorbed on GTiO2
The diffusion coefficient Dw in PHREEQC accounting for retardation was
calculated as Dw=x2(36t) where x stands for the diffusion length (estimated as the
radius of the particle size) and t represents equilibrium time adopted from the batch
kinetic data (Mertens et al 2012)
To well simulate the As breakthrough curve in columns four As(V) adsorption
reactions (Table 1) were employed Adsorption site density of 60 mmolg was
36
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
adopted from our previous study (Pena et al 2006) and the total adsorption sites were
calculated to be 1844 sitesnm2 The final optimized ratio of strong to weak sites was
51 The surface complexation constants were reasonably adjusted according to the
batch modeling results as the column reaction may not reach equilibrium in local
micro-interfacial areas due to much less contact time between As and GTiO2 than that
in batch experiments (Appelo and Postma 1999) In the modeling a stepwise
procedure was adopted to achieve a viable result An estimation of two thirds of the
surface site density being accessible for EBCT=011 min with large flow rate of 265
mLmin was optimized which could probably result from unavailable adsorption sites
due to fast transport through the column
The adsorbed As on GTiO2 in the column was calculated by mass balance
between the influent and effluent
where Asadsorbed is the adsorbed As on GTiO2 (mgg) n is the number of collected
samples Cin and Cout are influent and effluent As concentrations (mgL) respectively
Vi is volume (L) of groundwater passed through the column between sample i-1 and i
and m is the mass of GTiO2 (g)
Even though the oxidation of adsorbed As(III) occurred during filtration as
analyzed from XANES and mass balance analysis (Fig 7) no As(III) oxidation
reactions were considered in PHREEQC modeling which would not impact the
breakthrough of As(IIIV)
37
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
38
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
Fig S54 Effect of EBCT on Si Ca and Mg breakthrough curves using groundwater 1 The sample notation in panel c indicates field column experiments with EBCT in minutes
References
Appelo CAJ Postma D 1999 A consistent model for surface complexation on birnessite (MnO2) and its application to a column experiment Geochim Cosmochim Ac 63 (19-20) 3039-3048Badruzzaman M Westerhoff P Knappe DRU 2004 Intraparticle diffusion and adsorption of arsenate onto granular ferric hydroxide (GFH) Water Res 38 (18) 4002-4012Banerjee K Amy GL Prevost M Nour S Jekel M Gallagher PM Blumenschein CD 2008 Kinetic and thermodynamic aspects of adsorption of arsenic onto granular ferric hydroxide (GFH) Water Res 42 (13) 3371-3378Bang S Patel M Lippincott L Meng XG 2005 Removal of arsenic from groundwater by granular titanium dioxide adsorbent Chemosphere 60 (3) 389-397Bang S Pena ME Patel M Lippincott L Meng X Kim KW 2011 Removal of arsenate from water by adsorbents a comparative case study Environ Geochem Hlth 33 133-141Cui JL Shi JB Jiang GB Jing CY 2013 Arsenic levels and speciation from ingestion exposures to biomarkers in Shanxi China Implications for human health Environ Sci Technol 47 (10) 5419-5424Daus B Wennrich R Weiss H 2004 Sorption materials for arsenic removal from water A comparative study Water Res 38 (12) 2948-2954Dou XM Mohan D Pittman CU 2013 Arsenate adsorption on three types of granular schwertmannite Water Res 47 (9) 2938-2948Dou XM Zhang Y Yang M Pei YS Huang X Takayama T Kato S 2006 Occurrence of arsenic in groundwater in the suburbs of Beijing and its removal using an iron-cerium bimetal oxide adsorbent Water Qual Res J Can 41 (2) 140-146Gibbons MK Gagnon GA 2010 Adsorption of arsenic from a Nova Scotia groundwater onto water treatment residual solids Water Res 44 (19) 5740-5749Glocheux Y Mendez Pasarin M Albadarin AB Allen SJ Walker GM 2013 Removal of arsenic from groundwater by adsorption onto an acidified laterite by-product Chem Eng J 228 565-574Guan XH Wang JM Chusuei CC 2008 Removal of arsenic from water using granular ferric hydroxide Macroscopic and microscopic studies J Hazard Mater 156 (1-3) 178-185Gupta K Maity A Ghosh UC 2010 Manganese associated nanoparticles agglomerate of iron(III) oxide Synthesis characterization and arsenic(III) sorption behavior with mechanism J Hazard Mater 184 (1-3) 832-842Hao JM Han MJ Wang C Meng XG 2009 Enhanced removal of arsenite from water by a mesoporous hybrid material - Thiol-functionalized silica coated activated alumina Micropor Mesopor
Mat 124 (1-3) 1-7Hiemstra T Van Riemsdijk WH 2006 On the relationship between charge distribution surface hydration and the structure of the interface of metal hydroxides J Colloid Interf Sci 301 (1) 1-18Hristovski K Baumgardner A Westerhoff P 2007 Selecting metal oxide nanomaterials for arsenic removal in fixed bed columns From nanopowders to aggregated nanoparticle media J Hazard Mater 147 (1-2) 265-274Jang M Chen WF Cannon FS 2008 Preloading hydrous ferric oxide into granular activated carbon for arsenic removal Environ Sci Technol 42 (9) 3369-3374Jing CY Cui JL Huang YY Li AG 2012 Fabrication characterization and application of a composite adsorbent for simultaneous removal of arsenic and fluoride ACS Appl Mater Interfaces 4 (2) 714-720Kanematsu M Young TM Fukushi K Green PG Darby JL 2010 Extended triple layer modeling of arsenate and phosphate adsorption on a goethite-based granular porous adsorbent Environ Sci Technol 44 (9) 3388-3394Kong S Wang Y Zhan H Yuan S Liu M Zhou C 2013 Arsenite and Arsenate Removal from Contaminated Groundwater by Nanoscale Iron-Manganese Binary Oxides Column Studies Environmental Engineering Science 30 (11) 689-696Li Y Liu JR Jia SY Guo JW Zhuo J Na P 2012 TiO2 pillared montmorillonite as a photoactive adsorbent of arsenic under UV irradiation Chem Eng J 191 66-74Lin TF Wu JK 2001 Adsorption of arsenite and arsenate within activated alumina grains Equilibrium and kinetics Water Res 35 (8) 2049-2057Luo T Cui JL Hu S Huang YY Jing CY 2010 Arsenic removal and recovery from copper smelting wastewater using TiO2 Environ Sci Technol 44 (23) 9094-9098Maiti A Basu JK De S 2010a Development of a Treated Laterite for Arsenic Adsorption Effects of Treatment Parameters Industrial amp Engineering Chemistry Research 49 (10) 4873-4886Maiti A Basu JK De S 2010b Removal of Arsenic from Synthetic and Natural Groundwater Using Acid-Activated Laterite Environmental Progress amp Sustainable Energy 29 (4) 457-470Maiti A Basu JK De S 2012 Experimental and kinetic modeling of As(V) and As(III) adsorption on treated laterite using synthetic and contaminated groundwater Effects of phosphate silicate and carbonate ions Chem Eng J 191 1-12Maiti A Thakur BK Basu JK De S 2013a Comparison of treated laterite as arsenic adsorbent from different locations and performance of best filter under field conditions J Hazard Mater 262 1176-1186Maiti A Thakur BK Basu JK De S 2013b Comparison of treated laterite as arsenic adsorbent from different locations and performance of best filter under field conditions J Hazard Mater 262 (0) 1176-1186Maji SK Pal A Pal T 2008 Arsenic removal from real-life groundwater by adsorption on laterite soil J Hazard Mater 151 (2-3) 811-820Maji SK Kao YH Wang CJ Lu GS Wu JJ Liu CW 2012 Fixed bed adsorption of As(III) on iron-oxide-coated natural rock (IOCNR) and application to real arsenic-bearing groundwater Chem Eng J 203 285-293Mertens J Rose J Kagi R Chaurand P Plotze M Wehrli B Furrer G 2012 Adsorption of arsenic on polyaluminum granulate Environ Sci Technol 46 (13) 7310-7317Nguyen TV Vigneswaran S Ngo HH Pokhre D Viraraghavan T 2006 Iron-coated sponge as
effective media to remove arsenic from drinking water Water Qual Res J Can 41 (2) 164-170Parkhurst DL Appelo CAJ 2013 Description of input and examples for PHREEQC version 3-A computer program for speciation batch-reaction one-dimensional transport and inverse geochemical calculations US Geological SurveyPena M Meng XG Korfiatis GP Jing CY 2006 Adsorption mechanism of arsenic on nanocrystalline titanium dioxide Environ Sci Technol 40 (4) 1257-1262Ravel B Newville M 2005 ATHENA ARTEMIS HEPHAESTUS Data analysis for X-ray absorption spectroscopy using IFEFFIT J Synchrotron Radiat 12 537-541Saha B Bains R Greenwood F 2005 Physicochemical characterization of granular ferric hydroxide (GFH) for arsenic(V) sorption from water Separation Science and Technology 40 (14) 2909-2932Shan H Ma T Wang Y Zhao J Han H Deng Y He X Dong Y 2013 A cost-effective system for in-situ geological arsenic adsorption from groundwater J Contam Hydrol 154 1-9Stachowicz M Hiemstra T van Riemsdijk WH 2008 Multi-competitive interaction of As(III) and As(V) oxyanions with Ca2+ Mg2+ PO4
3- and CO32- ions on goethite J Colloid Interf Sci 320 (2) 400-
414Streat M Hellgardt K Newton NLR 2008 Hydrous ferric oxide as an adsorbent in water treatment - Part 3 Batch and mini-column adsorption of arsenic phosphorus fluorine and cadmium ions Process Safety and Environmental Protection 86 (B1) 21-30Thirunavukkarasu OS Viraraghavan T Subramanian KS 2003 Arsenic removal from drinking water using iron oxide-coated sand Water Air Soil Poll 142 (1-4) 95-111USEPA 2008 Assessing arsenic removal by metal (hydr)oxide adsorptive media using rapid small scale column tests Govenrnment Printing Office Washington DCWang J Xu W Chen L Huang X Liu J 2014 Preparation and evaluation of magnetic nanoparticles impregnated chitosan beads for arsenic removal from water Chem Eng J 251 25-34Westerhoff P Highfield D Badruzzaman M Yoon Y 2005 Rapid small-scale column tests for arsenate removal in iron oxide packed bed columns J Environ Eng-Asce 131 (2) 262-271Westerhoff P De Haan M Martindale A Badruzzaman M 2006 Arsenic adsorptive media technology selection strategies Water Qual Res J Can 41 (2) 171-184Yan L Huang Y Cui J Jing C 2015 Simultaneous As(III) and Cd removal from copper smelting wastewater using granular TiO2 columns Water Res 68 (0) 572-579Zhao K Guo HM 2014 Behavior and mechanism of arsenate adsorption on activated natural siderite Evidences from FTIR and XANES analysis Environ Sci Pollut Res 21 (3) 1944-1953Zhao K Guo H Zhou X 2014 Adsorption and heterogeneous oxidation of arsenite on modified granular natural siderite Characterization and behaviors Appl Geochem 48 184-192
Iron-Mn binary 15 40 145 176 321 22 253 347 754 (Maiti et al 2010a)
13
oxides
aUnit for ion concentration is mgL except as notedbestimated from bed volume breakthrough curves and influent As concentration if not explicitly expressed in the reference cThe species is As(V) if only one concentration is given
d
The groundwater As concentration was 385-440 μgL and additional ~600 μgL (As(III)As(V)=11) arsenic was added
14
222324252627
Fig S1 Boxplot of groundwater As levels in columns and filters in the literature in Table S1 Individual samples are shown as diamonds The range of each box represents the 25th
and 75th
percentile whereas the whiskers represent the 10th
and 90th
percentile
Synthesis of granular TiO2
Granular TiO2 (GTiO2) was prepared by hydrolysis of titanyl sulfate (TiOSO4)
Generally 300 g TiOSO4 was mixed with 1800 mL DI water in a 10 L jar reactor in an
ice bath at 4 oC Then 10 M NaOH was slowly added to adjust the pH to 6 The
precursor of TiO2 was obtained by washing the suspension with DI water several
times till the conductivity of the supernatant was less than 100 μScm Then 800 g
TiO2 precursor was mixed with 40 mL polyvinyl alcohol solution at 80 oC in a water
bath The product was crushed into 60-80 mesh and dried in an oven at 60 oC for 12 h
15
282930313233343536373839404142434445464748
49
50
51
52
53
54
55
56
57585960
Fig S2 Characterization of GTiO2 SEM (a) and XRD pattern with crystal face for each peak (b)
Fig S1 SEM images for GTiO2 in this study
Table S2 Average concentrations of As coexisting ions (mgL) and water chemistry for groundwater 1 and 2 from two wells
Table S3 Water parameters in the synthetic water used in the studyParameters Ca2+ Mg2+ HCO3
- Na+ Cl- pHConc (mgL) 401 1043 388 2460 3928 82
Table S4 PHREEQC input for a representative column with EBCT=054 min SOLUTION 0
This keyword is to define the influent groundwater chemistry parameters which are included in the adsorption reactions like ldquoArseniterdquo and ldquoArsenaterdquo and the experimental conditions including ldquopHrdquo The information defined in SOLUTION is available for subsequent transport and adsorptive reaction calculations
temp 23 pH 82 pe 4 redox pe units mgL density 1 Al 006 Arsenite 0374 Arsenate 0291 CO4
2-
4401 Ca 194 Cl 1456 F 115 Fe 047 K 137 Mg 395 Mn 012 NO3
-
34 Na 16872
17
79
80
8182
83
84858687888990919293949596979899
100101102103104105106107108109110111112
SO42-
1176 Si 89 -water 1 kg
SOLUTION 1-4 The small column was divided into four cells SOLUTION 1-4
are the groundwater chemistry parameters for the four cells temp 23 pH 83 pe 4 redox pe units ppm density 1 Al 006 C(4) 4401 Ca 194 Cl 1456 F 115 Fe 047 K 137 Mg 395 Mn 012 N(3) 34 Na 16872 S(6) 1176 Si 89 -water 1 kg
SOLUTION_SPECIES This keyword is to define the dissociation constant logK
and diffusion constant (dw) in solution for arsenite and arsenate
Arsenite adsorption equation on GTiO2 surface H3ArseniteO3 is the primary species of As(III) at the groundwater pH 82 (Surf_sO)2ArseniteOH-066 is the adsorptive bidentate binuclear structure of As(III) on GTiO2
log_k 1635 The adsorptive reaction constant for As(III) on GTiO2 in
the current condition which could be changed with different experimental conditions
-cd_music -2 -1 0 066 3 CD-MUSIC model is integrated in the PHREEQC
modeling The numbers represent -2 the change in charge at the plane of Surf_sOH due to loss of two hydrogens -1 the change in charge at 1 plane due to gain of one hydrogen and one oxygen on Arsenite 0 the change in charge at the 2 plane usually caused by the outer sphere adsorption 066 the fraction of the central ion (As) charge that is associated with plane 0 which reflecting the charge distribution 3 the charge on the central ion (As)
Table S54 Parameters of Weber-Morris intraparticle model for As(IIIV) adsorption kinetics on GTiO2 using synthetic water Initial As concentration = 800 μgL adsorbent dose = 02 gL pH = 82 in synthetic groundwater
External film diffusion
Intraparticle diffusion
aRex2 bkp1
cb1aRin
2 bkp2cb 2
As(V) 0984 0497 0022 0976 01331878
As(III) 0970 0583
-0088 0981 0218
1105
aRex is WM external proportion fitting parameter while Rin is WM intraparticle proportion fitting parameterbk The unit of kp is mggh05 cb The unit of b is mgg
Table S6 Comparison of the adsorption capacities of As(III) and As(V) on GTiO2 and the representative granular adsorbents in similar experimental condition from the literature
AdsorbentParticle size (mm) As
qm
(mgg)Dose (gL) Experimental conditions Literature
GTiO2 018~025 As(III) 980 1 0~500 mgL at pH 82 01 M NaCl This studyGTiO2 018~025 As(V) 358 1 0~500 mgL at pH 82 01 M NaCl This study
Granular TiO2 015~06 As(III) 392 10~60 mgL As at pH 70 in simulated groundwater (100 mgL Ca 20 mgL Mg 50 mgL Na 200 mgL Cl-
)(Bang et al 2005)
Granular TiO2 015~06 As(V) 400 10~60 mgL As at pH 70 in simulated groundwater (100 mgL Ca 20 mgL Mg 50 mgL Na 200 mgL Cl-
)(Bang et al 2005)
E33 (FeOOH)0044~0075 As(V) 202 1 0~15 mgL at pH 70 in 001 M NaCl
(Kanematsu et al 2010)
E33 (FeOOH) 05~2 As(V) 180 1 0~50 mgL at pH 70 in 004 M NaClO4 (Jing et al 2012)
GFH 02~06 As(V) 650 10 0~2000 mgL at pH 8 in 01 M NaNO3
(Guan et al 2008)
GFH0009~0125 As(V) 23 025 0~07 μgL at pH 65 in DI water
(Banerjee et al 2008)
GFH0009~0125 As(V) 200 - 0~01 μgL at pH 70 in DI water
(Badruzzaman et al 2004)
GFH 050~065 As(V) 155 - 0~06 μgL at pH 70 in DI water (Saha et al 2005)
GHFO-NN 015~030 As(V) 330 0001 0~225 mgL at pH 8 in DI water(Streat et al 2008)
GHFO-VL 015~030 As(V) 360 0001 0~225 mgL at pH 8 in DI water(Streat et al 2008)
25
374375
Spherical schwertmannite 1~15 As(V) 36 05 0~5 mgL at pH 70 in DI water (Dou et al 2013)Cylindrical schwertmannite 1~25 As(V) 223 05
0~5 mgL at pH 70 in DI water(Dou et al 2013)
Irregular schwertmannite 10~16 As(V) 317 05 0~5 mgL at pH 70 in DI water (Dou et al 2013)Fe impregnated chitosan beads (MICB) 25 As(III) 117 1 0~05 mgL at pH 60 in DI water
(Wang et al 2014)
MICB 25 As(V) 191 1 0~1 mgL at pH 60 in DI water(Wang et al 2014)
MICB 25 As(III) 353 1 0~15 mgL at pH 60 in DI water(Wang et al 2014)
MICB 25 As(V) 357 1 0~16 mgL at pH 60 in DI water(Wang et al 2014)
Iron hydroxide granules (GIH) 3~4 As(V) 23 4
5~100 mgL at pH 70 in 10 mgL SO42-
14 mgL NH4Cl buffer solution (Daus et al 2004)
Activated Al2O3
0074~0149 As(V) 159 - 285~115 mgL at pH 52 in DI water
(Lin and Wu 2001)
Activated Al2O3
0074~0149 As(III) 35 - 079~490 mgL at pH 70 in DI water
(Lin and Wu 2001)
Activated Al2O3 ~20 As(V) 73 at pH 70 in 004 M NaClO4 (Jing et al 2012)
Activated natural siderite 05~10 As(V) 22 10 0 1~20 mgL at pH 7 in DI water(Zhao and Guo 2014)
Polyaluminum Granulate 1~3 As(III) 705 10 0~150 mgL at pH 51-56 in DI water(Mertens et al 2012)
Polyaluminum Granulate 1~3 As(V) 180 10 0~150 mgL at pH 51-56 in DI water (Mertens et al
26
2012)
Acidified laterite 1~12 As(III) 19 1 025~5 mgL at pH 7 in 100 mgL NaHCO3
(Glocheux et al 2013)
Acidified laterite 1~12 As(V) 13 1 025~5 mgL at pH 7 in 100 mgL NaHCO3
(Glocheux et al 2013)
Laterite 1~12 As(III) 07 1025~5 mgL at pH 7 in 100 mgL NaHCO3 (Glocheux et al
2013)
Laterite 1~12 As(V) 04 1025~5 mgL at pH 7 in 100 mgL NaHCO3 (Glocheux et al
2013)
Treated laterite 03-05 As(V) 216 05 02-20 mgL at pH 70 in DI water(Maiti et al 2012)
Treated laterite 03-05 As(III) 94 05 02-20 mgL at pH 70 in DI water(Maiti et al 2012)
Treated laterite03-05
As(V) 241 05 02-20 mgL at pH 70 in DI water(Maiti et al 2010a)
Treated laterite03-05
As(III) 81 05 02-20 mgL at pH 70 in DI water(Maiti et al 2010a)
Acid-activated laterite-103-07
As(III) 0633 50 02-10 mgL at pH 66-70 in DI water(Maiti et al 2010b)
Acid-activated laterite-203-07
As(III) 087650 02-10 mgL at pH 66-70 in DI water (Maiti et al
2010b)
Acid-activated laterite-303-07
As(III) 063450 02-10 mgL at pH 66-70 in DI water (Maiti et al
2010b)
Acid-activated laterite-103-07
As(V) 059850 02-10 mgL at pH 66-70 in DI water (Maiti et al
2010b)
27
Acid-activated laterite-203-07
As(V) 07550 02-10 mgL at pH 66-70 in DI water (Maiti et al
2010b)
Acid-activated laterite-303-07
As(V) 07550 02-10 mgL at pH 66-70 in DI water (Maiti et al
2010b)
Treated laterite-1 03-06 As(V) 019 20 0-20 mgL As at pH 72 in DI water(Maiti et al 2013b)
Treated laterite-1 03-06 As(III) 018 20 0-20 mgL As at pH 72 in DI water(Maiti et al 2013b)
Treated laterite-2 03-06 As(V) 004 20 0-20 mgL As at pH 72 in DI water(Maiti et al 2013b)
Treated laterite-2 03-06 As(III) 003 20 0-20 mgL As at pH 72 in DI water(Maiti et al 2013b)
Treated laterite-3 03-06 As(V) 007 20 0-20 mgL As at pH 72 in DI water(Maiti et al 2013b)
Treated laterite-3 03-06 As(III) 004 20 0-20 mgL As at pH 72 in DI water(Maiti et al 2013b)
28
376377
Charge distribution multi-site surface complexation (CD-MUSIC) modeling
The CD-MUSIC model with the 2-pK TPM adsorption option was used to
describe adsorption behaviors of As cations and anions on GTiO2 The CD-MUSIC
model incorporates the structural information of surfaces adsorbed species and the
double layers by distributing the charge of an adsorbate between the surface and
interfacial water (Hiemstra and Van Riemsdijk 2006) The CD-MUSIC model has
been successfully used in describing As adsorption in batch experiments (Pena et al
2006 Stachowicz et al 2008)
The adsorption constants of counter ions were set to -1 and the proton affinity
constant was set to the PZC of 58 for TiOH-13 (Luo et al 2010) The charge
distribution (CD) value shows the fraction (f) of the charge of the central As ion
attributed to the surface plane and the remaining part (1-f) was attributed to the other
ligands of the complex which were positioned toward the diffuse layer The CD value
for As surface complexes was obtained by fitting the experimental data The
calculation was performed using the chemical equilibrium program MINTEQ to
simulate the adsorption and the aqueous reactions
29
378379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
Fig S32 Adsorption of silicate (a) calcium and magnesium (b) as a function of GTiO2
dose in groundwater 1 The solid lines represent the CD-MUSIC modeling result
30
400
401
402
403
404
405
406
407
408409410
Table S75 Surface parameters and species used in the CD-MUSIC modeling in As(IIIV) removal under different GTiO2 dose in 01 M NaCl and groundwater 1 in Fig 2 and Fig S32
= exp(-FΨ1RT) P2 = exp(-FΨ2RT) F the Faraday constant (C mol-1) R the gas constant (J mol-1 K-1) T the absolute temperature (K)
Ψ0 Ψ1 Ψ2 the electrostatic potential (V) of 0- 1- and 2-plane respectively alogK for 01 M NaCl at 6 hours blogK for 01 M NaCl at 6 days clogK for groundwater 1 at 6 days
31
411412
413414415
32
416
Table S86 The charge distribution (f) of central As atom to TiO2 surface in simulating the effect of cations and anions on As adsorption in 01 M NaCl at pH 82 in Fig 4 BK Si HCO3 All
As(V) 022 017 012 016As(III) 040 020 058 056
Fig S43 Molar percentage () of As Ca Mg and Si on pristine and spent GTiO2
surfaces using EDX analysis The spent GTiO2 samples after field column experiments using groundwater 1 were identified with EBCT in min under x-axis The value of molar percentage of each element was averaged from randomly-chosen positions on the adsorbent surface
33
417
418
419420
421422
423
424
425
426
427
428
429
430
431
432
433434435436437438
439
440
441
As speciation analysis on spent GTiO2 using XANES
The spent GTiO2 samples were ground using a mortar and pestle and then the
ground powder was spread on Scotch tape The As k-edge XANES spectra were
collected at beamline 01C1 at the National Synchrotron Radiation Research Center
(NSRRC) Taiwan Spectra were acquired from -150 to 300 eV relative to the As K-
edge of 11867 eV at cryogenic temperature (77 K) using a cryostat to prevent the
oxidation of As(III) by X-rays The fluorescence signals were collected using a Lytle
detector Two to four scans were collected for each sample and averaged to improve
the signalnoise ratio The XANES analysis was performed with the Athena program
in the IFEFFIT computer package for linear combination fit (LCF) (Cui et al 2013
Ravel and Newville 2005)
34
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
PHREEQC modeling for As breakthrough curves in field column experiments
PHREEQC a geochemical model integrates macroscopic mass transfer
processes with a microscopic surface complexation model (Parkhurst and Appelo
2013) It can be applied in calculating solution complex speciation batch-reaction
and one-dimensional reactive-transport and inverse modeling In our study the one-
dimensional column was defined by four cells with the same length The cell length
was calculated to be one-fourth of the actual column length Time step (s) was
calculated according to equation Time step = Lcell(Q60A) where Lcell is the cell
length (cm) Q is flow velocity (mLmin) A is the effective column cross section area
(cm2) which is the column cross-sectional area multiplied by porosity (060) Total
shift number was calculated by dividing actual column operation time by the time
step The transport block was modeled by shifting the solute content from one cell to
the next one In each cell the aqueous solute was mixed and adsorbed on GTiO2
according to the equations In each cell the aqueous solute was mixed and assumed to
be in equilibration with GTiO2 The sequence of shifting mixing and equilibrium
adsorption was repeated for each cell until the total number of shifts was completed
The diffusion coefficient Dw in PHREEQC accounting for retardation was
calculated as Dw=x2
(36t) where x stands for the diffusion length (estimated as the
radius of the particle size) and t represents equilibrium time adopted from the batch
kinetic data (Mertens et al 2012)
For CD-MUSIC modeling in the PHREEQC take As(III) as an example to
explain the adsorption equation The As(III) adsorption is considered as a ligand
35
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
exchange reaction with the hydroxide group on GTiO2 (Surf_sOH-033) forming a
H3ArseniteO3 is the master species in groundwater at pH 82
(Surf_sO)2ArseniteOH-066 is the common adsorbed bidentate binuclear complex
evidenced by our previous reports(Pena et al 2006 Yan et al 2015) LogK is the
adsorption equilibrium constants Generally every adsorption equation under certain
experimental condition has a unique value of logK In the adsorption equation ldquo-2rdquo
represents the lost two hydrogens by Surf_sOH-033 after it adsorbs H3ArseniteO3 ldquo-
1rdquo represents the change in charge on Arsenite at 1 plane due to gaining one hydrogen
(+1) and one oxygen (-2) ldquo0rdquo represents no change in charge at the 2 plane ldquo066rdquo is
the fraction of the central ion (As) on GTiO2 surface that is associated with plane 0
ldquo3rdquo is the charge on the central ion As(III) Following this equation and the relevant
parameters As(III) adsorbed on GTiO2
The diffusion coefficient Dw in PHREEQC accounting for retardation was
calculated as Dw=x2(36t) where x stands for the diffusion length (estimated as the
radius of the particle size) and t represents equilibrium time adopted from the batch
kinetic data (Mertens et al 2012)
To well simulate the As breakthrough curve in columns four As(V) adsorption
reactions (Table 1) were employed Adsorption site density of 60 mmolg was
36
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
adopted from our previous study (Pena et al 2006) and the total adsorption sites were
calculated to be 1844 sitesnm2 The final optimized ratio of strong to weak sites was
51 The surface complexation constants were reasonably adjusted according to the
batch modeling results as the column reaction may not reach equilibrium in local
micro-interfacial areas due to much less contact time between As and GTiO2 than that
in batch experiments (Appelo and Postma 1999) In the modeling a stepwise
procedure was adopted to achieve a viable result An estimation of two thirds of the
surface site density being accessible for EBCT=011 min with large flow rate of 265
mLmin was optimized which could probably result from unavailable adsorption sites
due to fast transport through the column
The adsorbed As on GTiO2 in the column was calculated by mass balance
between the influent and effluent
where Asadsorbed is the adsorbed As on GTiO2 (mgg) n is the number of collected
samples Cin and Cout are influent and effluent As concentrations (mgL) respectively
Vi is volume (L) of groundwater passed through the column between sample i-1 and i
and m is the mass of GTiO2 (g)
Even though the oxidation of adsorbed As(III) occurred during filtration as
analyzed from XANES and mass balance analysis (Fig 7) no As(III) oxidation
reactions were considered in PHREEQC modeling which would not impact the
breakthrough of As(IIIV)
37
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
38
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
Fig S54 Effect of EBCT on Si Ca and Mg breakthrough curves using groundwater 1 The sample notation in panel c indicates field column experiments with EBCT in minutes
References
Appelo CAJ Postma D 1999 A consistent model for surface complexation on birnessite (MnO2) and its application to a column experiment Geochim Cosmochim Ac 63 (19-20) 3039-3048Badruzzaman M Westerhoff P Knappe DRU 2004 Intraparticle diffusion and adsorption of arsenate onto granular ferric hydroxide (GFH) Water Res 38 (18) 4002-4012Banerjee K Amy GL Prevost M Nour S Jekel M Gallagher PM Blumenschein CD 2008 Kinetic and thermodynamic aspects of adsorption of arsenic onto granular ferric hydroxide (GFH) Water Res 42 (13) 3371-3378Bang S Patel M Lippincott L Meng XG 2005 Removal of arsenic from groundwater by granular titanium dioxide adsorbent Chemosphere 60 (3) 389-397Bang S Pena ME Patel M Lippincott L Meng X Kim KW 2011 Removal of arsenate from water by adsorbents a comparative case study Environ Geochem Hlth 33 133-141Cui JL Shi JB Jiang GB Jing CY 2013 Arsenic levels and speciation from ingestion exposures to biomarkers in Shanxi China Implications for human health Environ Sci Technol 47 (10) 5419-5424Daus B Wennrich R Weiss H 2004 Sorption materials for arsenic removal from water A comparative study Water Res 38 (12) 2948-2954Dou XM Mohan D Pittman CU 2013 Arsenate adsorption on three types of granular schwertmannite Water Res 47 (9) 2938-2948Dou XM Zhang Y Yang M Pei YS Huang X Takayama T Kato S 2006 Occurrence of arsenic in groundwater in the suburbs of Beijing and its removal using an iron-cerium bimetal oxide adsorbent Water Qual Res J Can 41 (2) 140-146Gibbons MK Gagnon GA 2010 Adsorption of arsenic from a Nova Scotia groundwater onto water treatment residual solids Water Res 44 (19) 5740-5749Glocheux Y Mendez Pasarin M Albadarin AB Allen SJ Walker GM 2013 Removal of arsenic from groundwater by adsorption onto an acidified laterite by-product Chem Eng J 228 565-574Guan XH Wang JM Chusuei CC 2008 Removal of arsenic from water using granular ferric hydroxide Macroscopic and microscopic studies J Hazard Mater 156 (1-3) 178-185Gupta K Maity A Ghosh UC 2010 Manganese associated nanoparticles agglomerate of iron(III) oxide Synthesis characterization and arsenic(III) sorption behavior with mechanism J Hazard Mater 184 (1-3) 832-842Hao JM Han MJ Wang C Meng XG 2009 Enhanced removal of arsenite from water by a mesoporous hybrid material - Thiol-functionalized silica coated activated alumina Micropor Mesopor
Mat 124 (1-3) 1-7Hiemstra T Van Riemsdijk WH 2006 On the relationship between charge distribution surface hydration and the structure of the interface of metal hydroxides J Colloid Interf Sci 301 (1) 1-18Hristovski K Baumgardner A Westerhoff P 2007 Selecting metal oxide nanomaterials for arsenic removal in fixed bed columns From nanopowders to aggregated nanoparticle media J Hazard Mater 147 (1-2) 265-274Jang M Chen WF Cannon FS 2008 Preloading hydrous ferric oxide into granular activated carbon for arsenic removal Environ Sci Technol 42 (9) 3369-3374Jing CY Cui JL Huang YY Li AG 2012 Fabrication characterization and application of a composite adsorbent for simultaneous removal of arsenic and fluoride ACS Appl Mater Interfaces 4 (2) 714-720Kanematsu M Young TM Fukushi K Green PG Darby JL 2010 Extended triple layer modeling of arsenate and phosphate adsorption on a goethite-based granular porous adsorbent Environ Sci Technol 44 (9) 3388-3394Kong S Wang Y Zhan H Yuan S Liu M Zhou C 2013 Arsenite and Arsenate Removal from Contaminated Groundwater by Nanoscale Iron-Manganese Binary Oxides Column Studies Environmental Engineering Science 30 (11) 689-696Li Y Liu JR Jia SY Guo JW Zhuo J Na P 2012 TiO2 pillared montmorillonite as a photoactive adsorbent of arsenic under UV irradiation Chem Eng J 191 66-74Lin TF Wu JK 2001 Adsorption of arsenite and arsenate within activated alumina grains Equilibrium and kinetics Water Res 35 (8) 2049-2057Luo T Cui JL Hu S Huang YY Jing CY 2010 Arsenic removal and recovery from copper smelting wastewater using TiO2 Environ Sci Technol 44 (23) 9094-9098Maiti A Basu JK De S 2010a Development of a Treated Laterite for Arsenic Adsorption Effects of Treatment Parameters Industrial amp Engineering Chemistry Research 49 (10) 4873-4886Maiti A Basu JK De S 2010b Removal of Arsenic from Synthetic and Natural Groundwater Using Acid-Activated Laterite Environmental Progress amp Sustainable Energy 29 (4) 457-470Maiti A Basu JK De S 2012 Experimental and kinetic modeling of As(V) and As(III) adsorption on treated laterite using synthetic and contaminated groundwater Effects of phosphate silicate and carbonate ions Chem Eng J 191 1-12Maiti A Thakur BK Basu JK De S 2013a Comparison of treated laterite as arsenic adsorbent from different locations and performance of best filter under field conditions J Hazard Mater 262 1176-1186Maiti A Thakur BK Basu JK De S 2013b Comparison of treated laterite as arsenic adsorbent from different locations and performance of best filter under field conditions J Hazard Mater 262 (0) 1176-1186Maji SK Pal A Pal T 2008 Arsenic removal from real-life groundwater by adsorption on laterite soil J Hazard Mater 151 (2-3) 811-820Maji SK Kao YH Wang CJ Lu GS Wu JJ Liu CW 2012 Fixed bed adsorption of As(III) on iron-oxide-coated natural rock (IOCNR) and application to real arsenic-bearing groundwater Chem Eng J 203 285-293Mertens J Rose J Kagi R Chaurand P Plotze M Wehrli B Furrer G 2012 Adsorption of arsenic on polyaluminum granulate Environ Sci Technol 46 (13) 7310-7317Nguyen TV Vigneswaran S Ngo HH Pokhre D Viraraghavan T 2006 Iron-coated sponge as
effective media to remove arsenic from drinking water Water Qual Res J Can 41 (2) 164-170Parkhurst DL Appelo CAJ 2013 Description of input and examples for PHREEQC version 3-A computer program for speciation batch-reaction one-dimensional transport and inverse geochemical calculations US Geological SurveyPena M Meng XG Korfiatis GP Jing CY 2006 Adsorption mechanism of arsenic on nanocrystalline titanium dioxide Environ Sci Technol 40 (4) 1257-1262Ravel B Newville M 2005 ATHENA ARTEMIS HEPHAESTUS Data analysis for X-ray absorption spectroscopy using IFEFFIT J Synchrotron Radiat 12 537-541Saha B Bains R Greenwood F 2005 Physicochemical characterization of granular ferric hydroxide (GFH) for arsenic(V) sorption from water Separation Science and Technology 40 (14) 2909-2932Shan H Ma T Wang Y Zhao J Han H Deng Y He X Dong Y 2013 A cost-effective system for in-situ geological arsenic adsorption from groundwater J Contam Hydrol 154 1-9Stachowicz M Hiemstra T van Riemsdijk WH 2008 Multi-competitive interaction of As(III) and As(V) oxyanions with Ca2+ Mg2+ PO4
3- and CO32- ions on goethite J Colloid Interf Sci 320 (2) 400-
414Streat M Hellgardt K Newton NLR 2008 Hydrous ferric oxide as an adsorbent in water treatment - Part 3 Batch and mini-column adsorption of arsenic phosphorus fluorine and cadmium ions Process Safety and Environmental Protection 86 (B1) 21-30Thirunavukkarasu OS Viraraghavan T Subramanian KS 2003 Arsenic removal from drinking water using iron oxide-coated sand Water Air Soil Poll 142 (1-4) 95-111USEPA 2008 Assessing arsenic removal by metal (hydr)oxide adsorptive media using rapid small scale column tests Govenrnment Printing Office Washington DCWang J Xu W Chen L Huang X Liu J 2014 Preparation and evaluation of magnetic nanoparticles impregnated chitosan beads for arsenic removal from water Chem Eng J 251 25-34Westerhoff P Highfield D Badruzzaman M Yoon Y 2005 Rapid small-scale column tests for arsenate removal in iron oxide packed bed columns J Environ Eng-Asce 131 (2) 262-271Westerhoff P De Haan M Martindale A Badruzzaman M 2006 Arsenic adsorptive media technology selection strategies Water Qual Res J Can 41 (2) 171-184Yan L Huang Y Cui J Jing C 2015 Simultaneous As(III) and Cd removal from copper smelting wastewater using granular TiO2 columns Water Res 68 (0) 572-579Zhao K Guo HM 2014 Behavior and mechanism of arsenate adsorption on activated natural siderite Evidences from FTIR and XANES analysis Environ Sci Pollut Res 21 (3) 1944-1953Zhao K Guo H Zhou X 2014 Adsorption and heterogeneous oxidation of arsenite on modified granular natural siderite Characterization and behaviors Appl Geochem 48 184-192
Iron-Mn binary 15 40 145 176 321 22 253 347 754 (Maiti et al 2010a)
13
oxides
aUnit for ion concentration is mgL except as notedbestimated from bed volume breakthrough curves and influent As concentration if not explicitly expressed in the reference cThe species is As(V) if only one concentration is given
d
The groundwater As concentration was 385-440 μgL and additional ~600 μgL (As(III)As(V)=11) arsenic was added
14
222324252627
Fig S1 Boxplot of groundwater As levels in columns and filters in the literature in Table S1 Individual samples are shown as diamonds The range of each box represents the 25th
and 75th
percentile whereas the whiskers represent the 10th
and 90th
percentile
Synthesis of granular TiO2
Granular TiO2 (GTiO2) was prepared by hydrolysis of titanyl sulfate (TiOSO4)
Generally 300 g TiOSO4 was mixed with 1800 mL DI water in a 10 L jar reactor in an
ice bath at 4 oC Then 10 M NaOH was slowly added to adjust the pH to 6 The
precursor of TiO2 was obtained by washing the suspension with DI water several
times till the conductivity of the supernatant was less than 100 μScm Then 800 g
TiO2 precursor was mixed with 40 mL polyvinyl alcohol solution at 80 oC in a water
bath The product was crushed into 60-80 mesh and dried in an oven at 60 oC for 12 h
15
282930313233343536373839404142434445464748
49
50
51
52
53
54
55
56
57585960
Fig S2 Characterization of GTiO2 SEM (a) and XRD pattern with crystal face for each peak (b)
Fig S1 SEM images for GTiO2 in this study
Table S2 Average concentrations of As coexisting ions (mgL) and water chemistry for groundwater 1 and 2 from two wells
Table S3 Water parameters in the synthetic water used in the studyParameters Ca2+ Mg2+ HCO3
- Na+ Cl- pHConc (mgL) 401 1043 388 2460 3928 82
Table S4 PHREEQC input for a representative column with EBCT=054 min SOLUTION 0
This keyword is to define the influent groundwater chemistry parameters which are included in the adsorption reactions like ldquoArseniterdquo and ldquoArsenaterdquo and the experimental conditions including ldquopHrdquo The information defined in SOLUTION is available for subsequent transport and adsorptive reaction calculations
temp 23 pH 82 pe 4 redox pe units mgL density 1 Al 006 Arsenite 0374 Arsenate 0291 CO4
2-
4401 Ca 194 Cl 1456 F 115 Fe 047 K 137 Mg 395 Mn 012 NO3
-
34 Na 16872
17
79
80
8182
83
84858687888990919293949596979899
100101102103104105106107108109110111112
SO42-
1176 Si 89 -water 1 kg
SOLUTION 1-4 The small column was divided into four cells SOLUTION 1-4
are the groundwater chemistry parameters for the four cells temp 23 pH 83 pe 4 redox pe units ppm density 1 Al 006 C(4) 4401 Ca 194 Cl 1456 F 115 Fe 047 K 137 Mg 395 Mn 012 N(3) 34 Na 16872 S(6) 1176 Si 89 -water 1 kg
SOLUTION_SPECIES This keyword is to define the dissociation constant logK
and diffusion constant (dw) in solution for arsenite and arsenate
Arsenite adsorption equation on GTiO2 surface H3ArseniteO3 is the primary species of As(III) at the groundwater pH 82 (Surf_sO)2ArseniteOH-066 is the adsorptive bidentate binuclear structure of As(III) on GTiO2
log_k 1635 The adsorptive reaction constant for As(III) on GTiO2 in
the current condition which could be changed with different experimental conditions
-cd_music -2 -1 0 066 3 CD-MUSIC model is integrated in the PHREEQC
modeling The numbers represent -2 the change in charge at the plane of Surf_sOH due to loss of two hydrogens -1 the change in charge at 1 plane due to gain of one hydrogen and one oxygen on Arsenite 0 the change in charge at the 2 plane usually caused by the outer sphere adsorption 066 the fraction of the central ion (As) charge that is associated with plane 0 which reflecting the charge distribution 3 the charge on the central ion (As)
Table S54 Parameters of Weber-Morris intraparticle model for As(IIIV) adsorption kinetics on GTiO2 using synthetic water Initial As concentration = 800 μgL adsorbent dose = 02 gL pH = 82 in synthetic groundwater
External film diffusion
Intraparticle diffusion
aRex2 bkp1
cb1aRin
2 bkp2cb 2
As(V) 0984 0497 0022 0976 01331878
As(III) 0970 0583
-0088 0981 0218
1105
aRex is WM external proportion fitting parameter while Rin is WM intraparticle proportion fitting parameterbk The unit of kp is mggh05 cb The unit of b is mgg
Table S6 Comparison of the adsorption capacities of As(III) and As(V) on GTiO2 and the representative granular adsorbents in similar experimental condition from the literature
AdsorbentParticle size (mm) As
qm
(mgg)Dose (gL) Experimental conditions Literature
GTiO2 018~025 As(III) 980 1 0~500 mgL at pH 82 01 M NaCl This studyGTiO2 018~025 As(V) 358 1 0~500 mgL at pH 82 01 M NaCl This study
Granular TiO2 015~06 As(III) 392 10~60 mgL As at pH 70 in simulated groundwater (100 mgL Ca 20 mgL Mg 50 mgL Na 200 mgL Cl-
)(Bang et al 2005)
Granular TiO2 015~06 As(V) 400 10~60 mgL As at pH 70 in simulated groundwater (100 mgL Ca 20 mgL Mg 50 mgL Na 200 mgL Cl-
)(Bang et al 2005)
E33 (FeOOH)0044~0075 As(V) 202 1 0~15 mgL at pH 70 in 001 M NaCl
(Kanematsu et al 2010)
E33 (FeOOH) 05~2 As(V) 180 1 0~50 mgL at pH 70 in 004 M NaClO4 (Jing et al 2012)
GFH 02~06 As(V) 650 10 0~2000 mgL at pH 8 in 01 M NaNO3
(Guan et al 2008)
GFH0009~0125 As(V) 23 025 0~07 μgL at pH 65 in DI water
(Banerjee et al 2008)
GFH0009~0125 As(V) 200 - 0~01 μgL at pH 70 in DI water
(Badruzzaman et al 2004)
GFH 050~065 As(V) 155 - 0~06 μgL at pH 70 in DI water (Saha et al 2005)
GHFO-NN 015~030 As(V) 330 0001 0~225 mgL at pH 8 in DI water(Streat et al 2008)
GHFO-VL 015~030 As(V) 360 0001 0~225 mgL at pH 8 in DI water(Streat et al 2008)
25
374375
Spherical schwertmannite 1~15 As(V) 36 05 0~5 mgL at pH 70 in DI water (Dou et al 2013)Cylindrical schwertmannite 1~25 As(V) 223 05
0~5 mgL at pH 70 in DI water(Dou et al 2013)
Irregular schwertmannite 10~16 As(V) 317 05 0~5 mgL at pH 70 in DI water (Dou et al 2013)Fe impregnated chitosan beads (MICB) 25 As(III) 117 1 0~05 mgL at pH 60 in DI water
(Wang et al 2014)
MICB 25 As(V) 191 1 0~1 mgL at pH 60 in DI water(Wang et al 2014)
MICB 25 As(III) 353 1 0~15 mgL at pH 60 in DI water(Wang et al 2014)
MICB 25 As(V) 357 1 0~16 mgL at pH 60 in DI water(Wang et al 2014)
Iron hydroxide granules (GIH) 3~4 As(V) 23 4
5~100 mgL at pH 70 in 10 mgL SO42-
14 mgL NH4Cl buffer solution (Daus et al 2004)
Activated Al2O3
0074~0149 As(V) 159 - 285~115 mgL at pH 52 in DI water
(Lin and Wu 2001)
Activated Al2O3
0074~0149 As(III) 35 - 079~490 mgL at pH 70 in DI water
(Lin and Wu 2001)
Activated Al2O3 ~20 As(V) 73 at pH 70 in 004 M NaClO4 (Jing et al 2012)
Activated natural siderite 05~10 As(V) 22 10 0 1~20 mgL at pH 7 in DI water(Zhao and Guo 2014)
Polyaluminum Granulate 1~3 As(III) 705 10 0~150 mgL at pH 51-56 in DI water(Mertens et al 2012)
Polyaluminum Granulate 1~3 As(V) 180 10 0~150 mgL at pH 51-56 in DI water (Mertens et al
26
2012)
Acidified laterite 1~12 As(III) 19 1 025~5 mgL at pH 7 in 100 mgL NaHCO3
(Glocheux et al 2013)
Acidified laterite 1~12 As(V) 13 1 025~5 mgL at pH 7 in 100 mgL NaHCO3
(Glocheux et al 2013)
Laterite 1~12 As(III) 07 1025~5 mgL at pH 7 in 100 mgL NaHCO3 (Glocheux et al
2013)
Laterite 1~12 As(V) 04 1025~5 mgL at pH 7 in 100 mgL NaHCO3 (Glocheux et al
2013)
Treated laterite 03-05 As(V) 216 05 02-20 mgL at pH 70 in DI water(Maiti et al 2012)
Treated laterite 03-05 As(III) 94 05 02-20 mgL at pH 70 in DI water(Maiti et al 2012)
Treated laterite03-05
As(V) 241 05 02-20 mgL at pH 70 in DI water(Maiti et al 2010a)
Treated laterite03-05
As(III) 81 05 02-20 mgL at pH 70 in DI water(Maiti et al 2010a)
Acid-activated laterite-103-07
As(III) 0633 50 02-10 mgL at pH 66-70 in DI water(Maiti et al 2010b)
Acid-activated laterite-203-07
As(III) 087650 02-10 mgL at pH 66-70 in DI water (Maiti et al
2010b)
Acid-activated laterite-303-07
As(III) 063450 02-10 mgL at pH 66-70 in DI water (Maiti et al
2010b)
Acid-activated laterite-103-07
As(V) 059850 02-10 mgL at pH 66-70 in DI water (Maiti et al
2010b)
27
Acid-activated laterite-203-07
As(V) 07550 02-10 mgL at pH 66-70 in DI water (Maiti et al
2010b)
Acid-activated laterite-303-07
As(V) 07550 02-10 mgL at pH 66-70 in DI water (Maiti et al
2010b)
Treated laterite-1 03-06 As(V) 019 20 0-20 mgL As at pH 72 in DI water(Maiti et al 2013b)
Treated laterite-1 03-06 As(III) 018 20 0-20 mgL As at pH 72 in DI water(Maiti et al 2013b)
Treated laterite-2 03-06 As(V) 004 20 0-20 mgL As at pH 72 in DI water(Maiti et al 2013b)
Treated laterite-2 03-06 As(III) 003 20 0-20 mgL As at pH 72 in DI water(Maiti et al 2013b)
Treated laterite-3 03-06 As(V) 007 20 0-20 mgL As at pH 72 in DI water(Maiti et al 2013b)
Treated laterite-3 03-06 As(III) 004 20 0-20 mgL As at pH 72 in DI water(Maiti et al 2013b)
28
376377
Charge distribution multi-site surface complexation (CD-MUSIC) modeling
The CD-MUSIC model with the 2-pK TPM adsorption option was used to
describe adsorption behaviors of As cations and anions on GTiO2 The CD-MUSIC
model incorporates the structural information of surfaces adsorbed species and the
double layers by distributing the charge of an adsorbate between the surface and
interfacial water (Hiemstra and Van Riemsdijk 2006) The CD-MUSIC model has
been successfully used in describing As adsorption in batch experiments (Pena et al
2006 Stachowicz et al 2008)
The adsorption constants of counter ions were set to -1 and the proton affinity
constant was set to the PZC of 58 for TiOH-13 (Luo et al 2010) The charge
distribution (CD) value shows the fraction (f) of the charge of the central As ion
attributed to the surface plane and the remaining part (1-f) was attributed to the other
ligands of the complex which were positioned toward the diffuse layer The CD value
for As surface complexes was obtained by fitting the experimental data The
calculation was performed using the chemical equilibrium program MINTEQ to
simulate the adsorption and the aqueous reactions
29
378379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
Fig S32 Adsorption of silicate (a) calcium and magnesium (b) as a function of GTiO2
dose in groundwater 1 The solid lines represent the CD-MUSIC modeling result
30
400
401
402
403
404
405
406
407
408409410
Table S75 Surface parameters and species used in the CD-MUSIC modeling in As(IIIV) removal under different GTiO2 dose in 01 M NaCl and groundwater 1 in Fig 2 and Fig S32
= exp(-FΨ1RT) P2 = exp(-FΨ2RT) F the Faraday constant (C mol-1) R the gas constant (J mol-1 K-1) T the absolute temperature (K)
Ψ0 Ψ1 Ψ2 the electrostatic potential (V) of 0- 1- and 2-plane respectively alogK for 01 M NaCl at 6 hours blogK for 01 M NaCl at 6 days clogK for groundwater 1 at 6 days
31
411412
413414415
32
416
Table S86 The charge distribution (f) of central As atom to TiO2 surface in simulating the effect of cations and anions on As adsorption in 01 M NaCl at pH 82 in Fig 4 BK Si HCO3 All
As(V) 022 017 012 016As(III) 040 020 058 056
Fig S43 Molar percentage () of As Ca Mg and Si on pristine and spent GTiO2
surfaces using EDX analysis The spent GTiO2 samples after field column experiments using groundwater 1 were identified with EBCT in min under x-axis The value of molar percentage of each element was averaged from randomly-chosen positions on the adsorbent surface
33
417
418
419420
421422
423
424
425
426
427
428
429
430
431
432
433434435436437438
439
440
441
As speciation analysis on spent GTiO2 using XANES
The spent GTiO2 samples were ground using a mortar and pestle and then the
ground powder was spread on Scotch tape The As k-edge XANES spectra were
collected at beamline 01C1 at the National Synchrotron Radiation Research Center
(NSRRC) Taiwan Spectra were acquired from -150 to 300 eV relative to the As K-
edge of 11867 eV at cryogenic temperature (77 K) using a cryostat to prevent the
oxidation of As(III) by X-rays The fluorescence signals were collected using a Lytle
detector Two to four scans were collected for each sample and averaged to improve
the signalnoise ratio The XANES analysis was performed with the Athena program
in the IFEFFIT computer package for linear combination fit (LCF) (Cui et al 2013
Ravel and Newville 2005)
34
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
PHREEQC modeling for As breakthrough curves in field column experiments
PHREEQC a geochemical model integrates macroscopic mass transfer
processes with a microscopic surface complexation model (Parkhurst and Appelo
2013) It can be applied in calculating solution complex speciation batch-reaction
and one-dimensional reactive-transport and inverse modeling In our study the one-
dimensional column was defined by four cells with the same length The cell length
was calculated to be one-fourth of the actual column length Time step (s) was
calculated according to equation Time step = Lcell(Q60A) where Lcell is the cell
length (cm) Q is flow velocity (mLmin) A is the effective column cross section area
(cm2) which is the column cross-sectional area multiplied by porosity (060) Total
shift number was calculated by dividing actual column operation time by the time
step The transport block was modeled by shifting the solute content from one cell to
the next one In each cell the aqueous solute was mixed and adsorbed on GTiO2
according to the equations In each cell the aqueous solute was mixed and assumed to
be in equilibration with GTiO2 The sequence of shifting mixing and equilibrium
adsorption was repeated for each cell until the total number of shifts was completed
The diffusion coefficient Dw in PHREEQC accounting for retardation was
calculated as Dw=x2
(36t) where x stands for the diffusion length (estimated as the
radius of the particle size) and t represents equilibrium time adopted from the batch
kinetic data (Mertens et al 2012)
For CD-MUSIC modeling in the PHREEQC take As(III) as an example to
explain the adsorption equation The As(III) adsorption is considered as a ligand
35
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
exchange reaction with the hydroxide group on GTiO2 (Surf_sOH-033) forming a
H3ArseniteO3 is the master species in groundwater at pH 82
(Surf_sO)2ArseniteOH-066 is the common adsorbed bidentate binuclear complex
evidenced by our previous reports(Pena et al 2006 Yan et al 2015) LogK is the
adsorption equilibrium constants Generally every adsorption equation under certain
experimental condition has a unique value of logK In the adsorption equation ldquo-2rdquo
represents the lost two hydrogens by Surf_sOH-033 after it adsorbs H3ArseniteO3 ldquo-
1rdquo represents the change in charge on Arsenite at 1 plane due to gaining one hydrogen
(+1) and one oxygen (-2) ldquo0rdquo represents no change in charge at the 2 plane ldquo066rdquo is
the fraction of the central ion (As) on GTiO2 surface that is associated with plane 0
ldquo3rdquo is the charge on the central ion As(III) Following this equation and the relevant
parameters As(III) adsorbed on GTiO2
The diffusion coefficient Dw in PHREEQC accounting for retardation was
calculated as Dw=x2(36t) where x stands for the diffusion length (estimated as the
radius of the particle size) and t represents equilibrium time adopted from the batch
kinetic data (Mertens et al 2012)
To well simulate the As breakthrough curve in columns four As(V) adsorption
reactions (Table 1) were employed Adsorption site density of 60 mmolg was
36
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
adopted from our previous study (Pena et al 2006) and the total adsorption sites were
calculated to be 1844 sitesnm2 The final optimized ratio of strong to weak sites was
51 The surface complexation constants were reasonably adjusted according to the
batch modeling results as the column reaction may not reach equilibrium in local
micro-interfacial areas due to much less contact time between As and GTiO2 than that
in batch experiments (Appelo and Postma 1999) In the modeling a stepwise
procedure was adopted to achieve a viable result An estimation of two thirds of the
surface site density being accessible for EBCT=011 min with large flow rate of 265
mLmin was optimized which could probably result from unavailable adsorption sites
due to fast transport through the column
The adsorbed As on GTiO2 in the column was calculated by mass balance
between the influent and effluent
where Asadsorbed is the adsorbed As on GTiO2 (mgg) n is the number of collected
samples Cin and Cout are influent and effluent As concentrations (mgL) respectively
Vi is volume (L) of groundwater passed through the column between sample i-1 and i
and m is the mass of GTiO2 (g)
Even though the oxidation of adsorbed As(III) occurred during filtration as
analyzed from XANES and mass balance analysis (Fig 7) no As(III) oxidation
reactions were considered in PHREEQC modeling which would not impact the
breakthrough of As(IIIV)
37
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
38
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
Fig S54 Effect of EBCT on Si Ca and Mg breakthrough curves using groundwater 1 The sample notation in panel c indicates field column experiments with EBCT in minutes
References
Appelo CAJ Postma D 1999 A consistent model for surface complexation on birnessite (MnO2) and its application to a column experiment Geochim Cosmochim Ac 63 (19-20) 3039-3048Badruzzaman M Westerhoff P Knappe DRU 2004 Intraparticle diffusion and adsorption of arsenate onto granular ferric hydroxide (GFH) Water Res 38 (18) 4002-4012Banerjee K Amy GL Prevost M Nour S Jekel M Gallagher PM Blumenschein CD 2008 Kinetic and thermodynamic aspects of adsorption of arsenic onto granular ferric hydroxide (GFH) Water Res 42 (13) 3371-3378Bang S Patel M Lippincott L Meng XG 2005 Removal of arsenic from groundwater by granular titanium dioxide adsorbent Chemosphere 60 (3) 389-397Bang S Pena ME Patel M Lippincott L Meng X Kim KW 2011 Removal of arsenate from water by adsorbents a comparative case study Environ Geochem Hlth 33 133-141Cui JL Shi JB Jiang GB Jing CY 2013 Arsenic levels and speciation from ingestion exposures to biomarkers in Shanxi China Implications for human health Environ Sci Technol 47 (10) 5419-5424Daus B Wennrich R Weiss H 2004 Sorption materials for arsenic removal from water A comparative study Water Res 38 (12) 2948-2954Dou XM Mohan D Pittman CU 2013 Arsenate adsorption on three types of granular schwertmannite Water Res 47 (9) 2938-2948Dou XM Zhang Y Yang M Pei YS Huang X Takayama T Kato S 2006 Occurrence of arsenic in groundwater in the suburbs of Beijing and its removal using an iron-cerium bimetal oxide adsorbent Water Qual Res J Can 41 (2) 140-146Gibbons MK Gagnon GA 2010 Adsorption of arsenic from a Nova Scotia groundwater onto water treatment residual solids Water Res 44 (19) 5740-5749Glocheux Y Mendez Pasarin M Albadarin AB Allen SJ Walker GM 2013 Removal of arsenic from groundwater by adsorption onto an acidified laterite by-product Chem Eng J 228 565-574Guan XH Wang JM Chusuei CC 2008 Removal of arsenic from water using granular ferric hydroxide Macroscopic and microscopic studies J Hazard Mater 156 (1-3) 178-185Gupta K Maity A Ghosh UC 2010 Manganese associated nanoparticles agglomerate of iron(III) oxide Synthesis characterization and arsenic(III) sorption behavior with mechanism J Hazard Mater 184 (1-3) 832-842Hao JM Han MJ Wang C Meng XG 2009 Enhanced removal of arsenite from water by a mesoporous hybrid material - Thiol-functionalized silica coated activated alumina Micropor Mesopor
Mat 124 (1-3) 1-7Hiemstra T Van Riemsdijk WH 2006 On the relationship between charge distribution surface hydration and the structure of the interface of metal hydroxides J Colloid Interf Sci 301 (1) 1-18Hristovski K Baumgardner A Westerhoff P 2007 Selecting metal oxide nanomaterials for arsenic removal in fixed bed columns From nanopowders to aggregated nanoparticle media J Hazard Mater 147 (1-2) 265-274Jang M Chen WF Cannon FS 2008 Preloading hydrous ferric oxide into granular activated carbon for arsenic removal Environ Sci Technol 42 (9) 3369-3374Jing CY Cui JL Huang YY Li AG 2012 Fabrication characterization and application of a composite adsorbent for simultaneous removal of arsenic and fluoride ACS Appl Mater Interfaces 4 (2) 714-720Kanematsu M Young TM Fukushi K Green PG Darby JL 2010 Extended triple layer modeling of arsenate and phosphate adsorption on a goethite-based granular porous adsorbent Environ Sci Technol 44 (9) 3388-3394Kong S Wang Y Zhan H Yuan S Liu M Zhou C 2013 Arsenite and Arsenate Removal from Contaminated Groundwater by Nanoscale Iron-Manganese Binary Oxides Column Studies Environmental Engineering Science 30 (11) 689-696Li Y Liu JR Jia SY Guo JW Zhuo J Na P 2012 TiO2 pillared montmorillonite as a photoactive adsorbent of arsenic under UV irradiation Chem Eng J 191 66-74Lin TF Wu JK 2001 Adsorption of arsenite and arsenate within activated alumina grains Equilibrium and kinetics Water Res 35 (8) 2049-2057Luo T Cui JL Hu S Huang YY Jing CY 2010 Arsenic removal and recovery from copper smelting wastewater using TiO2 Environ Sci Technol 44 (23) 9094-9098Maiti A Basu JK De S 2010a Development of a Treated Laterite for Arsenic Adsorption Effects of Treatment Parameters Industrial amp Engineering Chemistry Research 49 (10) 4873-4886Maiti A Basu JK De S 2010b Removal of Arsenic from Synthetic and Natural Groundwater Using Acid-Activated Laterite Environmental Progress amp Sustainable Energy 29 (4) 457-470Maiti A Basu JK De S 2012 Experimental and kinetic modeling of As(V) and As(III) adsorption on treated laterite using synthetic and contaminated groundwater Effects of phosphate silicate and carbonate ions Chem Eng J 191 1-12Maiti A Thakur BK Basu JK De S 2013a Comparison of treated laterite as arsenic adsorbent from different locations and performance of best filter under field conditions J Hazard Mater 262 1176-1186Maiti A Thakur BK Basu JK De S 2013b Comparison of treated laterite as arsenic adsorbent from different locations and performance of best filter under field conditions J Hazard Mater 262 (0) 1176-1186Maji SK Pal A Pal T 2008 Arsenic removal from real-life groundwater by adsorption on laterite soil J Hazard Mater 151 (2-3) 811-820Maji SK Kao YH Wang CJ Lu GS Wu JJ Liu CW 2012 Fixed bed adsorption of As(III) on iron-oxide-coated natural rock (IOCNR) and application to real arsenic-bearing groundwater Chem Eng J 203 285-293Mertens J Rose J Kagi R Chaurand P Plotze M Wehrli B Furrer G 2012 Adsorption of arsenic on polyaluminum granulate Environ Sci Technol 46 (13) 7310-7317Nguyen TV Vigneswaran S Ngo HH Pokhre D Viraraghavan T 2006 Iron-coated sponge as
effective media to remove arsenic from drinking water Water Qual Res J Can 41 (2) 164-170Parkhurst DL Appelo CAJ 2013 Description of input and examples for PHREEQC version 3-A computer program for speciation batch-reaction one-dimensional transport and inverse geochemical calculations US Geological SurveyPena M Meng XG Korfiatis GP Jing CY 2006 Adsorption mechanism of arsenic on nanocrystalline titanium dioxide Environ Sci Technol 40 (4) 1257-1262Ravel B Newville M 2005 ATHENA ARTEMIS HEPHAESTUS Data analysis for X-ray absorption spectroscopy using IFEFFIT J Synchrotron Radiat 12 537-541Saha B Bains R Greenwood F 2005 Physicochemical characterization of granular ferric hydroxide (GFH) for arsenic(V) sorption from water Separation Science and Technology 40 (14) 2909-2932Shan H Ma T Wang Y Zhao J Han H Deng Y He X Dong Y 2013 A cost-effective system for in-situ geological arsenic adsorption from groundwater J Contam Hydrol 154 1-9Stachowicz M Hiemstra T van Riemsdijk WH 2008 Multi-competitive interaction of As(III) and As(V) oxyanions with Ca2+ Mg2+ PO4
3- and CO32- ions on goethite J Colloid Interf Sci 320 (2) 400-
414Streat M Hellgardt K Newton NLR 2008 Hydrous ferric oxide as an adsorbent in water treatment - Part 3 Batch and mini-column adsorption of arsenic phosphorus fluorine and cadmium ions Process Safety and Environmental Protection 86 (B1) 21-30Thirunavukkarasu OS Viraraghavan T Subramanian KS 2003 Arsenic removal from drinking water using iron oxide-coated sand Water Air Soil Poll 142 (1-4) 95-111USEPA 2008 Assessing arsenic removal by metal (hydr)oxide adsorptive media using rapid small scale column tests Govenrnment Printing Office Washington DCWang J Xu W Chen L Huang X Liu J 2014 Preparation and evaluation of magnetic nanoparticles impregnated chitosan beads for arsenic removal from water Chem Eng J 251 25-34Westerhoff P Highfield D Badruzzaman M Yoon Y 2005 Rapid small-scale column tests for arsenate removal in iron oxide packed bed columns J Environ Eng-Asce 131 (2) 262-271Westerhoff P De Haan M Martindale A Badruzzaman M 2006 Arsenic adsorptive media technology selection strategies Water Qual Res J Can 41 (2) 171-184Yan L Huang Y Cui J Jing C 2015 Simultaneous As(III) and Cd removal from copper smelting wastewater using granular TiO2 columns Water Res 68 (0) 572-579Zhao K Guo HM 2014 Behavior and mechanism of arsenate adsorption on activated natural siderite Evidences from FTIR and XANES analysis Environ Sci Pollut Res 21 (3) 1944-1953Zhao K Guo H Zhou X 2014 Adsorption and heterogeneous oxidation of arsenite on modified granular natural siderite Characterization and behaviors Appl Geochem 48 184-192
Iron-Mn binary 15 40 145 176 321 22 253 347 754 (Maiti et al 2010a)
13
oxides
aUnit for ion concentration is mgL except as notedbestimated from bed volume breakthrough curves and influent As concentration if not explicitly expressed in the reference cThe species is As(V) if only one concentration is given
d
The groundwater As concentration was 385-440 μgL and additional ~600 μgL (As(III)As(V)=11) arsenic was added
14
222324252627
Fig S1 Boxplot of groundwater As levels in columns and filters in the literature in Table S1 Individual samples are shown as diamonds The range of each box represents the 25th
and 75th
percentile whereas the whiskers represent the 10th
and 90th
percentile
Synthesis of granular TiO2
Granular TiO2 (GTiO2) was prepared by hydrolysis of titanyl sulfate (TiOSO4)
Generally 300 g TiOSO4 was mixed with 1800 mL DI water in a 10 L jar reactor in an
ice bath at 4 oC Then 10 M NaOH was slowly added to adjust the pH to 6 The
precursor of TiO2 was obtained by washing the suspension with DI water several
times till the conductivity of the supernatant was less than 100 μScm Then 800 g
TiO2 precursor was mixed with 40 mL polyvinyl alcohol solution at 80 oC in a water
bath The product was crushed into 60-80 mesh and dried in an oven at 60 oC for 12 h
15
282930313233343536373839404142434445464748
49
50
51
52
53
54
55
56
57585960
Fig S2 Characterization of GTiO2 SEM (a) and XRD pattern with crystal face for each peak (b)
Fig S1 SEM images for GTiO2 in this study
Table S2 Average concentrations of As coexisting ions (mgL) and water chemistry for groundwater 1 and 2 from two wells
Table S3 Water parameters in the synthetic water used in the studyParameters Ca2+ Mg2+ HCO3
- Na+ Cl- pHConc (mgL) 401 1043 388 2460 3928 82
Table S4 PHREEQC input for a representative column with EBCT=054 min SOLUTION 0
This keyword is to define the influent groundwater chemistry parameters which are included in the adsorption reactions like ldquoArseniterdquo and ldquoArsenaterdquo and the experimental conditions including ldquopHrdquo The information defined in SOLUTION is available for subsequent transport and adsorptive reaction calculations
temp 23 pH 82 pe 4 redox pe units mgL density 1 Al 006 Arsenite 0374 Arsenate 0291 CO4
2-
4401 Ca 194 Cl 1456 F 115 Fe 047 K 137 Mg 395 Mn 012 NO3
-
34 Na 16872
17
79
80
8182
83
84858687888990919293949596979899
100101102103104105106107108109110111112
SO42-
1176 Si 89 -water 1 kg
SOLUTION 1-4 The small column was divided into four cells SOLUTION 1-4
are the groundwater chemistry parameters for the four cells temp 23 pH 83 pe 4 redox pe units ppm density 1 Al 006 C(4) 4401 Ca 194 Cl 1456 F 115 Fe 047 K 137 Mg 395 Mn 012 N(3) 34 Na 16872 S(6) 1176 Si 89 -water 1 kg
SOLUTION_SPECIES This keyword is to define the dissociation constant logK
and diffusion constant (dw) in solution for arsenite and arsenate
Arsenite adsorption equation on GTiO2 surface H3ArseniteO3 is the primary species of As(III) at the groundwater pH 82 (Surf_sO)2ArseniteOH-066 is the adsorptive bidentate binuclear structure of As(III) on GTiO2
log_k 1635 The adsorptive reaction constant for As(III) on GTiO2 in
the current condition which could be changed with different experimental conditions
-cd_music -2 -1 0 066 3 CD-MUSIC model is integrated in the PHREEQC
modeling The numbers represent -2 the change in charge at the plane of Surf_sOH due to loss of two hydrogens -1 the change in charge at 1 plane due to gain of one hydrogen and one oxygen on Arsenite 0 the change in charge at the 2 plane usually caused by the outer sphere adsorption 066 the fraction of the central ion (As) charge that is associated with plane 0 which reflecting the charge distribution 3 the charge on the central ion (As)
Table S54 Parameters of Weber-Morris intraparticle model for As(IIIV) adsorption kinetics on GTiO2 using synthetic water Initial As concentration = 800 μgL adsorbent dose = 02 gL pH = 82 in synthetic groundwater
External film diffusion
Intraparticle diffusion
aRex2 bkp1
cb1aRin
2 bkp2cb 2
As(V) 0984 0497 0022 0976 01331878
As(III) 0970 0583
-0088 0981 0218
1105
aRex is WM external proportion fitting parameter while Rin is WM intraparticle proportion fitting parameterbk The unit of kp is mggh05 cb The unit of b is mgg
Table S6 Comparison of the adsorption capacities of As(III) and As(V) on GTiO2 and the representative granular adsorbents in similar experimental condition from the literature
AdsorbentParticle size (mm) As
qm
(mgg)Dose (gL) Experimental conditions Literature
GTiO2 018~025 As(III) 980 1 0~500 mgL at pH 82 01 M NaCl This studyGTiO2 018~025 As(V) 358 1 0~500 mgL at pH 82 01 M NaCl This study
Granular TiO2 015~06 As(III) 392 10~60 mgL As at pH 70 in simulated groundwater (100 mgL Ca 20 mgL Mg 50 mgL Na 200 mgL Cl-
)(Bang et al 2005)
Granular TiO2 015~06 As(V) 400 10~60 mgL As at pH 70 in simulated groundwater (100 mgL Ca 20 mgL Mg 50 mgL Na 200 mgL Cl-
)(Bang et al 2005)
E33 (FeOOH)0044~0075 As(V) 202 1 0~15 mgL at pH 70 in 001 M NaCl
(Kanematsu et al 2010)
E33 (FeOOH) 05~2 As(V) 180 1 0~50 mgL at pH 70 in 004 M NaClO4 (Jing et al 2012)
GFH 02~06 As(V) 650 10 0~2000 mgL at pH 8 in 01 M NaNO3
(Guan et al 2008)
GFH0009~0125 As(V) 23 025 0~07 μgL at pH 65 in DI water
(Banerjee et al 2008)
GFH0009~0125 As(V) 200 - 0~01 μgL at pH 70 in DI water
(Badruzzaman et al 2004)
GFH 050~065 As(V) 155 - 0~06 μgL at pH 70 in DI water (Saha et al 2005)
GHFO-NN 015~030 As(V) 330 0001 0~225 mgL at pH 8 in DI water(Streat et al 2008)
GHFO-VL 015~030 As(V) 360 0001 0~225 mgL at pH 8 in DI water(Streat et al 2008)
25
374375
Spherical schwertmannite 1~15 As(V) 36 05 0~5 mgL at pH 70 in DI water (Dou et al 2013)Cylindrical schwertmannite 1~25 As(V) 223 05
0~5 mgL at pH 70 in DI water(Dou et al 2013)
Irregular schwertmannite 10~16 As(V) 317 05 0~5 mgL at pH 70 in DI water (Dou et al 2013)Fe impregnated chitosan beads (MICB) 25 As(III) 117 1 0~05 mgL at pH 60 in DI water
(Wang et al 2014)
MICB 25 As(V) 191 1 0~1 mgL at pH 60 in DI water(Wang et al 2014)
MICB 25 As(III) 353 1 0~15 mgL at pH 60 in DI water(Wang et al 2014)
MICB 25 As(V) 357 1 0~16 mgL at pH 60 in DI water(Wang et al 2014)
Iron hydroxide granules (GIH) 3~4 As(V) 23 4
5~100 mgL at pH 70 in 10 mgL SO42-
14 mgL NH4Cl buffer solution (Daus et al 2004)
Activated Al2O3
0074~0149 As(V) 159 - 285~115 mgL at pH 52 in DI water
(Lin and Wu 2001)
Activated Al2O3
0074~0149 As(III) 35 - 079~490 mgL at pH 70 in DI water
(Lin and Wu 2001)
Activated Al2O3 ~20 As(V) 73 at pH 70 in 004 M NaClO4 (Jing et al 2012)
Activated natural siderite 05~10 As(V) 22 10 0 1~20 mgL at pH 7 in DI water(Zhao and Guo 2014)
Polyaluminum Granulate 1~3 As(III) 705 10 0~150 mgL at pH 51-56 in DI water(Mertens et al 2012)
Polyaluminum Granulate 1~3 As(V) 180 10 0~150 mgL at pH 51-56 in DI water (Mertens et al
26
2012)
Acidified laterite 1~12 As(III) 19 1 025~5 mgL at pH 7 in 100 mgL NaHCO3
(Glocheux et al 2013)
Acidified laterite 1~12 As(V) 13 1 025~5 mgL at pH 7 in 100 mgL NaHCO3
(Glocheux et al 2013)
Laterite 1~12 As(III) 07 1025~5 mgL at pH 7 in 100 mgL NaHCO3 (Glocheux et al
2013)
Laterite 1~12 As(V) 04 1025~5 mgL at pH 7 in 100 mgL NaHCO3 (Glocheux et al
2013)
Treated laterite 03-05 As(V) 216 05 02-20 mgL at pH 70 in DI water(Maiti et al 2012)
Treated laterite 03-05 As(III) 94 05 02-20 mgL at pH 70 in DI water(Maiti et al 2012)
Treated laterite03-05
As(V) 241 05 02-20 mgL at pH 70 in DI water(Maiti et al 2010a)
Treated laterite03-05
As(III) 81 05 02-20 mgL at pH 70 in DI water(Maiti et al 2010a)
Acid-activated laterite-103-07
As(III) 0633 50 02-10 mgL at pH 66-70 in DI water(Maiti et al 2010b)
Acid-activated laterite-203-07
As(III) 087650 02-10 mgL at pH 66-70 in DI water (Maiti et al
2010b)
Acid-activated laterite-303-07
As(III) 063450 02-10 mgL at pH 66-70 in DI water (Maiti et al
2010b)
Acid-activated laterite-103-07
As(V) 059850 02-10 mgL at pH 66-70 in DI water (Maiti et al
2010b)
27
Acid-activated laterite-203-07
As(V) 07550 02-10 mgL at pH 66-70 in DI water (Maiti et al
2010b)
Acid-activated laterite-303-07
As(V) 07550 02-10 mgL at pH 66-70 in DI water (Maiti et al
2010b)
Treated laterite-1 03-06 As(V) 019 20 0-20 mgL As at pH 72 in DI water(Maiti et al 2013b)
Treated laterite-1 03-06 As(III) 018 20 0-20 mgL As at pH 72 in DI water(Maiti et al 2013b)
Treated laterite-2 03-06 As(V) 004 20 0-20 mgL As at pH 72 in DI water(Maiti et al 2013b)
Treated laterite-2 03-06 As(III) 003 20 0-20 mgL As at pH 72 in DI water(Maiti et al 2013b)
Treated laterite-3 03-06 As(V) 007 20 0-20 mgL As at pH 72 in DI water(Maiti et al 2013b)
Treated laterite-3 03-06 As(III) 004 20 0-20 mgL As at pH 72 in DI water(Maiti et al 2013b)
28
376377
Charge distribution multi-site surface complexation (CD-MUSIC) modeling
The CD-MUSIC model with the 2-pK TPM adsorption option was used to
describe adsorption behaviors of As cations and anions on GTiO2 The CD-MUSIC
model incorporates the structural information of surfaces adsorbed species and the
double layers by distributing the charge of an adsorbate between the surface and
interfacial water (Hiemstra and Van Riemsdijk 2006) The CD-MUSIC model has
been successfully used in describing As adsorption in batch experiments (Pena et al
2006 Stachowicz et al 2008)
The adsorption constants of counter ions were set to -1 and the proton affinity
constant was set to the PZC of 58 for TiOH-13 (Luo et al 2010) The charge
distribution (CD) value shows the fraction (f) of the charge of the central As ion
attributed to the surface plane and the remaining part (1-f) was attributed to the other
ligands of the complex which were positioned toward the diffuse layer The CD value
for As surface complexes was obtained by fitting the experimental data The
calculation was performed using the chemical equilibrium program MINTEQ to
simulate the adsorption and the aqueous reactions
29
378379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
Fig S32 Adsorption of silicate (a) calcium and magnesium (b) as a function of GTiO2
dose in groundwater 1 The solid lines represent the CD-MUSIC modeling result
30
400
401
402
403
404
405
406
407
408409410
Table S75 Surface parameters and species used in the CD-MUSIC modeling in As(IIIV) removal under different GTiO2 dose in 01 M NaCl and groundwater 1 in Fig 2 and Fig S32
= exp(-FΨ1RT) P2 = exp(-FΨ2RT) F the Faraday constant (C mol-1) R the gas constant (J mol-1 K-1) T the absolute temperature (K)
Ψ0 Ψ1 Ψ2 the electrostatic potential (V) of 0- 1- and 2-plane respectively alogK for 01 M NaCl at 6 hours blogK for 01 M NaCl at 6 days clogK for groundwater 1 at 6 days
31
411412
413414415
32
416
Table S86 The charge distribution (f) of central As atom to TiO2 surface in simulating the effect of cations and anions on As adsorption in 01 M NaCl at pH 82 in Fig 4 BK Si HCO3 All
As(V) 022 017 012 016As(III) 040 020 058 056
Fig S43 Molar percentage () of As Ca Mg and Si on pristine and spent GTiO2
surfaces using EDX analysis The spent GTiO2 samples after field column experiments using groundwater 1 were identified with EBCT in min under x-axis The value of molar percentage of each element was averaged from randomly-chosen positions on the adsorbent surface
33
417
418
419420
421422
423
424
425
426
427
428
429
430
431
432
433434435436437438
439
440
441
As speciation analysis on spent GTiO2 using XANES
The spent GTiO2 samples were ground using a mortar and pestle and then the
ground powder was spread on Scotch tape The As k-edge XANES spectra were
collected at beamline 01C1 at the National Synchrotron Radiation Research Center
(NSRRC) Taiwan Spectra were acquired from -150 to 300 eV relative to the As K-
edge of 11867 eV at cryogenic temperature (77 K) using a cryostat to prevent the
oxidation of As(III) by X-rays The fluorescence signals were collected using a Lytle
detector Two to four scans were collected for each sample and averaged to improve
the signalnoise ratio The XANES analysis was performed with the Athena program
in the IFEFFIT computer package for linear combination fit (LCF) (Cui et al 2013
Ravel and Newville 2005)
34
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
PHREEQC modeling for As breakthrough curves in field column experiments
PHREEQC a geochemical model integrates macroscopic mass transfer
processes with a microscopic surface complexation model (Parkhurst and Appelo
2013) It can be applied in calculating solution complex speciation batch-reaction
and one-dimensional reactive-transport and inverse modeling In our study the one-
dimensional column was defined by four cells with the same length The cell length
was calculated to be one-fourth of the actual column length Time step (s) was
calculated according to equation Time step = Lcell(Q60A) where Lcell is the cell
length (cm) Q is flow velocity (mLmin) A is the effective column cross section area
(cm2) which is the column cross-sectional area multiplied by porosity (060) Total
shift number was calculated by dividing actual column operation time by the time
step The transport block was modeled by shifting the solute content from one cell to
the next one In each cell the aqueous solute was mixed and adsorbed on GTiO2
according to the equations In each cell the aqueous solute was mixed and assumed to
be in equilibration with GTiO2 The sequence of shifting mixing and equilibrium
adsorption was repeated for each cell until the total number of shifts was completed
The diffusion coefficient Dw in PHREEQC accounting for retardation was
calculated as Dw=x2
(36t) where x stands for the diffusion length (estimated as the
radius of the particle size) and t represents equilibrium time adopted from the batch
kinetic data (Mertens et al 2012)
For CD-MUSIC modeling in the PHREEQC take As(III) as an example to
explain the adsorption equation The As(III) adsorption is considered as a ligand
35
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
exchange reaction with the hydroxide group on GTiO2 (Surf_sOH-033) forming a
H3ArseniteO3 is the master species in groundwater at pH 82
(Surf_sO)2ArseniteOH-066 is the common adsorbed bidentate binuclear complex
evidenced by our previous reports(Pena et al 2006 Yan et al 2015) LogK is the
adsorption equilibrium constants Generally every adsorption equation under certain
experimental condition has a unique value of logK In the adsorption equation ldquo-2rdquo
represents the lost two hydrogens by Surf_sOH-033 after it adsorbs H3ArseniteO3 ldquo-
1rdquo represents the change in charge on Arsenite at 1 plane due to gaining one hydrogen
(+1) and one oxygen (-2) ldquo0rdquo represents no change in charge at the 2 plane ldquo066rdquo is
the fraction of the central ion (As) on GTiO2 surface that is associated with plane 0
ldquo3rdquo is the charge on the central ion As(III) Following this equation and the relevant
parameters As(III) adsorbed on GTiO2
The diffusion coefficient Dw in PHREEQC accounting for retardation was
calculated as Dw=x2(36t) where x stands for the diffusion length (estimated as the
radius of the particle size) and t represents equilibrium time adopted from the batch
kinetic data (Mertens et al 2012)
To well simulate the As breakthrough curve in columns four As(V) adsorption
reactions (Table 1) were employed Adsorption site density of 60 mmolg was
36
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
adopted from our previous study (Pena et al 2006) and the total adsorption sites were
calculated to be 1844 sitesnm2 The final optimized ratio of strong to weak sites was
51 The surface complexation constants were reasonably adjusted according to the
batch modeling results as the column reaction may not reach equilibrium in local
micro-interfacial areas due to much less contact time between As and GTiO2 than that
in batch experiments (Appelo and Postma 1999) In the modeling a stepwise
procedure was adopted to achieve a viable result An estimation of two thirds of the
surface site density being accessible for EBCT=011 min with large flow rate of 265
mLmin was optimized which could probably result from unavailable adsorption sites
due to fast transport through the column
The adsorbed As on GTiO2 in the column was calculated by mass balance
between the influent and effluent
where Asadsorbed is the adsorbed As on GTiO2 (mgg) n is the number of collected
samples Cin and Cout are influent and effluent As concentrations (mgL) respectively
Vi is volume (L) of groundwater passed through the column between sample i-1 and i
and m is the mass of GTiO2 (g)
Even though the oxidation of adsorbed As(III) occurred during filtration as
analyzed from XANES and mass balance analysis (Fig 7) no As(III) oxidation
reactions were considered in PHREEQC modeling which would not impact the
breakthrough of As(IIIV)
37
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
38
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
Fig S54 Effect of EBCT on Si Ca and Mg breakthrough curves using groundwater 1 The sample notation in panel c indicates field column experiments with EBCT in minutes
References
Appelo CAJ Postma D 1999 A consistent model for surface complexation on birnessite (MnO2) and its application to a column experiment Geochim Cosmochim Ac 63 (19-20) 3039-3048Badruzzaman M Westerhoff P Knappe DRU 2004 Intraparticle diffusion and adsorption of arsenate onto granular ferric hydroxide (GFH) Water Res 38 (18) 4002-4012Banerjee K Amy GL Prevost M Nour S Jekel M Gallagher PM Blumenschein CD 2008 Kinetic and thermodynamic aspects of adsorption of arsenic onto granular ferric hydroxide (GFH) Water Res 42 (13) 3371-3378Bang S Patel M Lippincott L Meng XG 2005 Removal of arsenic from groundwater by granular titanium dioxide adsorbent Chemosphere 60 (3) 389-397Bang S Pena ME Patel M Lippincott L Meng X Kim KW 2011 Removal of arsenate from water by adsorbents a comparative case study Environ Geochem Hlth 33 133-141Cui JL Shi JB Jiang GB Jing CY 2013 Arsenic levels and speciation from ingestion exposures to biomarkers in Shanxi China Implications for human health Environ Sci Technol 47 (10) 5419-5424Daus B Wennrich R Weiss H 2004 Sorption materials for arsenic removal from water A comparative study Water Res 38 (12) 2948-2954Dou XM Mohan D Pittman CU 2013 Arsenate adsorption on three types of granular schwertmannite Water Res 47 (9) 2938-2948Dou XM Zhang Y Yang M Pei YS Huang X Takayama T Kato S 2006 Occurrence of arsenic in groundwater in the suburbs of Beijing and its removal using an iron-cerium bimetal oxide adsorbent Water Qual Res J Can 41 (2) 140-146Gibbons MK Gagnon GA 2010 Adsorption of arsenic from a Nova Scotia groundwater onto water treatment residual solids Water Res 44 (19) 5740-5749Glocheux Y Mendez Pasarin M Albadarin AB Allen SJ Walker GM 2013 Removal of arsenic from groundwater by adsorption onto an acidified laterite by-product Chem Eng J 228 565-574Guan XH Wang JM Chusuei CC 2008 Removal of arsenic from water using granular ferric hydroxide Macroscopic and microscopic studies J Hazard Mater 156 (1-3) 178-185Gupta K Maity A Ghosh UC 2010 Manganese associated nanoparticles agglomerate of iron(III) oxide Synthesis characterization and arsenic(III) sorption behavior with mechanism J Hazard Mater 184 (1-3) 832-842Hao JM Han MJ Wang C Meng XG 2009 Enhanced removal of arsenite from water by a mesoporous hybrid material - Thiol-functionalized silica coated activated alumina Micropor Mesopor
Mat 124 (1-3) 1-7Hiemstra T Van Riemsdijk WH 2006 On the relationship between charge distribution surface hydration and the structure of the interface of metal hydroxides J Colloid Interf Sci 301 (1) 1-18Hristovski K Baumgardner A Westerhoff P 2007 Selecting metal oxide nanomaterials for arsenic removal in fixed bed columns From nanopowders to aggregated nanoparticle media J Hazard Mater 147 (1-2) 265-274Jang M Chen WF Cannon FS 2008 Preloading hydrous ferric oxide into granular activated carbon for arsenic removal Environ Sci Technol 42 (9) 3369-3374Jing CY Cui JL Huang YY Li AG 2012 Fabrication characterization and application of a composite adsorbent for simultaneous removal of arsenic and fluoride ACS Appl Mater Interfaces 4 (2) 714-720Kanematsu M Young TM Fukushi K Green PG Darby JL 2010 Extended triple layer modeling of arsenate and phosphate adsorption on a goethite-based granular porous adsorbent Environ Sci Technol 44 (9) 3388-3394Kong S Wang Y Zhan H Yuan S Liu M Zhou C 2013 Arsenite and Arsenate Removal from Contaminated Groundwater by Nanoscale Iron-Manganese Binary Oxides Column Studies Environmental Engineering Science 30 (11) 689-696Li Y Liu JR Jia SY Guo JW Zhuo J Na P 2012 TiO2 pillared montmorillonite as a photoactive adsorbent of arsenic under UV irradiation Chem Eng J 191 66-74Lin TF Wu JK 2001 Adsorption of arsenite and arsenate within activated alumina grains Equilibrium and kinetics Water Res 35 (8) 2049-2057Luo T Cui JL Hu S Huang YY Jing CY 2010 Arsenic removal and recovery from copper smelting wastewater using TiO2 Environ Sci Technol 44 (23) 9094-9098Maiti A Basu JK De S 2010a Development of a Treated Laterite for Arsenic Adsorption Effects of Treatment Parameters Industrial amp Engineering Chemistry Research 49 (10) 4873-4886Maiti A Basu JK De S 2010b Removal of Arsenic from Synthetic and Natural Groundwater Using Acid-Activated Laterite Environmental Progress amp Sustainable Energy 29 (4) 457-470Maiti A Basu JK De S 2012 Experimental and kinetic modeling of As(V) and As(III) adsorption on treated laterite using synthetic and contaminated groundwater Effects of phosphate silicate and carbonate ions Chem Eng J 191 1-12Maiti A Thakur BK Basu JK De S 2013a Comparison of treated laterite as arsenic adsorbent from different locations and performance of best filter under field conditions J Hazard Mater 262 1176-1186Maiti A Thakur BK Basu JK De S 2013b Comparison of treated laterite as arsenic adsorbent from different locations and performance of best filter under field conditions J Hazard Mater 262 (0) 1176-1186Maji SK Pal A Pal T 2008 Arsenic removal from real-life groundwater by adsorption on laterite soil J Hazard Mater 151 (2-3) 811-820Maji SK Kao YH Wang CJ Lu GS Wu JJ Liu CW 2012 Fixed bed adsorption of As(III) on iron-oxide-coated natural rock (IOCNR) and application to real arsenic-bearing groundwater Chem Eng J 203 285-293Mertens J Rose J Kagi R Chaurand P Plotze M Wehrli B Furrer G 2012 Adsorption of arsenic on polyaluminum granulate Environ Sci Technol 46 (13) 7310-7317Nguyen TV Vigneswaran S Ngo HH Pokhre D Viraraghavan T 2006 Iron-coated sponge as
effective media to remove arsenic from drinking water Water Qual Res J Can 41 (2) 164-170Parkhurst DL Appelo CAJ 2013 Description of input and examples for PHREEQC version 3-A computer program for speciation batch-reaction one-dimensional transport and inverse geochemical calculations US Geological SurveyPena M Meng XG Korfiatis GP Jing CY 2006 Adsorption mechanism of arsenic on nanocrystalline titanium dioxide Environ Sci Technol 40 (4) 1257-1262Ravel B Newville M 2005 ATHENA ARTEMIS HEPHAESTUS Data analysis for X-ray absorption spectroscopy using IFEFFIT J Synchrotron Radiat 12 537-541Saha B Bains R Greenwood F 2005 Physicochemical characterization of granular ferric hydroxide (GFH) for arsenic(V) sorption from water Separation Science and Technology 40 (14) 2909-2932Shan H Ma T Wang Y Zhao J Han H Deng Y He X Dong Y 2013 A cost-effective system for in-situ geological arsenic adsorption from groundwater J Contam Hydrol 154 1-9Stachowicz M Hiemstra T van Riemsdijk WH 2008 Multi-competitive interaction of As(III) and As(V) oxyanions with Ca2+ Mg2+ PO4
3- and CO32- ions on goethite J Colloid Interf Sci 320 (2) 400-
414Streat M Hellgardt K Newton NLR 2008 Hydrous ferric oxide as an adsorbent in water treatment - Part 3 Batch and mini-column adsorption of arsenic phosphorus fluorine and cadmium ions Process Safety and Environmental Protection 86 (B1) 21-30Thirunavukkarasu OS Viraraghavan T Subramanian KS 2003 Arsenic removal from drinking water using iron oxide-coated sand Water Air Soil Poll 142 (1-4) 95-111USEPA 2008 Assessing arsenic removal by metal (hydr)oxide adsorptive media using rapid small scale column tests Govenrnment Printing Office Washington DCWang J Xu W Chen L Huang X Liu J 2014 Preparation and evaluation of magnetic nanoparticles impregnated chitosan beads for arsenic removal from water Chem Eng J 251 25-34Westerhoff P Highfield D Badruzzaman M Yoon Y 2005 Rapid small-scale column tests for arsenate removal in iron oxide packed bed columns J Environ Eng-Asce 131 (2) 262-271Westerhoff P De Haan M Martindale A Badruzzaman M 2006 Arsenic adsorptive media technology selection strategies Water Qual Res J Can 41 (2) 171-184Yan L Huang Y Cui J Jing C 2015 Simultaneous As(III) and Cd removal from copper smelting wastewater using granular TiO2 columns Water Res 68 (0) 572-579Zhao K Guo HM 2014 Behavior and mechanism of arsenate adsorption on activated natural siderite Evidences from FTIR and XANES analysis Environ Sci Pollut Res 21 (3) 1944-1953Zhao K Guo H Zhou X 2014 Adsorption and heterogeneous oxidation of arsenite on modified granular natural siderite Characterization and behaviors Appl Geochem 48 184-192
Iron-Mn binary 15 40 145 176 321 22 253 347 754 (Maiti et al 2010a)
13
oxides
aUnit for ion concentration is mgL except as notedbestimated from bed volume breakthrough curves and influent As concentration if not explicitly expressed in the reference cThe species is As(V) if only one concentration is given
d
The groundwater As concentration was 385-440 μgL and additional ~600 μgL (As(III)As(V)=11) arsenic was added
14
222324252627
Fig S1 Boxplot of groundwater As levels in columns and filters in the literature in Table S1 Individual samples are shown as diamonds The range of each box represents the 25th
and 75th
percentile whereas the whiskers represent the 10th
and 90th
percentile
Synthesis of granular TiO2
Granular TiO2 (GTiO2) was prepared by hydrolysis of titanyl sulfate (TiOSO4)
Generally 300 g TiOSO4 was mixed with 1800 mL DI water in a 10 L jar reactor in an
ice bath at 4 oC Then 10 M NaOH was slowly added to adjust the pH to 6 The
precursor of TiO2 was obtained by washing the suspension with DI water several
times till the conductivity of the supernatant was less than 100 μScm Then 800 g
TiO2 precursor was mixed with 40 mL polyvinyl alcohol solution at 80 oC in a water
bath The product was crushed into 60-80 mesh and dried in an oven at 60 oC for 12 h
15
282930313233343536373839404142434445464748
49
50
51
52
53
54
55
56
57585960
Fig S2 Characterization of GTiO2 SEM (a) and XRD pattern with crystal face for each peak (b)
Fig S1 SEM images for GTiO2 in this study
Table S2 Average concentrations of As coexisting ions (mgL) and water chemistry for groundwater 1 and 2 from two wells
Table S3 Water parameters in the synthetic water used in the studyParameters Ca2+ Mg2+ HCO3
- Na+ Cl- pHConc (mgL) 401 1043 388 2460 3928 82
Table S4 PHREEQC input for a representative column with EBCT=054 min SOLUTION 0
This keyword is to define the influent groundwater chemistry parameters which are included in the adsorption reactions like ldquoArseniterdquo and ldquoArsenaterdquo and the experimental conditions including ldquopHrdquo The information defined in SOLUTION is available for subsequent transport and adsorptive reaction calculations
temp 23 pH 82 pe 4 redox pe units mgL density 1 Al 006 Arsenite 0374 Arsenate 0291 CO4
2-
4401 Ca 194 Cl 1456 F 115 Fe 047 K 137 Mg 395 Mn 012 NO3
-
34 Na 16872
17
79
80
8182
83
84858687888990919293949596979899
100101102103104105106107108109110111112
SO42-
1176 Si 89 -water 1 kg
SOLUTION 1-4 The small column was divided into four cells SOLUTION 1-4
are the groundwater chemistry parameters for the four cells temp 23 pH 83 pe 4 redox pe units ppm density 1 Al 006 C(4) 4401 Ca 194 Cl 1456 F 115 Fe 047 K 137 Mg 395 Mn 012 N(3) 34 Na 16872 S(6) 1176 Si 89 -water 1 kg
SOLUTION_SPECIES This keyword is to define the dissociation constant logK
and diffusion constant (dw) in solution for arsenite and arsenate
Arsenite adsorption equation on GTiO2 surface H3ArseniteO3 is the primary species of As(III) at the groundwater pH 82 (Surf_sO)2ArseniteOH-066 is the adsorptive bidentate binuclear structure of As(III) on GTiO2
log_k 1635 The adsorptive reaction constant for As(III) on GTiO2 in
the current condition which could be changed with different experimental conditions
-cd_music -2 -1 0 066 3 CD-MUSIC model is integrated in the PHREEQC
modeling The numbers represent -2 the change in charge at the plane of Surf_sOH due to loss of two hydrogens -1 the change in charge at 1 plane due to gain of one hydrogen and one oxygen on Arsenite 0 the change in charge at the 2 plane usually caused by the outer sphere adsorption 066 the fraction of the central ion (As) charge that is associated with plane 0 which reflecting the charge distribution 3 the charge on the central ion (As)
Table S54 Parameters of Weber-Morris intraparticle model for As(IIIV) adsorption kinetics on GTiO2 using synthetic water Initial As concentration = 800 μgL adsorbent dose = 02 gL pH = 82 in synthetic groundwater
External film diffusion
Intraparticle diffusion
aRex2 bkp1
cb1aRin
2 bkp2cb 2
As(V) 0984 0497 0022 0976 01331878
As(III) 0970 0583
-0088 0981 0218
1105
aRex is WM external proportion fitting parameter while Rin is WM intraparticle proportion fitting parameterbk The unit of kp is mggh05 cb The unit of b is mgg
Table S6 Comparison of the adsorption capacities of As(III) and As(V) on GTiO2 and the representative granular adsorbents in similar experimental condition from the literature
AdsorbentParticle size (mm) As
qm
(mgg)Dose (gL) Experimental conditions Literature
GTiO2 018~025 As(III) 980 1 0~500 mgL at pH 82 01 M NaCl This studyGTiO2 018~025 As(V) 358 1 0~500 mgL at pH 82 01 M NaCl This study
Granular TiO2 015~06 As(III) 392 10~60 mgL As at pH 70 in simulated groundwater (100 mgL Ca 20 mgL Mg 50 mgL Na 200 mgL Cl-
)(Bang et al 2005)
Granular TiO2 015~06 As(V) 400 10~60 mgL As at pH 70 in simulated groundwater (100 mgL Ca 20 mgL Mg 50 mgL Na 200 mgL Cl-
)(Bang et al 2005)
E33 (FeOOH)0044~0075 As(V) 202 1 0~15 mgL at pH 70 in 001 M NaCl
(Kanematsu et al 2010)
E33 (FeOOH) 05~2 As(V) 180 1 0~50 mgL at pH 70 in 004 M NaClO4 (Jing et al 2012)
GFH 02~06 As(V) 650 10 0~2000 mgL at pH 8 in 01 M NaNO3
(Guan et al 2008)
GFH0009~0125 As(V) 23 025 0~07 μgL at pH 65 in DI water
(Banerjee et al 2008)
GFH0009~0125 As(V) 200 - 0~01 μgL at pH 70 in DI water
(Badruzzaman et al 2004)
GFH 050~065 As(V) 155 - 0~06 μgL at pH 70 in DI water (Saha et al 2005)
GHFO-NN 015~030 As(V) 330 0001 0~225 mgL at pH 8 in DI water(Streat et al 2008)
GHFO-VL 015~030 As(V) 360 0001 0~225 mgL at pH 8 in DI water(Streat et al 2008)
25
374375
Spherical schwertmannite 1~15 As(V) 36 05 0~5 mgL at pH 70 in DI water (Dou et al 2013)Cylindrical schwertmannite 1~25 As(V) 223 05
0~5 mgL at pH 70 in DI water(Dou et al 2013)
Irregular schwertmannite 10~16 As(V) 317 05 0~5 mgL at pH 70 in DI water (Dou et al 2013)Fe impregnated chitosan beads (MICB) 25 As(III) 117 1 0~05 mgL at pH 60 in DI water
(Wang et al 2014)
MICB 25 As(V) 191 1 0~1 mgL at pH 60 in DI water(Wang et al 2014)
MICB 25 As(III) 353 1 0~15 mgL at pH 60 in DI water(Wang et al 2014)
MICB 25 As(V) 357 1 0~16 mgL at pH 60 in DI water(Wang et al 2014)
Iron hydroxide granules (GIH) 3~4 As(V) 23 4
5~100 mgL at pH 70 in 10 mgL SO42-
14 mgL NH4Cl buffer solution (Daus et al 2004)
Activated Al2O3
0074~0149 As(V) 159 - 285~115 mgL at pH 52 in DI water
(Lin and Wu 2001)
Activated Al2O3
0074~0149 As(III) 35 - 079~490 mgL at pH 70 in DI water
(Lin and Wu 2001)
Activated Al2O3 ~20 As(V) 73 at pH 70 in 004 M NaClO4 (Jing et al 2012)
Activated natural siderite 05~10 As(V) 22 10 0 1~20 mgL at pH 7 in DI water(Zhao and Guo 2014)
Polyaluminum Granulate 1~3 As(III) 705 10 0~150 mgL at pH 51-56 in DI water(Mertens et al 2012)
Polyaluminum Granulate 1~3 As(V) 180 10 0~150 mgL at pH 51-56 in DI water (Mertens et al
26
2012)
Acidified laterite 1~12 As(III) 19 1 025~5 mgL at pH 7 in 100 mgL NaHCO3
(Glocheux et al 2013)
Acidified laterite 1~12 As(V) 13 1 025~5 mgL at pH 7 in 100 mgL NaHCO3
(Glocheux et al 2013)
Laterite 1~12 As(III) 07 1025~5 mgL at pH 7 in 100 mgL NaHCO3 (Glocheux et al
2013)
Laterite 1~12 As(V) 04 1025~5 mgL at pH 7 in 100 mgL NaHCO3 (Glocheux et al
2013)
Treated laterite 03-05 As(V) 216 05 02-20 mgL at pH 70 in DI water(Maiti et al 2012)
Treated laterite 03-05 As(III) 94 05 02-20 mgL at pH 70 in DI water(Maiti et al 2012)
Treated laterite03-05
As(V) 241 05 02-20 mgL at pH 70 in DI water(Maiti et al 2010a)
Treated laterite03-05
As(III) 81 05 02-20 mgL at pH 70 in DI water(Maiti et al 2010a)
Acid-activated laterite-103-07
As(III) 0633 50 02-10 mgL at pH 66-70 in DI water(Maiti et al 2010b)
Acid-activated laterite-203-07
As(III) 087650 02-10 mgL at pH 66-70 in DI water (Maiti et al
2010b)
Acid-activated laterite-303-07
As(III) 063450 02-10 mgL at pH 66-70 in DI water (Maiti et al
2010b)
Acid-activated laterite-103-07
As(V) 059850 02-10 mgL at pH 66-70 in DI water (Maiti et al
2010b)
27
Acid-activated laterite-203-07
As(V) 07550 02-10 mgL at pH 66-70 in DI water (Maiti et al
2010b)
Acid-activated laterite-303-07
As(V) 07550 02-10 mgL at pH 66-70 in DI water (Maiti et al
2010b)
Treated laterite-1 03-06 As(V) 019 20 0-20 mgL As at pH 72 in DI water(Maiti et al 2013b)
Treated laterite-1 03-06 As(III) 018 20 0-20 mgL As at pH 72 in DI water(Maiti et al 2013b)
Treated laterite-2 03-06 As(V) 004 20 0-20 mgL As at pH 72 in DI water(Maiti et al 2013b)
Treated laterite-2 03-06 As(III) 003 20 0-20 mgL As at pH 72 in DI water(Maiti et al 2013b)
Treated laterite-3 03-06 As(V) 007 20 0-20 mgL As at pH 72 in DI water(Maiti et al 2013b)
Treated laterite-3 03-06 As(III) 004 20 0-20 mgL As at pH 72 in DI water(Maiti et al 2013b)
28
376377
Charge distribution multi-site surface complexation (CD-MUSIC) modeling
The CD-MUSIC model with the 2-pK TPM adsorption option was used to
describe adsorption behaviors of As cations and anions on GTiO2 The CD-MUSIC
model incorporates the structural information of surfaces adsorbed species and the
double layers by distributing the charge of an adsorbate between the surface and
interfacial water (Hiemstra and Van Riemsdijk 2006) The CD-MUSIC model has
been successfully used in describing As adsorption in batch experiments (Pena et al
2006 Stachowicz et al 2008)
The adsorption constants of counter ions were set to -1 and the proton affinity
constant was set to the PZC of 58 for TiOH-13 (Luo et al 2010) The charge
distribution (CD) value shows the fraction (f) of the charge of the central As ion
attributed to the surface plane and the remaining part (1-f) was attributed to the other
ligands of the complex which were positioned toward the diffuse layer The CD value
for As surface complexes was obtained by fitting the experimental data The
calculation was performed using the chemical equilibrium program MINTEQ to
simulate the adsorption and the aqueous reactions
29
378379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
Fig S32 Adsorption of silicate (a) calcium and magnesium (b) as a function of GTiO2
dose in groundwater 1 The solid lines represent the CD-MUSIC modeling result
30
400
401
402
403
404
405
406
407
408409410
Table S75 Surface parameters and species used in the CD-MUSIC modeling in As(IIIV) removal under different GTiO2 dose in 01 M NaCl and groundwater 1 in Fig 2 and Fig S32
= exp(-FΨ1RT) P2 = exp(-FΨ2RT) F the Faraday constant (C mol-1) R the gas constant (J mol-1 K-1) T the absolute temperature (K)
Ψ0 Ψ1 Ψ2 the electrostatic potential (V) of 0- 1- and 2-plane respectively alogK for 01 M NaCl at 6 hours blogK for 01 M NaCl at 6 days clogK for groundwater 1 at 6 days
31
411412
413414415
32
416
Table S86 The charge distribution (f) of central As atom to TiO2 surface in simulating the effect of cations and anions on As adsorption in 01 M NaCl at pH 82 in Fig 4 BK Si HCO3 All
As(V) 022 017 012 016As(III) 040 020 058 056
Fig S43 Molar percentage () of As Ca Mg and Si on pristine and spent GTiO2
surfaces using EDX analysis The spent GTiO2 samples after field column experiments using groundwater 1 were identified with EBCT in min under x-axis The value of molar percentage of each element was averaged from randomly-chosen positions on the adsorbent surface
33
417
418
419420
421422
423
424
425
426
427
428
429
430
431
432
433434435436437438
439
440
441
As speciation analysis on spent GTiO2 using XANES
The spent GTiO2 samples were ground using a mortar and pestle and then the
ground powder was spread on Scotch tape The As k-edge XANES spectra were
collected at beamline 01C1 at the National Synchrotron Radiation Research Center
(NSRRC) Taiwan Spectra were acquired from -150 to 300 eV relative to the As K-
edge of 11867 eV at cryogenic temperature (77 K) using a cryostat to prevent the
oxidation of As(III) by X-rays The fluorescence signals were collected using a Lytle
detector Two to four scans were collected for each sample and averaged to improve
the signalnoise ratio The XANES analysis was performed with the Athena program
in the IFEFFIT computer package for linear combination fit (LCF) (Cui et al 2013
Ravel and Newville 2005)
34
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
PHREEQC modeling for As breakthrough curves in field column experiments
PHREEQC a geochemical model integrates macroscopic mass transfer
processes with a microscopic surface complexation model (Parkhurst and Appelo
2013) It can be applied in calculating solution complex speciation batch-reaction
and one-dimensional reactive-transport and inverse modeling In our study the one-
dimensional column was defined by four cells with the same length The cell length
was calculated to be one-fourth of the actual column length Time step (s) was
calculated according to equation Time step = Lcell(Q60A) where Lcell is the cell
length (cm) Q is flow velocity (mLmin) A is the effective column cross section area
(cm2) which is the column cross-sectional area multiplied by porosity (060) Total
shift number was calculated by dividing actual column operation time by the time
step The transport block was modeled by shifting the solute content from one cell to
the next one In each cell the aqueous solute was mixed and adsorbed on GTiO2
according to the equations In each cell the aqueous solute was mixed and assumed to
be in equilibration with GTiO2 The sequence of shifting mixing and equilibrium
adsorption was repeated for each cell until the total number of shifts was completed
The diffusion coefficient Dw in PHREEQC accounting for retardation was
calculated as Dw=x2
(36t) where x stands for the diffusion length (estimated as the
radius of the particle size) and t represents equilibrium time adopted from the batch
kinetic data (Mertens et al 2012)
For CD-MUSIC modeling in the PHREEQC take As(III) as an example to
explain the adsorption equation The As(III) adsorption is considered as a ligand
35
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
exchange reaction with the hydroxide group on GTiO2 (Surf_sOH-033) forming a
H3ArseniteO3 is the master species in groundwater at pH 82
(Surf_sO)2ArseniteOH-066 is the common adsorbed bidentate binuclear complex
evidenced by our previous reports(Pena et al 2006 Yan et al 2015) LogK is the
adsorption equilibrium constants Generally every adsorption equation under certain
experimental condition has a unique value of logK In the adsorption equation ldquo-2rdquo
represents the lost two hydrogens by Surf_sOH-033 after it adsorbs H3ArseniteO3 ldquo-
1rdquo represents the change in charge on Arsenite at 1 plane due to gaining one hydrogen
(+1) and one oxygen (-2) ldquo0rdquo represents no change in charge at the 2 plane ldquo066rdquo is
the fraction of the central ion (As) on GTiO2 surface that is associated with plane 0
ldquo3rdquo is the charge on the central ion As(III) Following this equation and the relevant
parameters As(III) adsorbed on GTiO2
The diffusion coefficient Dw in PHREEQC accounting for retardation was
calculated as Dw=x2(36t) where x stands for the diffusion length (estimated as the
radius of the particle size) and t represents equilibrium time adopted from the batch
kinetic data (Mertens et al 2012)
To well simulate the As breakthrough curve in columns four As(V) adsorption
reactions (Table 1) were employed Adsorption site density of 60 mmolg was
36
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
adopted from our previous study (Pena et al 2006) and the total adsorption sites were
calculated to be 1844 sitesnm2 The final optimized ratio of strong to weak sites was
51 The surface complexation constants were reasonably adjusted according to the
batch modeling results as the column reaction may not reach equilibrium in local
micro-interfacial areas due to much less contact time between As and GTiO2 than that
in batch experiments (Appelo and Postma 1999) In the modeling a stepwise
procedure was adopted to achieve a viable result An estimation of two thirds of the
surface site density being accessible for EBCT=011 min with large flow rate of 265
mLmin was optimized which could probably result from unavailable adsorption sites
due to fast transport through the column
The adsorbed As on GTiO2 in the column was calculated by mass balance
between the influent and effluent
where Asadsorbed is the adsorbed As on GTiO2 (mgg) n is the number of collected
samples Cin and Cout are influent and effluent As concentrations (mgL) respectively
Vi is volume (L) of groundwater passed through the column between sample i-1 and i
and m is the mass of GTiO2 (g)
Even though the oxidation of adsorbed As(III) occurred during filtration as
analyzed from XANES and mass balance analysis (Fig 7) no As(III) oxidation
reactions were considered in PHREEQC modeling which would not impact the
breakthrough of As(IIIV)
37
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
38
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
Fig S54 Effect of EBCT on Si Ca and Mg breakthrough curves using groundwater 1 The sample notation in panel c indicates field column experiments with EBCT in minutes
References
Appelo CAJ Postma D 1999 A consistent model for surface complexation on birnessite (MnO2) and its application to a column experiment Geochim Cosmochim Ac 63 (19-20) 3039-3048Badruzzaman M Westerhoff P Knappe DRU 2004 Intraparticle diffusion and adsorption of arsenate onto granular ferric hydroxide (GFH) Water Res 38 (18) 4002-4012Banerjee K Amy GL Prevost M Nour S Jekel M Gallagher PM Blumenschein CD 2008 Kinetic and thermodynamic aspects of adsorption of arsenic onto granular ferric hydroxide (GFH) Water Res 42 (13) 3371-3378Bang S Patel M Lippincott L Meng XG 2005 Removal of arsenic from groundwater by granular titanium dioxide adsorbent Chemosphere 60 (3) 389-397Bang S Pena ME Patel M Lippincott L Meng X Kim KW 2011 Removal of arsenate from water by adsorbents a comparative case study Environ Geochem Hlth 33 133-141Cui JL Shi JB Jiang GB Jing CY 2013 Arsenic levels and speciation from ingestion exposures to biomarkers in Shanxi China Implications for human health Environ Sci Technol 47 (10) 5419-5424Daus B Wennrich R Weiss H 2004 Sorption materials for arsenic removal from water A comparative study Water Res 38 (12) 2948-2954Dou XM Mohan D Pittman CU 2013 Arsenate adsorption on three types of granular schwertmannite Water Res 47 (9) 2938-2948Dou XM Zhang Y Yang M Pei YS Huang X Takayama T Kato S 2006 Occurrence of arsenic in groundwater in the suburbs of Beijing and its removal using an iron-cerium bimetal oxide adsorbent Water Qual Res J Can 41 (2) 140-146Gibbons MK Gagnon GA 2010 Adsorption of arsenic from a Nova Scotia groundwater onto water treatment residual solids Water Res 44 (19) 5740-5749Glocheux Y Mendez Pasarin M Albadarin AB Allen SJ Walker GM 2013 Removal of arsenic from groundwater by adsorption onto an acidified laterite by-product Chem Eng J 228 565-574Guan XH Wang JM Chusuei CC 2008 Removal of arsenic from water using granular ferric hydroxide Macroscopic and microscopic studies J Hazard Mater 156 (1-3) 178-185Gupta K Maity A Ghosh UC 2010 Manganese associated nanoparticles agglomerate of iron(III) oxide Synthesis characterization and arsenic(III) sorption behavior with mechanism J Hazard Mater 184 (1-3) 832-842Hao JM Han MJ Wang C Meng XG 2009 Enhanced removal of arsenite from water by a mesoporous hybrid material - Thiol-functionalized silica coated activated alumina Micropor Mesopor
Mat 124 (1-3) 1-7Hiemstra T Van Riemsdijk WH 2006 On the relationship between charge distribution surface hydration and the structure of the interface of metal hydroxides J Colloid Interf Sci 301 (1) 1-18Hristovski K Baumgardner A Westerhoff P 2007 Selecting metal oxide nanomaterials for arsenic removal in fixed bed columns From nanopowders to aggregated nanoparticle media J Hazard Mater 147 (1-2) 265-274Jang M Chen WF Cannon FS 2008 Preloading hydrous ferric oxide into granular activated carbon for arsenic removal Environ Sci Technol 42 (9) 3369-3374Jing CY Cui JL Huang YY Li AG 2012 Fabrication characterization and application of a composite adsorbent for simultaneous removal of arsenic and fluoride ACS Appl Mater Interfaces 4 (2) 714-720Kanematsu M Young TM Fukushi K Green PG Darby JL 2010 Extended triple layer modeling of arsenate and phosphate adsorption on a goethite-based granular porous adsorbent Environ Sci Technol 44 (9) 3388-3394Kong S Wang Y Zhan H Yuan S Liu M Zhou C 2013 Arsenite and Arsenate Removal from Contaminated Groundwater by Nanoscale Iron-Manganese Binary Oxides Column Studies Environmental Engineering Science 30 (11) 689-696Li Y Liu JR Jia SY Guo JW Zhuo J Na P 2012 TiO2 pillared montmorillonite as a photoactive adsorbent of arsenic under UV irradiation Chem Eng J 191 66-74Lin TF Wu JK 2001 Adsorption of arsenite and arsenate within activated alumina grains Equilibrium and kinetics Water Res 35 (8) 2049-2057Luo T Cui JL Hu S Huang YY Jing CY 2010 Arsenic removal and recovery from copper smelting wastewater using TiO2 Environ Sci Technol 44 (23) 9094-9098Maiti A Basu JK De S 2010a Development of a Treated Laterite for Arsenic Adsorption Effects of Treatment Parameters Industrial amp Engineering Chemistry Research 49 (10) 4873-4886Maiti A Basu JK De S 2010b Removal of Arsenic from Synthetic and Natural Groundwater Using Acid-Activated Laterite Environmental Progress amp Sustainable Energy 29 (4) 457-470Maiti A Basu JK De S 2012 Experimental and kinetic modeling of As(V) and As(III) adsorption on treated laterite using synthetic and contaminated groundwater Effects of phosphate silicate and carbonate ions Chem Eng J 191 1-12Maiti A Thakur BK Basu JK De S 2013a Comparison of treated laterite as arsenic adsorbent from different locations and performance of best filter under field conditions J Hazard Mater 262 1176-1186Maiti A Thakur BK Basu JK De S 2013b Comparison of treated laterite as arsenic adsorbent from different locations and performance of best filter under field conditions J Hazard Mater 262 (0) 1176-1186Maji SK Pal A Pal T 2008 Arsenic removal from real-life groundwater by adsorption on laterite soil J Hazard Mater 151 (2-3) 811-820Maji SK Kao YH Wang CJ Lu GS Wu JJ Liu CW 2012 Fixed bed adsorption of As(III) on iron-oxide-coated natural rock (IOCNR) and application to real arsenic-bearing groundwater Chem Eng J 203 285-293Mertens J Rose J Kagi R Chaurand P Plotze M Wehrli B Furrer G 2012 Adsorption of arsenic on polyaluminum granulate Environ Sci Technol 46 (13) 7310-7317Nguyen TV Vigneswaran S Ngo HH Pokhre D Viraraghavan T 2006 Iron-coated sponge as
effective media to remove arsenic from drinking water Water Qual Res J Can 41 (2) 164-170Parkhurst DL Appelo CAJ 2013 Description of input and examples for PHREEQC version 3-A computer program for speciation batch-reaction one-dimensional transport and inverse geochemical calculations US Geological SurveyPena M Meng XG Korfiatis GP Jing CY 2006 Adsorption mechanism of arsenic on nanocrystalline titanium dioxide Environ Sci Technol 40 (4) 1257-1262Ravel B Newville M 2005 ATHENA ARTEMIS HEPHAESTUS Data analysis for X-ray absorption spectroscopy using IFEFFIT J Synchrotron Radiat 12 537-541Saha B Bains R Greenwood F 2005 Physicochemical characterization of granular ferric hydroxide (GFH) for arsenic(V) sorption from water Separation Science and Technology 40 (14) 2909-2932Shan H Ma T Wang Y Zhao J Han H Deng Y He X Dong Y 2013 A cost-effective system for in-situ geological arsenic adsorption from groundwater J Contam Hydrol 154 1-9Stachowicz M Hiemstra T van Riemsdijk WH 2008 Multi-competitive interaction of As(III) and As(V) oxyanions with Ca2+ Mg2+ PO4
3- and CO32- ions on goethite J Colloid Interf Sci 320 (2) 400-
414Streat M Hellgardt K Newton NLR 2008 Hydrous ferric oxide as an adsorbent in water treatment - Part 3 Batch and mini-column adsorption of arsenic phosphorus fluorine and cadmium ions Process Safety and Environmental Protection 86 (B1) 21-30Thirunavukkarasu OS Viraraghavan T Subramanian KS 2003 Arsenic removal from drinking water using iron oxide-coated sand Water Air Soil Poll 142 (1-4) 95-111USEPA 2008 Assessing arsenic removal by metal (hydr)oxide adsorptive media using rapid small scale column tests Govenrnment Printing Office Washington DCWang J Xu W Chen L Huang X Liu J 2014 Preparation and evaluation of magnetic nanoparticles impregnated chitosan beads for arsenic removal from water Chem Eng J 251 25-34Westerhoff P Highfield D Badruzzaman M Yoon Y 2005 Rapid small-scale column tests for arsenate removal in iron oxide packed bed columns J Environ Eng-Asce 131 (2) 262-271Westerhoff P De Haan M Martindale A Badruzzaman M 2006 Arsenic adsorptive media technology selection strategies Water Qual Res J Can 41 (2) 171-184Yan L Huang Y Cui J Jing C 2015 Simultaneous As(III) and Cd removal from copper smelting wastewater using granular TiO2 columns Water Res 68 (0) 572-579Zhao K Guo HM 2014 Behavior and mechanism of arsenate adsorption on activated natural siderite Evidences from FTIR and XANES analysis Environ Sci Pollut Res 21 (3) 1944-1953Zhao K Guo H Zhou X 2014 Adsorption and heterogeneous oxidation of arsenite on modified granular natural siderite Characterization and behaviors Appl Geochem 48 184-192
Iron-Mn binary 15 40 145 176 321 22 253 347 754 (Maiti et al 2010a)
13
oxides
aUnit for ion concentration is mgL except as notedbestimated from bed volume breakthrough curves and influent As concentration if not explicitly expressed in the reference cThe species is As(V) if only one concentration is given
d
The groundwater As concentration was 385-440 μgL and additional ~600 μgL (As(III)As(V)=11) arsenic was added
14
222324252627
Fig S1 Boxplot of groundwater As levels in columns and filters in the literature in Table S1 Individual samples are shown as diamonds The range of each box represents the 25th
and 75th
percentile whereas the whiskers represent the 10th
and 90th
percentile
Synthesis of granular TiO2
Granular TiO2 (GTiO2) was prepared by hydrolysis of titanyl sulfate (TiOSO4)
Generally 300 g TiOSO4 was mixed with 1800 mL DI water in a 10 L jar reactor in an
ice bath at 4 oC Then 10 M NaOH was slowly added to adjust the pH to 6 The
precursor of TiO2 was obtained by washing the suspension with DI water several
times till the conductivity of the supernatant was less than 100 μScm Then 800 g
TiO2 precursor was mixed with 40 mL polyvinyl alcohol solution at 80 oC in a water
bath The product was crushed into 60-80 mesh and dried in an oven at 60 oC for 12 h
15
282930313233343536373839404142434445464748
49
50
51
52
53
54
55
56
57585960
Fig S2 Characterization of GTiO2 SEM (a) and XRD pattern with crystal face for each peak (b)
Fig S1 SEM images for GTiO2 in this study
Table S2 Average concentrations of As coexisting ions (mgL) and water chemistry for groundwater 1 and 2 from two wells
Table S3 Water parameters in the synthetic water used in the studyParameters Ca2+ Mg2+ HCO3
- Na+ Cl- pHConc (mgL) 401 1043 388 2460 3928 82
Table S4 PHREEQC input for a representative column with EBCT=054 min SOLUTION 0
This keyword is to define the influent groundwater chemistry parameters which are included in the adsorption reactions like ldquoArseniterdquo and ldquoArsenaterdquo and the experimental conditions including ldquopHrdquo The information defined in SOLUTION is available for subsequent transport and adsorptive reaction calculations
temp 23 pH 82 pe 4 redox pe units mgL density 1 Al 006 Arsenite 0374 Arsenate 0291 CO4
2-
4401 Ca 194 Cl 1456 F 115 Fe 047 K 137 Mg 395 Mn 012 NO3
-
34 Na 16872
17
79
80
8182
83
84858687888990919293949596979899
100101102103104105106107108109110111112
SO42-
1176 Si 89 -water 1 kg
SOLUTION 1-4 The small column was divided into four cells SOLUTION 1-4
are the groundwater chemistry parameters for the four cells temp 23 pH 83 pe 4 redox pe units ppm density 1 Al 006 C(4) 4401 Ca 194 Cl 1456 F 115 Fe 047 K 137 Mg 395 Mn 012 N(3) 34 Na 16872 S(6) 1176 Si 89 -water 1 kg
SOLUTION_SPECIES This keyword is to define the dissociation constant logK
and diffusion constant (dw) in solution for arsenite and arsenate
Arsenite adsorption equation on GTiO2 surface H3ArseniteO3 is the primary species of As(III) at the groundwater pH 82 (Surf_sO)2ArseniteOH-066 is the adsorptive bidentate binuclear structure of As(III) on GTiO2
log_k 1635 The adsorptive reaction constant for As(III) on GTiO2 in
the current condition which could be changed with different experimental conditions
-cd_music -2 -1 0 066 3 CD-MUSIC model is integrated in the PHREEQC
modeling The numbers represent -2 the change in charge at the plane of Surf_sOH due to loss of two hydrogens -1 the change in charge at 1 plane due to gain of one hydrogen and one oxygen on Arsenite 0 the change in charge at the 2 plane usually caused by the outer sphere adsorption 066 the fraction of the central ion (As) charge that is associated with plane 0 which reflecting the charge distribution 3 the charge on the central ion (As)
Table S54 Parameters of Weber-Morris intraparticle model for As(IIIV) adsorption kinetics on GTiO2 using synthetic water Initial As concentration = 800 μgL adsorbent dose = 02 gL pH = 82 in synthetic groundwater
External film diffusion
Intraparticle diffusion
aRex2 bkp1
cb1aRin
2 bkp2cb 2
As(V) 0984 0497 0022 0976 01331878
As(III) 0970 0583
-0088 0981 0218
1105
aRex is WM external proportion fitting parameter while Rin is WM intraparticle proportion fitting parameterbk The unit of kp is mggh05 cb The unit of b is mgg
Table S6 Comparison of the adsorption capacities of As(III) and As(V) on GTiO2 and the representative granular adsorbents in similar experimental condition from the literature
AdsorbentParticle size (mm) As
qm
(mgg)Dose (gL) Experimental conditions Literature
GTiO2 018~025 As(III) 980 1 0~500 mgL at pH 82 01 M NaCl This studyGTiO2 018~025 As(V) 358 1 0~500 mgL at pH 82 01 M NaCl This study
Granular TiO2 015~06 As(III) 392 10~60 mgL As at pH 70 in simulated groundwater (100 mgL Ca 20 mgL Mg 50 mgL Na 200 mgL Cl-
)(Bang et al 2005)
Granular TiO2 015~06 As(V) 400 10~60 mgL As at pH 70 in simulated groundwater (100 mgL Ca 20 mgL Mg 50 mgL Na 200 mgL Cl-
)(Bang et al 2005)
E33 (FeOOH)0044~0075 As(V) 202 1 0~15 mgL at pH 70 in 001 M NaCl
(Kanematsu et al 2010)
E33 (FeOOH) 05~2 As(V) 180 1 0~50 mgL at pH 70 in 004 M NaClO4 (Jing et al 2012)
GFH 02~06 As(V) 650 10 0~2000 mgL at pH 8 in 01 M NaNO3
(Guan et al 2008)
GFH0009~0125 As(V) 23 025 0~07 μgL at pH 65 in DI water
(Banerjee et al 2008)
GFH0009~0125 As(V) 200 - 0~01 μgL at pH 70 in DI water
(Badruzzaman et al 2004)
GFH 050~065 As(V) 155 - 0~06 μgL at pH 70 in DI water (Saha et al 2005)
GHFO-NN 015~030 As(V) 330 0001 0~225 mgL at pH 8 in DI water(Streat et al 2008)
GHFO-VL 015~030 As(V) 360 0001 0~225 mgL at pH 8 in DI water(Streat et al 2008)
25
374375
Spherical schwertmannite 1~15 As(V) 36 05 0~5 mgL at pH 70 in DI water (Dou et al 2013)Cylindrical schwertmannite 1~25 As(V) 223 05
0~5 mgL at pH 70 in DI water(Dou et al 2013)
Irregular schwertmannite 10~16 As(V) 317 05 0~5 mgL at pH 70 in DI water (Dou et al 2013)Fe impregnated chitosan beads (MICB) 25 As(III) 117 1 0~05 mgL at pH 60 in DI water
(Wang et al 2014)
MICB 25 As(V) 191 1 0~1 mgL at pH 60 in DI water(Wang et al 2014)
MICB 25 As(III) 353 1 0~15 mgL at pH 60 in DI water(Wang et al 2014)
MICB 25 As(V) 357 1 0~16 mgL at pH 60 in DI water(Wang et al 2014)
Iron hydroxide granules (GIH) 3~4 As(V) 23 4
5~100 mgL at pH 70 in 10 mgL SO42-
14 mgL NH4Cl buffer solution (Daus et al 2004)
Activated Al2O3
0074~0149 As(V) 159 - 285~115 mgL at pH 52 in DI water
(Lin and Wu 2001)
Activated Al2O3
0074~0149 As(III) 35 - 079~490 mgL at pH 70 in DI water
(Lin and Wu 2001)
Activated Al2O3 ~20 As(V) 73 at pH 70 in 004 M NaClO4 (Jing et al 2012)
Activated natural siderite 05~10 As(V) 22 10 0 1~20 mgL at pH 7 in DI water(Zhao and Guo 2014)
Polyaluminum Granulate 1~3 As(III) 705 10 0~150 mgL at pH 51-56 in DI water(Mertens et al 2012)
Polyaluminum Granulate 1~3 As(V) 180 10 0~150 mgL at pH 51-56 in DI water (Mertens et al
26
2012)
Acidified laterite 1~12 As(III) 19 1 025~5 mgL at pH 7 in 100 mgL NaHCO3
(Glocheux et al 2013)
Acidified laterite 1~12 As(V) 13 1 025~5 mgL at pH 7 in 100 mgL NaHCO3
(Glocheux et al 2013)
Laterite 1~12 As(III) 07 1025~5 mgL at pH 7 in 100 mgL NaHCO3 (Glocheux et al
2013)
Laterite 1~12 As(V) 04 1025~5 mgL at pH 7 in 100 mgL NaHCO3 (Glocheux et al
2013)
Treated laterite 03-05 As(V) 216 05 02-20 mgL at pH 70 in DI water(Maiti et al 2012)
Treated laterite 03-05 As(III) 94 05 02-20 mgL at pH 70 in DI water(Maiti et al 2012)
Treated laterite03-05
As(V) 241 05 02-20 mgL at pH 70 in DI water(Maiti et al 2010a)
Treated laterite03-05
As(III) 81 05 02-20 mgL at pH 70 in DI water(Maiti et al 2010a)
Acid-activated laterite-103-07
As(III) 0633 50 02-10 mgL at pH 66-70 in DI water(Maiti et al 2010b)
Acid-activated laterite-203-07
As(III) 087650 02-10 mgL at pH 66-70 in DI water (Maiti et al
2010b)
Acid-activated laterite-303-07
As(III) 063450 02-10 mgL at pH 66-70 in DI water (Maiti et al
2010b)
Acid-activated laterite-103-07
As(V) 059850 02-10 mgL at pH 66-70 in DI water (Maiti et al
2010b)
27
Acid-activated laterite-203-07
As(V) 07550 02-10 mgL at pH 66-70 in DI water (Maiti et al
2010b)
Acid-activated laterite-303-07
As(V) 07550 02-10 mgL at pH 66-70 in DI water (Maiti et al
2010b)
Treated laterite-1 03-06 As(V) 019 20 0-20 mgL As at pH 72 in DI water(Maiti et al 2013b)
Treated laterite-1 03-06 As(III) 018 20 0-20 mgL As at pH 72 in DI water(Maiti et al 2013b)
Treated laterite-2 03-06 As(V) 004 20 0-20 mgL As at pH 72 in DI water(Maiti et al 2013b)
Treated laterite-2 03-06 As(III) 003 20 0-20 mgL As at pH 72 in DI water(Maiti et al 2013b)
Treated laterite-3 03-06 As(V) 007 20 0-20 mgL As at pH 72 in DI water(Maiti et al 2013b)
Treated laterite-3 03-06 As(III) 004 20 0-20 mgL As at pH 72 in DI water(Maiti et al 2013b)
28
376377
Charge distribution multi-site surface complexation (CD-MUSIC) modeling
The CD-MUSIC model with the 2-pK TPM adsorption option was used to
describe adsorption behaviors of As cations and anions on GTiO2 The CD-MUSIC
model incorporates the structural information of surfaces adsorbed species and the
double layers by distributing the charge of an adsorbate between the surface and
interfacial water (Hiemstra and Van Riemsdijk 2006) The CD-MUSIC model has
been successfully used in describing As adsorption in batch experiments (Pena et al
2006 Stachowicz et al 2008)
The adsorption constants of counter ions were set to -1 and the proton affinity
constant was set to the PZC of 58 for TiOH-13 (Luo et al 2010) The charge
distribution (CD) value shows the fraction (f) of the charge of the central As ion
attributed to the surface plane and the remaining part (1-f) was attributed to the other
ligands of the complex which were positioned toward the diffuse layer The CD value
for As surface complexes was obtained by fitting the experimental data The
calculation was performed using the chemical equilibrium program MINTEQ to
simulate the adsorption and the aqueous reactions
29
378379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
Fig S32 Adsorption of silicate (a) calcium and magnesium (b) as a function of GTiO2
dose in groundwater 1 The solid lines represent the CD-MUSIC modeling result
30
400
401
402
403
404
405
406
407
408409410
Table S75 Surface parameters and species used in the CD-MUSIC modeling in As(IIIV) removal under different GTiO2 dose in 01 M NaCl and groundwater 1 in Fig 2 and Fig S32
= exp(-FΨ1RT) P2 = exp(-FΨ2RT) F the Faraday constant (C mol-1) R the gas constant (J mol-1 K-1) T the absolute temperature (K)
Ψ0 Ψ1 Ψ2 the electrostatic potential (V) of 0- 1- and 2-plane respectively alogK for 01 M NaCl at 6 hours blogK for 01 M NaCl at 6 days clogK for groundwater 1 at 6 days
31
411412
413414415
32
416
Table S86 The charge distribution (f) of central As atom to TiO2 surface in simulating the effect of cations and anions on As adsorption in 01 M NaCl at pH 82 in Fig 4 BK Si HCO3 All
As(V) 022 017 012 016As(III) 040 020 058 056
Fig S43 Molar percentage () of As Ca Mg and Si on pristine and spent GTiO2
surfaces using EDX analysis The spent GTiO2 samples after field column experiments using groundwater 1 were identified with EBCT in min under x-axis The value of molar percentage of each element was averaged from randomly-chosen positions on the adsorbent surface
33
417
418
419420
421422
423
424
425
426
427
428
429
430
431
432
433434435436437438
439
440
441
As speciation analysis on spent GTiO2 using XANES
The spent GTiO2 samples were ground using a mortar and pestle and then the
ground powder was spread on Scotch tape The As k-edge XANES spectra were
collected at beamline 01C1 at the National Synchrotron Radiation Research Center
(NSRRC) Taiwan Spectra were acquired from -150 to 300 eV relative to the As K-
edge of 11867 eV at cryogenic temperature (77 K) using a cryostat to prevent the
oxidation of As(III) by X-rays The fluorescence signals were collected using a Lytle
detector Two to four scans were collected for each sample and averaged to improve
the signalnoise ratio The XANES analysis was performed with the Athena program
in the IFEFFIT computer package for linear combination fit (LCF) (Cui et al 2013
Ravel and Newville 2005)
34
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
PHREEQC modeling for As breakthrough curves in field column experiments
PHREEQC a geochemical model integrates macroscopic mass transfer
processes with a microscopic surface complexation model (Parkhurst and Appelo
2013) It can be applied in calculating solution complex speciation batch-reaction
and one-dimensional reactive-transport and inverse modeling In our study the one-
dimensional column was defined by four cells with the same length The cell length
was calculated to be one-fourth of the actual column length Time step (s) was
calculated according to equation Time step = Lcell(Q60A) where Lcell is the cell
length (cm) Q is flow velocity (mLmin) A is the effective column cross section area
(cm2) which is the column cross-sectional area multiplied by porosity (060) Total
shift number was calculated by dividing actual column operation time by the time
step The transport block was modeled by shifting the solute content from one cell to
the next one In each cell the aqueous solute was mixed and adsorbed on GTiO2
according to the equations In each cell the aqueous solute was mixed and assumed to
be in equilibration with GTiO2 The sequence of shifting mixing and equilibrium
adsorption was repeated for each cell until the total number of shifts was completed
The diffusion coefficient Dw in PHREEQC accounting for retardation was
calculated as Dw=x2
(36t) where x stands for the diffusion length (estimated as the
radius of the particle size) and t represents equilibrium time adopted from the batch
kinetic data (Mertens et al 2012)
For CD-MUSIC modeling in the PHREEQC take As(III) as an example to
explain the adsorption equation The As(III) adsorption is considered as a ligand
35
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
exchange reaction with the hydroxide group on GTiO2 (Surf_sOH-033) forming a
H3ArseniteO3 is the master species in groundwater at pH 82
(Surf_sO)2ArseniteOH-066 is the common adsorbed bidentate binuclear complex
evidenced by our previous reports(Pena et al 2006 Yan et al 2015) LogK is the
adsorption equilibrium constants Generally every adsorption equation under certain
experimental condition has a unique value of logK In the adsorption equation ldquo-2rdquo
represents the lost two hydrogens by Surf_sOH-033 after it adsorbs H3ArseniteO3 ldquo-
1rdquo represents the change in charge on Arsenite at 1 plane due to gaining one hydrogen
(+1) and one oxygen (-2) ldquo0rdquo represents no change in charge at the 2 plane ldquo066rdquo is
the fraction of the central ion (As) on GTiO2 surface that is associated with plane 0
ldquo3rdquo is the charge on the central ion As(III) Following this equation and the relevant
parameters As(III) adsorbed on GTiO2
The diffusion coefficient Dw in PHREEQC accounting for retardation was
calculated as Dw=x2(36t) where x stands for the diffusion length (estimated as the
radius of the particle size) and t represents equilibrium time adopted from the batch
kinetic data (Mertens et al 2012)
To well simulate the As breakthrough curve in columns four As(V) adsorption
reactions (Table 1) were employed Adsorption site density of 60 mmolg was
36
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
adopted from our previous study (Pena et al 2006) and the total adsorption sites were
calculated to be 1844 sitesnm2 The final optimized ratio of strong to weak sites was
51 The surface complexation constants were reasonably adjusted according to the
batch modeling results as the column reaction may not reach equilibrium in local
micro-interfacial areas due to much less contact time between As and GTiO2 than that
in batch experiments (Appelo and Postma 1999) In the modeling a stepwise
procedure was adopted to achieve a viable result An estimation of two thirds of the
surface site density being accessible for EBCT=011 min with large flow rate of 265
mLmin was optimized which could probably result from unavailable adsorption sites
due to fast transport through the column
The adsorbed As on GTiO2 in the column was calculated by mass balance
between the influent and effluent
where Asadsorbed is the adsorbed As on GTiO2 (mgg) n is the number of collected
samples Cin and Cout are influent and effluent As concentrations (mgL) respectively
Vi is volume (L) of groundwater passed through the column between sample i-1 and i
and m is the mass of GTiO2 (g)
Even though the oxidation of adsorbed As(III) occurred during filtration as
analyzed from XANES and mass balance analysis (Fig 7) no As(III) oxidation
reactions were considered in PHREEQC modeling which would not impact the
breakthrough of As(IIIV)
37
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
38
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
Fig S54 Effect of EBCT on Si Ca and Mg breakthrough curves using groundwater 1 The sample notation in panel c indicates field column experiments with EBCT in minutes
References
Appelo CAJ Postma D 1999 A consistent model for surface complexation on birnessite (MnO2) and its application to a column experiment Geochim Cosmochim Ac 63 (19-20) 3039-3048Badruzzaman M Westerhoff P Knappe DRU 2004 Intraparticle diffusion and adsorption of arsenate onto granular ferric hydroxide (GFH) Water Res 38 (18) 4002-4012Banerjee K Amy GL Prevost M Nour S Jekel M Gallagher PM Blumenschein CD 2008 Kinetic and thermodynamic aspects of adsorption of arsenic onto granular ferric hydroxide (GFH) Water Res 42 (13) 3371-3378Bang S Patel M Lippincott L Meng XG 2005 Removal of arsenic from groundwater by granular titanium dioxide adsorbent Chemosphere 60 (3) 389-397Bang S Pena ME Patel M Lippincott L Meng X Kim KW 2011 Removal of arsenate from water by adsorbents a comparative case study Environ Geochem Hlth 33 133-141Cui JL Shi JB Jiang GB Jing CY 2013 Arsenic levels and speciation from ingestion exposures to biomarkers in Shanxi China Implications for human health Environ Sci Technol 47 (10) 5419-5424Daus B Wennrich R Weiss H 2004 Sorption materials for arsenic removal from water A comparative study Water Res 38 (12) 2948-2954Dou XM Mohan D Pittman CU 2013 Arsenate adsorption on three types of granular schwertmannite Water Res 47 (9) 2938-2948Dou XM Zhang Y Yang M Pei YS Huang X Takayama T Kato S 2006 Occurrence of arsenic in groundwater in the suburbs of Beijing and its removal using an iron-cerium bimetal oxide adsorbent Water Qual Res J Can 41 (2) 140-146Gibbons MK Gagnon GA 2010 Adsorption of arsenic from a Nova Scotia groundwater onto water treatment residual solids Water Res 44 (19) 5740-5749Glocheux Y Mendez Pasarin M Albadarin AB Allen SJ Walker GM 2013 Removal of arsenic from groundwater by adsorption onto an acidified laterite by-product Chem Eng J 228 565-574Guan XH Wang JM Chusuei CC 2008 Removal of arsenic from water using granular ferric hydroxide Macroscopic and microscopic studies J Hazard Mater 156 (1-3) 178-185Gupta K Maity A Ghosh UC 2010 Manganese associated nanoparticles agglomerate of iron(III) oxide Synthesis characterization and arsenic(III) sorption behavior with mechanism J Hazard Mater 184 (1-3) 832-842Hao JM Han MJ Wang C Meng XG 2009 Enhanced removal of arsenite from water by a mesoporous hybrid material - Thiol-functionalized silica coated activated alumina Micropor Mesopor
Mat 124 (1-3) 1-7Hiemstra T Van Riemsdijk WH 2006 On the relationship between charge distribution surface hydration and the structure of the interface of metal hydroxides J Colloid Interf Sci 301 (1) 1-18Hristovski K Baumgardner A Westerhoff P 2007 Selecting metal oxide nanomaterials for arsenic removal in fixed bed columns From nanopowders to aggregated nanoparticle media J Hazard Mater 147 (1-2) 265-274Jang M Chen WF Cannon FS 2008 Preloading hydrous ferric oxide into granular activated carbon for arsenic removal Environ Sci Technol 42 (9) 3369-3374Jing CY Cui JL Huang YY Li AG 2012 Fabrication characterization and application of a composite adsorbent for simultaneous removal of arsenic and fluoride ACS Appl Mater Interfaces 4 (2) 714-720Kanematsu M Young TM Fukushi K Green PG Darby JL 2010 Extended triple layer modeling of arsenate and phosphate adsorption on a goethite-based granular porous adsorbent Environ Sci Technol 44 (9) 3388-3394Kong S Wang Y Zhan H Yuan S Liu M Zhou C 2013 Arsenite and Arsenate Removal from Contaminated Groundwater by Nanoscale Iron-Manganese Binary Oxides Column Studies Environmental Engineering Science 30 (11) 689-696Li Y Liu JR Jia SY Guo JW Zhuo J Na P 2012 TiO2 pillared montmorillonite as a photoactive adsorbent of arsenic under UV irradiation Chem Eng J 191 66-74Lin TF Wu JK 2001 Adsorption of arsenite and arsenate within activated alumina grains Equilibrium and kinetics Water Res 35 (8) 2049-2057Luo T Cui JL Hu S Huang YY Jing CY 2010 Arsenic removal and recovery from copper smelting wastewater using TiO2 Environ Sci Technol 44 (23) 9094-9098Maiti A Basu JK De S 2010a Development of a Treated Laterite for Arsenic Adsorption Effects of Treatment Parameters Industrial amp Engineering Chemistry Research 49 (10) 4873-4886Maiti A Basu JK De S 2010b Removal of Arsenic from Synthetic and Natural Groundwater Using Acid-Activated Laterite Environmental Progress amp Sustainable Energy 29 (4) 457-470Maiti A Basu JK De S 2012 Experimental and kinetic modeling of As(V) and As(III) adsorption on treated laterite using synthetic and contaminated groundwater Effects of phosphate silicate and carbonate ions Chem Eng J 191 1-12Maiti A Thakur BK Basu JK De S 2013a Comparison of treated laterite as arsenic adsorbent from different locations and performance of best filter under field conditions J Hazard Mater 262 1176-1186Maiti A Thakur BK Basu JK De S 2013b Comparison of treated laterite as arsenic adsorbent from different locations and performance of best filter under field conditions J Hazard Mater 262 (0) 1176-1186Maji SK Pal A Pal T 2008 Arsenic removal from real-life groundwater by adsorption on laterite soil J Hazard Mater 151 (2-3) 811-820Maji SK Kao YH Wang CJ Lu GS Wu JJ Liu CW 2012 Fixed bed adsorption of As(III) on iron-oxide-coated natural rock (IOCNR) and application to real arsenic-bearing groundwater Chem Eng J 203 285-293Mertens J Rose J Kagi R Chaurand P Plotze M Wehrli B Furrer G 2012 Adsorption of arsenic on polyaluminum granulate Environ Sci Technol 46 (13) 7310-7317Nguyen TV Vigneswaran S Ngo HH Pokhre D Viraraghavan T 2006 Iron-coated sponge as
effective media to remove arsenic from drinking water Water Qual Res J Can 41 (2) 164-170Parkhurst DL Appelo CAJ 2013 Description of input and examples for PHREEQC version 3-A computer program for speciation batch-reaction one-dimensional transport and inverse geochemical calculations US Geological SurveyPena M Meng XG Korfiatis GP Jing CY 2006 Adsorption mechanism of arsenic on nanocrystalline titanium dioxide Environ Sci Technol 40 (4) 1257-1262Ravel B Newville M 2005 ATHENA ARTEMIS HEPHAESTUS Data analysis for X-ray absorption spectroscopy using IFEFFIT J Synchrotron Radiat 12 537-541Saha B Bains R Greenwood F 2005 Physicochemical characterization of granular ferric hydroxide (GFH) for arsenic(V) sorption from water Separation Science and Technology 40 (14) 2909-2932Shan H Ma T Wang Y Zhao J Han H Deng Y He X Dong Y 2013 A cost-effective system for in-situ geological arsenic adsorption from groundwater J Contam Hydrol 154 1-9Stachowicz M Hiemstra T van Riemsdijk WH 2008 Multi-competitive interaction of As(III) and As(V) oxyanions with Ca2+ Mg2+ PO4
3- and CO32- ions on goethite J Colloid Interf Sci 320 (2) 400-
414Streat M Hellgardt K Newton NLR 2008 Hydrous ferric oxide as an adsorbent in water treatment - Part 3 Batch and mini-column adsorption of arsenic phosphorus fluorine and cadmium ions Process Safety and Environmental Protection 86 (B1) 21-30Thirunavukkarasu OS Viraraghavan T Subramanian KS 2003 Arsenic removal from drinking water using iron oxide-coated sand Water Air Soil Poll 142 (1-4) 95-111USEPA 2008 Assessing arsenic removal by metal (hydr)oxide adsorptive media using rapid small scale column tests Govenrnment Printing Office Washington DCWang J Xu W Chen L Huang X Liu J 2014 Preparation and evaluation of magnetic nanoparticles impregnated chitosan beads for arsenic removal from water Chem Eng J 251 25-34Westerhoff P Highfield D Badruzzaman M Yoon Y 2005 Rapid small-scale column tests for arsenate removal in iron oxide packed bed columns J Environ Eng-Asce 131 (2) 262-271Westerhoff P De Haan M Martindale A Badruzzaman M 2006 Arsenic adsorptive media technology selection strategies Water Qual Res J Can 41 (2) 171-184Yan L Huang Y Cui J Jing C 2015 Simultaneous As(III) and Cd removal from copper smelting wastewater using granular TiO2 columns Water Res 68 (0) 572-579Zhao K Guo HM 2014 Behavior and mechanism of arsenate adsorption on activated natural siderite Evidences from FTIR and XANES analysis Environ Sci Pollut Res 21 (3) 1944-1953Zhao K Guo H Zhou X 2014 Adsorption and heterogeneous oxidation of arsenite on modified granular natural siderite Characterization and behaviors Appl Geochem 48 184-192
Iron-Mn binary 15 40 145 176 321 22 253 347 754 (Maiti et al 2010a)
13
oxides
aUnit for ion concentration is mgL except as notedbestimated from bed volume breakthrough curves and influent As concentration if not explicitly expressed in the reference cThe species is As(V) if only one concentration is given
d
The groundwater As concentration was 385-440 μgL and additional ~600 μgL (As(III)As(V)=11) arsenic was added
14
222324252627
Fig S1 Boxplot of groundwater As levels in columns and filters in the literature in Table S1 Individual samples are shown as diamonds The range of each box represents the 25th
and 75th
percentile whereas the whiskers represent the 10th
and 90th
percentile
Synthesis of granular TiO2
Granular TiO2 (GTiO2) was prepared by hydrolysis of titanyl sulfate (TiOSO4)
Generally 300 g TiOSO4 was mixed with 1800 mL DI water in a 10 L jar reactor in an
ice bath at 4 oC Then 10 M NaOH was slowly added to adjust the pH to 6 The
precursor of TiO2 was obtained by washing the suspension with DI water several
times till the conductivity of the supernatant was less than 100 μScm Then 800 g
TiO2 precursor was mixed with 40 mL polyvinyl alcohol solution at 80 oC in a water
bath The product was crushed into 60-80 mesh and dried in an oven at 60 oC for 12 h
15
282930313233343536373839404142434445464748
49
50
51
52
53
54
55
56
57585960
Fig S2 Characterization of GTiO2 SEM (a) and XRD pattern with crystal face for each peak (b)
Fig S1 SEM images for GTiO2 in this study
Table S2 Average concentrations of As coexisting ions (mgL) and water chemistry for groundwater 1 and 2 from two wells
Table S3 Water parameters in the synthetic water used in the studyParameters Ca2+ Mg2+ HCO3
- Na+ Cl- pHConc (mgL) 401 1043 388 2460 3928 82
Table S4 PHREEQC input for a representative column with EBCT=054 min SOLUTION 0
This keyword is to define the influent groundwater chemistry parameters which are included in the adsorption reactions like ldquoArseniterdquo and ldquoArsenaterdquo and the experimental conditions including ldquopHrdquo The information defined in SOLUTION is available for subsequent transport and adsorptive reaction calculations
temp 23 pH 82 pe 4 redox pe units mgL density 1 Al 006 Arsenite 0374 Arsenate 0291 CO4
2-
4401 Ca 194 Cl 1456 F 115 Fe 047 K 137 Mg 395 Mn 012 NO3
-
34 Na 16872
17
79
80
8182
83
84858687888990919293949596979899
100101102103104105106107108109110111112
SO42-
1176 Si 89 -water 1 kg
SOLUTION 1-4 The small column was divided into four cells SOLUTION 1-4
are the groundwater chemistry parameters for the four cells temp 23 pH 83 pe 4 redox pe units ppm density 1 Al 006 C(4) 4401 Ca 194 Cl 1456 F 115 Fe 047 K 137 Mg 395 Mn 012 N(3) 34 Na 16872 S(6) 1176 Si 89 -water 1 kg
SOLUTION_SPECIES This keyword is to define the dissociation constant logK
and diffusion constant (dw) in solution for arsenite and arsenate
Arsenite adsorption equation on GTiO2 surface H3ArseniteO3 is the primary species of As(III) at the groundwater pH 82 (Surf_sO)2ArseniteOH-066 is the adsorptive bidentate binuclear structure of As(III) on GTiO2
log_k 1635 The adsorptive reaction constant for As(III) on GTiO2 in
the current condition which could be changed with different experimental conditions
-cd_music -2 -1 0 066 3 CD-MUSIC model is integrated in the PHREEQC
modeling The numbers represent -2 the change in charge at the plane of Surf_sOH due to loss of two hydrogens -1 the change in charge at 1 plane due to gain of one hydrogen and one oxygen on Arsenite 0 the change in charge at the 2 plane usually caused by the outer sphere adsorption 066 the fraction of the central ion (As) charge that is associated with plane 0 which reflecting the charge distribution 3 the charge on the central ion (As)
Table S54 Parameters of Weber-Morris intraparticle model for As(IIIV) adsorption kinetics on GTiO2 using synthetic water Initial As concentration = 800 μgL adsorbent dose = 02 gL pH = 82 in synthetic groundwater
External film diffusion
Intraparticle diffusion
aRex2 bkp1
cb1aRin
2 bkp2cb 2
As(V) 0984 0497 0022 0976 01331878
As(III) 0970 0583
-0088 0981 0218
1105
aRex is WM external proportion fitting parameter while Rin is WM intraparticle proportion fitting parameterbk The unit of kp is mggh05 cb The unit of b is mgg
Table S6 Comparison of the adsorption capacities of As(III) and As(V) on GTiO2 and the representative granular adsorbents in similar experimental condition from the literature
AdsorbentParticle size (mm) As
qm
(mgg)Dose (gL) Experimental conditions Literature
GTiO2 018~025 As(III) 980 1 0~500 mgL at pH 82 01 M NaCl This studyGTiO2 018~025 As(V) 358 1 0~500 mgL at pH 82 01 M NaCl This study
Granular TiO2 015~06 As(III) 392 10~60 mgL As at pH 70 in simulated groundwater (100 mgL Ca 20 mgL Mg 50 mgL Na 200 mgL Cl-
)(Bang et al 2005)
Granular TiO2 015~06 As(V) 400 10~60 mgL As at pH 70 in simulated groundwater (100 mgL Ca 20 mgL Mg 50 mgL Na 200 mgL Cl-
)(Bang et al 2005)
E33 (FeOOH)0044~0075 As(V) 202 1 0~15 mgL at pH 70 in 001 M NaCl
(Kanematsu et al 2010)
E33 (FeOOH) 05~2 As(V) 180 1 0~50 mgL at pH 70 in 004 M NaClO4 (Jing et al 2012)
GFH 02~06 As(V) 650 10 0~2000 mgL at pH 8 in 01 M NaNO3
(Guan et al 2008)
GFH0009~0125 As(V) 23 025 0~07 μgL at pH 65 in DI water
(Banerjee et al 2008)
GFH0009~0125 As(V) 200 - 0~01 μgL at pH 70 in DI water
(Badruzzaman et al 2004)
GFH 050~065 As(V) 155 - 0~06 μgL at pH 70 in DI water (Saha et al 2005)
GHFO-NN 015~030 As(V) 330 0001 0~225 mgL at pH 8 in DI water(Streat et al 2008)
GHFO-VL 015~030 As(V) 360 0001 0~225 mgL at pH 8 in DI water(Streat et al 2008)
25
374375
Spherical schwertmannite 1~15 As(V) 36 05 0~5 mgL at pH 70 in DI water (Dou et al 2013)Cylindrical schwertmannite 1~25 As(V) 223 05
0~5 mgL at pH 70 in DI water(Dou et al 2013)
Irregular schwertmannite 10~16 As(V) 317 05 0~5 mgL at pH 70 in DI water (Dou et al 2013)Fe impregnated chitosan beads (MICB) 25 As(III) 117 1 0~05 mgL at pH 60 in DI water
(Wang et al 2014)
MICB 25 As(V) 191 1 0~1 mgL at pH 60 in DI water(Wang et al 2014)
MICB 25 As(III) 353 1 0~15 mgL at pH 60 in DI water(Wang et al 2014)
MICB 25 As(V) 357 1 0~16 mgL at pH 60 in DI water(Wang et al 2014)
Iron hydroxide granules (GIH) 3~4 As(V) 23 4
5~100 mgL at pH 70 in 10 mgL SO42-
14 mgL NH4Cl buffer solution (Daus et al 2004)
Activated Al2O3
0074~0149 As(V) 159 - 285~115 mgL at pH 52 in DI water
(Lin and Wu 2001)
Activated Al2O3
0074~0149 As(III) 35 - 079~490 mgL at pH 70 in DI water
(Lin and Wu 2001)
Activated Al2O3 ~20 As(V) 73 at pH 70 in 004 M NaClO4 (Jing et al 2012)
Activated natural siderite 05~10 As(V) 22 10 0 1~20 mgL at pH 7 in DI water(Zhao and Guo 2014)
Polyaluminum Granulate 1~3 As(III) 705 10 0~150 mgL at pH 51-56 in DI water(Mertens et al 2012)
Polyaluminum Granulate 1~3 As(V) 180 10 0~150 mgL at pH 51-56 in DI water (Mertens et al
26
2012)
Acidified laterite 1~12 As(III) 19 1 025~5 mgL at pH 7 in 100 mgL NaHCO3
(Glocheux et al 2013)
Acidified laterite 1~12 As(V) 13 1 025~5 mgL at pH 7 in 100 mgL NaHCO3
(Glocheux et al 2013)
Laterite 1~12 As(III) 07 1025~5 mgL at pH 7 in 100 mgL NaHCO3 (Glocheux et al
2013)
Laterite 1~12 As(V) 04 1025~5 mgL at pH 7 in 100 mgL NaHCO3 (Glocheux et al
2013)
Treated laterite 03-05 As(V) 216 05 02-20 mgL at pH 70 in DI water(Maiti et al 2012)
Treated laterite 03-05 As(III) 94 05 02-20 mgL at pH 70 in DI water(Maiti et al 2012)
Treated laterite03-05
As(V) 241 05 02-20 mgL at pH 70 in DI water(Maiti et al 2010a)
Treated laterite03-05
As(III) 81 05 02-20 mgL at pH 70 in DI water(Maiti et al 2010a)
Acid-activated laterite-103-07
As(III) 0633 50 02-10 mgL at pH 66-70 in DI water(Maiti et al 2010b)
Acid-activated laterite-203-07
As(III) 087650 02-10 mgL at pH 66-70 in DI water (Maiti et al
2010b)
Acid-activated laterite-303-07
As(III) 063450 02-10 mgL at pH 66-70 in DI water (Maiti et al
2010b)
Acid-activated laterite-103-07
As(V) 059850 02-10 mgL at pH 66-70 in DI water (Maiti et al
2010b)
27
Acid-activated laterite-203-07
As(V) 07550 02-10 mgL at pH 66-70 in DI water (Maiti et al
2010b)
Acid-activated laterite-303-07
As(V) 07550 02-10 mgL at pH 66-70 in DI water (Maiti et al
2010b)
Treated laterite-1 03-06 As(V) 019 20 0-20 mgL As at pH 72 in DI water(Maiti et al 2013b)
Treated laterite-1 03-06 As(III) 018 20 0-20 mgL As at pH 72 in DI water(Maiti et al 2013b)
Treated laterite-2 03-06 As(V) 004 20 0-20 mgL As at pH 72 in DI water(Maiti et al 2013b)
Treated laterite-2 03-06 As(III) 003 20 0-20 mgL As at pH 72 in DI water(Maiti et al 2013b)
Treated laterite-3 03-06 As(V) 007 20 0-20 mgL As at pH 72 in DI water(Maiti et al 2013b)
Treated laterite-3 03-06 As(III) 004 20 0-20 mgL As at pH 72 in DI water(Maiti et al 2013b)
28
376377
Charge distribution multi-site surface complexation (CD-MUSIC) modeling
The CD-MUSIC model with the 2-pK TPM adsorption option was used to
describe adsorption behaviors of As cations and anions on GTiO2 The CD-MUSIC
model incorporates the structural information of surfaces adsorbed species and the
double layers by distributing the charge of an adsorbate between the surface and
interfacial water (Hiemstra and Van Riemsdijk 2006) The CD-MUSIC model has
been successfully used in describing As adsorption in batch experiments (Pena et al
2006 Stachowicz et al 2008)
The adsorption constants of counter ions were set to -1 and the proton affinity
constant was set to the PZC of 58 for TiOH-13 (Luo et al 2010) The charge
distribution (CD) value shows the fraction (f) of the charge of the central As ion
attributed to the surface plane and the remaining part (1-f) was attributed to the other
ligands of the complex which were positioned toward the diffuse layer The CD value
for As surface complexes was obtained by fitting the experimental data The
calculation was performed using the chemical equilibrium program MINTEQ to
simulate the adsorption and the aqueous reactions
29
378379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
Fig S32 Adsorption of silicate (a) calcium and magnesium (b) as a function of GTiO2
dose in groundwater 1 The solid lines represent the CD-MUSIC modeling result
30
400
401
402
403
404
405
406
407
408409410
Table S75 Surface parameters and species used in the CD-MUSIC modeling in As(IIIV) removal under different GTiO2 dose in 01 M NaCl and groundwater 1 in Fig 2 and Fig S32
= exp(-FΨ1RT) P2 = exp(-FΨ2RT) F the Faraday constant (C mol-1) R the gas constant (J mol-1 K-1) T the absolute temperature (K)
Ψ0 Ψ1 Ψ2 the electrostatic potential (V) of 0- 1- and 2-plane respectively alogK for 01 M NaCl at 6 hours blogK for 01 M NaCl at 6 days clogK for groundwater 1 at 6 days
31
411412
413414415
32
416
Table S86 The charge distribution (f) of central As atom to TiO2 surface in simulating the effect of cations and anions on As adsorption in 01 M NaCl at pH 82 in Fig 4 BK Si HCO3 All
As(V) 022 017 012 016As(III) 040 020 058 056
Fig S43 Molar percentage () of As Ca Mg and Si on pristine and spent GTiO2
surfaces using EDX analysis The spent GTiO2 samples after field column experiments using groundwater 1 were identified with EBCT in min under x-axis The value of molar percentage of each element was averaged from randomly-chosen positions on the adsorbent surface
33
417
418
419420
421422
423
424
425
426
427
428
429
430
431
432
433434435436437438
439
440
441
As speciation analysis on spent GTiO2 using XANES
The spent GTiO2 samples were ground using a mortar and pestle and then the
ground powder was spread on Scotch tape The As k-edge XANES spectra were
collected at beamline 01C1 at the National Synchrotron Radiation Research Center
(NSRRC) Taiwan Spectra were acquired from -150 to 300 eV relative to the As K-
edge of 11867 eV at cryogenic temperature (77 K) using a cryostat to prevent the
oxidation of As(III) by X-rays The fluorescence signals were collected using a Lytle
detector Two to four scans were collected for each sample and averaged to improve
the signalnoise ratio The XANES analysis was performed with the Athena program
in the IFEFFIT computer package for linear combination fit (LCF) (Cui et al 2013
Ravel and Newville 2005)
34
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
PHREEQC modeling for As breakthrough curves in field column experiments
PHREEQC a geochemical model integrates macroscopic mass transfer
processes with a microscopic surface complexation model (Parkhurst and Appelo
2013) It can be applied in calculating solution complex speciation batch-reaction
and one-dimensional reactive-transport and inverse modeling In our study the one-
dimensional column was defined by four cells with the same length The cell length
was calculated to be one-fourth of the actual column length Time step (s) was
calculated according to equation Time step = Lcell(Q60A) where Lcell is the cell
length (cm) Q is flow velocity (mLmin) A is the effective column cross section area
(cm2) which is the column cross-sectional area multiplied by porosity (060) Total
shift number was calculated by dividing actual column operation time by the time
step The transport block was modeled by shifting the solute content from one cell to
the next one In each cell the aqueous solute was mixed and adsorbed on GTiO2
according to the equations In each cell the aqueous solute was mixed and assumed to
be in equilibration with GTiO2 The sequence of shifting mixing and equilibrium
adsorption was repeated for each cell until the total number of shifts was completed
The diffusion coefficient Dw in PHREEQC accounting for retardation was
calculated as Dw=x2
(36t) where x stands for the diffusion length (estimated as the
radius of the particle size) and t represents equilibrium time adopted from the batch
kinetic data (Mertens et al 2012)
For CD-MUSIC modeling in the PHREEQC take As(III) as an example to
explain the adsorption equation The As(III) adsorption is considered as a ligand
35
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
exchange reaction with the hydroxide group on GTiO2 (Surf_sOH-033) forming a
H3ArseniteO3 is the master species in groundwater at pH 82
(Surf_sO)2ArseniteOH-066 is the common adsorbed bidentate binuclear complex
evidenced by our previous reports(Pena et al 2006 Yan et al 2015) LogK is the
adsorption equilibrium constants Generally every adsorption equation under certain
experimental condition has a unique value of logK In the adsorption equation ldquo-2rdquo
represents the lost two hydrogens by Surf_sOH-033 after it adsorbs H3ArseniteO3 ldquo-
1rdquo represents the change in charge on Arsenite at 1 plane due to gaining one hydrogen
(+1) and one oxygen (-2) ldquo0rdquo represents no change in charge at the 2 plane ldquo066rdquo is
the fraction of the central ion (As) on GTiO2 surface that is associated with plane 0
ldquo3rdquo is the charge on the central ion As(III) Following this equation and the relevant
parameters As(III) adsorbed on GTiO2
The diffusion coefficient Dw in PHREEQC accounting for retardation was
calculated as Dw=x2(36t) where x stands for the diffusion length (estimated as the
radius of the particle size) and t represents equilibrium time adopted from the batch
kinetic data (Mertens et al 2012)
To well simulate the As breakthrough curve in columns four As(V) adsorption
reactions (Table 1) were employed Adsorption site density of 60 mmolg was
36
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
adopted from our previous study (Pena et al 2006) and the total adsorption sites were
calculated to be 1844 sitesnm2 The final optimized ratio of strong to weak sites was
51 The surface complexation constants were reasonably adjusted according to the
batch modeling results as the column reaction may not reach equilibrium in local
micro-interfacial areas due to much less contact time between As and GTiO2 than that
in batch experiments (Appelo and Postma 1999) In the modeling a stepwise
procedure was adopted to achieve a viable result An estimation of two thirds of the
surface site density being accessible for EBCT=011 min with large flow rate of 265
mLmin was optimized which could probably result from unavailable adsorption sites
due to fast transport through the column
The adsorbed As on GTiO2 in the column was calculated by mass balance
between the influent and effluent
where Asadsorbed is the adsorbed As on GTiO2 (mgg) n is the number of collected
samples Cin and Cout are influent and effluent As concentrations (mgL) respectively
Vi is volume (L) of groundwater passed through the column between sample i-1 and i
and m is the mass of GTiO2 (g)
Even though the oxidation of adsorbed As(III) occurred during filtration as
analyzed from XANES and mass balance analysis (Fig 7) no As(III) oxidation
reactions were considered in PHREEQC modeling which would not impact the
breakthrough of As(IIIV)
37
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
38
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
Fig S54 Effect of EBCT on Si Ca and Mg breakthrough curves using groundwater 1 The sample notation in panel c indicates field column experiments with EBCT in minutes
References
Appelo CAJ Postma D 1999 A consistent model for surface complexation on birnessite (MnO2) and its application to a column experiment Geochim Cosmochim Ac 63 (19-20) 3039-3048Badruzzaman M Westerhoff P Knappe DRU 2004 Intraparticle diffusion and adsorption of arsenate onto granular ferric hydroxide (GFH) Water Res 38 (18) 4002-4012Banerjee K Amy GL Prevost M Nour S Jekel M Gallagher PM Blumenschein CD 2008 Kinetic and thermodynamic aspects of adsorption of arsenic onto granular ferric hydroxide (GFH) Water Res 42 (13) 3371-3378Bang S Patel M Lippincott L Meng XG 2005 Removal of arsenic from groundwater by granular titanium dioxide adsorbent Chemosphere 60 (3) 389-397Bang S Pena ME Patel M Lippincott L Meng X Kim KW 2011 Removal of arsenate from water by adsorbents a comparative case study Environ Geochem Hlth 33 133-141Cui JL Shi JB Jiang GB Jing CY 2013 Arsenic levels and speciation from ingestion exposures to biomarkers in Shanxi China Implications for human health Environ Sci Technol 47 (10) 5419-5424Daus B Wennrich R Weiss H 2004 Sorption materials for arsenic removal from water A comparative study Water Res 38 (12) 2948-2954Dou XM Mohan D Pittman CU 2013 Arsenate adsorption on three types of granular schwertmannite Water Res 47 (9) 2938-2948Dou XM Zhang Y Yang M Pei YS Huang X Takayama T Kato S 2006 Occurrence of arsenic in groundwater in the suburbs of Beijing and its removal using an iron-cerium bimetal oxide adsorbent Water Qual Res J Can 41 (2) 140-146Gibbons MK Gagnon GA 2010 Adsorption of arsenic from a Nova Scotia groundwater onto water treatment residual solids Water Res 44 (19) 5740-5749Glocheux Y Mendez Pasarin M Albadarin AB Allen SJ Walker GM 2013 Removal of arsenic from groundwater by adsorption onto an acidified laterite by-product Chem Eng J 228 565-574Guan XH Wang JM Chusuei CC 2008 Removal of arsenic from water using granular ferric hydroxide Macroscopic and microscopic studies J Hazard Mater 156 (1-3) 178-185Gupta K Maity A Ghosh UC 2010 Manganese associated nanoparticles agglomerate of iron(III) oxide Synthesis characterization and arsenic(III) sorption behavior with mechanism J Hazard Mater 184 (1-3) 832-842Hao JM Han MJ Wang C Meng XG 2009 Enhanced removal of arsenite from water by a mesoporous hybrid material - Thiol-functionalized silica coated activated alumina Micropor Mesopor
Mat 124 (1-3) 1-7Hiemstra T Van Riemsdijk WH 2006 On the relationship between charge distribution surface hydration and the structure of the interface of metal hydroxides J Colloid Interf Sci 301 (1) 1-18Hristovski K Baumgardner A Westerhoff P 2007 Selecting metal oxide nanomaterials for arsenic removal in fixed bed columns From nanopowders to aggregated nanoparticle media J Hazard Mater 147 (1-2) 265-274Jang M Chen WF Cannon FS 2008 Preloading hydrous ferric oxide into granular activated carbon for arsenic removal Environ Sci Technol 42 (9) 3369-3374Jing CY Cui JL Huang YY Li AG 2012 Fabrication characterization and application of a composite adsorbent for simultaneous removal of arsenic and fluoride ACS Appl Mater Interfaces 4 (2) 714-720Kanematsu M Young TM Fukushi K Green PG Darby JL 2010 Extended triple layer modeling of arsenate and phosphate adsorption on a goethite-based granular porous adsorbent Environ Sci Technol 44 (9) 3388-3394Kong S Wang Y Zhan H Yuan S Liu M Zhou C 2013 Arsenite and Arsenate Removal from Contaminated Groundwater by Nanoscale Iron-Manganese Binary Oxides Column Studies Environmental Engineering Science 30 (11) 689-696Li Y Liu JR Jia SY Guo JW Zhuo J Na P 2012 TiO2 pillared montmorillonite as a photoactive adsorbent of arsenic under UV irradiation Chem Eng J 191 66-74Lin TF Wu JK 2001 Adsorption of arsenite and arsenate within activated alumina grains Equilibrium and kinetics Water Res 35 (8) 2049-2057Luo T Cui JL Hu S Huang YY Jing CY 2010 Arsenic removal and recovery from copper smelting wastewater using TiO2 Environ Sci Technol 44 (23) 9094-9098Maiti A Basu JK De S 2010a Development of a Treated Laterite for Arsenic Adsorption Effects of Treatment Parameters Industrial amp Engineering Chemistry Research 49 (10) 4873-4886Maiti A Basu JK De S 2010b Removal of Arsenic from Synthetic and Natural Groundwater Using Acid-Activated Laterite Environmental Progress amp Sustainable Energy 29 (4) 457-470Maiti A Basu JK De S 2012 Experimental and kinetic modeling of As(V) and As(III) adsorption on treated laterite using synthetic and contaminated groundwater Effects of phosphate silicate and carbonate ions Chem Eng J 191 1-12Maiti A Thakur BK Basu JK De S 2013a Comparison of treated laterite as arsenic adsorbent from different locations and performance of best filter under field conditions J Hazard Mater 262 1176-1186Maiti A Thakur BK Basu JK De S 2013b Comparison of treated laterite as arsenic adsorbent from different locations and performance of best filter under field conditions J Hazard Mater 262 (0) 1176-1186Maji SK Pal A Pal T 2008 Arsenic removal from real-life groundwater by adsorption on laterite soil J Hazard Mater 151 (2-3) 811-820Maji SK Kao YH Wang CJ Lu GS Wu JJ Liu CW 2012 Fixed bed adsorption of As(III) on iron-oxide-coated natural rock (IOCNR) and application to real arsenic-bearing groundwater Chem Eng J 203 285-293Mertens J Rose J Kagi R Chaurand P Plotze M Wehrli B Furrer G 2012 Adsorption of arsenic on polyaluminum granulate Environ Sci Technol 46 (13) 7310-7317Nguyen TV Vigneswaran S Ngo HH Pokhre D Viraraghavan T 2006 Iron-coated sponge as
effective media to remove arsenic from drinking water Water Qual Res J Can 41 (2) 164-170Parkhurst DL Appelo CAJ 2013 Description of input and examples for PHREEQC version 3-A computer program for speciation batch-reaction one-dimensional transport and inverse geochemical calculations US Geological SurveyPena M Meng XG Korfiatis GP Jing CY 2006 Adsorption mechanism of arsenic on nanocrystalline titanium dioxide Environ Sci Technol 40 (4) 1257-1262Ravel B Newville M 2005 ATHENA ARTEMIS HEPHAESTUS Data analysis for X-ray absorption spectroscopy using IFEFFIT J Synchrotron Radiat 12 537-541Saha B Bains R Greenwood F 2005 Physicochemical characterization of granular ferric hydroxide (GFH) for arsenic(V) sorption from water Separation Science and Technology 40 (14) 2909-2932Shan H Ma T Wang Y Zhao J Han H Deng Y He X Dong Y 2013 A cost-effective system for in-situ geological arsenic adsorption from groundwater J Contam Hydrol 154 1-9Stachowicz M Hiemstra T van Riemsdijk WH 2008 Multi-competitive interaction of As(III) and As(V) oxyanions with Ca2+ Mg2+ PO4
3- and CO32- ions on goethite J Colloid Interf Sci 320 (2) 400-
414Streat M Hellgardt K Newton NLR 2008 Hydrous ferric oxide as an adsorbent in water treatment - Part 3 Batch and mini-column adsorption of arsenic phosphorus fluorine and cadmium ions Process Safety and Environmental Protection 86 (B1) 21-30Thirunavukkarasu OS Viraraghavan T Subramanian KS 2003 Arsenic removal from drinking water using iron oxide-coated sand Water Air Soil Poll 142 (1-4) 95-111USEPA 2008 Assessing arsenic removal by metal (hydr)oxide adsorptive media using rapid small scale column tests Govenrnment Printing Office Washington DCWang J Xu W Chen L Huang X Liu J 2014 Preparation and evaluation of magnetic nanoparticles impregnated chitosan beads for arsenic removal from water Chem Eng J 251 25-34Westerhoff P Highfield D Badruzzaman M Yoon Y 2005 Rapid small-scale column tests for arsenate removal in iron oxide packed bed columns J Environ Eng-Asce 131 (2) 262-271Westerhoff P De Haan M Martindale A Badruzzaman M 2006 Arsenic adsorptive media technology selection strategies Water Qual Res J Can 41 (2) 171-184Yan L Huang Y Cui J Jing C 2015 Simultaneous As(III) and Cd removal from copper smelting wastewater using granular TiO2 columns Water Res 68 (0) 572-579Zhao K Guo HM 2014 Behavior and mechanism of arsenate adsorption on activated natural siderite Evidences from FTIR and XANES analysis Environ Sci Pollut Res 21 (3) 1944-1953Zhao K Guo H Zhou X 2014 Adsorption and heterogeneous oxidation of arsenite on modified granular natural siderite Characterization and behaviors Appl Geochem 48 184-192
Iron-Mn binary 15 40 145 176 321 22 253 347 754 (Maiti et al 2010a)
13
oxides
aUnit for ion concentration is mgL except as notedbestimated from bed volume breakthrough curves and influent As concentration if not explicitly expressed in the reference cThe species is As(V) if only one concentration is given
d
The groundwater As concentration was 385-440 μgL and additional ~600 μgL (As(III)As(V)=11) arsenic was added
14
222324252627
Fig S1 Boxplot of groundwater As levels in columns and filters in the literature in Table S1 Individual samples are shown as diamonds The range of each box represents the 25th
and 75th
percentile whereas the whiskers represent the 10th
and 90th
percentile
Synthesis of granular TiO2
Granular TiO2 (GTiO2) was prepared by hydrolysis of titanyl sulfate (TiOSO4)
Generally 300 g TiOSO4 was mixed with 1800 mL DI water in a 10 L jar reactor in an
ice bath at 4 oC Then 10 M NaOH was slowly added to adjust the pH to 6 The
precursor of TiO2 was obtained by washing the suspension with DI water several
times till the conductivity of the supernatant was less than 100 μScm Then 800 g
TiO2 precursor was mixed with 40 mL polyvinyl alcohol solution at 80 oC in a water
bath The product was crushed into 60-80 mesh and dried in an oven at 60 oC for 12 h
15
282930313233343536373839404142434445464748
49
50
51
52
53
54
55
56
57585960
Fig S2 Characterization of GTiO2 SEM (a) and XRD pattern with crystal face for each peak (b)
Fig S1 SEM images for GTiO2 in this study
Table S2 Average concentrations of As coexisting ions (mgL) and water chemistry for groundwater 1 and 2 from two wells
Table S3 Water parameters in the synthetic water used in the studyParameters Ca2+ Mg2+ HCO3
- Na+ Cl- pHConc (mgL) 401 1043 388 2460 3928 82
Table S4 PHREEQC input for a representative column with EBCT=054 min SOLUTION 0
This keyword is to define the influent groundwater chemistry parameters which are included in the adsorption reactions like ldquoArseniterdquo and ldquoArsenaterdquo and the experimental conditions including ldquopHrdquo The information defined in SOLUTION is available for subsequent transport and adsorptive reaction calculations
temp 23 pH 82 pe 4 redox pe units mgL density 1 Al 006 Arsenite 0374 Arsenate 0291 CO4
2-
4401 Ca 194 Cl 1456 F 115 Fe 047 K 137 Mg 395 Mn 012 NO3
-
34 Na 16872
17
79
80
8182
83
84858687888990919293949596979899
100101102103104105106107108109110111112
SO42-
1176 Si 89 -water 1 kg
SOLUTION 1-4 The small column was divided into four cells SOLUTION 1-4
are the groundwater chemistry parameters for the four cells temp 23 pH 83 pe 4 redox pe units ppm density 1 Al 006 C(4) 4401 Ca 194 Cl 1456 F 115 Fe 047 K 137 Mg 395 Mn 012 N(3) 34 Na 16872 S(6) 1176 Si 89 -water 1 kg
SOLUTION_SPECIES This keyword is to define the dissociation constant logK
and diffusion constant (dw) in solution for arsenite and arsenate
Arsenite adsorption equation on GTiO2 surface H3ArseniteO3 is the primary species of As(III) at the groundwater pH 82 (Surf_sO)2ArseniteOH-066 is the adsorptive bidentate binuclear structure of As(III) on GTiO2
log_k 1635 The adsorptive reaction constant for As(III) on GTiO2 in
the current condition which could be changed with different experimental conditions
-cd_music -2 -1 0 066 3 CD-MUSIC model is integrated in the PHREEQC
modeling The numbers represent -2 the change in charge at the plane of Surf_sOH due to loss of two hydrogens -1 the change in charge at 1 plane due to gain of one hydrogen and one oxygen on Arsenite 0 the change in charge at the 2 plane usually caused by the outer sphere adsorption 066 the fraction of the central ion (As) charge that is associated with plane 0 which reflecting the charge distribution 3 the charge on the central ion (As)
Table S54 Parameters of Weber-Morris intraparticle model for As(IIIV) adsorption kinetics on GTiO2 using synthetic water Initial As concentration = 800 μgL adsorbent dose = 02 gL pH = 82 in synthetic groundwater
External film diffusion
Intraparticle diffusion
aRex2 bkp1
cb1aRin
2 bkp2cb 2
As(V) 0984 0497 0022 0976 01331878
As(III) 0970 0583
-0088 0981 0218
1105
aRex is WM external proportion fitting parameter while Rin is WM intraparticle proportion fitting parameterbk The unit of kp is mggh05 cb The unit of b is mgg
Table S6 Comparison of the adsorption capacities of As(III) and As(V) on GTiO2 and the representative granular adsorbents in similar experimental condition from the literature
AdsorbentParticle size (mm) As
qm
(mgg)Dose (gL) Experimental conditions Literature
GTiO2 018~025 As(III) 980 1 0~500 mgL at pH 82 01 M NaCl This studyGTiO2 018~025 As(V) 358 1 0~500 mgL at pH 82 01 M NaCl This study
Granular TiO2 015~06 As(III) 392 10~60 mgL As at pH 70 in simulated groundwater (100 mgL Ca 20 mgL Mg 50 mgL Na 200 mgL Cl-
)(Bang et al 2005)
Granular TiO2 015~06 As(V) 400 10~60 mgL As at pH 70 in simulated groundwater (100 mgL Ca 20 mgL Mg 50 mgL Na 200 mgL Cl-
)(Bang et al 2005)
E33 (FeOOH)0044~0075 As(V) 202 1 0~15 mgL at pH 70 in 001 M NaCl
(Kanematsu et al 2010)
E33 (FeOOH) 05~2 As(V) 180 1 0~50 mgL at pH 70 in 004 M NaClO4 (Jing et al 2012)
GFH 02~06 As(V) 650 10 0~2000 mgL at pH 8 in 01 M NaNO3
(Guan et al 2008)
GFH0009~0125 As(V) 23 025 0~07 μgL at pH 65 in DI water
(Banerjee et al 2008)
GFH0009~0125 As(V) 200 - 0~01 μgL at pH 70 in DI water
(Badruzzaman et al 2004)
GFH 050~065 As(V) 155 - 0~06 μgL at pH 70 in DI water (Saha et al 2005)
GHFO-NN 015~030 As(V) 330 0001 0~225 mgL at pH 8 in DI water(Streat et al 2008)
GHFO-VL 015~030 As(V) 360 0001 0~225 mgL at pH 8 in DI water(Streat et al 2008)
25
374375
Spherical schwertmannite 1~15 As(V) 36 05 0~5 mgL at pH 70 in DI water (Dou et al 2013)Cylindrical schwertmannite 1~25 As(V) 223 05
0~5 mgL at pH 70 in DI water(Dou et al 2013)
Irregular schwertmannite 10~16 As(V) 317 05 0~5 mgL at pH 70 in DI water (Dou et al 2013)Fe impregnated chitosan beads (MICB) 25 As(III) 117 1 0~05 mgL at pH 60 in DI water
(Wang et al 2014)
MICB 25 As(V) 191 1 0~1 mgL at pH 60 in DI water(Wang et al 2014)
MICB 25 As(III) 353 1 0~15 mgL at pH 60 in DI water(Wang et al 2014)
MICB 25 As(V) 357 1 0~16 mgL at pH 60 in DI water(Wang et al 2014)
Iron hydroxide granules (GIH) 3~4 As(V) 23 4
5~100 mgL at pH 70 in 10 mgL SO42-
14 mgL NH4Cl buffer solution (Daus et al 2004)
Activated Al2O3
0074~0149 As(V) 159 - 285~115 mgL at pH 52 in DI water
(Lin and Wu 2001)
Activated Al2O3
0074~0149 As(III) 35 - 079~490 mgL at pH 70 in DI water
(Lin and Wu 2001)
Activated Al2O3 ~20 As(V) 73 at pH 70 in 004 M NaClO4 (Jing et al 2012)
Activated natural siderite 05~10 As(V) 22 10 0 1~20 mgL at pH 7 in DI water(Zhao and Guo 2014)
Polyaluminum Granulate 1~3 As(III) 705 10 0~150 mgL at pH 51-56 in DI water(Mertens et al 2012)
Polyaluminum Granulate 1~3 As(V) 180 10 0~150 mgL at pH 51-56 in DI water (Mertens et al
26
2012)
Acidified laterite 1~12 As(III) 19 1 025~5 mgL at pH 7 in 100 mgL NaHCO3
(Glocheux et al 2013)
Acidified laterite 1~12 As(V) 13 1 025~5 mgL at pH 7 in 100 mgL NaHCO3
(Glocheux et al 2013)
Laterite 1~12 As(III) 07 1025~5 mgL at pH 7 in 100 mgL NaHCO3 (Glocheux et al
2013)
Laterite 1~12 As(V) 04 1025~5 mgL at pH 7 in 100 mgL NaHCO3 (Glocheux et al
2013)
Treated laterite 03-05 As(V) 216 05 02-20 mgL at pH 70 in DI water(Maiti et al 2012)
Treated laterite 03-05 As(III) 94 05 02-20 mgL at pH 70 in DI water(Maiti et al 2012)
Treated laterite03-05
As(V) 241 05 02-20 mgL at pH 70 in DI water(Maiti et al 2010a)
Treated laterite03-05
As(III) 81 05 02-20 mgL at pH 70 in DI water(Maiti et al 2010a)
Acid-activated laterite-103-07
As(III) 0633 50 02-10 mgL at pH 66-70 in DI water(Maiti et al 2010b)
Acid-activated laterite-203-07
As(III) 087650 02-10 mgL at pH 66-70 in DI water (Maiti et al
2010b)
Acid-activated laterite-303-07
As(III) 063450 02-10 mgL at pH 66-70 in DI water (Maiti et al
2010b)
Acid-activated laterite-103-07
As(V) 059850 02-10 mgL at pH 66-70 in DI water (Maiti et al
2010b)
27
Acid-activated laterite-203-07
As(V) 07550 02-10 mgL at pH 66-70 in DI water (Maiti et al
2010b)
Acid-activated laterite-303-07
As(V) 07550 02-10 mgL at pH 66-70 in DI water (Maiti et al
2010b)
Treated laterite-1 03-06 As(V) 019 20 0-20 mgL As at pH 72 in DI water(Maiti et al 2013b)
Treated laterite-1 03-06 As(III) 018 20 0-20 mgL As at pH 72 in DI water(Maiti et al 2013b)
Treated laterite-2 03-06 As(V) 004 20 0-20 mgL As at pH 72 in DI water(Maiti et al 2013b)
Treated laterite-2 03-06 As(III) 003 20 0-20 mgL As at pH 72 in DI water(Maiti et al 2013b)
Treated laterite-3 03-06 As(V) 007 20 0-20 mgL As at pH 72 in DI water(Maiti et al 2013b)
Treated laterite-3 03-06 As(III) 004 20 0-20 mgL As at pH 72 in DI water(Maiti et al 2013b)
28
376377
Charge distribution multi-site surface complexation (CD-MUSIC) modeling
The CD-MUSIC model with the 2-pK TPM adsorption option was used to
describe adsorption behaviors of As cations and anions on GTiO2 The CD-MUSIC
model incorporates the structural information of surfaces adsorbed species and the
double layers by distributing the charge of an adsorbate between the surface and
interfacial water (Hiemstra and Van Riemsdijk 2006) The CD-MUSIC model has
been successfully used in describing As adsorption in batch experiments (Pena et al
2006 Stachowicz et al 2008)
The adsorption constants of counter ions were set to -1 and the proton affinity
constant was set to the PZC of 58 for TiOH-13 (Luo et al 2010) The charge
distribution (CD) value shows the fraction (f) of the charge of the central As ion
attributed to the surface plane and the remaining part (1-f) was attributed to the other
ligands of the complex which were positioned toward the diffuse layer The CD value
for As surface complexes was obtained by fitting the experimental data The
calculation was performed using the chemical equilibrium program MINTEQ to
simulate the adsorption and the aqueous reactions
29
378379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
Fig S32 Adsorption of silicate (a) calcium and magnesium (b) as a function of GTiO2
dose in groundwater 1 The solid lines represent the CD-MUSIC modeling result
30
400
401
402
403
404
405
406
407
408409410
Table S75 Surface parameters and species used in the CD-MUSIC modeling in As(IIIV) removal under different GTiO2 dose in 01 M NaCl and groundwater 1 in Fig 2 and Fig S32
= exp(-FΨ1RT) P2 = exp(-FΨ2RT) F the Faraday constant (C mol-1) R the gas constant (J mol-1 K-1) T the absolute temperature (K)
Ψ0 Ψ1 Ψ2 the electrostatic potential (V) of 0- 1- and 2-plane respectively alogK for 01 M NaCl at 6 hours blogK for 01 M NaCl at 6 days clogK for groundwater 1 at 6 days
31
411412
413414415
32
416
Table S86 The charge distribution (f) of central As atom to TiO2 surface in simulating the effect of cations and anions on As adsorption in 01 M NaCl at pH 82 in Fig 4 BK Si HCO3 All
As(V) 022 017 012 016As(III) 040 020 058 056
Fig S43 Molar percentage () of As Ca Mg and Si on pristine and spent GTiO2
surfaces using EDX analysis The spent GTiO2 samples after field column experiments using groundwater 1 were identified with EBCT in min under x-axis The value of molar percentage of each element was averaged from randomly-chosen positions on the adsorbent surface
33
417
418
419420
421422
423
424
425
426
427
428
429
430
431
432
433434435436437438
439
440
441
As speciation analysis on spent GTiO2 using XANES
The spent GTiO2 samples were ground using a mortar and pestle and then the
ground powder was spread on Scotch tape The As k-edge XANES spectra were
collected at beamline 01C1 at the National Synchrotron Radiation Research Center
(NSRRC) Taiwan Spectra were acquired from -150 to 300 eV relative to the As K-
edge of 11867 eV at cryogenic temperature (77 K) using a cryostat to prevent the
oxidation of As(III) by X-rays The fluorescence signals were collected using a Lytle
detector Two to four scans were collected for each sample and averaged to improve
the signalnoise ratio The XANES analysis was performed with the Athena program
in the IFEFFIT computer package for linear combination fit (LCF) (Cui et al 2013
Ravel and Newville 2005)
34
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
PHREEQC modeling for As breakthrough curves in field column experiments
PHREEQC a geochemical model integrates macroscopic mass transfer
processes with a microscopic surface complexation model (Parkhurst and Appelo
2013) It can be applied in calculating solution complex speciation batch-reaction
and one-dimensional reactive-transport and inverse modeling In our study the one-
dimensional column was defined by four cells with the same length The cell length
was calculated to be one-fourth of the actual column length Time step (s) was
calculated according to equation Time step = Lcell(Q60A) where Lcell is the cell
length (cm) Q is flow velocity (mLmin) A is the effective column cross section area
(cm2) which is the column cross-sectional area multiplied by porosity (060) Total
shift number was calculated by dividing actual column operation time by the time
step The transport block was modeled by shifting the solute content from one cell to
the next one In each cell the aqueous solute was mixed and adsorbed on GTiO2
according to the equations In each cell the aqueous solute was mixed and assumed to
be in equilibration with GTiO2 The sequence of shifting mixing and equilibrium
adsorption was repeated for each cell until the total number of shifts was completed
The diffusion coefficient Dw in PHREEQC accounting for retardation was
calculated as Dw=x2
(36t) where x stands for the diffusion length (estimated as the
radius of the particle size) and t represents equilibrium time adopted from the batch
kinetic data (Mertens et al 2012)
For CD-MUSIC modeling in the PHREEQC take As(III) as an example to
explain the adsorption equation The As(III) adsorption is considered as a ligand
35
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
exchange reaction with the hydroxide group on GTiO2 (Surf_sOH-033) forming a
H3ArseniteO3 is the master species in groundwater at pH 82
(Surf_sO)2ArseniteOH-066 is the common adsorbed bidentate binuclear complex
evidenced by our previous reports(Pena et al 2006 Yan et al 2015) LogK is the
adsorption equilibrium constants Generally every adsorption equation under certain
experimental condition has a unique value of logK In the adsorption equation ldquo-2rdquo
represents the lost two hydrogens by Surf_sOH-033 after it adsorbs H3ArseniteO3 ldquo-
1rdquo represents the change in charge on Arsenite at 1 plane due to gaining one hydrogen
(+1) and one oxygen (-2) ldquo0rdquo represents no change in charge at the 2 plane ldquo066rdquo is
the fraction of the central ion (As) on GTiO2 surface that is associated with plane 0
ldquo3rdquo is the charge on the central ion As(III) Following this equation and the relevant
parameters As(III) adsorbed on GTiO2
The diffusion coefficient Dw in PHREEQC accounting for retardation was
calculated as Dw=x2(36t) where x stands for the diffusion length (estimated as the
radius of the particle size) and t represents equilibrium time adopted from the batch
kinetic data (Mertens et al 2012)
To well simulate the As breakthrough curve in columns four As(V) adsorption
reactions (Table 1) were employed Adsorption site density of 60 mmolg was
36
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
adopted from our previous study (Pena et al 2006) and the total adsorption sites were
calculated to be 1844 sitesnm2 The final optimized ratio of strong to weak sites was
51 The surface complexation constants were reasonably adjusted according to the
batch modeling results as the column reaction may not reach equilibrium in local
micro-interfacial areas due to much less contact time between As and GTiO2 than that
in batch experiments (Appelo and Postma 1999) In the modeling a stepwise
procedure was adopted to achieve a viable result An estimation of two thirds of the
surface site density being accessible for EBCT=011 min with large flow rate of 265
mLmin was optimized which could probably result from unavailable adsorption sites
due to fast transport through the column
The adsorbed As on GTiO2 in the column was calculated by mass balance
between the influent and effluent
where Asadsorbed is the adsorbed As on GTiO2 (mgg) n is the number of collected
samples Cin and Cout are influent and effluent As concentrations (mgL) respectively
Vi is volume (L) of groundwater passed through the column between sample i-1 and i
and m is the mass of GTiO2 (g)
Even though the oxidation of adsorbed As(III) occurred during filtration as
analyzed from XANES and mass balance analysis (Fig 7) no As(III) oxidation
reactions were considered in PHREEQC modeling which would not impact the
breakthrough of As(IIIV)
37
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
38
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
Fig S54 Effect of EBCT on Si Ca and Mg breakthrough curves using groundwater 1 The sample notation in panel c indicates field column experiments with EBCT in minutes
References
Appelo CAJ Postma D 1999 A consistent model for surface complexation on birnessite (MnO2) and its application to a column experiment Geochim Cosmochim Ac 63 (19-20) 3039-3048Badruzzaman M Westerhoff P Knappe DRU 2004 Intraparticle diffusion and adsorption of arsenate onto granular ferric hydroxide (GFH) Water Res 38 (18) 4002-4012Banerjee K Amy GL Prevost M Nour S Jekel M Gallagher PM Blumenschein CD 2008 Kinetic and thermodynamic aspects of adsorption of arsenic onto granular ferric hydroxide (GFH) Water Res 42 (13) 3371-3378Bang S Patel M Lippincott L Meng XG 2005 Removal of arsenic from groundwater by granular titanium dioxide adsorbent Chemosphere 60 (3) 389-397Bang S Pena ME Patel M Lippincott L Meng X Kim KW 2011 Removal of arsenate from water by adsorbents a comparative case study Environ Geochem Hlth 33 133-141Cui JL Shi JB Jiang GB Jing CY 2013 Arsenic levels and speciation from ingestion exposures to biomarkers in Shanxi China Implications for human health Environ Sci Technol 47 (10) 5419-5424Daus B Wennrich R Weiss H 2004 Sorption materials for arsenic removal from water A comparative study Water Res 38 (12) 2948-2954Dou XM Mohan D Pittman CU 2013 Arsenate adsorption on three types of granular schwertmannite Water Res 47 (9) 2938-2948Dou XM Zhang Y Yang M Pei YS Huang X Takayama T Kato S 2006 Occurrence of arsenic in groundwater in the suburbs of Beijing and its removal using an iron-cerium bimetal oxide adsorbent Water Qual Res J Can 41 (2) 140-146Gibbons MK Gagnon GA 2010 Adsorption of arsenic from a Nova Scotia groundwater onto water treatment residual solids Water Res 44 (19) 5740-5749Glocheux Y Mendez Pasarin M Albadarin AB Allen SJ Walker GM 2013 Removal of arsenic from groundwater by adsorption onto an acidified laterite by-product Chem Eng J 228 565-574Guan XH Wang JM Chusuei CC 2008 Removal of arsenic from water using granular ferric hydroxide Macroscopic and microscopic studies J Hazard Mater 156 (1-3) 178-185Gupta K Maity A Ghosh UC 2010 Manganese associated nanoparticles agglomerate of iron(III) oxide Synthesis characterization and arsenic(III) sorption behavior with mechanism J Hazard Mater 184 (1-3) 832-842Hao JM Han MJ Wang C Meng XG 2009 Enhanced removal of arsenite from water by a mesoporous hybrid material - Thiol-functionalized silica coated activated alumina Micropor Mesopor
Mat 124 (1-3) 1-7Hiemstra T Van Riemsdijk WH 2006 On the relationship between charge distribution surface hydration and the structure of the interface of metal hydroxides J Colloid Interf Sci 301 (1) 1-18Hristovski K Baumgardner A Westerhoff P 2007 Selecting metal oxide nanomaterials for arsenic removal in fixed bed columns From nanopowders to aggregated nanoparticle media J Hazard Mater 147 (1-2) 265-274Jang M Chen WF Cannon FS 2008 Preloading hydrous ferric oxide into granular activated carbon for arsenic removal Environ Sci Technol 42 (9) 3369-3374Jing CY Cui JL Huang YY Li AG 2012 Fabrication characterization and application of a composite adsorbent for simultaneous removal of arsenic and fluoride ACS Appl Mater Interfaces 4 (2) 714-720Kanematsu M Young TM Fukushi K Green PG Darby JL 2010 Extended triple layer modeling of arsenate and phosphate adsorption on a goethite-based granular porous adsorbent Environ Sci Technol 44 (9) 3388-3394Kong S Wang Y Zhan H Yuan S Liu M Zhou C 2013 Arsenite and Arsenate Removal from Contaminated Groundwater by Nanoscale Iron-Manganese Binary Oxides Column Studies Environmental Engineering Science 30 (11) 689-696Li Y Liu JR Jia SY Guo JW Zhuo J Na P 2012 TiO2 pillared montmorillonite as a photoactive adsorbent of arsenic under UV irradiation Chem Eng J 191 66-74Lin TF Wu JK 2001 Adsorption of arsenite and arsenate within activated alumina grains Equilibrium and kinetics Water Res 35 (8) 2049-2057Luo T Cui JL Hu S Huang YY Jing CY 2010 Arsenic removal and recovery from copper smelting wastewater using TiO2 Environ Sci Technol 44 (23) 9094-9098Maiti A Basu JK De S 2010a Development of a Treated Laterite for Arsenic Adsorption Effects of Treatment Parameters Industrial amp Engineering Chemistry Research 49 (10) 4873-4886Maiti A Basu JK De S 2010b Removal of Arsenic from Synthetic and Natural Groundwater Using Acid-Activated Laterite Environmental Progress amp Sustainable Energy 29 (4) 457-470Maiti A Basu JK De S 2012 Experimental and kinetic modeling of As(V) and As(III) adsorption on treated laterite using synthetic and contaminated groundwater Effects of phosphate silicate and carbonate ions Chem Eng J 191 1-12Maiti A Thakur BK Basu JK De S 2013a Comparison of treated laterite as arsenic adsorbent from different locations and performance of best filter under field conditions J Hazard Mater 262 1176-1186Maiti A Thakur BK Basu JK De S 2013b Comparison of treated laterite as arsenic adsorbent from different locations and performance of best filter under field conditions J Hazard Mater 262 (0) 1176-1186Maji SK Pal A Pal T 2008 Arsenic removal from real-life groundwater by adsorption on laterite soil J Hazard Mater 151 (2-3) 811-820Maji SK Kao YH Wang CJ Lu GS Wu JJ Liu CW 2012 Fixed bed adsorption of As(III) on iron-oxide-coated natural rock (IOCNR) and application to real arsenic-bearing groundwater Chem Eng J 203 285-293Mertens J Rose J Kagi R Chaurand P Plotze M Wehrli B Furrer G 2012 Adsorption of arsenic on polyaluminum granulate Environ Sci Technol 46 (13) 7310-7317Nguyen TV Vigneswaran S Ngo HH Pokhre D Viraraghavan T 2006 Iron-coated sponge as
effective media to remove arsenic from drinking water Water Qual Res J Can 41 (2) 164-170Parkhurst DL Appelo CAJ 2013 Description of input and examples for PHREEQC version 3-A computer program for speciation batch-reaction one-dimensional transport and inverse geochemical calculations US Geological SurveyPena M Meng XG Korfiatis GP Jing CY 2006 Adsorption mechanism of arsenic on nanocrystalline titanium dioxide Environ Sci Technol 40 (4) 1257-1262Ravel B Newville M 2005 ATHENA ARTEMIS HEPHAESTUS Data analysis for X-ray absorption spectroscopy using IFEFFIT J Synchrotron Radiat 12 537-541Saha B Bains R Greenwood F 2005 Physicochemical characterization of granular ferric hydroxide (GFH) for arsenic(V) sorption from water Separation Science and Technology 40 (14) 2909-2932Shan H Ma T Wang Y Zhao J Han H Deng Y He X Dong Y 2013 A cost-effective system for in-situ geological arsenic adsorption from groundwater J Contam Hydrol 154 1-9Stachowicz M Hiemstra T van Riemsdijk WH 2008 Multi-competitive interaction of As(III) and As(V) oxyanions with Ca2+ Mg2+ PO4
3- and CO32- ions on goethite J Colloid Interf Sci 320 (2) 400-
414Streat M Hellgardt K Newton NLR 2008 Hydrous ferric oxide as an adsorbent in water treatment - Part 3 Batch and mini-column adsorption of arsenic phosphorus fluorine and cadmium ions Process Safety and Environmental Protection 86 (B1) 21-30Thirunavukkarasu OS Viraraghavan T Subramanian KS 2003 Arsenic removal from drinking water using iron oxide-coated sand Water Air Soil Poll 142 (1-4) 95-111USEPA 2008 Assessing arsenic removal by metal (hydr)oxide adsorptive media using rapid small scale column tests Govenrnment Printing Office Washington DCWang J Xu W Chen L Huang X Liu J 2014 Preparation and evaluation of magnetic nanoparticles impregnated chitosan beads for arsenic removal from water Chem Eng J 251 25-34Westerhoff P Highfield D Badruzzaman M Yoon Y 2005 Rapid small-scale column tests for arsenate removal in iron oxide packed bed columns J Environ Eng-Asce 131 (2) 262-271Westerhoff P De Haan M Martindale A Badruzzaman M 2006 Arsenic adsorptive media technology selection strategies Water Qual Res J Can 41 (2) 171-184Yan L Huang Y Cui J Jing C 2015 Simultaneous As(III) and Cd removal from copper smelting wastewater using granular TiO2 columns Water Res 68 (0) 572-579Zhao K Guo HM 2014 Behavior and mechanism of arsenate adsorption on activated natural siderite Evidences from FTIR and XANES analysis Environ Sci Pollut Res 21 (3) 1944-1953Zhao K Guo H Zhou X 2014 Adsorption and heterogeneous oxidation of arsenite on modified granular natural siderite Characterization and behaviors Appl Geochem 48 184-192
Iron-Mn binary 15 40 145 176 321 22 253 347 754 (Maiti et al 2010a)
13
oxides
aUnit for ion concentration is mgL except as notedbestimated from bed volume breakthrough curves and influent As concentration if not explicitly expressed in the reference cThe species is As(V) if only one concentration is given
d
The groundwater As concentration was 385-440 μgL and additional ~600 μgL (As(III)As(V)=11) arsenic was added
14
222324252627
Fig S1 Boxplot of groundwater As levels in columns and filters in the literature in Table S1 Individual samples are shown as diamonds The range of each box represents the 25th
and 75th
percentile whereas the whiskers represent the 10th
and 90th
percentile
Synthesis of granular TiO2
Granular TiO2 (GTiO2) was prepared by hydrolysis of titanyl sulfate (TiOSO4)
Generally 300 g TiOSO4 was mixed with 1800 mL DI water in a 10 L jar reactor in an
ice bath at 4 oC Then 10 M NaOH was slowly added to adjust the pH to 6 The
precursor of TiO2 was obtained by washing the suspension with DI water several
times till the conductivity of the supernatant was less than 100 μScm Then 800 g
TiO2 precursor was mixed with 40 mL polyvinyl alcohol solution at 80 oC in a water
bath The product was crushed into 60-80 mesh and dried in an oven at 60 oC for 12 h
15
282930313233343536373839404142434445464748
49
50
51
52
53
54
55
56
57585960
Fig S2 Characterization of GTiO2 SEM (a) and XRD pattern with crystal face for each peak (b)
Fig S1 SEM images for GTiO2 in this study
Table S2 Average concentrations of As coexisting ions (mgL) and water chemistry for groundwater 1 and 2 from two wells
Table S3 Water parameters in the synthetic water used in the studyParameters Ca2+ Mg2+ HCO3
- Na+ Cl- pHConc (mgL) 401 1043 388 2460 3928 82
Table S4 PHREEQC input for a representative column with EBCT=054 min SOLUTION 0
This keyword is to define the influent groundwater chemistry parameters which are included in the adsorption reactions like ldquoArseniterdquo and ldquoArsenaterdquo and the experimental conditions including ldquopHrdquo The information defined in SOLUTION is available for subsequent transport and adsorptive reaction calculations
temp 23 pH 82 pe 4 redox pe units mgL density 1 Al 006 Arsenite 0374 Arsenate 0291 CO4
2-
4401 Ca 194 Cl 1456 F 115 Fe 047 K 137 Mg 395 Mn 012 NO3
-
34 Na 16872
17
79
80
8182
83
84858687888990919293949596979899
100101102103104105106107108109110111112
SO42-
1176 Si 89 -water 1 kg
SOLUTION 1-4 The small column was divided into four cells SOLUTION 1-4
are the groundwater chemistry parameters for the four cells temp 23 pH 83 pe 4 redox pe units ppm density 1 Al 006 C(4) 4401 Ca 194 Cl 1456 F 115 Fe 047 K 137 Mg 395 Mn 012 N(3) 34 Na 16872 S(6) 1176 Si 89 -water 1 kg
SOLUTION_SPECIES This keyword is to define the dissociation constant logK
and diffusion constant (dw) in solution for arsenite and arsenate
Arsenite adsorption equation on GTiO2 surface H3ArseniteO3 is the primary species of As(III) at the groundwater pH 82 (Surf_sO)2ArseniteOH-066 is the adsorptive bidentate binuclear structure of As(III) on GTiO2
log_k 1635 The adsorptive reaction constant for As(III) on GTiO2 in
the current condition which could be changed with different experimental conditions
-cd_music -2 -1 0 066 3 CD-MUSIC model is integrated in the PHREEQC
modeling The numbers represent -2 the change in charge at the plane of Surf_sOH due to loss of two hydrogens -1 the change in charge at 1 plane due to gain of one hydrogen and one oxygen on Arsenite 0 the change in charge at the 2 plane usually caused by the outer sphere adsorption 066 the fraction of the central ion (As) charge that is associated with plane 0 which reflecting the charge distribution 3 the charge on the central ion (As)
Table S54 Parameters of Weber-Morris intraparticle model for As(IIIV) adsorption kinetics on GTiO2 using synthetic water Initial As concentration = 800 μgL adsorbent dose = 02 gL pH = 82 in synthetic groundwater
External film diffusion
Intraparticle diffusion
aRex2 bkp1
cb1aRin
2 bkp2cb 2
As(V) 0984 0497 0022 0976 01331878
As(III) 0970 0583
-0088 0981 0218
1105
aRex is WM external proportion fitting parameter while Rin is WM intraparticle proportion fitting parameterbk The unit of kp is mggh05 cb The unit of b is mgg
Table S6 Comparison of the adsorption capacities of As(III) and As(V) on GTiO2 and the representative granular adsorbents in similar experimental condition from the literature
AdsorbentParticle size (mm) As
qm
(mgg)Dose (gL) Experimental conditions Literature
GTiO2 018~025 As(III) 980 1 0~500 mgL at pH 82 01 M NaCl This studyGTiO2 018~025 As(V) 358 1 0~500 mgL at pH 82 01 M NaCl This study
Granular TiO2 015~06 As(III) 392 10~60 mgL As at pH 70 in simulated groundwater (100 mgL Ca 20 mgL Mg 50 mgL Na 200 mgL Cl-
)(Bang et al 2005)
Granular TiO2 015~06 As(V) 400 10~60 mgL As at pH 70 in simulated groundwater (100 mgL Ca 20 mgL Mg 50 mgL Na 200 mgL Cl-
)(Bang et al 2005)
E33 (FeOOH)0044~0075 As(V) 202 1 0~15 mgL at pH 70 in 001 M NaCl
(Kanematsu et al 2010)
E33 (FeOOH) 05~2 As(V) 180 1 0~50 mgL at pH 70 in 004 M NaClO4 (Jing et al 2012)
GFH 02~06 As(V) 650 10 0~2000 mgL at pH 8 in 01 M NaNO3
(Guan et al 2008)
GFH0009~0125 As(V) 23 025 0~07 μgL at pH 65 in DI water
(Banerjee et al 2008)
GFH0009~0125 As(V) 200 - 0~01 μgL at pH 70 in DI water
(Badruzzaman et al 2004)
GFH 050~065 As(V) 155 - 0~06 μgL at pH 70 in DI water (Saha et al 2005)
GHFO-NN 015~030 As(V) 330 0001 0~225 mgL at pH 8 in DI water(Streat et al 2008)
GHFO-VL 015~030 As(V) 360 0001 0~225 mgL at pH 8 in DI water(Streat et al 2008)
25
374375
Spherical schwertmannite 1~15 As(V) 36 05 0~5 mgL at pH 70 in DI water (Dou et al 2013)Cylindrical schwertmannite 1~25 As(V) 223 05
0~5 mgL at pH 70 in DI water(Dou et al 2013)
Irregular schwertmannite 10~16 As(V) 317 05 0~5 mgL at pH 70 in DI water (Dou et al 2013)Fe impregnated chitosan beads (MICB) 25 As(III) 117 1 0~05 mgL at pH 60 in DI water
(Wang et al 2014)
MICB 25 As(V) 191 1 0~1 mgL at pH 60 in DI water(Wang et al 2014)
MICB 25 As(III) 353 1 0~15 mgL at pH 60 in DI water(Wang et al 2014)
MICB 25 As(V) 357 1 0~16 mgL at pH 60 in DI water(Wang et al 2014)
Iron hydroxide granules (GIH) 3~4 As(V) 23 4
5~100 mgL at pH 70 in 10 mgL SO42-
14 mgL NH4Cl buffer solution (Daus et al 2004)
Activated Al2O3
0074~0149 As(V) 159 - 285~115 mgL at pH 52 in DI water
(Lin and Wu 2001)
Activated Al2O3
0074~0149 As(III) 35 - 079~490 mgL at pH 70 in DI water
(Lin and Wu 2001)
Activated Al2O3 ~20 As(V) 73 at pH 70 in 004 M NaClO4 (Jing et al 2012)
Activated natural siderite 05~10 As(V) 22 10 0 1~20 mgL at pH 7 in DI water(Zhao and Guo 2014)
Polyaluminum Granulate 1~3 As(III) 705 10 0~150 mgL at pH 51-56 in DI water(Mertens et al 2012)
Polyaluminum Granulate 1~3 As(V) 180 10 0~150 mgL at pH 51-56 in DI water (Mertens et al
26
2012)
Acidified laterite 1~12 As(III) 19 1 025~5 mgL at pH 7 in 100 mgL NaHCO3
(Glocheux et al 2013)
Acidified laterite 1~12 As(V) 13 1 025~5 mgL at pH 7 in 100 mgL NaHCO3
(Glocheux et al 2013)
Laterite 1~12 As(III) 07 1025~5 mgL at pH 7 in 100 mgL NaHCO3 (Glocheux et al
2013)
Laterite 1~12 As(V) 04 1025~5 mgL at pH 7 in 100 mgL NaHCO3 (Glocheux et al
2013)
Treated laterite 03-05 As(V) 216 05 02-20 mgL at pH 70 in DI water(Maiti et al 2012)
Treated laterite 03-05 As(III) 94 05 02-20 mgL at pH 70 in DI water(Maiti et al 2012)
Treated laterite03-05
As(V) 241 05 02-20 mgL at pH 70 in DI water(Maiti et al 2010a)
Treated laterite03-05
As(III) 81 05 02-20 mgL at pH 70 in DI water(Maiti et al 2010a)
Acid-activated laterite-103-07
As(III) 0633 50 02-10 mgL at pH 66-70 in DI water(Maiti et al 2010b)
Acid-activated laterite-203-07
As(III) 087650 02-10 mgL at pH 66-70 in DI water (Maiti et al
2010b)
Acid-activated laterite-303-07
As(III) 063450 02-10 mgL at pH 66-70 in DI water (Maiti et al
2010b)
Acid-activated laterite-103-07
As(V) 059850 02-10 mgL at pH 66-70 in DI water (Maiti et al
2010b)
27
Acid-activated laterite-203-07
As(V) 07550 02-10 mgL at pH 66-70 in DI water (Maiti et al
2010b)
Acid-activated laterite-303-07
As(V) 07550 02-10 mgL at pH 66-70 in DI water (Maiti et al
2010b)
Treated laterite-1 03-06 As(V) 019 20 0-20 mgL As at pH 72 in DI water(Maiti et al 2013b)
Treated laterite-1 03-06 As(III) 018 20 0-20 mgL As at pH 72 in DI water(Maiti et al 2013b)
Treated laterite-2 03-06 As(V) 004 20 0-20 mgL As at pH 72 in DI water(Maiti et al 2013b)
Treated laterite-2 03-06 As(III) 003 20 0-20 mgL As at pH 72 in DI water(Maiti et al 2013b)
Treated laterite-3 03-06 As(V) 007 20 0-20 mgL As at pH 72 in DI water(Maiti et al 2013b)
Treated laterite-3 03-06 As(III) 004 20 0-20 mgL As at pH 72 in DI water(Maiti et al 2013b)
28
376377
Charge distribution multi-site surface complexation (CD-MUSIC) modeling
The CD-MUSIC model with the 2-pK TPM adsorption option was used to
describe adsorption behaviors of As cations and anions on GTiO2 The CD-MUSIC
model incorporates the structural information of surfaces adsorbed species and the
double layers by distributing the charge of an adsorbate between the surface and
interfacial water (Hiemstra and Van Riemsdijk 2006) The CD-MUSIC model has
been successfully used in describing As adsorption in batch experiments (Pena et al
2006 Stachowicz et al 2008)
The adsorption constants of counter ions were set to -1 and the proton affinity
constant was set to the PZC of 58 for TiOH-13 (Luo et al 2010) The charge
distribution (CD) value shows the fraction (f) of the charge of the central As ion
attributed to the surface plane and the remaining part (1-f) was attributed to the other
ligands of the complex which were positioned toward the diffuse layer The CD value
for As surface complexes was obtained by fitting the experimental data The
calculation was performed using the chemical equilibrium program MINTEQ to
simulate the adsorption and the aqueous reactions
29
378379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
Fig S32 Adsorption of silicate (a) calcium and magnesium (b) as a function of GTiO2
dose in groundwater 1 The solid lines represent the CD-MUSIC modeling result
30
400
401
402
403
404
405
406
407
408409410
Table S75 Surface parameters and species used in the CD-MUSIC modeling in As(IIIV) removal under different GTiO2 dose in 01 M NaCl and groundwater 1 in Fig 2 and Fig S32
= exp(-FΨ1RT) P2 = exp(-FΨ2RT) F the Faraday constant (C mol-1) R the gas constant (J mol-1 K-1) T the absolute temperature (K)
Ψ0 Ψ1 Ψ2 the electrostatic potential (V) of 0- 1- and 2-plane respectively alogK for 01 M NaCl at 6 hours blogK for 01 M NaCl at 6 days clogK for groundwater 1 at 6 days
31
411412
413414415
32
416
Table S86 The charge distribution (f) of central As atom to TiO2 surface in simulating the effect of cations and anions on As adsorption in 01 M NaCl at pH 82 in Fig 4 BK Si HCO3 All
As(V) 022 017 012 016As(III) 040 020 058 056
Fig S43 Molar percentage () of As Ca Mg and Si on pristine and spent GTiO2
surfaces using EDX analysis The spent GTiO2 samples after field column experiments using groundwater 1 were identified with EBCT in min under x-axis The value of molar percentage of each element was averaged from randomly-chosen positions on the adsorbent surface
33
417
418
419420
421422
423
424
425
426
427
428
429
430
431
432
433434435436437438
439
440
441
As speciation analysis on spent GTiO2 using XANES
The spent GTiO2 samples were ground using a mortar and pestle and then the
ground powder was spread on Scotch tape The As k-edge XANES spectra were
collected at beamline 01C1 at the National Synchrotron Radiation Research Center
(NSRRC) Taiwan Spectra were acquired from -150 to 300 eV relative to the As K-
edge of 11867 eV at cryogenic temperature (77 K) using a cryostat to prevent the
oxidation of As(III) by X-rays The fluorescence signals were collected using a Lytle
detector Two to four scans were collected for each sample and averaged to improve
the signalnoise ratio The XANES analysis was performed with the Athena program
in the IFEFFIT computer package for linear combination fit (LCF) (Cui et al 2013
Ravel and Newville 2005)
34
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
PHREEQC modeling for As breakthrough curves in field column experiments
PHREEQC a geochemical model integrates macroscopic mass transfer
processes with a microscopic surface complexation model (Parkhurst and Appelo
2013) It can be applied in calculating solution complex speciation batch-reaction
and one-dimensional reactive-transport and inverse modeling In our study the one-
dimensional column was defined by four cells with the same length The cell length
was calculated to be one-fourth of the actual column length Time step (s) was
calculated according to equation Time step = Lcell(Q60A) where Lcell is the cell
length (cm) Q is flow velocity (mLmin) A is the effective column cross section area
(cm2) which is the column cross-sectional area multiplied by porosity (060) Total
shift number was calculated by dividing actual column operation time by the time
step The transport block was modeled by shifting the solute content from one cell to
the next one In each cell the aqueous solute was mixed and adsorbed on GTiO2
according to the equations In each cell the aqueous solute was mixed and assumed to
be in equilibration with GTiO2 The sequence of shifting mixing and equilibrium
adsorption was repeated for each cell until the total number of shifts was completed
The diffusion coefficient Dw in PHREEQC accounting for retardation was
calculated as Dw=x2
(36t) where x stands for the diffusion length (estimated as the
radius of the particle size) and t represents equilibrium time adopted from the batch
kinetic data (Mertens et al 2012)
For CD-MUSIC modeling in the PHREEQC take As(III) as an example to
explain the adsorption equation The As(III) adsorption is considered as a ligand
35
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
exchange reaction with the hydroxide group on GTiO2 (Surf_sOH-033) forming a
H3ArseniteO3 is the master species in groundwater at pH 82
(Surf_sO)2ArseniteOH-066 is the common adsorbed bidentate binuclear complex
evidenced by our previous reports(Pena et al 2006 Yan et al 2015) LogK is the
adsorption equilibrium constants Generally every adsorption equation under certain
experimental condition has a unique value of logK In the adsorption equation ldquo-2rdquo
represents the lost two hydrogens by Surf_sOH-033 after it adsorbs H3ArseniteO3 ldquo-
1rdquo represents the change in charge on Arsenite at 1 plane due to gaining one hydrogen
(+1) and one oxygen (-2) ldquo0rdquo represents no change in charge at the 2 plane ldquo066rdquo is
the fraction of the central ion (As) on GTiO2 surface that is associated with plane 0
ldquo3rdquo is the charge on the central ion As(III) Following this equation and the relevant
parameters As(III) adsorbed on GTiO2
The diffusion coefficient Dw in PHREEQC accounting for retardation was
calculated as Dw=x2(36t) where x stands for the diffusion length (estimated as the
radius of the particle size) and t represents equilibrium time adopted from the batch
kinetic data (Mertens et al 2012)
To well simulate the As breakthrough curve in columns four As(V) adsorption
reactions (Table 1) were employed Adsorption site density of 60 mmolg was
36
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
adopted from our previous study (Pena et al 2006) and the total adsorption sites were
calculated to be 1844 sitesnm2 The final optimized ratio of strong to weak sites was
51 The surface complexation constants were reasonably adjusted according to the
batch modeling results as the column reaction may not reach equilibrium in local
micro-interfacial areas due to much less contact time between As and GTiO2 than that
in batch experiments (Appelo and Postma 1999) In the modeling a stepwise
procedure was adopted to achieve a viable result An estimation of two thirds of the
surface site density being accessible for EBCT=011 min with large flow rate of 265
mLmin was optimized which could probably result from unavailable adsorption sites
due to fast transport through the column
The adsorbed As on GTiO2 in the column was calculated by mass balance
between the influent and effluent
where Asadsorbed is the adsorbed As on GTiO2 (mgg) n is the number of collected
samples Cin and Cout are influent and effluent As concentrations (mgL) respectively
Vi is volume (L) of groundwater passed through the column between sample i-1 and i
and m is the mass of GTiO2 (g)
Even though the oxidation of adsorbed As(III) occurred during filtration as
analyzed from XANES and mass balance analysis (Fig 7) no As(III) oxidation
reactions were considered in PHREEQC modeling which would not impact the
breakthrough of As(IIIV)
37
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
38
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
Fig S54 Effect of EBCT on Si Ca and Mg breakthrough curves using groundwater 1 The sample notation in panel c indicates field column experiments with EBCT in minutes
References
Appelo CAJ Postma D 1999 A consistent model for surface complexation on birnessite (MnO2) and its application to a column experiment Geochim Cosmochim Ac 63 (19-20) 3039-3048Badruzzaman M Westerhoff P Knappe DRU 2004 Intraparticle diffusion and adsorption of arsenate onto granular ferric hydroxide (GFH) Water Res 38 (18) 4002-4012Banerjee K Amy GL Prevost M Nour S Jekel M Gallagher PM Blumenschein CD 2008 Kinetic and thermodynamic aspects of adsorption of arsenic onto granular ferric hydroxide (GFH) Water Res 42 (13) 3371-3378Bang S Patel M Lippincott L Meng XG 2005 Removal of arsenic from groundwater by granular titanium dioxide adsorbent Chemosphere 60 (3) 389-397Bang S Pena ME Patel M Lippincott L Meng X Kim KW 2011 Removal of arsenate from water by adsorbents a comparative case study Environ Geochem Hlth 33 133-141Cui JL Shi JB Jiang GB Jing CY 2013 Arsenic levels and speciation from ingestion exposures to biomarkers in Shanxi China Implications for human health Environ Sci Technol 47 (10) 5419-5424Daus B Wennrich R Weiss H 2004 Sorption materials for arsenic removal from water A comparative study Water Res 38 (12) 2948-2954Dou XM Mohan D Pittman CU 2013 Arsenate adsorption on three types of granular schwertmannite Water Res 47 (9) 2938-2948Dou XM Zhang Y Yang M Pei YS Huang X Takayama T Kato S 2006 Occurrence of arsenic in groundwater in the suburbs of Beijing and its removal using an iron-cerium bimetal oxide adsorbent Water Qual Res J Can 41 (2) 140-146Gibbons MK Gagnon GA 2010 Adsorption of arsenic from a Nova Scotia groundwater onto water treatment residual solids Water Res 44 (19) 5740-5749Glocheux Y Mendez Pasarin M Albadarin AB Allen SJ Walker GM 2013 Removal of arsenic from groundwater by adsorption onto an acidified laterite by-product Chem Eng J 228 565-574Guan XH Wang JM Chusuei CC 2008 Removal of arsenic from water using granular ferric hydroxide Macroscopic and microscopic studies J Hazard Mater 156 (1-3) 178-185Gupta K Maity A Ghosh UC 2010 Manganese associated nanoparticles agglomerate of iron(III) oxide Synthesis characterization and arsenic(III) sorption behavior with mechanism J Hazard Mater 184 (1-3) 832-842Hao JM Han MJ Wang C Meng XG 2009 Enhanced removal of arsenite from water by a mesoporous hybrid material - Thiol-functionalized silica coated activated alumina Micropor Mesopor
Mat 124 (1-3) 1-7Hiemstra T Van Riemsdijk WH 2006 On the relationship between charge distribution surface hydration and the structure of the interface of metal hydroxides J Colloid Interf Sci 301 (1) 1-18Hristovski K Baumgardner A Westerhoff P 2007 Selecting metal oxide nanomaterials for arsenic removal in fixed bed columns From nanopowders to aggregated nanoparticle media J Hazard Mater 147 (1-2) 265-274Jang M Chen WF Cannon FS 2008 Preloading hydrous ferric oxide into granular activated carbon for arsenic removal Environ Sci Technol 42 (9) 3369-3374Jing CY Cui JL Huang YY Li AG 2012 Fabrication characterization and application of a composite adsorbent for simultaneous removal of arsenic and fluoride ACS Appl Mater Interfaces 4 (2) 714-720Kanematsu M Young TM Fukushi K Green PG Darby JL 2010 Extended triple layer modeling of arsenate and phosphate adsorption on a goethite-based granular porous adsorbent Environ Sci Technol 44 (9) 3388-3394Kong S Wang Y Zhan H Yuan S Liu M Zhou C 2013 Arsenite and Arsenate Removal from Contaminated Groundwater by Nanoscale Iron-Manganese Binary Oxides Column Studies Environmental Engineering Science 30 (11) 689-696Li Y Liu JR Jia SY Guo JW Zhuo J Na P 2012 TiO2 pillared montmorillonite as a photoactive adsorbent of arsenic under UV irradiation Chem Eng J 191 66-74Lin TF Wu JK 2001 Adsorption of arsenite and arsenate within activated alumina grains Equilibrium and kinetics Water Res 35 (8) 2049-2057Luo T Cui JL Hu S Huang YY Jing CY 2010 Arsenic removal and recovery from copper smelting wastewater using TiO2 Environ Sci Technol 44 (23) 9094-9098Maiti A Basu JK De S 2010a Development of a Treated Laterite for Arsenic Adsorption Effects of Treatment Parameters Industrial amp Engineering Chemistry Research 49 (10) 4873-4886Maiti A Basu JK De S 2010b Removal of Arsenic from Synthetic and Natural Groundwater Using Acid-Activated Laterite Environmental Progress amp Sustainable Energy 29 (4) 457-470Maiti A Basu JK De S 2012 Experimental and kinetic modeling of As(V) and As(III) adsorption on treated laterite using synthetic and contaminated groundwater Effects of phosphate silicate and carbonate ions Chem Eng J 191 1-12Maiti A Thakur BK Basu JK De S 2013a Comparison of treated laterite as arsenic adsorbent from different locations and performance of best filter under field conditions J Hazard Mater 262 1176-1186Maiti A Thakur BK Basu JK De S 2013b Comparison of treated laterite as arsenic adsorbent from different locations and performance of best filter under field conditions J Hazard Mater 262 (0) 1176-1186Maji SK Pal A Pal T 2008 Arsenic removal from real-life groundwater by adsorption on laterite soil J Hazard Mater 151 (2-3) 811-820Maji SK Kao YH Wang CJ Lu GS Wu JJ Liu CW 2012 Fixed bed adsorption of As(III) on iron-oxide-coated natural rock (IOCNR) and application to real arsenic-bearing groundwater Chem Eng J 203 285-293Mertens J Rose J Kagi R Chaurand P Plotze M Wehrli B Furrer G 2012 Adsorption of arsenic on polyaluminum granulate Environ Sci Technol 46 (13) 7310-7317Nguyen TV Vigneswaran S Ngo HH Pokhre D Viraraghavan T 2006 Iron-coated sponge as
effective media to remove arsenic from drinking water Water Qual Res J Can 41 (2) 164-170Parkhurst DL Appelo CAJ 2013 Description of input and examples for PHREEQC version 3-A computer program for speciation batch-reaction one-dimensional transport and inverse geochemical calculations US Geological SurveyPena M Meng XG Korfiatis GP Jing CY 2006 Adsorption mechanism of arsenic on nanocrystalline titanium dioxide Environ Sci Technol 40 (4) 1257-1262Ravel B Newville M 2005 ATHENA ARTEMIS HEPHAESTUS Data analysis for X-ray absorption spectroscopy using IFEFFIT J Synchrotron Radiat 12 537-541Saha B Bains R Greenwood F 2005 Physicochemical characterization of granular ferric hydroxide (GFH) for arsenic(V) sorption from water Separation Science and Technology 40 (14) 2909-2932Shan H Ma T Wang Y Zhao J Han H Deng Y He X Dong Y 2013 A cost-effective system for in-situ geological arsenic adsorption from groundwater J Contam Hydrol 154 1-9Stachowicz M Hiemstra T van Riemsdijk WH 2008 Multi-competitive interaction of As(III) and As(V) oxyanions with Ca2+ Mg2+ PO4
3- and CO32- ions on goethite J Colloid Interf Sci 320 (2) 400-
414Streat M Hellgardt K Newton NLR 2008 Hydrous ferric oxide as an adsorbent in water treatment - Part 3 Batch and mini-column adsorption of arsenic phosphorus fluorine and cadmium ions Process Safety and Environmental Protection 86 (B1) 21-30Thirunavukkarasu OS Viraraghavan T Subramanian KS 2003 Arsenic removal from drinking water using iron oxide-coated sand Water Air Soil Poll 142 (1-4) 95-111USEPA 2008 Assessing arsenic removal by metal (hydr)oxide adsorptive media using rapid small scale column tests Govenrnment Printing Office Washington DCWang J Xu W Chen L Huang X Liu J 2014 Preparation and evaluation of magnetic nanoparticles impregnated chitosan beads for arsenic removal from water Chem Eng J 251 25-34Westerhoff P Highfield D Badruzzaman M Yoon Y 2005 Rapid small-scale column tests for arsenate removal in iron oxide packed bed columns J Environ Eng-Asce 131 (2) 262-271Westerhoff P De Haan M Martindale A Badruzzaman M 2006 Arsenic adsorptive media technology selection strategies Water Qual Res J Can 41 (2) 171-184Yan L Huang Y Cui J Jing C 2015 Simultaneous As(III) and Cd removal from copper smelting wastewater using granular TiO2 columns Water Res 68 (0) 572-579Zhao K Guo HM 2014 Behavior and mechanism of arsenate adsorption on activated natural siderite Evidences from FTIR and XANES analysis Environ Sci Pollut Res 21 (3) 1944-1953Zhao K Guo H Zhou X 2014 Adsorption and heterogeneous oxidation of arsenite on modified granular natural siderite Characterization and behaviors Appl Geochem 48 184-192
Iron-Mn binary 15 40 145 176 321 22 253 347 754 (Maiti et al 2010a)
13
oxides
aUnit for ion concentration is mgL except as notedbestimated from bed volume breakthrough curves and influent As concentration if not explicitly expressed in the reference cThe species is As(V) if only one concentration is given
d
The groundwater As concentration was 385-440 μgL and additional ~600 μgL (As(III)As(V)=11) arsenic was added
14
222324252627
Fig S1 Boxplot of groundwater As levels in columns and filters in the literature in Table S1 Individual samples are shown as diamonds The range of each box represents the 25th
and 75th
percentile whereas the whiskers represent the 10th
and 90th
percentile
Synthesis of granular TiO2
Granular TiO2 (GTiO2) was prepared by hydrolysis of titanyl sulfate (TiOSO4)
Generally 300 g TiOSO4 was mixed with 1800 mL DI water in a 10 L jar reactor in an
ice bath at 4 oC Then 10 M NaOH was slowly added to adjust the pH to 6 The
precursor of TiO2 was obtained by washing the suspension with DI water several
times till the conductivity of the supernatant was less than 100 μScm Then 800 g
TiO2 precursor was mixed with 40 mL polyvinyl alcohol solution at 80 oC in a water
bath The product was crushed into 60-80 mesh and dried in an oven at 60 oC for 12 h
15
282930313233343536373839404142434445464748
49
50
51
52
53
54
55
56
57585960
Fig S2 Characterization of GTiO2 SEM (a) and XRD pattern with crystal face for each peak (b)
Fig S1 SEM images for GTiO2 in this study
Table S2 Average concentrations of As coexisting ions (mgL) and water chemistry for groundwater 1 and 2 from two wells
Table S3 Water parameters in the synthetic water used in the studyParameters Ca2+ Mg2+ HCO3
- Na+ Cl- pHConc (mgL) 401 1043 388 2460 3928 82
Table S4 PHREEQC input for a representative column with EBCT=054 min SOLUTION 0
This keyword is to define the influent groundwater chemistry parameters which are included in the adsorption reactions like ldquoArseniterdquo and ldquoArsenaterdquo and the experimental conditions including ldquopHrdquo The information defined in SOLUTION is available for subsequent transport and adsorptive reaction calculations
temp 23 pH 82 pe 4 redox pe units mgL density 1 Al 006 Arsenite 0374 Arsenate 0291 CO4
2-
4401 Ca 194 Cl 1456 F 115 Fe 047 K 137 Mg 395 Mn 012 NO3
-
34 Na 16872
17
79
80
8182
83
84858687888990919293949596979899
100101102103104105106107108109110111112
SO42-
1176 Si 89 -water 1 kg
SOLUTION 1-4 The small column was divided into four cells SOLUTION 1-4
are the groundwater chemistry parameters for the four cells temp 23 pH 83 pe 4 redox pe units ppm density 1 Al 006 C(4) 4401 Ca 194 Cl 1456 F 115 Fe 047 K 137 Mg 395 Mn 012 N(3) 34 Na 16872 S(6) 1176 Si 89 -water 1 kg
SOLUTION_SPECIES This keyword is to define the dissociation constant logK
and diffusion constant (dw) in solution for arsenite and arsenate
Arsenite adsorption equation on GTiO2 surface H3ArseniteO3 is the primary species of As(III) at the groundwater pH 82 (Surf_sO)2ArseniteOH-066 is the adsorptive bidentate binuclear structure of As(III) on GTiO2
log_k 1635 The adsorptive reaction constant for As(III) on GTiO2 in
the current condition which could be changed with different experimental conditions
-cd_music -2 -1 0 066 3 CD-MUSIC model is integrated in the PHREEQC
modeling The numbers represent -2 the change in charge at the plane of Surf_sOH due to loss of two hydrogens -1 the change in charge at 1 plane due to gain of one hydrogen and one oxygen on Arsenite 0 the change in charge at the 2 plane usually caused by the outer sphere adsorption 066 the fraction of the central ion (As) charge that is associated with plane 0 which reflecting the charge distribution 3 the charge on the central ion (As)
Table S54 Parameters of Weber-Morris intraparticle model for As(IIIV) adsorption kinetics on GTiO2 using synthetic water Initial As concentration = 800 μgL adsorbent dose = 02 gL pH = 82 in synthetic groundwater
External film diffusion
Intraparticle diffusion
aRex2 bkp1
cb1aRin
2 bkp2cb 2
As(V) 0984 0497 0022 0976 01331878
As(III) 0970 0583
-0088 0981 0218
1105
aRex is WM external proportion fitting parameter while Rin is WM intraparticle proportion fitting parameterbk The unit of kp is mggh05 cb The unit of b is mgg
Table S6 Comparison of the adsorption capacities of As(III) and As(V) on GTiO2 and the representative granular adsorbents in similar experimental condition from the literature
AdsorbentParticle size (mm) As
qm
(mgg)Dose (gL) Experimental conditions Literature
GTiO2 018~025 As(III) 980 1 0~500 mgL at pH 82 01 M NaCl This studyGTiO2 018~025 As(V) 358 1 0~500 mgL at pH 82 01 M NaCl This study
Granular TiO2 015~06 As(III) 392 10~60 mgL As at pH 70 in simulated groundwater (100 mgL Ca 20 mgL Mg 50 mgL Na 200 mgL Cl-
)(Bang et al 2005)
Granular TiO2 015~06 As(V) 400 10~60 mgL As at pH 70 in simulated groundwater (100 mgL Ca 20 mgL Mg 50 mgL Na 200 mgL Cl-
)(Bang et al 2005)
E33 (FeOOH)0044~0075 As(V) 202 1 0~15 mgL at pH 70 in 001 M NaCl
(Kanematsu et al 2010)
E33 (FeOOH) 05~2 As(V) 180 1 0~50 mgL at pH 70 in 004 M NaClO4 (Jing et al 2012)
GFH 02~06 As(V) 650 10 0~2000 mgL at pH 8 in 01 M NaNO3
(Guan et al 2008)
GFH0009~0125 As(V) 23 025 0~07 μgL at pH 65 in DI water
(Banerjee et al 2008)
GFH0009~0125 As(V) 200 - 0~01 μgL at pH 70 in DI water
(Badruzzaman et al 2004)
GFH 050~065 As(V) 155 - 0~06 μgL at pH 70 in DI water (Saha et al 2005)
GHFO-NN 015~030 As(V) 330 0001 0~225 mgL at pH 8 in DI water(Streat et al 2008)
GHFO-VL 015~030 As(V) 360 0001 0~225 mgL at pH 8 in DI water(Streat et al 2008)
25
374375
Spherical schwertmannite 1~15 As(V) 36 05 0~5 mgL at pH 70 in DI water (Dou et al 2013)Cylindrical schwertmannite 1~25 As(V) 223 05
0~5 mgL at pH 70 in DI water(Dou et al 2013)
Irregular schwertmannite 10~16 As(V) 317 05 0~5 mgL at pH 70 in DI water (Dou et al 2013)Fe impregnated chitosan beads (MICB) 25 As(III) 117 1 0~05 mgL at pH 60 in DI water
(Wang et al 2014)
MICB 25 As(V) 191 1 0~1 mgL at pH 60 in DI water(Wang et al 2014)
MICB 25 As(III) 353 1 0~15 mgL at pH 60 in DI water(Wang et al 2014)
MICB 25 As(V) 357 1 0~16 mgL at pH 60 in DI water(Wang et al 2014)
Iron hydroxide granules (GIH) 3~4 As(V) 23 4
5~100 mgL at pH 70 in 10 mgL SO42-
14 mgL NH4Cl buffer solution (Daus et al 2004)
Activated Al2O3
0074~0149 As(V) 159 - 285~115 mgL at pH 52 in DI water
(Lin and Wu 2001)
Activated Al2O3
0074~0149 As(III) 35 - 079~490 mgL at pH 70 in DI water
(Lin and Wu 2001)
Activated Al2O3 ~20 As(V) 73 at pH 70 in 004 M NaClO4 (Jing et al 2012)
Activated natural siderite 05~10 As(V) 22 10 0 1~20 mgL at pH 7 in DI water(Zhao and Guo 2014)
Polyaluminum Granulate 1~3 As(III) 705 10 0~150 mgL at pH 51-56 in DI water(Mertens et al 2012)
Polyaluminum Granulate 1~3 As(V) 180 10 0~150 mgL at pH 51-56 in DI water (Mertens et al
26
2012)
Acidified laterite 1~12 As(III) 19 1 025~5 mgL at pH 7 in 100 mgL NaHCO3
(Glocheux et al 2013)
Acidified laterite 1~12 As(V) 13 1 025~5 mgL at pH 7 in 100 mgL NaHCO3
(Glocheux et al 2013)
Laterite 1~12 As(III) 07 1025~5 mgL at pH 7 in 100 mgL NaHCO3 (Glocheux et al
2013)
Laterite 1~12 As(V) 04 1025~5 mgL at pH 7 in 100 mgL NaHCO3 (Glocheux et al
2013)
Treated laterite 03-05 As(V) 216 05 02-20 mgL at pH 70 in DI water(Maiti et al 2012)
Treated laterite 03-05 As(III) 94 05 02-20 mgL at pH 70 in DI water(Maiti et al 2012)
Treated laterite03-05
As(V) 241 05 02-20 mgL at pH 70 in DI water(Maiti et al 2010a)
Treated laterite03-05
As(III) 81 05 02-20 mgL at pH 70 in DI water(Maiti et al 2010a)
Acid-activated laterite-103-07
As(III) 0633 50 02-10 mgL at pH 66-70 in DI water(Maiti et al 2010b)
Acid-activated laterite-203-07
As(III) 087650 02-10 mgL at pH 66-70 in DI water (Maiti et al
2010b)
Acid-activated laterite-303-07
As(III) 063450 02-10 mgL at pH 66-70 in DI water (Maiti et al
2010b)
Acid-activated laterite-103-07
As(V) 059850 02-10 mgL at pH 66-70 in DI water (Maiti et al
2010b)
27
Acid-activated laterite-203-07
As(V) 07550 02-10 mgL at pH 66-70 in DI water (Maiti et al
2010b)
Acid-activated laterite-303-07
As(V) 07550 02-10 mgL at pH 66-70 in DI water (Maiti et al
2010b)
Treated laterite-1 03-06 As(V) 019 20 0-20 mgL As at pH 72 in DI water(Maiti et al 2013b)
Treated laterite-1 03-06 As(III) 018 20 0-20 mgL As at pH 72 in DI water(Maiti et al 2013b)
Treated laterite-2 03-06 As(V) 004 20 0-20 mgL As at pH 72 in DI water(Maiti et al 2013b)
Treated laterite-2 03-06 As(III) 003 20 0-20 mgL As at pH 72 in DI water(Maiti et al 2013b)
Treated laterite-3 03-06 As(V) 007 20 0-20 mgL As at pH 72 in DI water(Maiti et al 2013b)
Treated laterite-3 03-06 As(III) 004 20 0-20 mgL As at pH 72 in DI water(Maiti et al 2013b)
28
376377
Charge distribution multi-site surface complexation (CD-MUSIC) modeling
The CD-MUSIC model with the 2-pK TPM adsorption option was used to
describe adsorption behaviors of As cations and anions on GTiO2 The CD-MUSIC
model incorporates the structural information of surfaces adsorbed species and the
double layers by distributing the charge of an adsorbate between the surface and
interfacial water (Hiemstra and Van Riemsdijk 2006) The CD-MUSIC model has
been successfully used in describing As adsorption in batch experiments (Pena et al
2006 Stachowicz et al 2008)
The adsorption constants of counter ions were set to -1 and the proton affinity
constant was set to the PZC of 58 for TiOH-13 (Luo et al 2010) The charge
distribution (CD) value shows the fraction (f) of the charge of the central As ion
attributed to the surface plane and the remaining part (1-f) was attributed to the other
ligands of the complex which were positioned toward the diffuse layer The CD value
for As surface complexes was obtained by fitting the experimental data The
calculation was performed using the chemical equilibrium program MINTEQ to
simulate the adsorption and the aqueous reactions
29
378379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
Fig S32 Adsorption of silicate (a) calcium and magnesium (b) as a function of GTiO2
dose in groundwater 1 The solid lines represent the CD-MUSIC modeling result
30
400
401
402
403
404
405
406
407
408409410
Table S75 Surface parameters and species used in the CD-MUSIC modeling in As(IIIV) removal under different GTiO2 dose in 01 M NaCl and groundwater 1 in Fig 2 and Fig S32
= exp(-FΨ1RT) P2 = exp(-FΨ2RT) F the Faraday constant (C mol-1) R the gas constant (J mol-1 K-1) T the absolute temperature (K)
Ψ0 Ψ1 Ψ2 the electrostatic potential (V) of 0- 1- and 2-plane respectively alogK for 01 M NaCl at 6 hours blogK for 01 M NaCl at 6 days clogK for groundwater 1 at 6 days
31
411412
413414415
32
416
Table S86 The charge distribution (f) of central As atom to TiO2 surface in simulating the effect of cations and anions on As adsorption in 01 M NaCl at pH 82 in Fig 4 BK Si HCO3 All
As(V) 022 017 012 016As(III) 040 020 058 056
Fig S43 Molar percentage () of As Ca Mg and Si on pristine and spent GTiO2
surfaces using EDX analysis The spent GTiO2 samples after field column experiments using groundwater 1 were identified with EBCT in min under x-axis The value of molar percentage of each element was averaged from randomly-chosen positions on the adsorbent surface
33
417
418
419420
421422
423
424
425
426
427
428
429
430
431
432
433434435436437438
439
440
441
As speciation analysis on spent GTiO2 using XANES
The spent GTiO2 samples were ground using a mortar and pestle and then the
ground powder was spread on Scotch tape The As k-edge XANES spectra were
collected at beamline 01C1 at the National Synchrotron Radiation Research Center
(NSRRC) Taiwan Spectra were acquired from -150 to 300 eV relative to the As K-
edge of 11867 eV at cryogenic temperature (77 K) using a cryostat to prevent the
oxidation of As(III) by X-rays The fluorescence signals were collected using a Lytle
detector Two to four scans were collected for each sample and averaged to improve
the signalnoise ratio The XANES analysis was performed with the Athena program
in the IFEFFIT computer package for linear combination fit (LCF) (Cui et al 2013
Ravel and Newville 2005)
34
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
PHREEQC modeling for As breakthrough curves in field column experiments
PHREEQC a geochemical model integrates macroscopic mass transfer
processes with a microscopic surface complexation model (Parkhurst and Appelo
2013) It can be applied in calculating solution complex speciation batch-reaction
and one-dimensional reactive-transport and inverse modeling In our study the one-
dimensional column was defined by four cells with the same length The cell length
was calculated to be one-fourth of the actual column length Time step (s) was
calculated according to equation Time step = Lcell(Q60A) where Lcell is the cell
length (cm) Q is flow velocity (mLmin) A is the effective column cross section area
(cm2) which is the column cross-sectional area multiplied by porosity (060) Total
shift number was calculated by dividing actual column operation time by the time
step The transport block was modeled by shifting the solute content from one cell to
the next one In each cell the aqueous solute was mixed and adsorbed on GTiO2
according to the equations In each cell the aqueous solute was mixed and assumed to
be in equilibration with GTiO2 The sequence of shifting mixing and equilibrium
adsorption was repeated for each cell until the total number of shifts was completed
The diffusion coefficient Dw in PHREEQC accounting for retardation was
calculated as Dw=x2
(36t) where x stands for the diffusion length (estimated as the
radius of the particle size) and t represents equilibrium time adopted from the batch
kinetic data (Mertens et al 2012)
For CD-MUSIC modeling in the PHREEQC take As(III) as an example to
explain the adsorption equation The As(III) adsorption is considered as a ligand
35
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
exchange reaction with the hydroxide group on GTiO2 (Surf_sOH-033) forming a
H3ArseniteO3 is the master species in groundwater at pH 82
(Surf_sO)2ArseniteOH-066 is the common adsorbed bidentate binuclear complex
evidenced by our previous reports(Pena et al 2006 Yan et al 2015) LogK is the
adsorption equilibrium constants Generally every adsorption equation under certain
experimental condition has a unique value of logK In the adsorption equation ldquo-2rdquo
represents the lost two hydrogens by Surf_sOH-033 after it adsorbs H3ArseniteO3 ldquo-
1rdquo represents the change in charge on Arsenite at 1 plane due to gaining one hydrogen
(+1) and one oxygen (-2) ldquo0rdquo represents no change in charge at the 2 plane ldquo066rdquo is
the fraction of the central ion (As) on GTiO2 surface that is associated with plane 0
ldquo3rdquo is the charge on the central ion As(III) Following this equation and the relevant
parameters As(III) adsorbed on GTiO2
The diffusion coefficient Dw in PHREEQC accounting for retardation was
calculated as Dw=x2(36t) where x stands for the diffusion length (estimated as the
radius of the particle size) and t represents equilibrium time adopted from the batch
kinetic data (Mertens et al 2012)
To well simulate the As breakthrough curve in columns four As(V) adsorption
reactions (Table 1) were employed Adsorption site density of 60 mmolg was
36
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
adopted from our previous study (Pena et al 2006) and the total adsorption sites were
calculated to be 1844 sitesnm2 The final optimized ratio of strong to weak sites was
51 The surface complexation constants were reasonably adjusted according to the
batch modeling results as the column reaction may not reach equilibrium in local
micro-interfacial areas due to much less contact time between As and GTiO2 than that
in batch experiments (Appelo and Postma 1999) In the modeling a stepwise
procedure was adopted to achieve a viable result An estimation of two thirds of the
surface site density being accessible for EBCT=011 min with large flow rate of 265
mLmin was optimized which could probably result from unavailable adsorption sites
due to fast transport through the column
The adsorbed As on GTiO2 in the column was calculated by mass balance
between the influent and effluent
where Asadsorbed is the adsorbed As on GTiO2 (mgg) n is the number of collected
samples Cin and Cout are influent and effluent As concentrations (mgL) respectively
Vi is volume (L) of groundwater passed through the column between sample i-1 and i
and m is the mass of GTiO2 (g)
Even though the oxidation of adsorbed As(III) occurred during filtration as
analyzed from XANES and mass balance analysis (Fig 7) no As(III) oxidation
reactions were considered in PHREEQC modeling which would not impact the
breakthrough of As(IIIV)
37
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
38
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
Fig S54 Effect of EBCT on Si Ca and Mg breakthrough curves using groundwater 1 The sample notation in panel c indicates field column experiments with EBCT in minutes
References
Appelo CAJ Postma D 1999 A consistent model for surface complexation on birnessite (MnO2) and its application to a column experiment Geochim Cosmochim Ac 63 (19-20) 3039-3048Badruzzaman M Westerhoff P Knappe DRU 2004 Intraparticle diffusion and adsorption of arsenate onto granular ferric hydroxide (GFH) Water Res 38 (18) 4002-4012Banerjee K Amy GL Prevost M Nour S Jekel M Gallagher PM Blumenschein CD 2008 Kinetic and thermodynamic aspects of adsorption of arsenic onto granular ferric hydroxide (GFH) Water Res 42 (13) 3371-3378Bang S Patel M Lippincott L Meng XG 2005 Removal of arsenic from groundwater by granular titanium dioxide adsorbent Chemosphere 60 (3) 389-397Bang S Pena ME Patel M Lippincott L Meng X Kim KW 2011 Removal of arsenate from water by adsorbents a comparative case study Environ Geochem Hlth 33 133-141Cui JL Shi JB Jiang GB Jing CY 2013 Arsenic levels and speciation from ingestion exposures to biomarkers in Shanxi China Implications for human health Environ Sci Technol 47 (10) 5419-5424Daus B Wennrich R Weiss H 2004 Sorption materials for arsenic removal from water A comparative study Water Res 38 (12) 2948-2954Dou XM Mohan D Pittman CU 2013 Arsenate adsorption on three types of granular schwertmannite Water Res 47 (9) 2938-2948Dou XM Zhang Y Yang M Pei YS Huang X Takayama T Kato S 2006 Occurrence of arsenic in groundwater in the suburbs of Beijing and its removal using an iron-cerium bimetal oxide adsorbent Water Qual Res J Can 41 (2) 140-146Gibbons MK Gagnon GA 2010 Adsorption of arsenic from a Nova Scotia groundwater onto water treatment residual solids Water Res 44 (19) 5740-5749Glocheux Y Mendez Pasarin M Albadarin AB Allen SJ Walker GM 2013 Removal of arsenic from groundwater by adsorption onto an acidified laterite by-product Chem Eng J 228 565-574Guan XH Wang JM Chusuei CC 2008 Removal of arsenic from water using granular ferric hydroxide Macroscopic and microscopic studies J Hazard Mater 156 (1-3) 178-185Gupta K Maity A Ghosh UC 2010 Manganese associated nanoparticles agglomerate of iron(III) oxide Synthesis characterization and arsenic(III) sorption behavior with mechanism J Hazard Mater 184 (1-3) 832-842Hao JM Han MJ Wang C Meng XG 2009 Enhanced removal of arsenite from water by a mesoporous hybrid material - Thiol-functionalized silica coated activated alumina Micropor Mesopor
Mat 124 (1-3) 1-7Hiemstra T Van Riemsdijk WH 2006 On the relationship between charge distribution surface hydration and the structure of the interface of metal hydroxides J Colloid Interf Sci 301 (1) 1-18Hristovski K Baumgardner A Westerhoff P 2007 Selecting metal oxide nanomaterials for arsenic removal in fixed bed columns From nanopowders to aggregated nanoparticle media J Hazard Mater 147 (1-2) 265-274Jang M Chen WF Cannon FS 2008 Preloading hydrous ferric oxide into granular activated carbon for arsenic removal Environ Sci Technol 42 (9) 3369-3374Jing CY Cui JL Huang YY Li AG 2012 Fabrication characterization and application of a composite adsorbent for simultaneous removal of arsenic and fluoride ACS Appl Mater Interfaces 4 (2) 714-720Kanematsu M Young TM Fukushi K Green PG Darby JL 2010 Extended triple layer modeling of arsenate and phosphate adsorption on a goethite-based granular porous adsorbent Environ Sci Technol 44 (9) 3388-3394Kong S Wang Y Zhan H Yuan S Liu M Zhou C 2013 Arsenite and Arsenate Removal from Contaminated Groundwater by Nanoscale Iron-Manganese Binary Oxides Column Studies Environmental Engineering Science 30 (11) 689-696Li Y Liu JR Jia SY Guo JW Zhuo J Na P 2012 TiO2 pillared montmorillonite as a photoactive adsorbent of arsenic under UV irradiation Chem Eng J 191 66-74Lin TF Wu JK 2001 Adsorption of arsenite and arsenate within activated alumina grains Equilibrium and kinetics Water Res 35 (8) 2049-2057Luo T Cui JL Hu S Huang YY Jing CY 2010 Arsenic removal and recovery from copper smelting wastewater using TiO2 Environ Sci Technol 44 (23) 9094-9098Maiti A Basu JK De S 2010a Development of a Treated Laterite for Arsenic Adsorption Effects of Treatment Parameters Industrial amp Engineering Chemistry Research 49 (10) 4873-4886Maiti A Basu JK De S 2010b Removal of Arsenic from Synthetic and Natural Groundwater Using Acid-Activated Laterite Environmental Progress amp Sustainable Energy 29 (4) 457-470Maiti A Basu JK De S 2012 Experimental and kinetic modeling of As(V) and As(III) adsorption on treated laterite using synthetic and contaminated groundwater Effects of phosphate silicate and carbonate ions Chem Eng J 191 1-12Maiti A Thakur BK Basu JK De S 2013a Comparison of treated laterite as arsenic adsorbent from different locations and performance of best filter under field conditions J Hazard Mater 262 1176-1186Maiti A Thakur BK Basu JK De S 2013b Comparison of treated laterite as arsenic adsorbent from different locations and performance of best filter under field conditions J Hazard Mater 262 (0) 1176-1186Maji SK Pal A Pal T 2008 Arsenic removal from real-life groundwater by adsorption on laterite soil J Hazard Mater 151 (2-3) 811-820Maji SK Kao YH Wang CJ Lu GS Wu JJ Liu CW 2012 Fixed bed adsorption of As(III) on iron-oxide-coated natural rock (IOCNR) and application to real arsenic-bearing groundwater Chem Eng J 203 285-293Mertens J Rose J Kagi R Chaurand P Plotze M Wehrli B Furrer G 2012 Adsorption of arsenic on polyaluminum granulate Environ Sci Technol 46 (13) 7310-7317Nguyen TV Vigneswaran S Ngo HH Pokhre D Viraraghavan T 2006 Iron-coated sponge as
effective media to remove arsenic from drinking water Water Qual Res J Can 41 (2) 164-170Parkhurst DL Appelo CAJ 2013 Description of input and examples for PHREEQC version 3-A computer program for speciation batch-reaction one-dimensional transport and inverse geochemical calculations US Geological SurveyPena M Meng XG Korfiatis GP Jing CY 2006 Adsorption mechanism of arsenic on nanocrystalline titanium dioxide Environ Sci Technol 40 (4) 1257-1262Ravel B Newville M 2005 ATHENA ARTEMIS HEPHAESTUS Data analysis for X-ray absorption spectroscopy using IFEFFIT J Synchrotron Radiat 12 537-541Saha B Bains R Greenwood F 2005 Physicochemical characterization of granular ferric hydroxide (GFH) for arsenic(V) sorption from water Separation Science and Technology 40 (14) 2909-2932Shan H Ma T Wang Y Zhao J Han H Deng Y He X Dong Y 2013 A cost-effective system for in-situ geological arsenic adsorption from groundwater J Contam Hydrol 154 1-9Stachowicz M Hiemstra T van Riemsdijk WH 2008 Multi-competitive interaction of As(III) and As(V) oxyanions with Ca2+ Mg2+ PO4
3- and CO32- ions on goethite J Colloid Interf Sci 320 (2) 400-
414Streat M Hellgardt K Newton NLR 2008 Hydrous ferric oxide as an adsorbent in water treatment - Part 3 Batch and mini-column adsorption of arsenic phosphorus fluorine and cadmium ions Process Safety and Environmental Protection 86 (B1) 21-30Thirunavukkarasu OS Viraraghavan T Subramanian KS 2003 Arsenic removal from drinking water using iron oxide-coated sand Water Air Soil Poll 142 (1-4) 95-111USEPA 2008 Assessing arsenic removal by metal (hydr)oxide adsorptive media using rapid small scale column tests Govenrnment Printing Office Washington DCWang J Xu W Chen L Huang X Liu J 2014 Preparation and evaluation of magnetic nanoparticles impregnated chitosan beads for arsenic removal from water Chem Eng J 251 25-34Westerhoff P Highfield D Badruzzaman M Yoon Y 2005 Rapid small-scale column tests for arsenate removal in iron oxide packed bed columns J Environ Eng-Asce 131 (2) 262-271Westerhoff P De Haan M Martindale A Badruzzaman M 2006 Arsenic adsorptive media technology selection strategies Water Qual Res J Can 41 (2) 171-184Yan L Huang Y Cui J Jing C 2015 Simultaneous As(III) and Cd removal from copper smelting wastewater using granular TiO2 columns Water Res 68 (0) 572-579Zhao K Guo HM 2014 Behavior and mechanism of arsenate adsorption on activated natural siderite Evidences from FTIR and XANES analysis Environ Sci Pollut Res 21 (3) 1944-1953Zhao K Guo H Zhou X 2014 Adsorption and heterogeneous oxidation of arsenite on modified granular natural siderite Characterization and behaviors Appl Geochem 48 184-192
Iron-Mn binary 15 40 145 176 321 22 253 347 754 (Maiti et al 2010a)
13
oxides
aUnit for ion concentration is mgL except as notedbestimated from bed volume breakthrough curves and influent As concentration if not explicitly expressed in the reference cThe species is As(V) if only one concentration is given
d
The groundwater As concentration was 385-440 μgL and additional ~600 μgL (As(III)As(V)=11) arsenic was added
14
222324252627
Fig S1 Boxplot of groundwater As levels in columns and filters in the literature in Table S1 Individual samples are shown as diamonds The range of each box represents the 25th
and 75th
percentile whereas the whiskers represent the 10th
and 90th
percentile
Synthesis of granular TiO2
Granular TiO2 (GTiO2) was prepared by hydrolysis of titanyl sulfate (TiOSO4)
Generally 300 g TiOSO4 was mixed with 1800 mL DI water in a 10 L jar reactor in an
ice bath at 4 oC Then 10 M NaOH was slowly added to adjust the pH to 6 The
precursor of TiO2 was obtained by washing the suspension with DI water several
times till the conductivity of the supernatant was less than 100 μScm Then 800 g
TiO2 precursor was mixed with 40 mL polyvinyl alcohol solution at 80 oC in a water
bath The product was crushed into 60-80 mesh and dried in an oven at 60 oC for 12 h
15
282930313233343536373839404142434445464748
49
50
51
52
53
54
55
56
57585960
Fig S2 Characterization of GTiO2 SEM (a) and XRD pattern with crystal face for each peak (b)
Fig S1 SEM images for GTiO2 in this study
Table S2 Average concentrations of As coexisting ions (mgL) and water chemistry for groundwater 1 and 2 from two wells
Table S3 Water parameters in the synthetic water used in the studyParameters Ca2+ Mg2+ HCO3
- Na+ Cl- pHConc (mgL) 401 1043 388 2460 3928 82
Table S4 PHREEQC input for a representative column with EBCT=054 min SOLUTION 0
This keyword is to define the influent groundwater chemistry parameters which are included in the adsorption reactions like ldquoArseniterdquo and ldquoArsenaterdquo and the experimental conditions including ldquopHrdquo The information defined in SOLUTION is available for subsequent transport and adsorptive reaction calculations
temp 23 pH 82 pe 4 redox pe units mgL density 1 Al 006 Arsenite 0374 Arsenate 0291 CO4
2-
4401 Ca 194 Cl 1456 F 115 Fe 047 K 137 Mg 395 Mn 012 NO3
-
34 Na 16872
17
79
80
8182
83
84858687888990919293949596979899
100101102103104105106107108109110111112
SO42-
1176 Si 89 -water 1 kg
SOLUTION 1-4 The small column was divided into four cells SOLUTION 1-4
are the groundwater chemistry parameters for the four cells temp 23 pH 83 pe 4 redox pe units ppm density 1 Al 006 C(4) 4401 Ca 194 Cl 1456 F 115 Fe 047 K 137 Mg 395 Mn 012 N(3) 34 Na 16872 S(6) 1176 Si 89 -water 1 kg
SOLUTION_SPECIES This keyword is to define the dissociation constant logK
and diffusion constant (dw) in solution for arsenite and arsenate
Arsenite adsorption equation on GTiO2 surface H3ArseniteO3 is the primary species of As(III) at the groundwater pH 82 (Surf_sO)2ArseniteOH-066 is the adsorptive bidentate binuclear structure of As(III) on GTiO2
log_k 1635 The adsorptive reaction constant for As(III) on GTiO2 in
the current condition which could be changed with different experimental conditions
-cd_music -2 -1 0 066 3 CD-MUSIC model is integrated in the PHREEQC
modeling The numbers represent -2 the change in charge at the plane of Surf_sOH due to loss of two hydrogens -1 the change in charge at 1 plane due to gain of one hydrogen and one oxygen on Arsenite 0 the change in charge at the 2 plane usually caused by the outer sphere adsorption 066 the fraction of the central ion (As) charge that is associated with plane 0 which reflecting the charge distribution 3 the charge on the central ion (As)
Table S54 Parameters of Weber-Morris intraparticle model for As(IIIV) adsorption kinetics on GTiO2 using synthetic water Initial As concentration = 800 μgL adsorbent dose = 02 gL pH = 82 in synthetic groundwater
External film diffusion
Intraparticle diffusion
aRex2 bkp1
cb1aRin
2 bkp2cb 2
As(V) 0984 0497 0022 0976 01331878
As(III) 0970 0583
-0088 0981 0218
1105
aRex is WM external proportion fitting parameter while Rin is WM intraparticle proportion fitting parameterbk The unit of kp is mggh05 cb The unit of b is mgg
Table S6 Comparison of the adsorption capacities of As(III) and As(V) on GTiO2 and the representative granular adsorbents in similar experimental condition from the literature
AdsorbentParticle size (mm) As
qm
(mgg)Dose (gL) Experimental conditions Literature
GTiO2 018~025 As(III) 980 1 0~500 mgL at pH 82 01 M NaCl This studyGTiO2 018~025 As(V) 358 1 0~500 mgL at pH 82 01 M NaCl This study
Granular TiO2 015~06 As(III) 392 10~60 mgL As at pH 70 in simulated groundwater (100 mgL Ca 20 mgL Mg 50 mgL Na 200 mgL Cl-
)(Bang et al 2005)
Granular TiO2 015~06 As(V) 400 10~60 mgL As at pH 70 in simulated groundwater (100 mgL Ca 20 mgL Mg 50 mgL Na 200 mgL Cl-
)(Bang et al 2005)
E33 (FeOOH)0044~0075 As(V) 202 1 0~15 mgL at pH 70 in 001 M NaCl
(Kanematsu et al 2010)
E33 (FeOOH) 05~2 As(V) 180 1 0~50 mgL at pH 70 in 004 M NaClO4 (Jing et al 2012)
GFH 02~06 As(V) 650 10 0~2000 mgL at pH 8 in 01 M NaNO3
(Guan et al 2008)
GFH0009~0125 As(V) 23 025 0~07 μgL at pH 65 in DI water
(Banerjee et al 2008)
GFH0009~0125 As(V) 200 - 0~01 μgL at pH 70 in DI water
(Badruzzaman et al 2004)
GFH 050~065 As(V) 155 - 0~06 μgL at pH 70 in DI water (Saha et al 2005)
GHFO-NN 015~030 As(V) 330 0001 0~225 mgL at pH 8 in DI water(Streat et al 2008)
GHFO-VL 015~030 As(V) 360 0001 0~225 mgL at pH 8 in DI water(Streat et al 2008)
25
374375
Spherical schwertmannite 1~15 As(V) 36 05 0~5 mgL at pH 70 in DI water (Dou et al 2013)Cylindrical schwertmannite 1~25 As(V) 223 05
0~5 mgL at pH 70 in DI water(Dou et al 2013)
Irregular schwertmannite 10~16 As(V) 317 05 0~5 mgL at pH 70 in DI water (Dou et al 2013)Fe impregnated chitosan beads (MICB) 25 As(III) 117 1 0~05 mgL at pH 60 in DI water
(Wang et al 2014)
MICB 25 As(V) 191 1 0~1 mgL at pH 60 in DI water(Wang et al 2014)
MICB 25 As(III) 353 1 0~15 mgL at pH 60 in DI water(Wang et al 2014)
MICB 25 As(V) 357 1 0~16 mgL at pH 60 in DI water(Wang et al 2014)
Iron hydroxide granules (GIH) 3~4 As(V) 23 4
5~100 mgL at pH 70 in 10 mgL SO42-
14 mgL NH4Cl buffer solution (Daus et al 2004)
Activated Al2O3
0074~0149 As(V) 159 - 285~115 mgL at pH 52 in DI water
(Lin and Wu 2001)
Activated Al2O3
0074~0149 As(III) 35 - 079~490 mgL at pH 70 in DI water
(Lin and Wu 2001)
Activated Al2O3 ~20 As(V) 73 at pH 70 in 004 M NaClO4 (Jing et al 2012)
Activated natural siderite 05~10 As(V) 22 10 0 1~20 mgL at pH 7 in DI water(Zhao and Guo 2014)
Polyaluminum Granulate 1~3 As(III) 705 10 0~150 mgL at pH 51-56 in DI water(Mertens et al 2012)
Polyaluminum Granulate 1~3 As(V) 180 10 0~150 mgL at pH 51-56 in DI water (Mertens et al
26
2012)
Acidified laterite 1~12 As(III) 19 1 025~5 mgL at pH 7 in 100 mgL NaHCO3
(Glocheux et al 2013)
Acidified laterite 1~12 As(V) 13 1 025~5 mgL at pH 7 in 100 mgL NaHCO3
(Glocheux et al 2013)
Laterite 1~12 As(III) 07 1025~5 mgL at pH 7 in 100 mgL NaHCO3 (Glocheux et al
2013)
Laterite 1~12 As(V) 04 1025~5 mgL at pH 7 in 100 mgL NaHCO3 (Glocheux et al
2013)
Treated laterite 03-05 As(V) 216 05 02-20 mgL at pH 70 in DI water(Maiti et al 2012)
Treated laterite 03-05 As(III) 94 05 02-20 mgL at pH 70 in DI water(Maiti et al 2012)
Treated laterite03-05
As(V) 241 05 02-20 mgL at pH 70 in DI water(Maiti et al 2010a)
Treated laterite03-05
As(III) 81 05 02-20 mgL at pH 70 in DI water(Maiti et al 2010a)
Acid-activated laterite-103-07
As(III) 0633 50 02-10 mgL at pH 66-70 in DI water(Maiti et al 2010b)
Acid-activated laterite-203-07
As(III) 087650 02-10 mgL at pH 66-70 in DI water (Maiti et al
2010b)
Acid-activated laterite-303-07
As(III) 063450 02-10 mgL at pH 66-70 in DI water (Maiti et al
2010b)
Acid-activated laterite-103-07
As(V) 059850 02-10 mgL at pH 66-70 in DI water (Maiti et al
2010b)
27
Acid-activated laterite-203-07
As(V) 07550 02-10 mgL at pH 66-70 in DI water (Maiti et al
2010b)
Acid-activated laterite-303-07
As(V) 07550 02-10 mgL at pH 66-70 in DI water (Maiti et al
2010b)
Treated laterite-1 03-06 As(V) 019 20 0-20 mgL As at pH 72 in DI water(Maiti et al 2013b)
Treated laterite-1 03-06 As(III) 018 20 0-20 mgL As at pH 72 in DI water(Maiti et al 2013b)
Treated laterite-2 03-06 As(V) 004 20 0-20 mgL As at pH 72 in DI water(Maiti et al 2013b)
Treated laterite-2 03-06 As(III) 003 20 0-20 mgL As at pH 72 in DI water(Maiti et al 2013b)
Treated laterite-3 03-06 As(V) 007 20 0-20 mgL As at pH 72 in DI water(Maiti et al 2013b)
Treated laterite-3 03-06 As(III) 004 20 0-20 mgL As at pH 72 in DI water(Maiti et al 2013b)
28
376377
Charge distribution multi-site surface complexation (CD-MUSIC) modeling
The CD-MUSIC model with the 2-pK TPM adsorption option was used to
describe adsorption behaviors of As cations and anions on GTiO2 The CD-MUSIC
model incorporates the structural information of surfaces adsorbed species and the
double layers by distributing the charge of an adsorbate between the surface and
interfacial water (Hiemstra and Van Riemsdijk 2006) The CD-MUSIC model has
been successfully used in describing As adsorption in batch experiments (Pena et al
2006 Stachowicz et al 2008)
The adsorption constants of counter ions were set to -1 and the proton affinity
constant was set to the PZC of 58 for TiOH-13 (Luo et al 2010) The charge
distribution (CD) value shows the fraction (f) of the charge of the central As ion
attributed to the surface plane and the remaining part (1-f) was attributed to the other
ligands of the complex which were positioned toward the diffuse layer The CD value
for As surface complexes was obtained by fitting the experimental data The
calculation was performed using the chemical equilibrium program MINTEQ to
simulate the adsorption and the aqueous reactions
29
378379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
Fig S32 Adsorption of silicate (a) calcium and magnesium (b) as a function of GTiO2
dose in groundwater 1 The solid lines represent the CD-MUSIC modeling result
30
400
401
402
403
404
405
406
407
408409410
Table S75 Surface parameters and species used in the CD-MUSIC modeling in As(IIIV) removal under different GTiO2 dose in 01 M NaCl and groundwater 1 in Fig 2 and Fig S32
= exp(-FΨ1RT) P2 = exp(-FΨ2RT) F the Faraday constant (C mol-1) R the gas constant (J mol-1 K-1) T the absolute temperature (K)
Ψ0 Ψ1 Ψ2 the electrostatic potential (V) of 0- 1- and 2-plane respectively alogK for 01 M NaCl at 6 hours blogK for 01 M NaCl at 6 days clogK for groundwater 1 at 6 days
31
411412
413414415
32
416
Table S86 The charge distribution (f) of central As atom to TiO2 surface in simulating the effect of cations and anions on As adsorption in 01 M NaCl at pH 82 in Fig 4 BK Si HCO3 All
As(V) 022 017 012 016As(III) 040 020 058 056
Fig S43 Molar percentage () of As Ca Mg and Si on pristine and spent GTiO2
surfaces using EDX analysis The spent GTiO2 samples after field column experiments using groundwater 1 were identified with EBCT in min under x-axis The value of molar percentage of each element was averaged from randomly-chosen positions on the adsorbent surface
33
417
418
419420
421422
423
424
425
426
427
428
429
430
431
432
433434435436437438
439
440
441
As speciation analysis on spent GTiO2 using XANES
The spent GTiO2 samples were ground using a mortar and pestle and then the
ground powder was spread on Scotch tape The As k-edge XANES spectra were
collected at beamline 01C1 at the National Synchrotron Radiation Research Center
(NSRRC) Taiwan Spectra were acquired from -150 to 300 eV relative to the As K-
edge of 11867 eV at cryogenic temperature (77 K) using a cryostat to prevent the
oxidation of As(III) by X-rays The fluorescence signals were collected using a Lytle
detector Two to four scans were collected for each sample and averaged to improve
the signalnoise ratio The XANES analysis was performed with the Athena program
in the IFEFFIT computer package for linear combination fit (LCF) (Cui et al 2013
Ravel and Newville 2005)
34
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
PHREEQC modeling for As breakthrough curves in field column experiments
PHREEQC a geochemical model integrates macroscopic mass transfer
processes with a microscopic surface complexation model (Parkhurst and Appelo
2013) It can be applied in calculating solution complex speciation batch-reaction
and one-dimensional reactive-transport and inverse modeling In our study the one-
dimensional column was defined by four cells with the same length The cell length
was calculated to be one-fourth of the actual column length Time step (s) was
calculated according to equation Time step = Lcell(Q60A) where Lcell is the cell
length (cm) Q is flow velocity (mLmin) A is the effective column cross section area
(cm2) which is the column cross-sectional area multiplied by porosity (060) Total
shift number was calculated by dividing actual column operation time by the time
step The transport block was modeled by shifting the solute content from one cell to
the next one In each cell the aqueous solute was mixed and adsorbed on GTiO2
according to the equations In each cell the aqueous solute was mixed and assumed to
be in equilibration with GTiO2 The sequence of shifting mixing and equilibrium
adsorption was repeated for each cell until the total number of shifts was completed
The diffusion coefficient Dw in PHREEQC accounting for retardation was
calculated as Dw=x2
(36t) where x stands for the diffusion length (estimated as the
radius of the particle size) and t represents equilibrium time adopted from the batch
kinetic data (Mertens et al 2012)
For CD-MUSIC modeling in the PHREEQC take As(III) as an example to
explain the adsorption equation The As(III) adsorption is considered as a ligand
35
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
exchange reaction with the hydroxide group on GTiO2 (Surf_sOH-033) forming a
H3ArseniteO3 is the master species in groundwater at pH 82
(Surf_sO)2ArseniteOH-066 is the common adsorbed bidentate binuclear complex
evidenced by our previous reports(Pena et al 2006 Yan et al 2015) LogK is the
adsorption equilibrium constants Generally every adsorption equation under certain
experimental condition has a unique value of logK In the adsorption equation ldquo-2rdquo
represents the lost two hydrogens by Surf_sOH-033 after it adsorbs H3ArseniteO3 ldquo-
1rdquo represents the change in charge on Arsenite at 1 plane due to gaining one hydrogen
(+1) and one oxygen (-2) ldquo0rdquo represents no change in charge at the 2 plane ldquo066rdquo is
the fraction of the central ion (As) on GTiO2 surface that is associated with plane 0
ldquo3rdquo is the charge on the central ion As(III) Following this equation and the relevant
parameters As(III) adsorbed on GTiO2
The diffusion coefficient Dw in PHREEQC accounting for retardation was
calculated as Dw=x2(36t) where x stands for the diffusion length (estimated as the
radius of the particle size) and t represents equilibrium time adopted from the batch
kinetic data (Mertens et al 2012)
To well simulate the As breakthrough curve in columns four As(V) adsorption
reactions (Table 1) were employed Adsorption site density of 60 mmolg was
36
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
adopted from our previous study (Pena et al 2006) and the total adsorption sites were
calculated to be 1844 sitesnm2 The final optimized ratio of strong to weak sites was
51 The surface complexation constants were reasonably adjusted according to the
batch modeling results as the column reaction may not reach equilibrium in local
micro-interfacial areas due to much less contact time between As and GTiO2 than that
in batch experiments (Appelo and Postma 1999) In the modeling a stepwise
procedure was adopted to achieve a viable result An estimation of two thirds of the
surface site density being accessible for EBCT=011 min with large flow rate of 265
mLmin was optimized which could probably result from unavailable adsorption sites
due to fast transport through the column
The adsorbed As on GTiO2 in the column was calculated by mass balance
between the influent and effluent
where Asadsorbed is the adsorbed As on GTiO2 (mgg) n is the number of collected
samples Cin and Cout are influent and effluent As concentrations (mgL) respectively
Vi is volume (L) of groundwater passed through the column between sample i-1 and i
and m is the mass of GTiO2 (g)
Even though the oxidation of adsorbed As(III) occurred during filtration as
analyzed from XANES and mass balance analysis (Fig 7) no As(III) oxidation
reactions were considered in PHREEQC modeling which would not impact the
breakthrough of As(IIIV)
37
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
38
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
Fig S54 Effect of EBCT on Si Ca and Mg breakthrough curves using groundwater 1 The sample notation in panel c indicates field column experiments with EBCT in minutes
References
Appelo CAJ Postma D 1999 A consistent model for surface complexation on birnessite (MnO2) and its application to a column experiment Geochim Cosmochim Ac 63 (19-20) 3039-3048Badruzzaman M Westerhoff P Knappe DRU 2004 Intraparticle diffusion and adsorption of arsenate onto granular ferric hydroxide (GFH) Water Res 38 (18) 4002-4012Banerjee K Amy GL Prevost M Nour S Jekel M Gallagher PM Blumenschein CD 2008 Kinetic and thermodynamic aspects of adsorption of arsenic onto granular ferric hydroxide (GFH) Water Res 42 (13) 3371-3378Bang S Patel M Lippincott L Meng XG 2005 Removal of arsenic from groundwater by granular titanium dioxide adsorbent Chemosphere 60 (3) 389-397Bang S Pena ME Patel M Lippincott L Meng X Kim KW 2011 Removal of arsenate from water by adsorbents a comparative case study Environ Geochem Hlth 33 133-141Cui JL Shi JB Jiang GB Jing CY 2013 Arsenic levels and speciation from ingestion exposures to biomarkers in Shanxi China Implications for human health Environ Sci Technol 47 (10) 5419-5424Daus B Wennrich R Weiss H 2004 Sorption materials for arsenic removal from water A comparative study Water Res 38 (12) 2948-2954Dou XM Mohan D Pittman CU 2013 Arsenate adsorption on three types of granular schwertmannite Water Res 47 (9) 2938-2948Dou XM Zhang Y Yang M Pei YS Huang X Takayama T Kato S 2006 Occurrence of arsenic in groundwater in the suburbs of Beijing and its removal using an iron-cerium bimetal oxide adsorbent Water Qual Res J Can 41 (2) 140-146Gibbons MK Gagnon GA 2010 Adsorption of arsenic from a Nova Scotia groundwater onto water treatment residual solids Water Res 44 (19) 5740-5749Glocheux Y Mendez Pasarin M Albadarin AB Allen SJ Walker GM 2013 Removal of arsenic from groundwater by adsorption onto an acidified laterite by-product Chem Eng J 228 565-574Guan XH Wang JM Chusuei CC 2008 Removal of arsenic from water using granular ferric hydroxide Macroscopic and microscopic studies J Hazard Mater 156 (1-3) 178-185Gupta K Maity A Ghosh UC 2010 Manganese associated nanoparticles agglomerate of iron(III) oxide Synthesis characterization and arsenic(III) sorption behavior with mechanism J Hazard Mater 184 (1-3) 832-842Hao JM Han MJ Wang C Meng XG 2009 Enhanced removal of arsenite from water by a mesoporous hybrid material - Thiol-functionalized silica coated activated alumina Micropor Mesopor
Mat 124 (1-3) 1-7Hiemstra T Van Riemsdijk WH 2006 On the relationship between charge distribution surface hydration and the structure of the interface of metal hydroxides J Colloid Interf Sci 301 (1) 1-18Hristovski K Baumgardner A Westerhoff P 2007 Selecting metal oxide nanomaterials for arsenic removal in fixed bed columns From nanopowders to aggregated nanoparticle media J Hazard Mater 147 (1-2) 265-274Jang M Chen WF Cannon FS 2008 Preloading hydrous ferric oxide into granular activated carbon for arsenic removal Environ Sci Technol 42 (9) 3369-3374Jing CY Cui JL Huang YY Li AG 2012 Fabrication characterization and application of a composite adsorbent for simultaneous removal of arsenic and fluoride ACS Appl Mater Interfaces 4 (2) 714-720Kanematsu M Young TM Fukushi K Green PG Darby JL 2010 Extended triple layer modeling of arsenate and phosphate adsorption on a goethite-based granular porous adsorbent Environ Sci Technol 44 (9) 3388-3394Kong S Wang Y Zhan H Yuan S Liu M Zhou C 2013 Arsenite and Arsenate Removal from Contaminated Groundwater by Nanoscale Iron-Manganese Binary Oxides Column Studies Environmental Engineering Science 30 (11) 689-696Li Y Liu JR Jia SY Guo JW Zhuo J Na P 2012 TiO2 pillared montmorillonite as a photoactive adsorbent of arsenic under UV irradiation Chem Eng J 191 66-74Lin TF Wu JK 2001 Adsorption of arsenite and arsenate within activated alumina grains Equilibrium and kinetics Water Res 35 (8) 2049-2057Luo T Cui JL Hu S Huang YY Jing CY 2010 Arsenic removal and recovery from copper smelting wastewater using TiO2 Environ Sci Technol 44 (23) 9094-9098Maiti A Basu JK De S 2010a Development of a Treated Laterite for Arsenic Adsorption Effects of Treatment Parameters Industrial amp Engineering Chemistry Research 49 (10) 4873-4886Maiti A Basu JK De S 2010b Removal of Arsenic from Synthetic and Natural Groundwater Using Acid-Activated Laterite Environmental Progress amp Sustainable Energy 29 (4) 457-470Maiti A Basu JK De S 2012 Experimental and kinetic modeling of As(V) and As(III) adsorption on treated laterite using synthetic and contaminated groundwater Effects of phosphate silicate and carbonate ions Chem Eng J 191 1-12Maiti A Thakur BK Basu JK De S 2013a Comparison of treated laterite as arsenic adsorbent from different locations and performance of best filter under field conditions J Hazard Mater 262 1176-1186Maiti A Thakur BK Basu JK De S 2013b Comparison of treated laterite as arsenic adsorbent from different locations and performance of best filter under field conditions J Hazard Mater 262 (0) 1176-1186Maji SK Pal A Pal T 2008 Arsenic removal from real-life groundwater by adsorption on laterite soil J Hazard Mater 151 (2-3) 811-820Maji SK Kao YH Wang CJ Lu GS Wu JJ Liu CW 2012 Fixed bed adsorption of As(III) on iron-oxide-coated natural rock (IOCNR) and application to real arsenic-bearing groundwater Chem Eng J 203 285-293Mertens J Rose J Kagi R Chaurand P Plotze M Wehrli B Furrer G 2012 Adsorption of arsenic on polyaluminum granulate Environ Sci Technol 46 (13) 7310-7317Nguyen TV Vigneswaran S Ngo HH Pokhre D Viraraghavan T 2006 Iron-coated sponge as
effective media to remove arsenic from drinking water Water Qual Res J Can 41 (2) 164-170Parkhurst DL Appelo CAJ 2013 Description of input and examples for PHREEQC version 3-A computer program for speciation batch-reaction one-dimensional transport and inverse geochemical calculations US Geological SurveyPena M Meng XG Korfiatis GP Jing CY 2006 Adsorption mechanism of arsenic on nanocrystalline titanium dioxide Environ Sci Technol 40 (4) 1257-1262Ravel B Newville M 2005 ATHENA ARTEMIS HEPHAESTUS Data analysis for X-ray absorption spectroscopy using IFEFFIT J Synchrotron Radiat 12 537-541Saha B Bains R Greenwood F 2005 Physicochemical characterization of granular ferric hydroxide (GFH) for arsenic(V) sorption from water Separation Science and Technology 40 (14) 2909-2932Shan H Ma T Wang Y Zhao J Han H Deng Y He X Dong Y 2013 A cost-effective system for in-situ geological arsenic adsorption from groundwater J Contam Hydrol 154 1-9Stachowicz M Hiemstra T van Riemsdijk WH 2008 Multi-competitive interaction of As(III) and As(V) oxyanions with Ca2+ Mg2+ PO4
3- and CO32- ions on goethite J Colloid Interf Sci 320 (2) 400-
414Streat M Hellgardt K Newton NLR 2008 Hydrous ferric oxide as an adsorbent in water treatment - Part 3 Batch and mini-column adsorption of arsenic phosphorus fluorine and cadmium ions Process Safety and Environmental Protection 86 (B1) 21-30Thirunavukkarasu OS Viraraghavan T Subramanian KS 2003 Arsenic removal from drinking water using iron oxide-coated sand Water Air Soil Poll 142 (1-4) 95-111USEPA 2008 Assessing arsenic removal by metal (hydr)oxide adsorptive media using rapid small scale column tests Govenrnment Printing Office Washington DCWang J Xu W Chen L Huang X Liu J 2014 Preparation and evaluation of magnetic nanoparticles impregnated chitosan beads for arsenic removal from water Chem Eng J 251 25-34Westerhoff P Highfield D Badruzzaman M Yoon Y 2005 Rapid small-scale column tests for arsenate removal in iron oxide packed bed columns J Environ Eng-Asce 131 (2) 262-271Westerhoff P De Haan M Martindale A Badruzzaman M 2006 Arsenic adsorptive media technology selection strategies Water Qual Res J Can 41 (2) 171-184Yan L Huang Y Cui J Jing C 2015 Simultaneous As(III) and Cd removal from copper smelting wastewater using granular TiO2 columns Water Res 68 (0) 572-579Zhao K Guo HM 2014 Behavior and mechanism of arsenate adsorption on activated natural siderite Evidences from FTIR and XANES analysis Environ Sci Pollut Res 21 (3) 1944-1953Zhao K Guo H Zhou X 2014 Adsorption and heterogeneous oxidation of arsenite on modified granular natural siderite Characterization and behaviors Appl Geochem 48 184-192
Iron-Mn binary 15 40 145 176 321 22 253 347 754 (Maiti et al 2010a)
13
oxides
aUnit for ion concentration is mgL except as notedbestimated from bed volume breakthrough curves and influent As concentration if not explicitly expressed in the reference cThe species is As(V) if only one concentration is given
d
The groundwater As concentration was 385-440 μgL and additional ~600 μgL (As(III)As(V)=11) arsenic was added
14
222324252627
Fig S1 Boxplot of groundwater As levels in columns and filters in the literature in Table S1 Individual samples are shown as diamonds The range of each box represents the 25th
and 75th
percentile whereas the whiskers represent the 10th
and 90th
percentile
Synthesis of granular TiO2
Granular TiO2 (GTiO2) was prepared by hydrolysis of titanyl sulfate (TiOSO4)
Generally 300 g TiOSO4 was mixed with 1800 mL DI water in a 10 L jar reactor in an
ice bath at 4 oC Then 10 M NaOH was slowly added to adjust the pH to 6 The
precursor of TiO2 was obtained by washing the suspension with DI water several
times till the conductivity of the supernatant was less than 100 μScm Then 800 g
TiO2 precursor was mixed with 40 mL polyvinyl alcohol solution at 80 oC in a water
bath The product was crushed into 60-80 mesh and dried in an oven at 60 oC for 12 h
15
282930313233343536373839404142434445464748
49
50
51
52
53
54
55
56
57585960
Fig S2 Characterization of GTiO2 SEM (a) and XRD pattern with crystal face for each peak (b)
Fig S1 SEM images for GTiO2 in this study
Table S2 Average concentrations of As coexisting ions (mgL) and water chemistry for groundwater 1 and 2 from two wells
Table S3 Water parameters in the synthetic water used in the studyParameters Ca2+ Mg2+ HCO3
- Na+ Cl- pHConc (mgL) 401 1043 388 2460 3928 82
Table S4 PHREEQC input for a representative column with EBCT=054 min SOLUTION 0
This keyword is to define the influent groundwater chemistry parameters which are included in the adsorption reactions like ldquoArseniterdquo and ldquoArsenaterdquo and the experimental conditions including ldquopHrdquo The information defined in SOLUTION is available for subsequent transport and adsorptive reaction calculations
temp 23 pH 82 pe 4 redox pe units mgL density 1 Al 006 Arsenite 0374 Arsenate 0291 CO4
2-
4401 Ca 194 Cl 1456 F 115 Fe 047 K 137 Mg 395 Mn 012 NO3
-
34 Na 16872
17
79
80
8182
83
84858687888990919293949596979899
100101102103104105106107108109110111112
SO42-
1176 Si 89 -water 1 kg
SOLUTION 1-4 The small column was divided into four cells SOLUTION 1-4
are the groundwater chemistry parameters for the four cells temp 23 pH 83 pe 4 redox pe units ppm density 1 Al 006 C(4) 4401 Ca 194 Cl 1456 F 115 Fe 047 K 137 Mg 395 Mn 012 N(3) 34 Na 16872 S(6) 1176 Si 89 -water 1 kg
SOLUTION_SPECIES This keyword is to define the dissociation constant logK
and diffusion constant (dw) in solution for arsenite and arsenate
Arsenite adsorption equation on GTiO2 surface H3ArseniteO3 is the primary species of As(III) at the groundwater pH 82 (Surf_sO)2ArseniteOH-066 is the adsorptive bidentate binuclear structure of As(III) on GTiO2
log_k 1635 The adsorptive reaction constant for As(III) on GTiO2 in
the current condition which could be changed with different experimental conditions
-cd_music -2 -1 0 066 3 CD-MUSIC model is integrated in the PHREEQC
modeling The numbers represent -2 the change in charge at the plane of Surf_sOH due to loss of two hydrogens -1 the change in charge at 1 plane due to gain of one hydrogen and one oxygen on Arsenite 0 the change in charge at the 2 plane usually caused by the outer sphere adsorption 066 the fraction of the central ion (As) charge that is associated with plane 0 which reflecting the charge distribution 3 the charge on the central ion (As)
Table S54 Parameters of Weber-Morris intraparticle model for As(IIIV) adsorption kinetics on GTiO2 using synthetic water Initial As concentration = 800 μgL adsorbent dose = 02 gL pH = 82 in synthetic groundwater
External film diffusion
Intraparticle diffusion
aRex2 bkp1
cb1aRin
2 bkp2cb 2
As(V) 0984 0497 0022 0976 01331878
As(III) 0970 0583
-0088 0981 0218
1105
aRex is WM external proportion fitting parameter while Rin is WM intraparticle proportion fitting parameterbk The unit of kp is mggh05 cb The unit of b is mgg
Table S6 Comparison of the adsorption capacities of As(III) and As(V) on GTiO2 and the representative granular adsorbents in similar experimental condition from the literature
AdsorbentParticle size (mm) As
qm
(mgg)Dose (gL) Experimental conditions Literature
GTiO2 018~025 As(III) 980 1 0~500 mgL at pH 82 01 M NaCl This studyGTiO2 018~025 As(V) 358 1 0~500 mgL at pH 82 01 M NaCl This study
Granular TiO2 015~06 As(III) 392 10~60 mgL As at pH 70 in simulated groundwater (100 mgL Ca 20 mgL Mg 50 mgL Na 200 mgL Cl-
)(Bang et al 2005)
Granular TiO2 015~06 As(V) 400 10~60 mgL As at pH 70 in simulated groundwater (100 mgL Ca 20 mgL Mg 50 mgL Na 200 mgL Cl-
)(Bang et al 2005)
E33 (FeOOH)0044~0075 As(V) 202 1 0~15 mgL at pH 70 in 001 M NaCl
(Kanematsu et al 2010)
E33 (FeOOH) 05~2 As(V) 180 1 0~50 mgL at pH 70 in 004 M NaClO4 (Jing et al 2012)
GFH 02~06 As(V) 650 10 0~2000 mgL at pH 8 in 01 M NaNO3
(Guan et al 2008)
GFH0009~0125 As(V) 23 025 0~07 μgL at pH 65 in DI water
(Banerjee et al 2008)
GFH0009~0125 As(V) 200 - 0~01 μgL at pH 70 in DI water
(Badruzzaman et al 2004)
GFH 050~065 As(V) 155 - 0~06 μgL at pH 70 in DI water (Saha et al 2005)
GHFO-NN 015~030 As(V) 330 0001 0~225 mgL at pH 8 in DI water(Streat et al 2008)
GHFO-VL 015~030 As(V) 360 0001 0~225 mgL at pH 8 in DI water(Streat et al 2008)
25
374375
Spherical schwertmannite 1~15 As(V) 36 05 0~5 mgL at pH 70 in DI water (Dou et al 2013)Cylindrical schwertmannite 1~25 As(V) 223 05
0~5 mgL at pH 70 in DI water(Dou et al 2013)
Irregular schwertmannite 10~16 As(V) 317 05 0~5 mgL at pH 70 in DI water (Dou et al 2013)Fe impregnated chitosan beads (MICB) 25 As(III) 117 1 0~05 mgL at pH 60 in DI water
(Wang et al 2014)
MICB 25 As(V) 191 1 0~1 mgL at pH 60 in DI water(Wang et al 2014)
MICB 25 As(III) 353 1 0~15 mgL at pH 60 in DI water(Wang et al 2014)
MICB 25 As(V) 357 1 0~16 mgL at pH 60 in DI water(Wang et al 2014)
Iron hydroxide granules (GIH) 3~4 As(V) 23 4
5~100 mgL at pH 70 in 10 mgL SO42-
14 mgL NH4Cl buffer solution (Daus et al 2004)
Activated Al2O3
0074~0149 As(V) 159 - 285~115 mgL at pH 52 in DI water
(Lin and Wu 2001)
Activated Al2O3
0074~0149 As(III) 35 - 079~490 mgL at pH 70 in DI water
(Lin and Wu 2001)
Activated Al2O3 ~20 As(V) 73 at pH 70 in 004 M NaClO4 (Jing et al 2012)
Activated natural siderite 05~10 As(V) 22 10 0 1~20 mgL at pH 7 in DI water(Zhao and Guo 2014)
Polyaluminum Granulate 1~3 As(III) 705 10 0~150 mgL at pH 51-56 in DI water(Mertens et al 2012)
Polyaluminum Granulate 1~3 As(V) 180 10 0~150 mgL at pH 51-56 in DI water (Mertens et al
26
2012)
Acidified laterite 1~12 As(III) 19 1 025~5 mgL at pH 7 in 100 mgL NaHCO3
(Glocheux et al 2013)
Acidified laterite 1~12 As(V) 13 1 025~5 mgL at pH 7 in 100 mgL NaHCO3
(Glocheux et al 2013)
Laterite 1~12 As(III) 07 1025~5 mgL at pH 7 in 100 mgL NaHCO3 (Glocheux et al
2013)
Laterite 1~12 As(V) 04 1025~5 mgL at pH 7 in 100 mgL NaHCO3 (Glocheux et al
2013)
Treated laterite 03-05 As(V) 216 05 02-20 mgL at pH 70 in DI water(Maiti et al 2012)
Treated laterite 03-05 As(III) 94 05 02-20 mgL at pH 70 in DI water(Maiti et al 2012)
Treated laterite03-05
As(V) 241 05 02-20 mgL at pH 70 in DI water(Maiti et al 2010a)
Treated laterite03-05
As(III) 81 05 02-20 mgL at pH 70 in DI water(Maiti et al 2010a)
Acid-activated laterite-103-07
As(III) 0633 50 02-10 mgL at pH 66-70 in DI water(Maiti et al 2010b)
Acid-activated laterite-203-07
As(III) 087650 02-10 mgL at pH 66-70 in DI water (Maiti et al
2010b)
Acid-activated laterite-303-07
As(III) 063450 02-10 mgL at pH 66-70 in DI water (Maiti et al
2010b)
Acid-activated laterite-103-07
As(V) 059850 02-10 mgL at pH 66-70 in DI water (Maiti et al
2010b)
27
Acid-activated laterite-203-07
As(V) 07550 02-10 mgL at pH 66-70 in DI water (Maiti et al
2010b)
Acid-activated laterite-303-07
As(V) 07550 02-10 mgL at pH 66-70 in DI water (Maiti et al
2010b)
Treated laterite-1 03-06 As(V) 019 20 0-20 mgL As at pH 72 in DI water(Maiti et al 2013b)
Treated laterite-1 03-06 As(III) 018 20 0-20 mgL As at pH 72 in DI water(Maiti et al 2013b)
Treated laterite-2 03-06 As(V) 004 20 0-20 mgL As at pH 72 in DI water(Maiti et al 2013b)
Treated laterite-2 03-06 As(III) 003 20 0-20 mgL As at pH 72 in DI water(Maiti et al 2013b)
Treated laterite-3 03-06 As(V) 007 20 0-20 mgL As at pH 72 in DI water(Maiti et al 2013b)
Treated laterite-3 03-06 As(III) 004 20 0-20 mgL As at pH 72 in DI water(Maiti et al 2013b)
28
376377
Charge distribution multi-site surface complexation (CD-MUSIC) modeling
The CD-MUSIC model with the 2-pK TPM adsorption option was used to
describe adsorption behaviors of As cations and anions on GTiO2 The CD-MUSIC
model incorporates the structural information of surfaces adsorbed species and the
double layers by distributing the charge of an adsorbate between the surface and
interfacial water (Hiemstra and Van Riemsdijk 2006) The CD-MUSIC model has
been successfully used in describing As adsorption in batch experiments (Pena et al
2006 Stachowicz et al 2008)
The adsorption constants of counter ions were set to -1 and the proton affinity
constant was set to the PZC of 58 for TiOH-13 (Luo et al 2010) The charge
distribution (CD) value shows the fraction (f) of the charge of the central As ion
attributed to the surface plane and the remaining part (1-f) was attributed to the other
ligands of the complex which were positioned toward the diffuse layer The CD value
for As surface complexes was obtained by fitting the experimental data The
calculation was performed using the chemical equilibrium program MINTEQ to
simulate the adsorption and the aqueous reactions
29
378379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
Fig S32 Adsorption of silicate (a) calcium and magnesium (b) as a function of GTiO2
dose in groundwater 1 The solid lines represent the CD-MUSIC modeling result
30
400
401
402
403
404
405
406
407
408409410
Table S75 Surface parameters and species used in the CD-MUSIC modeling in As(IIIV) removal under different GTiO2 dose in 01 M NaCl and groundwater 1 in Fig 2 and Fig S32
= exp(-FΨ1RT) P2 = exp(-FΨ2RT) F the Faraday constant (C mol-1) R the gas constant (J mol-1 K-1) T the absolute temperature (K)
Ψ0 Ψ1 Ψ2 the electrostatic potential (V) of 0- 1- and 2-plane respectively alogK for 01 M NaCl at 6 hours blogK for 01 M NaCl at 6 days clogK for groundwater 1 at 6 days
31
411412
413414415
32
416
Table S86 The charge distribution (f) of central As atom to TiO2 surface in simulating the effect of cations and anions on As adsorption in 01 M NaCl at pH 82 in Fig 4 BK Si HCO3 All
As(V) 022 017 012 016As(III) 040 020 058 056
Fig S43 Molar percentage () of As Ca Mg and Si on pristine and spent GTiO2
surfaces using EDX analysis The spent GTiO2 samples after field column experiments using groundwater 1 were identified with EBCT in min under x-axis The value of molar percentage of each element was averaged from randomly-chosen positions on the adsorbent surface
33
417
418
419420
421422
423
424
425
426
427
428
429
430
431
432
433434435436437438
439
440
441
As speciation analysis on spent GTiO2 using XANES
The spent GTiO2 samples were ground using a mortar and pestle and then the
ground powder was spread on Scotch tape The As k-edge XANES spectra were
collected at beamline 01C1 at the National Synchrotron Radiation Research Center
(NSRRC) Taiwan Spectra were acquired from -150 to 300 eV relative to the As K-
edge of 11867 eV at cryogenic temperature (77 K) using a cryostat to prevent the
oxidation of As(III) by X-rays The fluorescence signals were collected using a Lytle
detector Two to four scans were collected for each sample and averaged to improve
the signalnoise ratio The XANES analysis was performed with the Athena program
in the IFEFFIT computer package for linear combination fit (LCF) (Cui et al 2013
Ravel and Newville 2005)
34
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
PHREEQC modeling for As breakthrough curves in field column experiments
PHREEQC a geochemical model integrates macroscopic mass transfer
processes with a microscopic surface complexation model (Parkhurst and Appelo
2013) It can be applied in calculating solution complex speciation batch-reaction
and one-dimensional reactive-transport and inverse modeling In our study the one-
dimensional column was defined by four cells with the same length The cell length
was calculated to be one-fourth of the actual column length Time step (s) was
calculated according to equation Time step = Lcell(Q60A) where Lcell is the cell
length (cm) Q is flow velocity (mLmin) A is the effective column cross section area
(cm2) which is the column cross-sectional area multiplied by porosity (060) Total
shift number was calculated by dividing actual column operation time by the time
step The transport block was modeled by shifting the solute content from one cell to
the next one In each cell the aqueous solute was mixed and adsorbed on GTiO2
according to the equations In each cell the aqueous solute was mixed and assumed to
be in equilibration with GTiO2 The sequence of shifting mixing and equilibrium
adsorption was repeated for each cell until the total number of shifts was completed
The diffusion coefficient Dw in PHREEQC accounting for retardation was
calculated as Dw=x2
(36t) where x stands for the diffusion length (estimated as the
radius of the particle size) and t represents equilibrium time adopted from the batch
kinetic data (Mertens et al 2012)
For CD-MUSIC modeling in the PHREEQC take As(III) as an example to
explain the adsorption equation The As(III) adsorption is considered as a ligand
35
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
exchange reaction with the hydroxide group on GTiO2 (Surf_sOH-033) forming a
H3ArseniteO3 is the master species in groundwater at pH 82
(Surf_sO)2ArseniteOH-066 is the common adsorbed bidentate binuclear complex
evidenced by our previous reports(Pena et al 2006 Yan et al 2015) LogK is the
adsorption equilibrium constants Generally every adsorption equation under certain
experimental condition has a unique value of logK In the adsorption equation ldquo-2rdquo
represents the lost two hydrogens by Surf_sOH-033 after it adsorbs H3ArseniteO3 ldquo-
1rdquo represents the change in charge on Arsenite at 1 plane due to gaining one hydrogen
(+1) and one oxygen (-2) ldquo0rdquo represents no change in charge at the 2 plane ldquo066rdquo is
the fraction of the central ion (As) on GTiO2 surface that is associated with plane 0
ldquo3rdquo is the charge on the central ion As(III) Following this equation and the relevant
parameters As(III) adsorbed on GTiO2
The diffusion coefficient Dw in PHREEQC accounting for retardation was
calculated as Dw=x2(36t) where x stands for the diffusion length (estimated as the
radius of the particle size) and t represents equilibrium time adopted from the batch
kinetic data (Mertens et al 2012)
To well simulate the As breakthrough curve in columns four As(V) adsorption
reactions (Table 1) were employed Adsorption site density of 60 mmolg was
36
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
adopted from our previous study (Pena et al 2006) and the total adsorption sites were
calculated to be 1844 sitesnm2 The final optimized ratio of strong to weak sites was
51 The surface complexation constants were reasonably adjusted according to the
batch modeling results as the column reaction may not reach equilibrium in local
micro-interfacial areas due to much less contact time between As and GTiO2 than that
in batch experiments (Appelo and Postma 1999) In the modeling a stepwise
procedure was adopted to achieve a viable result An estimation of two thirds of the
surface site density being accessible for EBCT=011 min with large flow rate of 265
mLmin was optimized which could probably result from unavailable adsorption sites
due to fast transport through the column
The adsorbed As on GTiO2 in the column was calculated by mass balance
between the influent and effluent
where Asadsorbed is the adsorbed As on GTiO2 (mgg) n is the number of collected
samples Cin and Cout are influent and effluent As concentrations (mgL) respectively
Vi is volume (L) of groundwater passed through the column between sample i-1 and i
and m is the mass of GTiO2 (g)
Even though the oxidation of adsorbed As(III) occurred during filtration as
analyzed from XANES and mass balance analysis (Fig 7) no As(III) oxidation
reactions were considered in PHREEQC modeling which would not impact the
breakthrough of As(IIIV)
37
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
38
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
Fig S54 Effect of EBCT on Si Ca and Mg breakthrough curves using groundwater 1 The sample notation in panel c indicates field column experiments with EBCT in minutes
References
Appelo CAJ Postma D 1999 A consistent model for surface complexation on birnessite (MnO2) and its application to a column experiment Geochim Cosmochim Ac 63 (19-20) 3039-3048Badruzzaman M Westerhoff P Knappe DRU 2004 Intraparticle diffusion and adsorption of arsenate onto granular ferric hydroxide (GFH) Water Res 38 (18) 4002-4012Banerjee K Amy GL Prevost M Nour S Jekel M Gallagher PM Blumenschein CD 2008 Kinetic and thermodynamic aspects of adsorption of arsenic onto granular ferric hydroxide (GFH) Water Res 42 (13) 3371-3378Bang S Patel M Lippincott L Meng XG 2005 Removal of arsenic from groundwater by granular titanium dioxide adsorbent Chemosphere 60 (3) 389-397Bang S Pena ME Patel M Lippincott L Meng X Kim KW 2011 Removal of arsenate from water by adsorbents a comparative case study Environ Geochem Hlth 33 133-141Cui JL Shi JB Jiang GB Jing CY 2013 Arsenic levels and speciation from ingestion exposures to biomarkers in Shanxi China Implications for human health Environ Sci Technol 47 (10) 5419-5424Daus B Wennrich R Weiss H 2004 Sorption materials for arsenic removal from water A comparative study Water Res 38 (12) 2948-2954Dou XM Mohan D Pittman CU 2013 Arsenate adsorption on three types of granular schwertmannite Water Res 47 (9) 2938-2948Dou XM Zhang Y Yang M Pei YS Huang X Takayama T Kato S 2006 Occurrence of arsenic in groundwater in the suburbs of Beijing and its removal using an iron-cerium bimetal oxide adsorbent Water Qual Res J Can 41 (2) 140-146Gibbons MK Gagnon GA 2010 Adsorption of arsenic from a Nova Scotia groundwater onto water treatment residual solids Water Res 44 (19) 5740-5749Glocheux Y Mendez Pasarin M Albadarin AB Allen SJ Walker GM 2013 Removal of arsenic from groundwater by adsorption onto an acidified laterite by-product Chem Eng J 228 565-574Guan XH Wang JM Chusuei CC 2008 Removal of arsenic from water using granular ferric hydroxide Macroscopic and microscopic studies J Hazard Mater 156 (1-3) 178-185Gupta K Maity A Ghosh UC 2010 Manganese associated nanoparticles agglomerate of iron(III) oxide Synthesis characterization and arsenic(III) sorption behavior with mechanism J Hazard Mater 184 (1-3) 832-842Hao JM Han MJ Wang C Meng XG 2009 Enhanced removal of arsenite from water by a mesoporous hybrid material - Thiol-functionalized silica coated activated alumina Micropor Mesopor
Mat 124 (1-3) 1-7Hiemstra T Van Riemsdijk WH 2006 On the relationship between charge distribution surface hydration and the structure of the interface of metal hydroxides J Colloid Interf Sci 301 (1) 1-18Hristovski K Baumgardner A Westerhoff P 2007 Selecting metal oxide nanomaterials for arsenic removal in fixed bed columns From nanopowders to aggregated nanoparticle media J Hazard Mater 147 (1-2) 265-274Jang M Chen WF Cannon FS 2008 Preloading hydrous ferric oxide into granular activated carbon for arsenic removal Environ Sci Technol 42 (9) 3369-3374Jing CY Cui JL Huang YY Li AG 2012 Fabrication characterization and application of a composite adsorbent for simultaneous removal of arsenic and fluoride ACS Appl Mater Interfaces 4 (2) 714-720Kanematsu M Young TM Fukushi K Green PG Darby JL 2010 Extended triple layer modeling of arsenate and phosphate adsorption on a goethite-based granular porous adsorbent Environ Sci Technol 44 (9) 3388-3394Kong S Wang Y Zhan H Yuan S Liu M Zhou C 2013 Arsenite and Arsenate Removal from Contaminated Groundwater by Nanoscale Iron-Manganese Binary Oxides Column Studies Environmental Engineering Science 30 (11) 689-696Li Y Liu JR Jia SY Guo JW Zhuo J Na P 2012 TiO2 pillared montmorillonite as a photoactive adsorbent of arsenic under UV irradiation Chem Eng J 191 66-74Lin TF Wu JK 2001 Adsorption of arsenite and arsenate within activated alumina grains Equilibrium and kinetics Water Res 35 (8) 2049-2057Luo T Cui JL Hu S Huang YY Jing CY 2010 Arsenic removal and recovery from copper smelting wastewater using TiO2 Environ Sci Technol 44 (23) 9094-9098Maiti A Basu JK De S 2010a Development of a Treated Laterite for Arsenic Adsorption Effects of Treatment Parameters Industrial amp Engineering Chemistry Research 49 (10) 4873-4886Maiti A Basu JK De S 2010b Removal of Arsenic from Synthetic and Natural Groundwater Using Acid-Activated Laterite Environmental Progress amp Sustainable Energy 29 (4) 457-470Maiti A Basu JK De S 2012 Experimental and kinetic modeling of As(V) and As(III) adsorption on treated laterite using synthetic and contaminated groundwater Effects of phosphate silicate and carbonate ions Chem Eng J 191 1-12Maiti A Thakur BK Basu JK De S 2013a Comparison of treated laterite as arsenic adsorbent from different locations and performance of best filter under field conditions J Hazard Mater 262 1176-1186Maiti A Thakur BK Basu JK De S 2013b Comparison of treated laterite as arsenic adsorbent from different locations and performance of best filter under field conditions J Hazard Mater 262 (0) 1176-1186Maji SK Pal A Pal T 2008 Arsenic removal from real-life groundwater by adsorption on laterite soil J Hazard Mater 151 (2-3) 811-820Maji SK Kao YH Wang CJ Lu GS Wu JJ Liu CW 2012 Fixed bed adsorption of As(III) on iron-oxide-coated natural rock (IOCNR) and application to real arsenic-bearing groundwater Chem Eng J 203 285-293Mertens J Rose J Kagi R Chaurand P Plotze M Wehrli B Furrer G 2012 Adsorption of arsenic on polyaluminum granulate Environ Sci Technol 46 (13) 7310-7317Nguyen TV Vigneswaran S Ngo HH Pokhre D Viraraghavan T 2006 Iron-coated sponge as
effective media to remove arsenic from drinking water Water Qual Res J Can 41 (2) 164-170Parkhurst DL Appelo CAJ 2013 Description of input and examples for PHREEQC version 3-A computer program for speciation batch-reaction one-dimensional transport and inverse geochemical calculations US Geological SurveyPena M Meng XG Korfiatis GP Jing CY 2006 Adsorption mechanism of arsenic on nanocrystalline titanium dioxide Environ Sci Technol 40 (4) 1257-1262Ravel B Newville M 2005 ATHENA ARTEMIS HEPHAESTUS Data analysis for X-ray absorption spectroscopy using IFEFFIT J Synchrotron Radiat 12 537-541Saha B Bains R Greenwood F 2005 Physicochemical characterization of granular ferric hydroxide (GFH) for arsenic(V) sorption from water Separation Science and Technology 40 (14) 2909-2932Shan H Ma T Wang Y Zhao J Han H Deng Y He X Dong Y 2013 A cost-effective system for in-situ geological arsenic adsorption from groundwater J Contam Hydrol 154 1-9Stachowicz M Hiemstra T van Riemsdijk WH 2008 Multi-competitive interaction of As(III) and As(V) oxyanions with Ca2+ Mg2+ PO4
3- and CO32- ions on goethite J Colloid Interf Sci 320 (2) 400-
414Streat M Hellgardt K Newton NLR 2008 Hydrous ferric oxide as an adsorbent in water treatment - Part 3 Batch and mini-column adsorption of arsenic phosphorus fluorine and cadmium ions Process Safety and Environmental Protection 86 (B1) 21-30Thirunavukkarasu OS Viraraghavan T Subramanian KS 2003 Arsenic removal from drinking water using iron oxide-coated sand Water Air Soil Poll 142 (1-4) 95-111USEPA 2008 Assessing arsenic removal by metal (hydr)oxide adsorptive media using rapid small scale column tests Govenrnment Printing Office Washington DCWang J Xu W Chen L Huang X Liu J 2014 Preparation and evaluation of magnetic nanoparticles impregnated chitosan beads for arsenic removal from water Chem Eng J 251 25-34Westerhoff P Highfield D Badruzzaman M Yoon Y 2005 Rapid small-scale column tests for arsenate removal in iron oxide packed bed columns J Environ Eng-Asce 131 (2) 262-271Westerhoff P De Haan M Martindale A Badruzzaman M 2006 Arsenic adsorptive media technology selection strategies Water Qual Res J Can 41 (2) 171-184Yan L Huang Y Cui J Jing C 2015 Simultaneous As(III) and Cd removal from copper smelting wastewater using granular TiO2 columns Water Res 68 (0) 572-579Zhao K Guo HM 2014 Behavior and mechanism of arsenate adsorption on activated natural siderite Evidences from FTIR and XANES analysis Environ Sci Pollut Res 21 (3) 1944-1953Zhao K Guo H Zhou X 2014 Adsorption and heterogeneous oxidation of arsenite on modified granular natural siderite Characterization and behaviors Appl Geochem 48 184-192
aUnit for ion concentration is mgL except as notedbestimated from bed volume breakthrough curves and influent As concentration if not explicitly expressed in the reference cThe species is As(V) if only one concentration is given
d
The groundwater As concentration was 385-440 μgL and additional ~600 μgL (As(III)As(V)=11) arsenic was added
14
222324252627
Fig S1 Boxplot of groundwater As levels in columns and filters in the literature in Table S1 Individual samples are shown as diamonds The range of each box represents the 25th
and 75th
percentile whereas the whiskers represent the 10th
and 90th
percentile
Synthesis of granular TiO2
Granular TiO2 (GTiO2) was prepared by hydrolysis of titanyl sulfate (TiOSO4)
Generally 300 g TiOSO4 was mixed with 1800 mL DI water in a 10 L jar reactor in an
ice bath at 4 oC Then 10 M NaOH was slowly added to adjust the pH to 6 The
precursor of TiO2 was obtained by washing the suspension with DI water several
times till the conductivity of the supernatant was less than 100 μScm Then 800 g
TiO2 precursor was mixed with 40 mL polyvinyl alcohol solution at 80 oC in a water
bath The product was crushed into 60-80 mesh and dried in an oven at 60 oC for 12 h
15
282930313233343536373839404142434445464748
49
50
51
52
53
54
55
56
57585960
Fig S2 Characterization of GTiO2 SEM (a) and XRD pattern with crystal face for each peak (b)
Fig S1 SEM images for GTiO2 in this study
Table S2 Average concentrations of As coexisting ions (mgL) and water chemistry for groundwater 1 and 2 from two wells
Table S3 Water parameters in the synthetic water used in the studyParameters Ca2+ Mg2+ HCO3
- Na+ Cl- pHConc (mgL) 401 1043 388 2460 3928 82
Table S4 PHREEQC input for a representative column with EBCT=054 min SOLUTION 0
This keyword is to define the influent groundwater chemistry parameters which are included in the adsorption reactions like ldquoArseniterdquo and ldquoArsenaterdquo and the experimental conditions including ldquopHrdquo The information defined in SOLUTION is available for subsequent transport and adsorptive reaction calculations
temp 23 pH 82 pe 4 redox pe units mgL density 1 Al 006 Arsenite 0374 Arsenate 0291 CO4
2-
4401 Ca 194 Cl 1456 F 115 Fe 047 K 137 Mg 395 Mn 012 NO3
-
34 Na 16872
17
79
80
8182
83
84858687888990919293949596979899
100101102103104105106107108109110111112
SO42-
1176 Si 89 -water 1 kg
SOLUTION 1-4 The small column was divided into four cells SOLUTION 1-4
are the groundwater chemistry parameters for the four cells temp 23 pH 83 pe 4 redox pe units ppm density 1 Al 006 C(4) 4401 Ca 194 Cl 1456 F 115 Fe 047 K 137 Mg 395 Mn 012 N(3) 34 Na 16872 S(6) 1176 Si 89 -water 1 kg
SOLUTION_SPECIES This keyword is to define the dissociation constant logK
and diffusion constant (dw) in solution for arsenite and arsenate
Arsenite adsorption equation on GTiO2 surface H3ArseniteO3 is the primary species of As(III) at the groundwater pH 82 (Surf_sO)2ArseniteOH-066 is the adsorptive bidentate binuclear structure of As(III) on GTiO2
log_k 1635 The adsorptive reaction constant for As(III) on GTiO2 in
the current condition which could be changed with different experimental conditions
-cd_music -2 -1 0 066 3 CD-MUSIC model is integrated in the PHREEQC
modeling The numbers represent -2 the change in charge at the plane of Surf_sOH due to loss of two hydrogens -1 the change in charge at 1 plane due to gain of one hydrogen and one oxygen on Arsenite 0 the change in charge at the 2 plane usually caused by the outer sphere adsorption 066 the fraction of the central ion (As) charge that is associated with plane 0 which reflecting the charge distribution 3 the charge on the central ion (As)
Table S54 Parameters of Weber-Morris intraparticle model for As(IIIV) adsorption kinetics on GTiO2 using synthetic water Initial As concentration = 800 μgL adsorbent dose = 02 gL pH = 82 in synthetic groundwater
External film diffusion
Intraparticle diffusion
aRex2 bkp1
cb1aRin
2 bkp2cb 2
As(V) 0984 0497 0022 0976 01331878
As(III) 0970 0583
-0088 0981 0218
1105
aRex is WM external proportion fitting parameter while Rin is WM intraparticle proportion fitting parameterbk The unit of kp is mggh05 cb The unit of b is mgg
Table S6 Comparison of the adsorption capacities of As(III) and As(V) on GTiO2 and the representative granular adsorbents in similar experimental condition from the literature
AdsorbentParticle size (mm) As
qm
(mgg)Dose (gL) Experimental conditions Literature
GTiO2 018~025 As(III) 980 1 0~500 mgL at pH 82 01 M NaCl This studyGTiO2 018~025 As(V) 358 1 0~500 mgL at pH 82 01 M NaCl This study
Granular TiO2 015~06 As(III) 392 10~60 mgL As at pH 70 in simulated groundwater (100 mgL Ca 20 mgL Mg 50 mgL Na 200 mgL Cl-
)(Bang et al 2005)
Granular TiO2 015~06 As(V) 400 10~60 mgL As at pH 70 in simulated groundwater (100 mgL Ca 20 mgL Mg 50 mgL Na 200 mgL Cl-
)(Bang et al 2005)
E33 (FeOOH)0044~0075 As(V) 202 1 0~15 mgL at pH 70 in 001 M NaCl
(Kanematsu et al 2010)
E33 (FeOOH) 05~2 As(V) 180 1 0~50 mgL at pH 70 in 004 M NaClO4 (Jing et al 2012)
GFH 02~06 As(V) 650 10 0~2000 mgL at pH 8 in 01 M NaNO3
(Guan et al 2008)
GFH0009~0125 As(V) 23 025 0~07 μgL at pH 65 in DI water
(Banerjee et al 2008)
GFH0009~0125 As(V) 200 - 0~01 μgL at pH 70 in DI water
(Badruzzaman et al 2004)
GFH 050~065 As(V) 155 - 0~06 μgL at pH 70 in DI water (Saha et al 2005)
GHFO-NN 015~030 As(V) 330 0001 0~225 mgL at pH 8 in DI water(Streat et al 2008)
GHFO-VL 015~030 As(V) 360 0001 0~225 mgL at pH 8 in DI water(Streat et al 2008)
25
374375
Spherical schwertmannite 1~15 As(V) 36 05 0~5 mgL at pH 70 in DI water (Dou et al 2013)Cylindrical schwertmannite 1~25 As(V) 223 05
0~5 mgL at pH 70 in DI water(Dou et al 2013)
Irregular schwertmannite 10~16 As(V) 317 05 0~5 mgL at pH 70 in DI water (Dou et al 2013)Fe impregnated chitosan beads (MICB) 25 As(III) 117 1 0~05 mgL at pH 60 in DI water
(Wang et al 2014)
MICB 25 As(V) 191 1 0~1 mgL at pH 60 in DI water(Wang et al 2014)
MICB 25 As(III) 353 1 0~15 mgL at pH 60 in DI water(Wang et al 2014)
MICB 25 As(V) 357 1 0~16 mgL at pH 60 in DI water(Wang et al 2014)
Iron hydroxide granules (GIH) 3~4 As(V) 23 4
5~100 mgL at pH 70 in 10 mgL SO42-
14 mgL NH4Cl buffer solution (Daus et al 2004)
Activated Al2O3
0074~0149 As(V) 159 - 285~115 mgL at pH 52 in DI water
(Lin and Wu 2001)
Activated Al2O3
0074~0149 As(III) 35 - 079~490 mgL at pH 70 in DI water
(Lin and Wu 2001)
Activated Al2O3 ~20 As(V) 73 at pH 70 in 004 M NaClO4 (Jing et al 2012)
Activated natural siderite 05~10 As(V) 22 10 0 1~20 mgL at pH 7 in DI water(Zhao and Guo 2014)
Polyaluminum Granulate 1~3 As(III) 705 10 0~150 mgL at pH 51-56 in DI water(Mertens et al 2012)
Polyaluminum Granulate 1~3 As(V) 180 10 0~150 mgL at pH 51-56 in DI water (Mertens et al
26
2012)
Acidified laterite 1~12 As(III) 19 1 025~5 mgL at pH 7 in 100 mgL NaHCO3
(Glocheux et al 2013)
Acidified laterite 1~12 As(V) 13 1 025~5 mgL at pH 7 in 100 mgL NaHCO3
(Glocheux et al 2013)
Laterite 1~12 As(III) 07 1025~5 mgL at pH 7 in 100 mgL NaHCO3 (Glocheux et al
2013)
Laterite 1~12 As(V) 04 1025~5 mgL at pH 7 in 100 mgL NaHCO3 (Glocheux et al
2013)
Treated laterite 03-05 As(V) 216 05 02-20 mgL at pH 70 in DI water(Maiti et al 2012)
Treated laterite 03-05 As(III) 94 05 02-20 mgL at pH 70 in DI water(Maiti et al 2012)
Treated laterite03-05
As(V) 241 05 02-20 mgL at pH 70 in DI water(Maiti et al 2010a)
Treated laterite03-05
As(III) 81 05 02-20 mgL at pH 70 in DI water(Maiti et al 2010a)
Acid-activated laterite-103-07
As(III) 0633 50 02-10 mgL at pH 66-70 in DI water(Maiti et al 2010b)
Acid-activated laterite-203-07
As(III) 087650 02-10 mgL at pH 66-70 in DI water (Maiti et al
2010b)
Acid-activated laterite-303-07
As(III) 063450 02-10 mgL at pH 66-70 in DI water (Maiti et al
2010b)
Acid-activated laterite-103-07
As(V) 059850 02-10 mgL at pH 66-70 in DI water (Maiti et al
2010b)
27
Acid-activated laterite-203-07
As(V) 07550 02-10 mgL at pH 66-70 in DI water (Maiti et al
2010b)
Acid-activated laterite-303-07
As(V) 07550 02-10 mgL at pH 66-70 in DI water (Maiti et al
2010b)
Treated laterite-1 03-06 As(V) 019 20 0-20 mgL As at pH 72 in DI water(Maiti et al 2013b)
Treated laterite-1 03-06 As(III) 018 20 0-20 mgL As at pH 72 in DI water(Maiti et al 2013b)
Treated laterite-2 03-06 As(V) 004 20 0-20 mgL As at pH 72 in DI water(Maiti et al 2013b)
Treated laterite-2 03-06 As(III) 003 20 0-20 mgL As at pH 72 in DI water(Maiti et al 2013b)
Treated laterite-3 03-06 As(V) 007 20 0-20 mgL As at pH 72 in DI water(Maiti et al 2013b)
Treated laterite-3 03-06 As(III) 004 20 0-20 mgL As at pH 72 in DI water(Maiti et al 2013b)
28
376377
Charge distribution multi-site surface complexation (CD-MUSIC) modeling
The CD-MUSIC model with the 2-pK TPM adsorption option was used to
describe adsorption behaviors of As cations and anions on GTiO2 The CD-MUSIC
model incorporates the structural information of surfaces adsorbed species and the
double layers by distributing the charge of an adsorbate between the surface and
interfacial water (Hiemstra and Van Riemsdijk 2006) The CD-MUSIC model has
been successfully used in describing As adsorption in batch experiments (Pena et al
2006 Stachowicz et al 2008)
The adsorption constants of counter ions were set to -1 and the proton affinity
constant was set to the PZC of 58 for TiOH-13 (Luo et al 2010) The charge
distribution (CD) value shows the fraction (f) of the charge of the central As ion
attributed to the surface plane and the remaining part (1-f) was attributed to the other
ligands of the complex which were positioned toward the diffuse layer The CD value
for As surface complexes was obtained by fitting the experimental data The
calculation was performed using the chemical equilibrium program MINTEQ to
simulate the adsorption and the aqueous reactions
29
378379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
Fig S32 Adsorption of silicate (a) calcium and magnesium (b) as a function of GTiO2
dose in groundwater 1 The solid lines represent the CD-MUSIC modeling result
30
400
401
402
403
404
405
406
407
408409410
Table S75 Surface parameters and species used in the CD-MUSIC modeling in As(IIIV) removal under different GTiO2 dose in 01 M NaCl and groundwater 1 in Fig 2 and Fig S32
= exp(-FΨ1RT) P2 = exp(-FΨ2RT) F the Faraday constant (C mol-1) R the gas constant (J mol-1 K-1) T the absolute temperature (K)
Ψ0 Ψ1 Ψ2 the electrostatic potential (V) of 0- 1- and 2-plane respectively alogK for 01 M NaCl at 6 hours blogK for 01 M NaCl at 6 days clogK for groundwater 1 at 6 days
31
411412
413414415
32
416
Table S86 The charge distribution (f) of central As atom to TiO2 surface in simulating the effect of cations and anions on As adsorption in 01 M NaCl at pH 82 in Fig 4 BK Si HCO3 All
As(V) 022 017 012 016As(III) 040 020 058 056
Fig S43 Molar percentage () of As Ca Mg and Si on pristine and spent GTiO2
surfaces using EDX analysis The spent GTiO2 samples after field column experiments using groundwater 1 were identified with EBCT in min under x-axis The value of molar percentage of each element was averaged from randomly-chosen positions on the adsorbent surface
33
417
418
419420
421422
423
424
425
426
427
428
429
430
431
432
433434435436437438
439
440
441
As speciation analysis on spent GTiO2 using XANES
The spent GTiO2 samples were ground using a mortar and pestle and then the
ground powder was spread on Scotch tape The As k-edge XANES spectra were
collected at beamline 01C1 at the National Synchrotron Radiation Research Center
(NSRRC) Taiwan Spectra were acquired from -150 to 300 eV relative to the As K-
edge of 11867 eV at cryogenic temperature (77 K) using a cryostat to prevent the
oxidation of As(III) by X-rays The fluorescence signals were collected using a Lytle
detector Two to four scans were collected for each sample and averaged to improve
the signalnoise ratio The XANES analysis was performed with the Athena program
in the IFEFFIT computer package for linear combination fit (LCF) (Cui et al 2013
Ravel and Newville 2005)
34
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
PHREEQC modeling for As breakthrough curves in field column experiments
PHREEQC a geochemical model integrates macroscopic mass transfer
processes with a microscopic surface complexation model (Parkhurst and Appelo
2013) It can be applied in calculating solution complex speciation batch-reaction
and one-dimensional reactive-transport and inverse modeling In our study the one-
dimensional column was defined by four cells with the same length The cell length
was calculated to be one-fourth of the actual column length Time step (s) was
calculated according to equation Time step = Lcell(Q60A) where Lcell is the cell
length (cm) Q is flow velocity (mLmin) A is the effective column cross section area
(cm2) which is the column cross-sectional area multiplied by porosity (060) Total
shift number was calculated by dividing actual column operation time by the time
step The transport block was modeled by shifting the solute content from one cell to
the next one In each cell the aqueous solute was mixed and adsorbed on GTiO2
according to the equations In each cell the aqueous solute was mixed and assumed to
be in equilibration with GTiO2 The sequence of shifting mixing and equilibrium
adsorption was repeated for each cell until the total number of shifts was completed
The diffusion coefficient Dw in PHREEQC accounting for retardation was
calculated as Dw=x2
(36t) where x stands for the diffusion length (estimated as the
radius of the particle size) and t represents equilibrium time adopted from the batch
kinetic data (Mertens et al 2012)
For CD-MUSIC modeling in the PHREEQC take As(III) as an example to
explain the adsorption equation The As(III) adsorption is considered as a ligand
35
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
exchange reaction with the hydroxide group on GTiO2 (Surf_sOH-033) forming a
H3ArseniteO3 is the master species in groundwater at pH 82
(Surf_sO)2ArseniteOH-066 is the common adsorbed bidentate binuclear complex
evidenced by our previous reports(Pena et al 2006 Yan et al 2015) LogK is the
adsorption equilibrium constants Generally every adsorption equation under certain
experimental condition has a unique value of logK In the adsorption equation ldquo-2rdquo
represents the lost two hydrogens by Surf_sOH-033 after it adsorbs H3ArseniteO3 ldquo-
1rdquo represents the change in charge on Arsenite at 1 plane due to gaining one hydrogen
(+1) and one oxygen (-2) ldquo0rdquo represents no change in charge at the 2 plane ldquo066rdquo is
the fraction of the central ion (As) on GTiO2 surface that is associated with plane 0
ldquo3rdquo is the charge on the central ion As(III) Following this equation and the relevant
parameters As(III) adsorbed on GTiO2
The diffusion coefficient Dw in PHREEQC accounting for retardation was
calculated as Dw=x2(36t) where x stands for the diffusion length (estimated as the
radius of the particle size) and t represents equilibrium time adopted from the batch
kinetic data (Mertens et al 2012)
To well simulate the As breakthrough curve in columns four As(V) adsorption
reactions (Table 1) were employed Adsorption site density of 60 mmolg was
36
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
adopted from our previous study (Pena et al 2006) and the total adsorption sites were
calculated to be 1844 sitesnm2 The final optimized ratio of strong to weak sites was
51 The surface complexation constants were reasonably adjusted according to the
batch modeling results as the column reaction may not reach equilibrium in local
micro-interfacial areas due to much less contact time between As and GTiO2 than that
in batch experiments (Appelo and Postma 1999) In the modeling a stepwise
procedure was adopted to achieve a viable result An estimation of two thirds of the
surface site density being accessible for EBCT=011 min with large flow rate of 265
mLmin was optimized which could probably result from unavailable adsorption sites
due to fast transport through the column
The adsorbed As on GTiO2 in the column was calculated by mass balance
between the influent and effluent
where Asadsorbed is the adsorbed As on GTiO2 (mgg) n is the number of collected
samples Cin and Cout are influent and effluent As concentrations (mgL) respectively
Vi is volume (L) of groundwater passed through the column between sample i-1 and i
and m is the mass of GTiO2 (g)
Even though the oxidation of adsorbed As(III) occurred during filtration as
analyzed from XANES and mass balance analysis (Fig 7) no As(III) oxidation
reactions were considered in PHREEQC modeling which would not impact the
breakthrough of As(IIIV)
37
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
38
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
Fig S54 Effect of EBCT on Si Ca and Mg breakthrough curves using groundwater 1 The sample notation in panel c indicates field column experiments with EBCT in minutes
References
Appelo CAJ Postma D 1999 A consistent model for surface complexation on birnessite (MnO2) and its application to a column experiment Geochim Cosmochim Ac 63 (19-20) 3039-3048Badruzzaman M Westerhoff P Knappe DRU 2004 Intraparticle diffusion and adsorption of arsenate onto granular ferric hydroxide (GFH) Water Res 38 (18) 4002-4012Banerjee K Amy GL Prevost M Nour S Jekel M Gallagher PM Blumenschein CD 2008 Kinetic and thermodynamic aspects of adsorption of arsenic onto granular ferric hydroxide (GFH) Water Res 42 (13) 3371-3378Bang S Patel M Lippincott L Meng XG 2005 Removal of arsenic from groundwater by granular titanium dioxide adsorbent Chemosphere 60 (3) 389-397Bang S Pena ME Patel M Lippincott L Meng X Kim KW 2011 Removal of arsenate from water by adsorbents a comparative case study Environ Geochem Hlth 33 133-141Cui JL Shi JB Jiang GB Jing CY 2013 Arsenic levels and speciation from ingestion exposures to biomarkers in Shanxi China Implications for human health Environ Sci Technol 47 (10) 5419-5424Daus B Wennrich R Weiss H 2004 Sorption materials for arsenic removal from water A comparative study Water Res 38 (12) 2948-2954Dou XM Mohan D Pittman CU 2013 Arsenate adsorption on three types of granular schwertmannite Water Res 47 (9) 2938-2948Dou XM Zhang Y Yang M Pei YS Huang X Takayama T Kato S 2006 Occurrence of arsenic in groundwater in the suburbs of Beijing and its removal using an iron-cerium bimetal oxide adsorbent Water Qual Res J Can 41 (2) 140-146Gibbons MK Gagnon GA 2010 Adsorption of arsenic from a Nova Scotia groundwater onto water treatment residual solids Water Res 44 (19) 5740-5749Glocheux Y Mendez Pasarin M Albadarin AB Allen SJ Walker GM 2013 Removal of arsenic from groundwater by adsorption onto an acidified laterite by-product Chem Eng J 228 565-574Guan XH Wang JM Chusuei CC 2008 Removal of arsenic from water using granular ferric hydroxide Macroscopic and microscopic studies J Hazard Mater 156 (1-3) 178-185Gupta K Maity A Ghosh UC 2010 Manganese associated nanoparticles agglomerate of iron(III) oxide Synthesis characterization and arsenic(III) sorption behavior with mechanism J Hazard Mater 184 (1-3) 832-842Hao JM Han MJ Wang C Meng XG 2009 Enhanced removal of arsenite from water by a mesoporous hybrid material - Thiol-functionalized silica coated activated alumina Micropor Mesopor
Mat 124 (1-3) 1-7Hiemstra T Van Riemsdijk WH 2006 On the relationship between charge distribution surface hydration and the structure of the interface of metal hydroxides J Colloid Interf Sci 301 (1) 1-18Hristovski K Baumgardner A Westerhoff P 2007 Selecting metal oxide nanomaterials for arsenic removal in fixed bed columns From nanopowders to aggregated nanoparticle media J Hazard Mater 147 (1-2) 265-274Jang M Chen WF Cannon FS 2008 Preloading hydrous ferric oxide into granular activated carbon for arsenic removal Environ Sci Technol 42 (9) 3369-3374Jing CY Cui JL Huang YY Li AG 2012 Fabrication characterization and application of a composite adsorbent for simultaneous removal of arsenic and fluoride ACS Appl Mater Interfaces 4 (2) 714-720Kanematsu M Young TM Fukushi K Green PG Darby JL 2010 Extended triple layer modeling of arsenate and phosphate adsorption on a goethite-based granular porous adsorbent Environ Sci Technol 44 (9) 3388-3394Kong S Wang Y Zhan H Yuan S Liu M Zhou C 2013 Arsenite and Arsenate Removal from Contaminated Groundwater by Nanoscale Iron-Manganese Binary Oxides Column Studies Environmental Engineering Science 30 (11) 689-696Li Y Liu JR Jia SY Guo JW Zhuo J Na P 2012 TiO2 pillared montmorillonite as a photoactive adsorbent of arsenic under UV irradiation Chem Eng J 191 66-74Lin TF Wu JK 2001 Adsorption of arsenite and arsenate within activated alumina grains Equilibrium and kinetics Water Res 35 (8) 2049-2057Luo T Cui JL Hu S Huang YY Jing CY 2010 Arsenic removal and recovery from copper smelting wastewater using TiO2 Environ Sci Technol 44 (23) 9094-9098Maiti A Basu JK De S 2010a Development of a Treated Laterite for Arsenic Adsorption Effects of Treatment Parameters Industrial amp Engineering Chemistry Research 49 (10) 4873-4886Maiti A Basu JK De S 2010b Removal of Arsenic from Synthetic and Natural Groundwater Using Acid-Activated Laterite Environmental Progress amp Sustainable Energy 29 (4) 457-470Maiti A Basu JK De S 2012 Experimental and kinetic modeling of As(V) and As(III) adsorption on treated laterite using synthetic and contaminated groundwater Effects of phosphate silicate and carbonate ions Chem Eng J 191 1-12Maiti A Thakur BK Basu JK De S 2013a Comparison of treated laterite as arsenic adsorbent from different locations and performance of best filter under field conditions J Hazard Mater 262 1176-1186Maiti A Thakur BK Basu JK De S 2013b Comparison of treated laterite as arsenic adsorbent from different locations and performance of best filter under field conditions J Hazard Mater 262 (0) 1176-1186Maji SK Pal A Pal T 2008 Arsenic removal from real-life groundwater by adsorption on laterite soil J Hazard Mater 151 (2-3) 811-820Maji SK Kao YH Wang CJ Lu GS Wu JJ Liu CW 2012 Fixed bed adsorption of As(III) on iron-oxide-coated natural rock (IOCNR) and application to real arsenic-bearing groundwater Chem Eng J 203 285-293Mertens J Rose J Kagi R Chaurand P Plotze M Wehrli B Furrer G 2012 Adsorption of arsenic on polyaluminum granulate Environ Sci Technol 46 (13) 7310-7317Nguyen TV Vigneswaran S Ngo HH Pokhre D Viraraghavan T 2006 Iron-coated sponge as
effective media to remove arsenic from drinking water Water Qual Res J Can 41 (2) 164-170Parkhurst DL Appelo CAJ 2013 Description of input and examples for PHREEQC version 3-A computer program for speciation batch-reaction one-dimensional transport and inverse geochemical calculations US Geological SurveyPena M Meng XG Korfiatis GP Jing CY 2006 Adsorption mechanism of arsenic on nanocrystalline titanium dioxide Environ Sci Technol 40 (4) 1257-1262Ravel B Newville M 2005 ATHENA ARTEMIS HEPHAESTUS Data analysis for X-ray absorption spectroscopy using IFEFFIT J Synchrotron Radiat 12 537-541Saha B Bains R Greenwood F 2005 Physicochemical characterization of granular ferric hydroxide (GFH) for arsenic(V) sorption from water Separation Science and Technology 40 (14) 2909-2932Shan H Ma T Wang Y Zhao J Han H Deng Y He X Dong Y 2013 A cost-effective system for in-situ geological arsenic adsorption from groundwater J Contam Hydrol 154 1-9Stachowicz M Hiemstra T van Riemsdijk WH 2008 Multi-competitive interaction of As(III) and As(V) oxyanions with Ca2+ Mg2+ PO4
3- and CO32- ions on goethite J Colloid Interf Sci 320 (2) 400-
414Streat M Hellgardt K Newton NLR 2008 Hydrous ferric oxide as an adsorbent in water treatment - Part 3 Batch and mini-column adsorption of arsenic phosphorus fluorine and cadmium ions Process Safety and Environmental Protection 86 (B1) 21-30Thirunavukkarasu OS Viraraghavan T Subramanian KS 2003 Arsenic removal from drinking water using iron oxide-coated sand Water Air Soil Poll 142 (1-4) 95-111USEPA 2008 Assessing arsenic removal by metal (hydr)oxide adsorptive media using rapid small scale column tests Govenrnment Printing Office Washington DCWang J Xu W Chen L Huang X Liu J 2014 Preparation and evaluation of magnetic nanoparticles impregnated chitosan beads for arsenic removal from water Chem Eng J 251 25-34Westerhoff P Highfield D Badruzzaman M Yoon Y 2005 Rapid small-scale column tests for arsenate removal in iron oxide packed bed columns J Environ Eng-Asce 131 (2) 262-271Westerhoff P De Haan M Martindale A Badruzzaman M 2006 Arsenic adsorptive media technology selection strategies Water Qual Res J Can 41 (2) 171-184Yan L Huang Y Cui J Jing C 2015 Simultaneous As(III) and Cd removal from copper smelting wastewater using granular TiO2 columns Water Res 68 (0) 572-579Zhao K Guo HM 2014 Behavior and mechanism of arsenate adsorption on activated natural siderite Evidences from FTIR and XANES analysis Environ Sci Pollut Res 21 (3) 1944-1953Zhao K Guo H Zhou X 2014 Adsorption and heterogeneous oxidation of arsenite on modified granular natural siderite Characterization and behaviors Appl Geochem 48 184-192
Fig S1 Boxplot of groundwater As levels in columns and filters in the literature in Table S1 Individual samples are shown as diamonds The range of each box represents the 25th
and 75th
percentile whereas the whiskers represent the 10th
and 90th
percentile
Synthesis of granular TiO2
Granular TiO2 (GTiO2) was prepared by hydrolysis of titanyl sulfate (TiOSO4)
Generally 300 g TiOSO4 was mixed with 1800 mL DI water in a 10 L jar reactor in an
ice bath at 4 oC Then 10 M NaOH was slowly added to adjust the pH to 6 The
precursor of TiO2 was obtained by washing the suspension with DI water several
times till the conductivity of the supernatant was less than 100 μScm Then 800 g
TiO2 precursor was mixed with 40 mL polyvinyl alcohol solution at 80 oC in a water
bath The product was crushed into 60-80 mesh and dried in an oven at 60 oC for 12 h
15
282930313233343536373839404142434445464748
49
50
51
52
53
54
55
56
57585960
Fig S2 Characterization of GTiO2 SEM (a) and XRD pattern with crystal face for each peak (b)
Fig S1 SEM images for GTiO2 in this study
Table S2 Average concentrations of As coexisting ions (mgL) and water chemistry for groundwater 1 and 2 from two wells
Table S3 Water parameters in the synthetic water used in the studyParameters Ca2+ Mg2+ HCO3
- Na+ Cl- pHConc (mgL) 401 1043 388 2460 3928 82
Table S4 PHREEQC input for a representative column with EBCT=054 min SOLUTION 0
This keyword is to define the influent groundwater chemistry parameters which are included in the adsorption reactions like ldquoArseniterdquo and ldquoArsenaterdquo and the experimental conditions including ldquopHrdquo The information defined in SOLUTION is available for subsequent transport and adsorptive reaction calculations
temp 23 pH 82 pe 4 redox pe units mgL density 1 Al 006 Arsenite 0374 Arsenate 0291 CO4
2-
4401 Ca 194 Cl 1456 F 115 Fe 047 K 137 Mg 395 Mn 012 NO3
-
34 Na 16872
17
79
80
8182
83
84858687888990919293949596979899
100101102103104105106107108109110111112
SO42-
1176 Si 89 -water 1 kg
SOLUTION 1-4 The small column was divided into four cells SOLUTION 1-4
are the groundwater chemistry parameters for the four cells temp 23 pH 83 pe 4 redox pe units ppm density 1 Al 006 C(4) 4401 Ca 194 Cl 1456 F 115 Fe 047 K 137 Mg 395 Mn 012 N(3) 34 Na 16872 S(6) 1176 Si 89 -water 1 kg
SOLUTION_SPECIES This keyword is to define the dissociation constant logK
and diffusion constant (dw) in solution for arsenite and arsenate
Arsenite adsorption equation on GTiO2 surface H3ArseniteO3 is the primary species of As(III) at the groundwater pH 82 (Surf_sO)2ArseniteOH-066 is the adsorptive bidentate binuclear structure of As(III) on GTiO2
log_k 1635 The adsorptive reaction constant for As(III) on GTiO2 in
the current condition which could be changed with different experimental conditions
-cd_music -2 -1 0 066 3 CD-MUSIC model is integrated in the PHREEQC
modeling The numbers represent -2 the change in charge at the plane of Surf_sOH due to loss of two hydrogens -1 the change in charge at 1 plane due to gain of one hydrogen and one oxygen on Arsenite 0 the change in charge at the 2 plane usually caused by the outer sphere adsorption 066 the fraction of the central ion (As) charge that is associated with plane 0 which reflecting the charge distribution 3 the charge on the central ion (As)
Table S54 Parameters of Weber-Morris intraparticle model for As(IIIV) adsorption kinetics on GTiO2 using synthetic water Initial As concentration = 800 μgL adsorbent dose = 02 gL pH = 82 in synthetic groundwater
External film diffusion
Intraparticle diffusion
aRex2 bkp1
cb1aRin
2 bkp2cb 2
As(V) 0984 0497 0022 0976 01331878
As(III) 0970 0583
-0088 0981 0218
1105
aRex is WM external proportion fitting parameter while Rin is WM intraparticle proportion fitting parameterbk The unit of kp is mggh05 cb The unit of b is mgg
Table S6 Comparison of the adsorption capacities of As(III) and As(V) on GTiO2 and the representative granular adsorbents in similar experimental condition from the literature
AdsorbentParticle size (mm) As
qm
(mgg)Dose (gL) Experimental conditions Literature
GTiO2 018~025 As(III) 980 1 0~500 mgL at pH 82 01 M NaCl This studyGTiO2 018~025 As(V) 358 1 0~500 mgL at pH 82 01 M NaCl This study
Granular TiO2 015~06 As(III) 392 10~60 mgL As at pH 70 in simulated groundwater (100 mgL Ca 20 mgL Mg 50 mgL Na 200 mgL Cl-
)(Bang et al 2005)
Granular TiO2 015~06 As(V) 400 10~60 mgL As at pH 70 in simulated groundwater (100 mgL Ca 20 mgL Mg 50 mgL Na 200 mgL Cl-
)(Bang et al 2005)
E33 (FeOOH)0044~0075 As(V) 202 1 0~15 mgL at pH 70 in 001 M NaCl
(Kanematsu et al 2010)
E33 (FeOOH) 05~2 As(V) 180 1 0~50 mgL at pH 70 in 004 M NaClO4 (Jing et al 2012)
GFH 02~06 As(V) 650 10 0~2000 mgL at pH 8 in 01 M NaNO3
(Guan et al 2008)
GFH0009~0125 As(V) 23 025 0~07 μgL at pH 65 in DI water
(Banerjee et al 2008)
GFH0009~0125 As(V) 200 - 0~01 μgL at pH 70 in DI water
(Badruzzaman et al 2004)
GFH 050~065 As(V) 155 - 0~06 μgL at pH 70 in DI water (Saha et al 2005)
GHFO-NN 015~030 As(V) 330 0001 0~225 mgL at pH 8 in DI water(Streat et al 2008)
GHFO-VL 015~030 As(V) 360 0001 0~225 mgL at pH 8 in DI water(Streat et al 2008)
25
374375
Spherical schwertmannite 1~15 As(V) 36 05 0~5 mgL at pH 70 in DI water (Dou et al 2013)Cylindrical schwertmannite 1~25 As(V) 223 05
0~5 mgL at pH 70 in DI water(Dou et al 2013)
Irregular schwertmannite 10~16 As(V) 317 05 0~5 mgL at pH 70 in DI water (Dou et al 2013)Fe impregnated chitosan beads (MICB) 25 As(III) 117 1 0~05 mgL at pH 60 in DI water
(Wang et al 2014)
MICB 25 As(V) 191 1 0~1 mgL at pH 60 in DI water(Wang et al 2014)
MICB 25 As(III) 353 1 0~15 mgL at pH 60 in DI water(Wang et al 2014)
MICB 25 As(V) 357 1 0~16 mgL at pH 60 in DI water(Wang et al 2014)
Iron hydroxide granules (GIH) 3~4 As(V) 23 4
5~100 mgL at pH 70 in 10 mgL SO42-
14 mgL NH4Cl buffer solution (Daus et al 2004)
Activated Al2O3
0074~0149 As(V) 159 - 285~115 mgL at pH 52 in DI water
(Lin and Wu 2001)
Activated Al2O3
0074~0149 As(III) 35 - 079~490 mgL at pH 70 in DI water
(Lin and Wu 2001)
Activated Al2O3 ~20 As(V) 73 at pH 70 in 004 M NaClO4 (Jing et al 2012)
Activated natural siderite 05~10 As(V) 22 10 0 1~20 mgL at pH 7 in DI water(Zhao and Guo 2014)
Polyaluminum Granulate 1~3 As(III) 705 10 0~150 mgL at pH 51-56 in DI water(Mertens et al 2012)
Polyaluminum Granulate 1~3 As(V) 180 10 0~150 mgL at pH 51-56 in DI water (Mertens et al
26
2012)
Acidified laterite 1~12 As(III) 19 1 025~5 mgL at pH 7 in 100 mgL NaHCO3
(Glocheux et al 2013)
Acidified laterite 1~12 As(V) 13 1 025~5 mgL at pH 7 in 100 mgL NaHCO3
(Glocheux et al 2013)
Laterite 1~12 As(III) 07 1025~5 mgL at pH 7 in 100 mgL NaHCO3 (Glocheux et al
2013)
Laterite 1~12 As(V) 04 1025~5 mgL at pH 7 in 100 mgL NaHCO3 (Glocheux et al
2013)
Treated laterite 03-05 As(V) 216 05 02-20 mgL at pH 70 in DI water(Maiti et al 2012)
Treated laterite 03-05 As(III) 94 05 02-20 mgL at pH 70 in DI water(Maiti et al 2012)
Treated laterite03-05
As(V) 241 05 02-20 mgL at pH 70 in DI water(Maiti et al 2010a)
Treated laterite03-05
As(III) 81 05 02-20 mgL at pH 70 in DI water(Maiti et al 2010a)
Acid-activated laterite-103-07
As(III) 0633 50 02-10 mgL at pH 66-70 in DI water(Maiti et al 2010b)
Acid-activated laterite-203-07
As(III) 087650 02-10 mgL at pH 66-70 in DI water (Maiti et al
2010b)
Acid-activated laterite-303-07
As(III) 063450 02-10 mgL at pH 66-70 in DI water (Maiti et al
2010b)
Acid-activated laterite-103-07
As(V) 059850 02-10 mgL at pH 66-70 in DI water (Maiti et al
2010b)
27
Acid-activated laterite-203-07
As(V) 07550 02-10 mgL at pH 66-70 in DI water (Maiti et al
2010b)
Acid-activated laterite-303-07
As(V) 07550 02-10 mgL at pH 66-70 in DI water (Maiti et al
2010b)
Treated laterite-1 03-06 As(V) 019 20 0-20 mgL As at pH 72 in DI water(Maiti et al 2013b)
Treated laterite-1 03-06 As(III) 018 20 0-20 mgL As at pH 72 in DI water(Maiti et al 2013b)
Treated laterite-2 03-06 As(V) 004 20 0-20 mgL As at pH 72 in DI water(Maiti et al 2013b)
Treated laterite-2 03-06 As(III) 003 20 0-20 mgL As at pH 72 in DI water(Maiti et al 2013b)
Treated laterite-3 03-06 As(V) 007 20 0-20 mgL As at pH 72 in DI water(Maiti et al 2013b)
Treated laterite-3 03-06 As(III) 004 20 0-20 mgL As at pH 72 in DI water(Maiti et al 2013b)
28
376377
Charge distribution multi-site surface complexation (CD-MUSIC) modeling
The CD-MUSIC model with the 2-pK TPM adsorption option was used to
describe adsorption behaviors of As cations and anions on GTiO2 The CD-MUSIC
model incorporates the structural information of surfaces adsorbed species and the
double layers by distributing the charge of an adsorbate between the surface and
interfacial water (Hiemstra and Van Riemsdijk 2006) The CD-MUSIC model has
been successfully used in describing As adsorption in batch experiments (Pena et al
2006 Stachowicz et al 2008)
The adsorption constants of counter ions were set to -1 and the proton affinity
constant was set to the PZC of 58 for TiOH-13 (Luo et al 2010) The charge
distribution (CD) value shows the fraction (f) of the charge of the central As ion
attributed to the surface plane and the remaining part (1-f) was attributed to the other
ligands of the complex which were positioned toward the diffuse layer The CD value
for As surface complexes was obtained by fitting the experimental data The
calculation was performed using the chemical equilibrium program MINTEQ to
simulate the adsorption and the aqueous reactions
29
378379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
Fig S32 Adsorption of silicate (a) calcium and magnesium (b) as a function of GTiO2
dose in groundwater 1 The solid lines represent the CD-MUSIC modeling result
30
400
401
402
403
404
405
406
407
408409410
Table S75 Surface parameters and species used in the CD-MUSIC modeling in As(IIIV) removal under different GTiO2 dose in 01 M NaCl and groundwater 1 in Fig 2 and Fig S32
= exp(-FΨ1RT) P2 = exp(-FΨ2RT) F the Faraday constant (C mol-1) R the gas constant (J mol-1 K-1) T the absolute temperature (K)
Ψ0 Ψ1 Ψ2 the electrostatic potential (V) of 0- 1- and 2-plane respectively alogK for 01 M NaCl at 6 hours blogK for 01 M NaCl at 6 days clogK for groundwater 1 at 6 days
31
411412
413414415
32
416
Table S86 The charge distribution (f) of central As atom to TiO2 surface in simulating the effect of cations and anions on As adsorption in 01 M NaCl at pH 82 in Fig 4 BK Si HCO3 All
As(V) 022 017 012 016As(III) 040 020 058 056
Fig S43 Molar percentage () of As Ca Mg and Si on pristine and spent GTiO2
surfaces using EDX analysis The spent GTiO2 samples after field column experiments using groundwater 1 were identified with EBCT in min under x-axis The value of molar percentage of each element was averaged from randomly-chosen positions on the adsorbent surface
33
417
418
419420
421422
423
424
425
426
427
428
429
430
431
432
433434435436437438
439
440
441
As speciation analysis on spent GTiO2 using XANES
The spent GTiO2 samples were ground using a mortar and pestle and then the
ground powder was spread on Scotch tape The As k-edge XANES spectra were
collected at beamline 01C1 at the National Synchrotron Radiation Research Center
(NSRRC) Taiwan Spectra were acquired from -150 to 300 eV relative to the As K-
edge of 11867 eV at cryogenic temperature (77 K) using a cryostat to prevent the
oxidation of As(III) by X-rays The fluorescence signals were collected using a Lytle
detector Two to four scans were collected for each sample and averaged to improve
the signalnoise ratio The XANES analysis was performed with the Athena program
in the IFEFFIT computer package for linear combination fit (LCF) (Cui et al 2013
Ravel and Newville 2005)
34
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
PHREEQC modeling for As breakthrough curves in field column experiments
PHREEQC a geochemical model integrates macroscopic mass transfer
processes with a microscopic surface complexation model (Parkhurst and Appelo
2013) It can be applied in calculating solution complex speciation batch-reaction
and one-dimensional reactive-transport and inverse modeling In our study the one-
dimensional column was defined by four cells with the same length The cell length
was calculated to be one-fourth of the actual column length Time step (s) was
calculated according to equation Time step = Lcell(Q60A) where Lcell is the cell
length (cm) Q is flow velocity (mLmin) A is the effective column cross section area
(cm2) which is the column cross-sectional area multiplied by porosity (060) Total
shift number was calculated by dividing actual column operation time by the time
step The transport block was modeled by shifting the solute content from one cell to
the next one In each cell the aqueous solute was mixed and adsorbed on GTiO2
according to the equations In each cell the aqueous solute was mixed and assumed to
be in equilibration with GTiO2 The sequence of shifting mixing and equilibrium
adsorption was repeated for each cell until the total number of shifts was completed
The diffusion coefficient Dw in PHREEQC accounting for retardation was
calculated as Dw=x2
(36t) where x stands for the diffusion length (estimated as the
radius of the particle size) and t represents equilibrium time adopted from the batch
kinetic data (Mertens et al 2012)
For CD-MUSIC modeling in the PHREEQC take As(III) as an example to
explain the adsorption equation The As(III) adsorption is considered as a ligand
35
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
exchange reaction with the hydroxide group on GTiO2 (Surf_sOH-033) forming a
H3ArseniteO3 is the master species in groundwater at pH 82
(Surf_sO)2ArseniteOH-066 is the common adsorbed bidentate binuclear complex
evidenced by our previous reports(Pena et al 2006 Yan et al 2015) LogK is the
adsorption equilibrium constants Generally every adsorption equation under certain
experimental condition has a unique value of logK In the adsorption equation ldquo-2rdquo
represents the lost two hydrogens by Surf_sOH-033 after it adsorbs H3ArseniteO3 ldquo-
1rdquo represents the change in charge on Arsenite at 1 plane due to gaining one hydrogen
(+1) and one oxygen (-2) ldquo0rdquo represents no change in charge at the 2 plane ldquo066rdquo is
the fraction of the central ion (As) on GTiO2 surface that is associated with plane 0
ldquo3rdquo is the charge on the central ion As(III) Following this equation and the relevant
parameters As(III) adsorbed on GTiO2
The diffusion coefficient Dw in PHREEQC accounting for retardation was
calculated as Dw=x2(36t) where x stands for the diffusion length (estimated as the
radius of the particle size) and t represents equilibrium time adopted from the batch
kinetic data (Mertens et al 2012)
To well simulate the As breakthrough curve in columns four As(V) adsorption
reactions (Table 1) were employed Adsorption site density of 60 mmolg was
36
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
adopted from our previous study (Pena et al 2006) and the total adsorption sites were
calculated to be 1844 sitesnm2 The final optimized ratio of strong to weak sites was
51 The surface complexation constants were reasonably adjusted according to the
batch modeling results as the column reaction may not reach equilibrium in local
micro-interfacial areas due to much less contact time between As and GTiO2 than that
in batch experiments (Appelo and Postma 1999) In the modeling a stepwise
procedure was adopted to achieve a viable result An estimation of two thirds of the
surface site density being accessible for EBCT=011 min with large flow rate of 265
mLmin was optimized which could probably result from unavailable adsorption sites
due to fast transport through the column
The adsorbed As on GTiO2 in the column was calculated by mass balance
between the influent and effluent
where Asadsorbed is the adsorbed As on GTiO2 (mgg) n is the number of collected
samples Cin and Cout are influent and effluent As concentrations (mgL) respectively
Vi is volume (L) of groundwater passed through the column between sample i-1 and i
and m is the mass of GTiO2 (g)
Even though the oxidation of adsorbed As(III) occurred during filtration as
analyzed from XANES and mass balance analysis (Fig 7) no As(III) oxidation
reactions were considered in PHREEQC modeling which would not impact the
breakthrough of As(IIIV)
37
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
38
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
Fig S54 Effect of EBCT on Si Ca and Mg breakthrough curves using groundwater 1 The sample notation in panel c indicates field column experiments with EBCT in minutes
References
Appelo CAJ Postma D 1999 A consistent model for surface complexation on birnessite (MnO2) and its application to a column experiment Geochim Cosmochim Ac 63 (19-20) 3039-3048Badruzzaman M Westerhoff P Knappe DRU 2004 Intraparticle diffusion and adsorption of arsenate onto granular ferric hydroxide (GFH) Water Res 38 (18) 4002-4012Banerjee K Amy GL Prevost M Nour S Jekel M Gallagher PM Blumenschein CD 2008 Kinetic and thermodynamic aspects of adsorption of arsenic onto granular ferric hydroxide (GFH) Water Res 42 (13) 3371-3378Bang S Patel M Lippincott L Meng XG 2005 Removal of arsenic from groundwater by granular titanium dioxide adsorbent Chemosphere 60 (3) 389-397Bang S Pena ME Patel M Lippincott L Meng X Kim KW 2011 Removal of arsenate from water by adsorbents a comparative case study Environ Geochem Hlth 33 133-141Cui JL Shi JB Jiang GB Jing CY 2013 Arsenic levels and speciation from ingestion exposures to biomarkers in Shanxi China Implications for human health Environ Sci Technol 47 (10) 5419-5424Daus B Wennrich R Weiss H 2004 Sorption materials for arsenic removal from water A comparative study Water Res 38 (12) 2948-2954Dou XM Mohan D Pittman CU 2013 Arsenate adsorption on three types of granular schwertmannite Water Res 47 (9) 2938-2948Dou XM Zhang Y Yang M Pei YS Huang X Takayama T Kato S 2006 Occurrence of arsenic in groundwater in the suburbs of Beijing and its removal using an iron-cerium bimetal oxide adsorbent Water Qual Res J Can 41 (2) 140-146Gibbons MK Gagnon GA 2010 Adsorption of arsenic from a Nova Scotia groundwater onto water treatment residual solids Water Res 44 (19) 5740-5749Glocheux Y Mendez Pasarin M Albadarin AB Allen SJ Walker GM 2013 Removal of arsenic from groundwater by adsorption onto an acidified laterite by-product Chem Eng J 228 565-574Guan XH Wang JM Chusuei CC 2008 Removal of arsenic from water using granular ferric hydroxide Macroscopic and microscopic studies J Hazard Mater 156 (1-3) 178-185Gupta K Maity A Ghosh UC 2010 Manganese associated nanoparticles agglomerate of iron(III) oxide Synthesis characterization and arsenic(III) sorption behavior with mechanism J Hazard Mater 184 (1-3) 832-842Hao JM Han MJ Wang C Meng XG 2009 Enhanced removal of arsenite from water by a mesoporous hybrid material - Thiol-functionalized silica coated activated alumina Micropor Mesopor
Mat 124 (1-3) 1-7Hiemstra T Van Riemsdijk WH 2006 On the relationship between charge distribution surface hydration and the structure of the interface of metal hydroxides J Colloid Interf Sci 301 (1) 1-18Hristovski K Baumgardner A Westerhoff P 2007 Selecting metal oxide nanomaterials for arsenic removal in fixed bed columns From nanopowders to aggregated nanoparticle media J Hazard Mater 147 (1-2) 265-274Jang M Chen WF Cannon FS 2008 Preloading hydrous ferric oxide into granular activated carbon for arsenic removal Environ Sci Technol 42 (9) 3369-3374Jing CY Cui JL Huang YY Li AG 2012 Fabrication characterization and application of a composite adsorbent for simultaneous removal of arsenic and fluoride ACS Appl Mater Interfaces 4 (2) 714-720Kanematsu M Young TM Fukushi K Green PG Darby JL 2010 Extended triple layer modeling of arsenate and phosphate adsorption on a goethite-based granular porous adsorbent Environ Sci Technol 44 (9) 3388-3394Kong S Wang Y Zhan H Yuan S Liu M Zhou C 2013 Arsenite and Arsenate Removal from Contaminated Groundwater by Nanoscale Iron-Manganese Binary Oxides Column Studies Environmental Engineering Science 30 (11) 689-696Li Y Liu JR Jia SY Guo JW Zhuo J Na P 2012 TiO2 pillared montmorillonite as a photoactive adsorbent of arsenic under UV irradiation Chem Eng J 191 66-74Lin TF Wu JK 2001 Adsorption of arsenite and arsenate within activated alumina grains Equilibrium and kinetics Water Res 35 (8) 2049-2057Luo T Cui JL Hu S Huang YY Jing CY 2010 Arsenic removal and recovery from copper smelting wastewater using TiO2 Environ Sci Technol 44 (23) 9094-9098Maiti A Basu JK De S 2010a Development of a Treated Laterite for Arsenic Adsorption Effects of Treatment Parameters Industrial amp Engineering Chemistry Research 49 (10) 4873-4886Maiti A Basu JK De S 2010b Removal of Arsenic from Synthetic and Natural Groundwater Using Acid-Activated Laterite Environmental Progress amp Sustainable Energy 29 (4) 457-470Maiti A Basu JK De S 2012 Experimental and kinetic modeling of As(V) and As(III) adsorption on treated laterite using synthetic and contaminated groundwater Effects of phosphate silicate and carbonate ions Chem Eng J 191 1-12Maiti A Thakur BK Basu JK De S 2013a Comparison of treated laterite as arsenic adsorbent from different locations and performance of best filter under field conditions J Hazard Mater 262 1176-1186Maiti A Thakur BK Basu JK De S 2013b Comparison of treated laterite as arsenic adsorbent from different locations and performance of best filter under field conditions J Hazard Mater 262 (0) 1176-1186Maji SK Pal A Pal T 2008 Arsenic removal from real-life groundwater by adsorption on laterite soil J Hazard Mater 151 (2-3) 811-820Maji SK Kao YH Wang CJ Lu GS Wu JJ Liu CW 2012 Fixed bed adsorption of As(III) on iron-oxide-coated natural rock (IOCNR) and application to real arsenic-bearing groundwater Chem Eng J 203 285-293Mertens J Rose J Kagi R Chaurand P Plotze M Wehrli B Furrer G 2012 Adsorption of arsenic on polyaluminum granulate Environ Sci Technol 46 (13) 7310-7317Nguyen TV Vigneswaran S Ngo HH Pokhre D Viraraghavan T 2006 Iron-coated sponge as
effective media to remove arsenic from drinking water Water Qual Res J Can 41 (2) 164-170Parkhurst DL Appelo CAJ 2013 Description of input and examples for PHREEQC version 3-A computer program for speciation batch-reaction one-dimensional transport and inverse geochemical calculations US Geological SurveyPena M Meng XG Korfiatis GP Jing CY 2006 Adsorption mechanism of arsenic on nanocrystalline titanium dioxide Environ Sci Technol 40 (4) 1257-1262Ravel B Newville M 2005 ATHENA ARTEMIS HEPHAESTUS Data analysis for X-ray absorption spectroscopy using IFEFFIT J Synchrotron Radiat 12 537-541Saha B Bains R Greenwood F 2005 Physicochemical characterization of granular ferric hydroxide (GFH) for arsenic(V) sorption from water Separation Science and Technology 40 (14) 2909-2932Shan H Ma T Wang Y Zhao J Han H Deng Y He X Dong Y 2013 A cost-effective system for in-situ geological arsenic adsorption from groundwater J Contam Hydrol 154 1-9Stachowicz M Hiemstra T van Riemsdijk WH 2008 Multi-competitive interaction of As(III) and As(V) oxyanions with Ca2+ Mg2+ PO4
3- and CO32- ions on goethite J Colloid Interf Sci 320 (2) 400-
414Streat M Hellgardt K Newton NLR 2008 Hydrous ferric oxide as an adsorbent in water treatment - Part 3 Batch and mini-column adsorption of arsenic phosphorus fluorine and cadmium ions Process Safety and Environmental Protection 86 (B1) 21-30Thirunavukkarasu OS Viraraghavan T Subramanian KS 2003 Arsenic removal from drinking water using iron oxide-coated sand Water Air Soil Poll 142 (1-4) 95-111USEPA 2008 Assessing arsenic removal by metal (hydr)oxide adsorptive media using rapid small scale column tests Govenrnment Printing Office Washington DCWang J Xu W Chen L Huang X Liu J 2014 Preparation and evaluation of magnetic nanoparticles impregnated chitosan beads for arsenic removal from water Chem Eng J 251 25-34Westerhoff P Highfield D Badruzzaman M Yoon Y 2005 Rapid small-scale column tests for arsenate removal in iron oxide packed bed columns J Environ Eng-Asce 131 (2) 262-271Westerhoff P De Haan M Martindale A Badruzzaman M 2006 Arsenic adsorptive media technology selection strategies Water Qual Res J Can 41 (2) 171-184Yan L Huang Y Cui J Jing C 2015 Simultaneous As(III) and Cd removal from copper smelting wastewater using granular TiO2 columns Water Res 68 (0) 572-579Zhao K Guo HM 2014 Behavior and mechanism of arsenate adsorption on activated natural siderite Evidences from FTIR and XANES analysis Environ Sci Pollut Res 21 (3) 1944-1953Zhao K Guo H Zhou X 2014 Adsorption and heterogeneous oxidation of arsenite on modified granular natural siderite Characterization and behaviors Appl Geochem 48 184-192
Table S3 Water parameters in the synthetic water used in the studyParameters Ca2+ Mg2+ HCO3
- Na+ Cl- pHConc (mgL) 401 1043 388 2460 3928 82
Table S4 PHREEQC input for a representative column with EBCT=054 min SOLUTION 0
This keyword is to define the influent groundwater chemistry parameters which are included in the adsorption reactions like ldquoArseniterdquo and ldquoArsenaterdquo and the experimental conditions including ldquopHrdquo The information defined in SOLUTION is available for subsequent transport and adsorptive reaction calculations
temp 23 pH 82 pe 4 redox pe units mgL density 1 Al 006 Arsenite 0374 Arsenate 0291 CO4
2-
4401 Ca 194 Cl 1456 F 115 Fe 047 K 137 Mg 395 Mn 012 NO3
-
34 Na 16872
17
79
80
8182
83
84858687888990919293949596979899
100101102103104105106107108109110111112
SO42-
1176 Si 89 -water 1 kg
SOLUTION 1-4 The small column was divided into four cells SOLUTION 1-4
are the groundwater chemistry parameters for the four cells temp 23 pH 83 pe 4 redox pe units ppm density 1 Al 006 C(4) 4401 Ca 194 Cl 1456 F 115 Fe 047 K 137 Mg 395 Mn 012 N(3) 34 Na 16872 S(6) 1176 Si 89 -water 1 kg
SOLUTION_SPECIES This keyword is to define the dissociation constant logK
and diffusion constant (dw) in solution for arsenite and arsenate
Arsenite adsorption equation on GTiO2 surface H3ArseniteO3 is the primary species of As(III) at the groundwater pH 82 (Surf_sO)2ArseniteOH-066 is the adsorptive bidentate binuclear structure of As(III) on GTiO2
log_k 1635 The adsorptive reaction constant for As(III) on GTiO2 in
the current condition which could be changed with different experimental conditions
-cd_music -2 -1 0 066 3 CD-MUSIC model is integrated in the PHREEQC
modeling The numbers represent -2 the change in charge at the plane of Surf_sOH due to loss of two hydrogens -1 the change in charge at 1 plane due to gain of one hydrogen and one oxygen on Arsenite 0 the change in charge at the 2 plane usually caused by the outer sphere adsorption 066 the fraction of the central ion (As) charge that is associated with plane 0 which reflecting the charge distribution 3 the charge on the central ion (As)
Table S54 Parameters of Weber-Morris intraparticle model for As(IIIV) adsorption kinetics on GTiO2 using synthetic water Initial As concentration = 800 μgL adsorbent dose = 02 gL pH = 82 in synthetic groundwater
External film diffusion
Intraparticle diffusion
aRex2 bkp1
cb1aRin
2 bkp2cb 2
As(V) 0984 0497 0022 0976 01331878
As(III) 0970 0583
-0088 0981 0218
1105
aRex is WM external proportion fitting parameter while Rin is WM intraparticle proportion fitting parameterbk The unit of kp is mggh05 cb The unit of b is mgg
Table S6 Comparison of the adsorption capacities of As(III) and As(V) on GTiO2 and the representative granular adsorbents in similar experimental condition from the literature
AdsorbentParticle size (mm) As
qm
(mgg)Dose (gL) Experimental conditions Literature
GTiO2 018~025 As(III) 980 1 0~500 mgL at pH 82 01 M NaCl This studyGTiO2 018~025 As(V) 358 1 0~500 mgL at pH 82 01 M NaCl This study
Granular TiO2 015~06 As(III) 392 10~60 mgL As at pH 70 in simulated groundwater (100 mgL Ca 20 mgL Mg 50 mgL Na 200 mgL Cl-
)(Bang et al 2005)
Granular TiO2 015~06 As(V) 400 10~60 mgL As at pH 70 in simulated groundwater (100 mgL Ca 20 mgL Mg 50 mgL Na 200 mgL Cl-
)(Bang et al 2005)
E33 (FeOOH)0044~0075 As(V) 202 1 0~15 mgL at pH 70 in 001 M NaCl
(Kanematsu et al 2010)
E33 (FeOOH) 05~2 As(V) 180 1 0~50 mgL at pH 70 in 004 M NaClO4 (Jing et al 2012)
GFH 02~06 As(V) 650 10 0~2000 mgL at pH 8 in 01 M NaNO3
(Guan et al 2008)
GFH0009~0125 As(V) 23 025 0~07 μgL at pH 65 in DI water
(Banerjee et al 2008)
GFH0009~0125 As(V) 200 - 0~01 μgL at pH 70 in DI water
(Badruzzaman et al 2004)
GFH 050~065 As(V) 155 - 0~06 μgL at pH 70 in DI water (Saha et al 2005)
GHFO-NN 015~030 As(V) 330 0001 0~225 mgL at pH 8 in DI water(Streat et al 2008)
GHFO-VL 015~030 As(V) 360 0001 0~225 mgL at pH 8 in DI water(Streat et al 2008)
25
374375
Spherical schwertmannite 1~15 As(V) 36 05 0~5 mgL at pH 70 in DI water (Dou et al 2013)Cylindrical schwertmannite 1~25 As(V) 223 05
0~5 mgL at pH 70 in DI water(Dou et al 2013)
Irregular schwertmannite 10~16 As(V) 317 05 0~5 mgL at pH 70 in DI water (Dou et al 2013)Fe impregnated chitosan beads (MICB) 25 As(III) 117 1 0~05 mgL at pH 60 in DI water
(Wang et al 2014)
MICB 25 As(V) 191 1 0~1 mgL at pH 60 in DI water(Wang et al 2014)
MICB 25 As(III) 353 1 0~15 mgL at pH 60 in DI water(Wang et al 2014)
MICB 25 As(V) 357 1 0~16 mgL at pH 60 in DI water(Wang et al 2014)
Iron hydroxide granules (GIH) 3~4 As(V) 23 4
5~100 mgL at pH 70 in 10 mgL SO42-
14 mgL NH4Cl buffer solution (Daus et al 2004)
Activated Al2O3
0074~0149 As(V) 159 - 285~115 mgL at pH 52 in DI water
(Lin and Wu 2001)
Activated Al2O3
0074~0149 As(III) 35 - 079~490 mgL at pH 70 in DI water
(Lin and Wu 2001)
Activated Al2O3 ~20 As(V) 73 at pH 70 in 004 M NaClO4 (Jing et al 2012)
Activated natural siderite 05~10 As(V) 22 10 0 1~20 mgL at pH 7 in DI water(Zhao and Guo 2014)
Polyaluminum Granulate 1~3 As(III) 705 10 0~150 mgL at pH 51-56 in DI water(Mertens et al 2012)
Polyaluminum Granulate 1~3 As(V) 180 10 0~150 mgL at pH 51-56 in DI water (Mertens et al
26
2012)
Acidified laterite 1~12 As(III) 19 1 025~5 mgL at pH 7 in 100 mgL NaHCO3
(Glocheux et al 2013)
Acidified laterite 1~12 As(V) 13 1 025~5 mgL at pH 7 in 100 mgL NaHCO3
(Glocheux et al 2013)
Laterite 1~12 As(III) 07 1025~5 mgL at pH 7 in 100 mgL NaHCO3 (Glocheux et al
2013)
Laterite 1~12 As(V) 04 1025~5 mgL at pH 7 in 100 mgL NaHCO3 (Glocheux et al
2013)
Treated laterite 03-05 As(V) 216 05 02-20 mgL at pH 70 in DI water(Maiti et al 2012)
Treated laterite 03-05 As(III) 94 05 02-20 mgL at pH 70 in DI water(Maiti et al 2012)
Treated laterite03-05
As(V) 241 05 02-20 mgL at pH 70 in DI water(Maiti et al 2010a)
Treated laterite03-05
As(III) 81 05 02-20 mgL at pH 70 in DI water(Maiti et al 2010a)
Acid-activated laterite-103-07
As(III) 0633 50 02-10 mgL at pH 66-70 in DI water(Maiti et al 2010b)
Acid-activated laterite-203-07
As(III) 087650 02-10 mgL at pH 66-70 in DI water (Maiti et al
2010b)
Acid-activated laterite-303-07
As(III) 063450 02-10 mgL at pH 66-70 in DI water (Maiti et al
2010b)
Acid-activated laterite-103-07
As(V) 059850 02-10 mgL at pH 66-70 in DI water (Maiti et al
2010b)
27
Acid-activated laterite-203-07
As(V) 07550 02-10 mgL at pH 66-70 in DI water (Maiti et al
2010b)
Acid-activated laterite-303-07
As(V) 07550 02-10 mgL at pH 66-70 in DI water (Maiti et al
2010b)
Treated laterite-1 03-06 As(V) 019 20 0-20 mgL As at pH 72 in DI water(Maiti et al 2013b)
Treated laterite-1 03-06 As(III) 018 20 0-20 mgL As at pH 72 in DI water(Maiti et al 2013b)
Treated laterite-2 03-06 As(V) 004 20 0-20 mgL As at pH 72 in DI water(Maiti et al 2013b)
Treated laterite-2 03-06 As(III) 003 20 0-20 mgL As at pH 72 in DI water(Maiti et al 2013b)
Treated laterite-3 03-06 As(V) 007 20 0-20 mgL As at pH 72 in DI water(Maiti et al 2013b)
Treated laterite-3 03-06 As(III) 004 20 0-20 mgL As at pH 72 in DI water(Maiti et al 2013b)
28
376377
Charge distribution multi-site surface complexation (CD-MUSIC) modeling
The CD-MUSIC model with the 2-pK TPM adsorption option was used to
describe adsorption behaviors of As cations and anions on GTiO2 The CD-MUSIC
model incorporates the structural information of surfaces adsorbed species and the
double layers by distributing the charge of an adsorbate between the surface and
interfacial water (Hiemstra and Van Riemsdijk 2006) The CD-MUSIC model has
been successfully used in describing As adsorption in batch experiments (Pena et al
2006 Stachowicz et al 2008)
The adsorption constants of counter ions were set to -1 and the proton affinity
constant was set to the PZC of 58 for TiOH-13 (Luo et al 2010) The charge
distribution (CD) value shows the fraction (f) of the charge of the central As ion
attributed to the surface plane and the remaining part (1-f) was attributed to the other
ligands of the complex which were positioned toward the diffuse layer The CD value
for As surface complexes was obtained by fitting the experimental data The
calculation was performed using the chemical equilibrium program MINTEQ to
simulate the adsorption and the aqueous reactions
29
378379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
Fig S32 Adsorption of silicate (a) calcium and magnesium (b) as a function of GTiO2
dose in groundwater 1 The solid lines represent the CD-MUSIC modeling result
30
400
401
402
403
404
405
406
407
408409410
Table S75 Surface parameters and species used in the CD-MUSIC modeling in As(IIIV) removal under different GTiO2 dose in 01 M NaCl and groundwater 1 in Fig 2 and Fig S32
= exp(-FΨ1RT) P2 = exp(-FΨ2RT) F the Faraday constant (C mol-1) R the gas constant (J mol-1 K-1) T the absolute temperature (K)
Ψ0 Ψ1 Ψ2 the electrostatic potential (V) of 0- 1- and 2-plane respectively alogK for 01 M NaCl at 6 hours blogK for 01 M NaCl at 6 days clogK for groundwater 1 at 6 days
31
411412
413414415
32
416
Table S86 The charge distribution (f) of central As atom to TiO2 surface in simulating the effect of cations and anions on As adsorption in 01 M NaCl at pH 82 in Fig 4 BK Si HCO3 All
As(V) 022 017 012 016As(III) 040 020 058 056
Fig S43 Molar percentage () of As Ca Mg and Si on pristine and spent GTiO2
surfaces using EDX analysis The spent GTiO2 samples after field column experiments using groundwater 1 were identified with EBCT in min under x-axis The value of molar percentage of each element was averaged from randomly-chosen positions on the adsorbent surface
33
417
418
419420
421422
423
424
425
426
427
428
429
430
431
432
433434435436437438
439
440
441
As speciation analysis on spent GTiO2 using XANES
The spent GTiO2 samples were ground using a mortar and pestle and then the
ground powder was spread on Scotch tape The As k-edge XANES spectra were
collected at beamline 01C1 at the National Synchrotron Radiation Research Center
(NSRRC) Taiwan Spectra were acquired from -150 to 300 eV relative to the As K-
edge of 11867 eV at cryogenic temperature (77 K) using a cryostat to prevent the
oxidation of As(III) by X-rays The fluorescence signals were collected using a Lytle
detector Two to four scans were collected for each sample and averaged to improve
the signalnoise ratio The XANES analysis was performed with the Athena program
in the IFEFFIT computer package for linear combination fit (LCF) (Cui et al 2013
Ravel and Newville 2005)
34
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
PHREEQC modeling for As breakthrough curves in field column experiments
PHREEQC a geochemical model integrates macroscopic mass transfer
processes with a microscopic surface complexation model (Parkhurst and Appelo
2013) It can be applied in calculating solution complex speciation batch-reaction
and one-dimensional reactive-transport and inverse modeling In our study the one-
dimensional column was defined by four cells with the same length The cell length
was calculated to be one-fourth of the actual column length Time step (s) was
calculated according to equation Time step = Lcell(Q60A) where Lcell is the cell
length (cm) Q is flow velocity (mLmin) A is the effective column cross section area
(cm2) which is the column cross-sectional area multiplied by porosity (060) Total
shift number was calculated by dividing actual column operation time by the time
step The transport block was modeled by shifting the solute content from one cell to
the next one In each cell the aqueous solute was mixed and adsorbed on GTiO2
according to the equations In each cell the aqueous solute was mixed and assumed to
be in equilibration with GTiO2 The sequence of shifting mixing and equilibrium
adsorption was repeated for each cell until the total number of shifts was completed
The diffusion coefficient Dw in PHREEQC accounting for retardation was
calculated as Dw=x2
(36t) where x stands for the diffusion length (estimated as the
radius of the particle size) and t represents equilibrium time adopted from the batch
kinetic data (Mertens et al 2012)
For CD-MUSIC modeling in the PHREEQC take As(III) as an example to
explain the adsorption equation The As(III) adsorption is considered as a ligand
35
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
exchange reaction with the hydroxide group on GTiO2 (Surf_sOH-033) forming a
H3ArseniteO3 is the master species in groundwater at pH 82
(Surf_sO)2ArseniteOH-066 is the common adsorbed bidentate binuclear complex
evidenced by our previous reports(Pena et al 2006 Yan et al 2015) LogK is the
adsorption equilibrium constants Generally every adsorption equation under certain
experimental condition has a unique value of logK In the adsorption equation ldquo-2rdquo
represents the lost two hydrogens by Surf_sOH-033 after it adsorbs H3ArseniteO3 ldquo-
1rdquo represents the change in charge on Arsenite at 1 plane due to gaining one hydrogen
(+1) and one oxygen (-2) ldquo0rdquo represents no change in charge at the 2 plane ldquo066rdquo is
the fraction of the central ion (As) on GTiO2 surface that is associated with plane 0
ldquo3rdquo is the charge on the central ion As(III) Following this equation and the relevant
parameters As(III) adsorbed on GTiO2
The diffusion coefficient Dw in PHREEQC accounting for retardation was
calculated as Dw=x2(36t) where x stands for the diffusion length (estimated as the
radius of the particle size) and t represents equilibrium time adopted from the batch
kinetic data (Mertens et al 2012)
To well simulate the As breakthrough curve in columns four As(V) adsorption
reactions (Table 1) were employed Adsorption site density of 60 mmolg was
36
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
adopted from our previous study (Pena et al 2006) and the total adsorption sites were
calculated to be 1844 sitesnm2 The final optimized ratio of strong to weak sites was
51 The surface complexation constants were reasonably adjusted according to the
batch modeling results as the column reaction may not reach equilibrium in local
micro-interfacial areas due to much less contact time between As and GTiO2 than that
in batch experiments (Appelo and Postma 1999) In the modeling a stepwise
procedure was adopted to achieve a viable result An estimation of two thirds of the
surface site density being accessible for EBCT=011 min with large flow rate of 265
mLmin was optimized which could probably result from unavailable adsorption sites
due to fast transport through the column
The adsorbed As on GTiO2 in the column was calculated by mass balance
between the influent and effluent
where Asadsorbed is the adsorbed As on GTiO2 (mgg) n is the number of collected
samples Cin and Cout are influent and effluent As concentrations (mgL) respectively
Vi is volume (L) of groundwater passed through the column between sample i-1 and i
and m is the mass of GTiO2 (g)
Even though the oxidation of adsorbed As(III) occurred during filtration as
analyzed from XANES and mass balance analysis (Fig 7) no As(III) oxidation
reactions were considered in PHREEQC modeling which would not impact the
breakthrough of As(IIIV)
37
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
38
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
Fig S54 Effect of EBCT on Si Ca and Mg breakthrough curves using groundwater 1 The sample notation in panel c indicates field column experiments with EBCT in minutes
References
Appelo CAJ Postma D 1999 A consistent model for surface complexation on birnessite (MnO2) and its application to a column experiment Geochim Cosmochim Ac 63 (19-20) 3039-3048Badruzzaman M Westerhoff P Knappe DRU 2004 Intraparticle diffusion and adsorption of arsenate onto granular ferric hydroxide (GFH) Water Res 38 (18) 4002-4012Banerjee K Amy GL Prevost M Nour S Jekel M Gallagher PM Blumenschein CD 2008 Kinetic and thermodynamic aspects of adsorption of arsenic onto granular ferric hydroxide (GFH) Water Res 42 (13) 3371-3378Bang S Patel M Lippincott L Meng XG 2005 Removal of arsenic from groundwater by granular titanium dioxide adsorbent Chemosphere 60 (3) 389-397Bang S Pena ME Patel M Lippincott L Meng X Kim KW 2011 Removal of arsenate from water by adsorbents a comparative case study Environ Geochem Hlth 33 133-141Cui JL Shi JB Jiang GB Jing CY 2013 Arsenic levels and speciation from ingestion exposures to biomarkers in Shanxi China Implications for human health Environ Sci Technol 47 (10) 5419-5424Daus B Wennrich R Weiss H 2004 Sorption materials for arsenic removal from water A comparative study Water Res 38 (12) 2948-2954Dou XM Mohan D Pittman CU 2013 Arsenate adsorption on three types of granular schwertmannite Water Res 47 (9) 2938-2948Dou XM Zhang Y Yang M Pei YS Huang X Takayama T Kato S 2006 Occurrence of arsenic in groundwater in the suburbs of Beijing and its removal using an iron-cerium bimetal oxide adsorbent Water Qual Res J Can 41 (2) 140-146Gibbons MK Gagnon GA 2010 Adsorption of arsenic from a Nova Scotia groundwater onto water treatment residual solids Water Res 44 (19) 5740-5749Glocheux Y Mendez Pasarin M Albadarin AB Allen SJ Walker GM 2013 Removal of arsenic from groundwater by adsorption onto an acidified laterite by-product Chem Eng J 228 565-574Guan XH Wang JM Chusuei CC 2008 Removal of arsenic from water using granular ferric hydroxide Macroscopic and microscopic studies J Hazard Mater 156 (1-3) 178-185Gupta K Maity A Ghosh UC 2010 Manganese associated nanoparticles agglomerate of iron(III) oxide Synthesis characterization and arsenic(III) sorption behavior with mechanism J Hazard Mater 184 (1-3) 832-842Hao JM Han MJ Wang C Meng XG 2009 Enhanced removal of arsenite from water by a mesoporous hybrid material - Thiol-functionalized silica coated activated alumina Micropor Mesopor
Mat 124 (1-3) 1-7Hiemstra T Van Riemsdijk WH 2006 On the relationship between charge distribution surface hydration and the structure of the interface of metal hydroxides J Colloid Interf Sci 301 (1) 1-18Hristovski K Baumgardner A Westerhoff P 2007 Selecting metal oxide nanomaterials for arsenic removal in fixed bed columns From nanopowders to aggregated nanoparticle media J Hazard Mater 147 (1-2) 265-274Jang M Chen WF Cannon FS 2008 Preloading hydrous ferric oxide into granular activated carbon for arsenic removal Environ Sci Technol 42 (9) 3369-3374Jing CY Cui JL Huang YY Li AG 2012 Fabrication characterization and application of a composite adsorbent for simultaneous removal of arsenic and fluoride ACS Appl Mater Interfaces 4 (2) 714-720Kanematsu M Young TM Fukushi K Green PG Darby JL 2010 Extended triple layer modeling of arsenate and phosphate adsorption on a goethite-based granular porous adsorbent Environ Sci Technol 44 (9) 3388-3394Kong S Wang Y Zhan H Yuan S Liu M Zhou C 2013 Arsenite and Arsenate Removal from Contaminated Groundwater by Nanoscale Iron-Manganese Binary Oxides Column Studies Environmental Engineering Science 30 (11) 689-696Li Y Liu JR Jia SY Guo JW Zhuo J Na P 2012 TiO2 pillared montmorillonite as a photoactive adsorbent of arsenic under UV irradiation Chem Eng J 191 66-74Lin TF Wu JK 2001 Adsorption of arsenite and arsenate within activated alumina grains Equilibrium and kinetics Water Res 35 (8) 2049-2057Luo T Cui JL Hu S Huang YY Jing CY 2010 Arsenic removal and recovery from copper smelting wastewater using TiO2 Environ Sci Technol 44 (23) 9094-9098Maiti A Basu JK De S 2010a Development of a Treated Laterite for Arsenic Adsorption Effects of Treatment Parameters Industrial amp Engineering Chemistry Research 49 (10) 4873-4886Maiti A Basu JK De S 2010b Removal of Arsenic from Synthetic and Natural Groundwater Using Acid-Activated Laterite Environmental Progress amp Sustainable Energy 29 (4) 457-470Maiti A Basu JK De S 2012 Experimental and kinetic modeling of As(V) and As(III) adsorption on treated laterite using synthetic and contaminated groundwater Effects of phosphate silicate and carbonate ions Chem Eng J 191 1-12Maiti A Thakur BK Basu JK De S 2013a Comparison of treated laterite as arsenic adsorbent from different locations and performance of best filter under field conditions J Hazard Mater 262 1176-1186Maiti A Thakur BK Basu JK De S 2013b Comparison of treated laterite as arsenic adsorbent from different locations and performance of best filter under field conditions J Hazard Mater 262 (0) 1176-1186Maji SK Pal A Pal T 2008 Arsenic removal from real-life groundwater by adsorption on laterite soil J Hazard Mater 151 (2-3) 811-820Maji SK Kao YH Wang CJ Lu GS Wu JJ Liu CW 2012 Fixed bed adsorption of As(III) on iron-oxide-coated natural rock (IOCNR) and application to real arsenic-bearing groundwater Chem Eng J 203 285-293Mertens J Rose J Kagi R Chaurand P Plotze M Wehrli B Furrer G 2012 Adsorption of arsenic on polyaluminum granulate Environ Sci Technol 46 (13) 7310-7317Nguyen TV Vigneswaran S Ngo HH Pokhre D Viraraghavan T 2006 Iron-coated sponge as
effective media to remove arsenic from drinking water Water Qual Res J Can 41 (2) 164-170Parkhurst DL Appelo CAJ 2013 Description of input and examples for PHREEQC version 3-A computer program for speciation batch-reaction one-dimensional transport and inverse geochemical calculations US Geological SurveyPena M Meng XG Korfiatis GP Jing CY 2006 Adsorption mechanism of arsenic on nanocrystalline titanium dioxide Environ Sci Technol 40 (4) 1257-1262Ravel B Newville M 2005 ATHENA ARTEMIS HEPHAESTUS Data analysis for X-ray absorption spectroscopy using IFEFFIT J Synchrotron Radiat 12 537-541Saha B Bains R Greenwood F 2005 Physicochemical characterization of granular ferric hydroxide (GFH) for arsenic(V) sorption from water Separation Science and Technology 40 (14) 2909-2932Shan H Ma T Wang Y Zhao J Han H Deng Y He X Dong Y 2013 A cost-effective system for in-situ geological arsenic adsorption from groundwater J Contam Hydrol 154 1-9Stachowicz M Hiemstra T van Riemsdijk WH 2008 Multi-competitive interaction of As(III) and As(V) oxyanions with Ca2+ Mg2+ PO4
3- and CO32- ions on goethite J Colloid Interf Sci 320 (2) 400-
414Streat M Hellgardt K Newton NLR 2008 Hydrous ferric oxide as an adsorbent in water treatment - Part 3 Batch and mini-column adsorption of arsenic phosphorus fluorine and cadmium ions Process Safety and Environmental Protection 86 (B1) 21-30Thirunavukkarasu OS Viraraghavan T Subramanian KS 2003 Arsenic removal from drinking water using iron oxide-coated sand Water Air Soil Poll 142 (1-4) 95-111USEPA 2008 Assessing arsenic removal by metal (hydr)oxide adsorptive media using rapid small scale column tests Govenrnment Printing Office Washington DCWang J Xu W Chen L Huang X Liu J 2014 Preparation and evaluation of magnetic nanoparticles impregnated chitosan beads for arsenic removal from water Chem Eng J 251 25-34Westerhoff P Highfield D Badruzzaman M Yoon Y 2005 Rapid small-scale column tests for arsenate removal in iron oxide packed bed columns J Environ Eng-Asce 131 (2) 262-271Westerhoff P De Haan M Martindale A Badruzzaman M 2006 Arsenic adsorptive media technology selection strategies Water Qual Res J Can 41 (2) 171-184Yan L Huang Y Cui J Jing C 2015 Simultaneous As(III) and Cd removal from copper smelting wastewater using granular TiO2 columns Water Res 68 (0) 572-579Zhao K Guo HM 2014 Behavior and mechanism of arsenate adsorption on activated natural siderite Evidences from FTIR and XANES analysis Environ Sci Pollut Res 21 (3) 1944-1953Zhao K Guo H Zhou X 2014 Adsorption and heterogeneous oxidation of arsenite on modified granular natural siderite Characterization and behaviors Appl Geochem 48 184-192
Table S3 Water parameters in the synthetic water used in the studyParameters Ca2+ Mg2+ HCO3
- Na+ Cl- pHConc (mgL) 401 1043 388 2460 3928 82
Table S4 PHREEQC input for a representative column with EBCT=054 min SOLUTION 0
This keyword is to define the influent groundwater chemistry parameters which are included in the adsorption reactions like ldquoArseniterdquo and ldquoArsenaterdquo and the experimental conditions including ldquopHrdquo The information defined in SOLUTION is available for subsequent transport and adsorptive reaction calculations
temp 23 pH 82 pe 4 redox pe units mgL density 1 Al 006 Arsenite 0374 Arsenate 0291 CO4
2-
4401 Ca 194 Cl 1456 F 115 Fe 047 K 137 Mg 395 Mn 012 NO3
-
34 Na 16872
17
79
80
8182
83
84858687888990919293949596979899
100101102103104105106107108109110111112
SO42-
1176 Si 89 -water 1 kg
SOLUTION 1-4 The small column was divided into four cells SOLUTION 1-4
are the groundwater chemistry parameters for the four cells temp 23 pH 83 pe 4 redox pe units ppm density 1 Al 006 C(4) 4401 Ca 194 Cl 1456 F 115 Fe 047 K 137 Mg 395 Mn 012 N(3) 34 Na 16872 S(6) 1176 Si 89 -water 1 kg
SOLUTION_SPECIES This keyword is to define the dissociation constant logK
and diffusion constant (dw) in solution for arsenite and arsenate
Arsenite adsorption equation on GTiO2 surface H3ArseniteO3 is the primary species of As(III) at the groundwater pH 82 (Surf_sO)2ArseniteOH-066 is the adsorptive bidentate binuclear structure of As(III) on GTiO2
log_k 1635 The adsorptive reaction constant for As(III) on GTiO2 in
the current condition which could be changed with different experimental conditions
-cd_music -2 -1 0 066 3 CD-MUSIC model is integrated in the PHREEQC
modeling The numbers represent -2 the change in charge at the plane of Surf_sOH due to loss of two hydrogens -1 the change in charge at 1 plane due to gain of one hydrogen and one oxygen on Arsenite 0 the change in charge at the 2 plane usually caused by the outer sphere adsorption 066 the fraction of the central ion (As) charge that is associated with plane 0 which reflecting the charge distribution 3 the charge on the central ion (As)
Table S54 Parameters of Weber-Morris intraparticle model for As(IIIV) adsorption kinetics on GTiO2 using synthetic water Initial As concentration = 800 μgL adsorbent dose = 02 gL pH = 82 in synthetic groundwater
External film diffusion
Intraparticle diffusion
aRex2 bkp1
cb1aRin
2 bkp2cb 2
As(V) 0984 0497 0022 0976 01331878
As(III) 0970 0583
-0088 0981 0218
1105
aRex is WM external proportion fitting parameter while Rin is WM intraparticle proportion fitting parameterbk The unit of kp is mggh05 cb The unit of b is mgg
Table S6 Comparison of the adsorption capacities of As(III) and As(V) on GTiO2 and the representative granular adsorbents in similar experimental condition from the literature
AdsorbentParticle size (mm) As
qm
(mgg)Dose (gL) Experimental conditions Literature
GTiO2 018~025 As(III) 980 1 0~500 mgL at pH 82 01 M NaCl This studyGTiO2 018~025 As(V) 358 1 0~500 mgL at pH 82 01 M NaCl This study
Granular TiO2 015~06 As(III) 392 10~60 mgL As at pH 70 in simulated groundwater (100 mgL Ca 20 mgL Mg 50 mgL Na 200 mgL Cl-
)(Bang et al 2005)
Granular TiO2 015~06 As(V) 400 10~60 mgL As at pH 70 in simulated groundwater (100 mgL Ca 20 mgL Mg 50 mgL Na 200 mgL Cl-
)(Bang et al 2005)
E33 (FeOOH)0044~0075 As(V) 202 1 0~15 mgL at pH 70 in 001 M NaCl
(Kanematsu et al 2010)
E33 (FeOOH) 05~2 As(V) 180 1 0~50 mgL at pH 70 in 004 M NaClO4 (Jing et al 2012)
GFH 02~06 As(V) 650 10 0~2000 mgL at pH 8 in 01 M NaNO3
(Guan et al 2008)
GFH0009~0125 As(V) 23 025 0~07 μgL at pH 65 in DI water
(Banerjee et al 2008)
GFH0009~0125 As(V) 200 - 0~01 μgL at pH 70 in DI water
(Badruzzaman et al 2004)
GFH 050~065 As(V) 155 - 0~06 μgL at pH 70 in DI water (Saha et al 2005)
GHFO-NN 015~030 As(V) 330 0001 0~225 mgL at pH 8 in DI water(Streat et al 2008)
GHFO-VL 015~030 As(V) 360 0001 0~225 mgL at pH 8 in DI water(Streat et al 2008)
25
374375
Spherical schwertmannite 1~15 As(V) 36 05 0~5 mgL at pH 70 in DI water (Dou et al 2013)Cylindrical schwertmannite 1~25 As(V) 223 05
0~5 mgL at pH 70 in DI water(Dou et al 2013)
Irregular schwertmannite 10~16 As(V) 317 05 0~5 mgL at pH 70 in DI water (Dou et al 2013)Fe impregnated chitosan beads (MICB) 25 As(III) 117 1 0~05 mgL at pH 60 in DI water
(Wang et al 2014)
MICB 25 As(V) 191 1 0~1 mgL at pH 60 in DI water(Wang et al 2014)
MICB 25 As(III) 353 1 0~15 mgL at pH 60 in DI water(Wang et al 2014)
MICB 25 As(V) 357 1 0~16 mgL at pH 60 in DI water(Wang et al 2014)
Iron hydroxide granules (GIH) 3~4 As(V) 23 4
5~100 mgL at pH 70 in 10 mgL SO42-
14 mgL NH4Cl buffer solution (Daus et al 2004)
Activated Al2O3
0074~0149 As(V) 159 - 285~115 mgL at pH 52 in DI water
(Lin and Wu 2001)
Activated Al2O3
0074~0149 As(III) 35 - 079~490 mgL at pH 70 in DI water
(Lin and Wu 2001)
Activated Al2O3 ~20 As(V) 73 at pH 70 in 004 M NaClO4 (Jing et al 2012)
Activated natural siderite 05~10 As(V) 22 10 0 1~20 mgL at pH 7 in DI water(Zhao and Guo 2014)
Polyaluminum Granulate 1~3 As(III) 705 10 0~150 mgL at pH 51-56 in DI water(Mertens et al 2012)
Polyaluminum Granulate 1~3 As(V) 180 10 0~150 mgL at pH 51-56 in DI water (Mertens et al
26
2012)
Acidified laterite 1~12 As(III) 19 1 025~5 mgL at pH 7 in 100 mgL NaHCO3
(Glocheux et al 2013)
Acidified laterite 1~12 As(V) 13 1 025~5 mgL at pH 7 in 100 mgL NaHCO3
(Glocheux et al 2013)
Laterite 1~12 As(III) 07 1025~5 mgL at pH 7 in 100 mgL NaHCO3 (Glocheux et al
2013)
Laterite 1~12 As(V) 04 1025~5 mgL at pH 7 in 100 mgL NaHCO3 (Glocheux et al
2013)
Treated laterite 03-05 As(V) 216 05 02-20 mgL at pH 70 in DI water(Maiti et al 2012)
Treated laterite 03-05 As(III) 94 05 02-20 mgL at pH 70 in DI water(Maiti et al 2012)
Treated laterite03-05
As(V) 241 05 02-20 mgL at pH 70 in DI water(Maiti et al 2010a)
Treated laterite03-05
As(III) 81 05 02-20 mgL at pH 70 in DI water(Maiti et al 2010a)
Acid-activated laterite-103-07
As(III) 0633 50 02-10 mgL at pH 66-70 in DI water(Maiti et al 2010b)
Acid-activated laterite-203-07
As(III) 087650 02-10 mgL at pH 66-70 in DI water (Maiti et al
2010b)
Acid-activated laterite-303-07
As(III) 063450 02-10 mgL at pH 66-70 in DI water (Maiti et al
2010b)
Acid-activated laterite-103-07
As(V) 059850 02-10 mgL at pH 66-70 in DI water (Maiti et al
2010b)
27
Acid-activated laterite-203-07
As(V) 07550 02-10 mgL at pH 66-70 in DI water (Maiti et al
2010b)
Acid-activated laterite-303-07
As(V) 07550 02-10 mgL at pH 66-70 in DI water (Maiti et al
2010b)
Treated laterite-1 03-06 As(V) 019 20 0-20 mgL As at pH 72 in DI water(Maiti et al 2013b)
Treated laterite-1 03-06 As(III) 018 20 0-20 mgL As at pH 72 in DI water(Maiti et al 2013b)
Treated laterite-2 03-06 As(V) 004 20 0-20 mgL As at pH 72 in DI water(Maiti et al 2013b)
Treated laterite-2 03-06 As(III) 003 20 0-20 mgL As at pH 72 in DI water(Maiti et al 2013b)
Treated laterite-3 03-06 As(V) 007 20 0-20 mgL As at pH 72 in DI water(Maiti et al 2013b)
Treated laterite-3 03-06 As(III) 004 20 0-20 mgL As at pH 72 in DI water(Maiti et al 2013b)
28
376377
Charge distribution multi-site surface complexation (CD-MUSIC) modeling
The CD-MUSIC model with the 2-pK TPM adsorption option was used to
describe adsorption behaviors of As cations and anions on GTiO2 The CD-MUSIC
model incorporates the structural information of surfaces adsorbed species and the
double layers by distributing the charge of an adsorbate between the surface and
interfacial water (Hiemstra and Van Riemsdijk 2006) The CD-MUSIC model has
been successfully used in describing As adsorption in batch experiments (Pena et al
2006 Stachowicz et al 2008)
The adsorption constants of counter ions were set to -1 and the proton affinity
constant was set to the PZC of 58 for TiOH-13 (Luo et al 2010) The charge
distribution (CD) value shows the fraction (f) of the charge of the central As ion
attributed to the surface plane and the remaining part (1-f) was attributed to the other
ligands of the complex which were positioned toward the diffuse layer The CD value
for As surface complexes was obtained by fitting the experimental data The
calculation was performed using the chemical equilibrium program MINTEQ to
simulate the adsorption and the aqueous reactions
29
378379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
Fig S32 Adsorption of silicate (a) calcium and magnesium (b) as a function of GTiO2
dose in groundwater 1 The solid lines represent the CD-MUSIC modeling result
30
400
401
402
403
404
405
406
407
408409410
Table S75 Surface parameters and species used in the CD-MUSIC modeling in As(IIIV) removal under different GTiO2 dose in 01 M NaCl and groundwater 1 in Fig 2 and Fig S32
= exp(-FΨ1RT) P2 = exp(-FΨ2RT) F the Faraday constant (C mol-1) R the gas constant (J mol-1 K-1) T the absolute temperature (K)
Ψ0 Ψ1 Ψ2 the electrostatic potential (V) of 0- 1- and 2-plane respectively alogK for 01 M NaCl at 6 hours blogK for 01 M NaCl at 6 days clogK for groundwater 1 at 6 days
31
411412
413414415
32
416
Table S86 The charge distribution (f) of central As atom to TiO2 surface in simulating the effect of cations and anions on As adsorption in 01 M NaCl at pH 82 in Fig 4 BK Si HCO3 All
As(V) 022 017 012 016As(III) 040 020 058 056
Fig S43 Molar percentage () of As Ca Mg and Si on pristine and spent GTiO2
surfaces using EDX analysis The spent GTiO2 samples after field column experiments using groundwater 1 were identified with EBCT in min under x-axis The value of molar percentage of each element was averaged from randomly-chosen positions on the adsorbent surface
33
417
418
419420
421422
423
424
425
426
427
428
429
430
431
432
433434435436437438
439
440
441
As speciation analysis on spent GTiO2 using XANES
The spent GTiO2 samples were ground using a mortar and pestle and then the
ground powder was spread on Scotch tape The As k-edge XANES spectra were
collected at beamline 01C1 at the National Synchrotron Radiation Research Center
(NSRRC) Taiwan Spectra were acquired from -150 to 300 eV relative to the As K-
edge of 11867 eV at cryogenic temperature (77 K) using a cryostat to prevent the
oxidation of As(III) by X-rays The fluorescence signals were collected using a Lytle
detector Two to four scans were collected for each sample and averaged to improve
the signalnoise ratio The XANES analysis was performed with the Athena program
in the IFEFFIT computer package for linear combination fit (LCF) (Cui et al 2013
Ravel and Newville 2005)
34
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
PHREEQC modeling for As breakthrough curves in field column experiments
PHREEQC a geochemical model integrates macroscopic mass transfer
processes with a microscopic surface complexation model (Parkhurst and Appelo
2013) It can be applied in calculating solution complex speciation batch-reaction
and one-dimensional reactive-transport and inverse modeling In our study the one-
dimensional column was defined by four cells with the same length The cell length
was calculated to be one-fourth of the actual column length Time step (s) was
calculated according to equation Time step = Lcell(Q60A) where Lcell is the cell
length (cm) Q is flow velocity (mLmin) A is the effective column cross section area
(cm2) which is the column cross-sectional area multiplied by porosity (060) Total
shift number was calculated by dividing actual column operation time by the time
step The transport block was modeled by shifting the solute content from one cell to
the next one In each cell the aqueous solute was mixed and adsorbed on GTiO2
according to the equations In each cell the aqueous solute was mixed and assumed to
be in equilibration with GTiO2 The sequence of shifting mixing and equilibrium
adsorption was repeated for each cell until the total number of shifts was completed
The diffusion coefficient Dw in PHREEQC accounting for retardation was
calculated as Dw=x2
(36t) where x stands for the diffusion length (estimated as the
radius of the particle size) and t represents equilibrium time adopted from the batch
kinetic data (Mertens et al 2012)
For CD-MUSIC modeling in the PHREEQC take As(III) as an example to
explain the adsorption equation The As(III) adsorption is considered as a ligand
35
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
exchange reaction with the hydroxide group on GTiO2 (Surf_sOH-033) forming a
H3ArseniteO3 is the master species in groundwater at pH 82
(Surf_sO)2ArseniteOH-066 is the common adsorbed bidentate binuclear complex
evidenced by our previous reports(Pena et al 2006 Yan et al 2015) LogK is the
adsorption equilibrium constants Generally every adsorption equation under certain
experimental condition has a unique value of logK In the adsorption equation ldquo-2rdquo
represents the lost two hydrogens by Surf_sOH-033 after it adsorbs H3ArseniteO3 ldquo-
1rdquo represents the change in charge on Arsenite at 1 plane due to gaining one hydrogen
(+1) and one oxygen (-2) ldquo0rdquo represents no change in charge at the 2 plane ldquo066rdquo is
the fraction of the central ion (As) on GTiO2 surface that is associated with plane 0
ldquo3rdquo is the charge on the central ion As(III) Following this equation and the relevant
parameters As(III) adsorbed on GTiO2
The diffusion coefficient Dw in PHREEQC accounting for retardation was
calculated as Dw=x2(36t) where x stands for the diffusion length (estimated as the
radius of the particle size) and t represents equilibrium time adopted from the batch
kinetic data (Mertens et al 2012)
To well simulate the As breakthrough curve in columns four As(V) adsorption
reactions (Table 1) were employed Adsorption site density of 60 mmolg was
36
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
adopted from our previous study (Pena et al 2006) and the total adsorption sites were
calculated to be 1844 sitesnm2 The final optimized ratio of strong to weak sites was
51 The surface complexation constants were reasonably adjusted according to the
batch modeling results as the column reaction may not reach equilibrium in local
micro-interfacial areas due to much less contact time between As and GTiO2 than that
in batch experiments (Appelo and Postma 1999) In the modeling a stepwise
procedure was adopted to achieve a viable result An estimation of two thirds of the
surface site density being accessible for EBCT=011 min with large flow rate of 265
mLmin was optimized which could probably result from unavailable adsorption sites
due to fast transport through the column
The adsorbed As on GTiO2 in the column was calculated by mass balance
between the influent and effluent
where Asadsorbed is the adsorbed As on GTiO2 (mgg) n is the number of collected
samples Cin and Cout are influent and effluent As concentrations (mgL) respectively
Vi is volume (L) of groundwater passed through the column between sample i-1 and i
and m is the mass of GTiO2 (g)
Even though the oxidation of adsorbed As(III) occurred during filtration as
analyzed from XANES and mass balance analysis (Fig 7) no As(III) oxidation
reactions were considered in PHREEQC modeling which would not impact the
breakthrough of As(IIIV)
37
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
38
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
Fig S54 Effect of EBCT on Si Ca and Mg breakthrough curves using groundwater 1 The sample notation in panel c indicates field column experiments with EBCT in minutes
References
Appelo CAJ Postma D 1999 A consistent model for surface complexation on birnessite (MnO2) and its application to a column experiment Geochim Cosmochim Ac 63 (19-20) 3039-3048Badruzzaman M Westerhoff P Knappe DRU 2004 Intraparticle diffusion and adsorption of arsenate onto granular ferric hydroxide (GFH) Water Res 38 (18) 4002-4012Banerjee K Amy GL Prevost M Nour S Jekel M Gallagher PM Blumenschein CD 2008 Kinetic and thermodynamic aspects of adsorption of arsenic onto granular ferric hydroxide (GFH) Water Res 42 (13) 3371-3378Bang S Patel M Lippincott L Meng XG 2005 Removal of arsenic from groundwater by granular titanium dioxide adsorbent Chemosphere 60 (3) 389-397Bang S Pena ME Patel M Lippincott L Meng X Kim KW 2011 Removal of arsenate from water by adsorbents a comparative case study Environ Geochem Hlth 33 133-141Cui JL Shi JB Jiang GB Jing CY 2013 Arsenic levels and speciation from ingestion exposures to biomarkers in Shanxi China Implications for human health Environ Sci Technol 47 (10) 5419-5424Daus B Wennrich R Weiss H 2004 Sorption materials for arsenic removal from water A comparative study Water Res 38 (12) 2948-2954Dou XM Mohan D Pittman CU 2013 Arsenate adsorption on three types of granular schwertmannite Water Res 47 (9) 2938-2948Dou XM Zhang Y Yang M Pei YS Huang X Takayama T Kato S 2006 Occurrence of arsenic in groundwater in the suburbs of Beijing and its removal using an iron-cerium bimetal oxide adsorbent Water Qual Res J Can 41 (2) 140-146Gibbons MK Gagnon GA 2010 Adsorption of arsenic from a Nova Scotia groundwater onto water treatment residual solids Water Res 44 (19) 5740-5749Glocheux Y Mendez Pasarin M Albadarin AB Allen SJ Walker GM 2013 Removal of arsenic from groundwater by adsorption onto an acidified laterite by-product Chem Eng J 228 565-574Guan XH Wang JM Chusuei CC 2008 Removal of arsenic from water using granular ferric hydroxide Macroscopic and microscopic studies J Hazard Mater 156 (1-3) 178-185Gupta K Maity A Ghosh UC 2010 Manganese associated nanoparticles agglomerate of iron(III) oxide Synthesis characterization and arsenic(III) sorption behavior with mechanism J Hazard Mater 184 (1-3) 832-842Hao JM Han MJ Wang C Meng XG 2009 Enhanced removal of arsenite from water by a mesoporous hybrid material - Thiol-functionalized silica coated activated alumina Micropor Mesopor
Mat 124 (1-3) 1-7Hiemstra T Van Riemsdijk WH 2006 On the relationship between charge distribution surface hydration and the structure of the interface of metal hydroxides J Colloid Interf Sci 301 (1) 1-18Hristovski K Baumgardner A Westerhoff P 2007 Selecting metal oxide nanomaterials for arsenic removal in fixed bed columns From nanopowders to aggregated nanoparticle media J Hazard Mater 147 (1-2) 265-274Jang M Chen WF Cannon FS 2008 Preloading hydrous ferric oxide into granular activated carbon for arsenic removal Environ Sci Technol 42 (9) 3369-3374Jing CY Cui JL Huang YY Li AG 2012 Fabrication characterization and application of a composite adsorbent for simultaneous removal of arsenic and fluoride ACS Appl Mater Interfaces 4 (2) 714-720Kanematsu M Young TM Fukushi K Green PG Darby JL 2010 Extended triple layer modeling of arsenate and phosphate adsorption on a goethite-based granular porous adsorbent Environ Sci Technol 44 (9) 3388-3394Kong S Wang Y Zhan H Yuan S Liu M Zhou C 2013 Arsenite and Arsenate Removal from Contaminated Groundwater by Nanoscale Iron-Manganese Binary Oxides Column Studies Environmental Engineering Science 30 (11) 689-696Li Y Liu JR Jia SY Guo JW Zhuo J Na P 2012 TiO2 pillared montmorillonite as a photoactive adsorbent of arsenic under UV irradiation Chem Eng J 191 66-74Lin TF Wu JK 2001 Adsorption of arsenite and arsenate within activated alumina grains Equilibrium and kinetics Water Res 35 (8) 2049-2057Luo T Cui JL Hu S Huang YY Jing CY 2010 Arsenic removal and recovery from copper smelting wastewater using TiO2 Environ Sci Technol 44 (23) 9094-9098Maiti A Basu JK De S 2010a Development of a Treated Laterite for Arsenic Adsorption Effects of Treatment Parameters Industrial amp Engineering Chemistry Research 49 (10) 4873-4886Maiti A Basu JK De S 2010b Removal of Arsenic from Synthetic and Natural Groundwater Using Acid-Activated Laterite Environmental Progress amp Sustainable Energy 29 (4) 457-470Maiti A Basu JK De S 2012 Experimental and kinetic modeling of As(V) and As(III) adsorption on treated laterite using synthetic and contaminated groundwater Effects of phosphate silicate and carbonate ions Chem Eng J 191 1-12Maiti A Thakur BK Basu JK De S 2013a Comparison of treated laterite as arsenic adsorbent from different locations and performance of best filter under field conditions J Hazard Mater 262 1176-1186Maiti A Thakur BK Basu JK De S 2013b Comparison of treated laterite as arsenic adsorbent from different locations and performance of best filter under field conditions J Hazard Mater 262 (0) 1176-1186Maji SK Pal A Pal T 2008 Arsenic removal from real-life groundwater by adsorption on laterite soil J Hazard Mater 151 (2-3) 811-820Maji SK Kao YH Wang CJ Lu GS Wu JJ Liu CW 2012 Fixed bed adsorption of As(III) on iron-oxide-coated natural rock (IOCNR) and application to real arsenic-bearing groundwater Chem Eng J 203 285-293Mertens J Rose J Kagi R Chaurand P Plotze M Wehrli B Furrer G 2012 Adsorption of arsenic on polyaluminum granulate Environ Sci Technol 46 (13) 7310-7317Nguyen TV Vigneswaran S Ngo HH Pokhre D Viraraghavan T 2006 Iron-coated sponge as
effective media to remove arsenic from drinking water Water Qual Res J Can 41 (2) 164-170Parkhurst DL Appelo CAJ 2013 Description of input and examples for PHREEQC version 3-A computer program for speciation batch-reaction one-dimensional transport and inverse geochemical calculations US Geological SurveyPena M Meng XG Korfiatis GP Jing CY 2006 Adsorption mechanism of arsenic on nanocrystalline titanium dioxide Environ Sci Technol 40 (4) 1257-1262Ravel B Newville M 2005 ATHENA ARTEMIS HEPHAESTUS Data analysis for X-ray absorption spectroscopy using IFEFFIT J Synchrotron Radiat 12 537-541Saha B Bains R Greenwood F 2005 Physicochemical characterization of granular ferric hydroxide (GFH) for arsenic(V) sorption from water Separation Science and Technology 40 (14) 2909-2932Shan H Ma T Wang Y Zhao J Han H Deng Y He X Dong Y 2013 A cost-effective system for in-situ geological arsenic adsorption from groundwater J Contam Hydrol 154 1-9Stachowicz M Hiemstra T van Riemsdijk WH 2008 Multi-competitive interaction of As(III) and As(V) oxyanions with Ca2+ Mg2+ PO4
3- and CO32- ions on goethite J Colloid Interf Sci 320 (2) 400-
414Streat M Hellgardt K Newton NLR 2008 Hydrous ferric oxide as an adsorbent in water treatment - Part 3 Batch and mini-column adsorption of arsenic phosphorus fluorine and cadmium ions Process Safety and Environmental Protection 86 (B1) 21-30Thirunavukkarasu OS Viraraghavan T Subramanian KS 2003 Arsenic removal from drinking water using iron oxide-coated sand Water Air Soil Poll 142 (1-4) 95-111USEPA 2008 Assessing arsenic removal by metal (hydr)oxide adsorptive media using rapid small scale column tests Govenrnment Printing Office Washington DCWang J Xu W Chen L Huang X Liu J 2014 Preparation and evaluation of magnetic nanoparticles impregnated chitosan beads for arsenic removal from water Chem Eng J 251 25-34Westerhoff P Highfield D Badruzzaman M Yoon Y 2005 Rapid small-scale column tests for arsenate removal in iron oxide packed bed columns J Environ Eng-Asce 131 (2) 262-271Westerhoff P De Haan M Martindale A Badruzzaman M 2006 Arsenic adsorptive media technology selection strategies Water Qual Res J Can 41 (2) 171-184Yan L Huang Y Cui J Jing C 2015 Simultaneous As(III) and Cd removal from copper smelting wastewater using granular TiO2 columns Water Res 68 (0) 572-579Zhao K Guo HM 2014 Behavior and mechanism of arsenate adsorption on activated natural siderite Evidences from FTIR and XANES analysis Environ Sci Pollut Res 21 (3) 1944-1953Zhao K Guo H Zhou X 2014 Adsorption and heterogeneous oxidation of arsenite on modified granular natural siderite Characterization and behaviors Appl Geochem 48 184-192
SOLUTION 1-4 The small column was divided into four cells SOLUTION 1-4
are the groundwater chemistry parameters for the four cells temp 23 pH 83 pe 4 redox pe units ppm density 1 Al 006 C(4) 4401 Ca 194 Cl 1456 F 115 Fe 047 K 137 Mg 395 Mn 012 N(3) 34 Na 16872 S(6) 1176 Si 89 -water 1 kg
SOLUTION_SPECIES This keyword is to define the dissociation constant logK
and diffusion constant (dw) in solution for arsenite and arsenate
Arsenite adsorption equation on GTiO2 surface H3ArseniteO3 is the primary species of As(III) at the groundwater pH 82 (Surf_sO)2ArseniteOH-066 is the adsorptive bidentate binuclear structure of As(III) on GTiO2
log_k 1635 The adsorptive reaction constant for As(III) on GTiO2 in
the current condition which could be changed with different experimental conditions
-cd_music -2 -1 0 066 3 CD-MUSIC model is integrated in the PHREEQC
modeling The numbers represent -2 the change in charge at the plane of Surf_sOH due to loss of two hydrogens -1 the change in charge at 1 plane due to gain of one hydrogen and one oxygen on Arsenite 0 the change in charge at the 2 plane usually caused by the outer sphere adsorption 066 the fraction of the central ion (As) charge that is associated with plane 0 which reflecting the charge distribution 3 the charge on the central ion (As)
Table S54 Parameters of Weber-Morris intraparticle model for As(IIIV) adsorption kinetics on GTiO2 using synthetic water Initial As concentration = 800 μgL adsorbent dose = 02 gL pH = 82 in synthetic groundwater
External film diffusion
Intraparticle diffusion
aRex2 bkp1
cb1aRin
2 bkp2cb 2
As(V) 0984 0497 0022 0976 01331878
As(III) 0970 0583
-0088 0981 0218
1105
aRex is WM external proportion fitting parameter while Rin is WM intraparticle proportion fitting parameterbk The unit of kp is mggh05 cb The unit of b is mgg
Table S6 Comparison of the adsorption capacities of As(III) and As(V) on GTiO2 and the representative granular adsorbents in similar experimental condition from the literature
AdsorbentParticle size (mm) As
qm
(mgg)Dose (gL) Experimental conditions Literature
GTiO2 018~025 As(III) 980 1 0~500 mgL at pH 82 01 M NaCl This studyGTiO2 018~025 As(V) 358 1 0~500 mgL at pH 82 01 M NaCl This study
Granular TiO2 015~06 As(III) 392 10~60 mgL As at pH 70 in simulated groundwater (100 mgL Ca 20 mgL Mg 50 mgL Na 200 mgL Cl-
)(Bang et al 2005)
Granular TiO2 015~06 As(V) 400 10~60 mgL As at pH 70 in simulated groundwater (100 mgL Ca 20 mgL Mg 50 mgL Na 200 mgL Cl-
)(Bang et al 2005)
E33 (FeOOH)0044~0075 As(V) 202 1 0~15 mgL at pH 70 in 001 M NaCl
(Kanematsu et al 2010)
E33 (FeOOH) 05~2 As(V) 180 1 0~50 mgL at pH 70 in 004 M NaClO4 (Jing et al 2012)
GFH 02~06 As(V) 650 10 0~2000 mgL at pH 8 in 01 M NaNO3
(Guan et al 2008)
GFH0009~0125 As(V) 23 025 0~07 μgL at pH 65 in DI water
(Banerjee et al 2008)
GFH0009~0125 As(V) 200 - 0~01 μgL at pH 70 in DI water
(Badruzzaman et al 2004)
GFH 050~065 As(V) 155 - 0~06 μgL at pH 70 in DI water (Saha et al 2005)
GHFO-NN 015~030 As(V) 330 0001 0~225 mgL at pH 8 in DI water(Streat et al 2008)
GHFO-VL 015~030 As(V) 360 0001 0~225 mgL at pH 8 in DI water(Streat et al 2008)
25
374375
Spherical schwertmannite 1~15 As(V) 36 05 0~5 mgL at pH 70 in DI water (Dou et al 2013)Cylindrical schwertmannite 1~25 As(V) 223 05
0~5 mgL at pH 70 in DI water(Dou et al 2013)
Irregular schwertmannite 10~16 As(V) 317 05 0~5 mgL at pH 70 in DI water (Dou et al 2013)Fe impregnated chitosan beads (MICB) 25 As(III) 117 1 0~05 mgL at pH 60 in DI water
(Wang et al 2014)
MICB 25 As(V) 191 1 0~1 mgL at pH 60 in DI water(Wang et al 2014)
MICB 25 As(III) 353 1 0~15 mgL at pH 60 in DI water(Wang et al 2014)
MICB 25 As(V) 357 1 0~16 mgL at pH 60 in DI water(Wang et al 2014)
Iron hydroxide granules (GIH) 3~4 As(V) 23 4
5~100 mgL at pH 70 in 10 mgL SO42-
14 mgL NH4Cl buffer solution (Daus et al 2004)
Activated Al2O3
0074~0149 As(V) 159 - 285~115 mgL at pH 52 in DI water
(Lin and Wu 2001)
Activated Al2O3
0074~0149 As(III) 35 - 079~490 mgL at pH 70 in DI water
(Lin and Wu 2001)
Activated Al2O3 ~20 As(V) 73 at pH 70 in 004 M NaClO4 (Jing et al 2012)
Activated natural siderite 05~10 As(V) 22 10 0 1~20 mgL at pH 7 in DI water(Zhao and Guo 2014)
Polyaluminum Granulate 1~3 As(III) 705 10 0~150 mgL at pH 51-56 in DI water(Mertens et al 2012)
Polyaluminum Granulate 1~3 As(V) 180 10 0~150 mgL at pH 51-56 in DI water (Mertens et al
26
2012)
Acidified laterite 1~12 As(III) 19 1 025~5 mgL at pH 7 in 100 mgL NaHCO3
(Glocheux et al 2013)
Acidified laterite 1~12 As(V) 13 1 025~5 mgL at pH 7 in 100 mgL NaHCO3
(Glocheux et al 2013)
Laterite 1~12 As(III) 07 1025~5 mgL at pH 7 in 100 mgL NaHCO3 (Glocheux et al
2013)
Laterite 1~12 As(V) 04 1025~5 mgL at pH 7 in 100 mgL NaHCO3 (Glocheux et al
2013)
Treated laterite 03-05 As(V) 216 05 02-20 mgL at pH 70 in DI water(Maiti et al 2012)
Treated laterite 03-05 As(III) 94 05 02-20 mgL at pH 70 in DI water(Maiti et al 2012)
Treated laterite03-05
As(V) 241 05 02-20 mgL at pH 70 in DI water(Maiti et al 2010a)
Treated laterite03-05
As(III) 81 05 02-20 mgL at pH 70 in DI water(Maiti et al 2010a)
Acid-activated laterite-103-07
As(III) 0633 50 02-10 mgL at pH 66-70 in DI water(Maiti et al 2010b)
Acid-activated laterite-203-07
As(III) 087650 02-10 mgL at pH 66-70 in DI water (Maiti et al
2010b)
Acid-activated laterite-303-07
As(III) 063450 02-10 mgL at pH 66-70 in DI water (Maiti et al
2010b)
Acid-activated laterite-103-07
As(V) 059850 02-10 mgL at pH 66-70 in DI water (Maiti et al
2010b)
27
Acid-activated laterite-203-07
As(V) 07550 02-10 mgL at pH 66-70 in DI water (Maiti et al
2010b)
Acid-activated laterite-303-07
As(V) 07550 02-10 mgL at pH 66-70 in DI water (Maiti et al
2010b)
Treated laterite-1 03-06 As(V) 019 20 0-20 mgL As at pH 72 in DI water(Maiti et al 2013b)
Treated laterite-1 03-06 As(III) 018 20 0-20 mgL As at pH 72 in DI water(Maiti et al 2013b)
Treated laterite-2 03-06 As(V) 004 20 0-20 mgL As at pH 72 in DI water(Maiti et al 2013b)
Treated laterite-2 03-06 As(III) 003 20 0-20 mgL As at pH 72 in DI water(Maiti et al 2013b)
Treated laterite-3 03-06 As(V) 007 20 0-20 mgL As at pH 72 in DI water(Maiti et al 2013b)
Treated laterite-3 03-06 As(III) 004 20 0-20 mgL As at pH 72 in DI water(Maiti et al 2013b)
28
376377
Charge distribution multi-site surface complexation (CD-MUSIC) modeling
The CD-MUSIC model with the 2-pK TPM adsorption option was used to
describe adsorption behaviors of As cations and anions on GTiO2 The CD-MUSIC
model incorporates the structural information of surfaces adsorbed species and the
double layers by distributing the charge of an adsorbate between the surface and
interfacial water (Hiemstra and Van Riemsdijk 2006) The CD-MUSIC model has
been successfully used in describing As adsorption in batch experiments (Pena et al
2006 Stachowicz et al 2008)
The adsorption constants of counter ions were set to -1 and the proton affinity
constant was set to the PZC of 58 for TiOH-13 (Luo et al 2010) The charge
distribution (CD) value shows the fraction (f) of the charge of the central As ion
attributed to the surface plane and the remaining part (1-f) was attributed to the other
ligands of the complex which were positioned toward the diffuse layer The CD value
for As surface complexes was obtained by fitting the experimental data The
calculation was performed using the chemical equilibrium program MINTEQ to
simulate the adsorption and the aqueous reactions
29
378379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
Fig S32 Adsorption of silicate (a) calcium and magnesium (b) as a function of GTiO2
dose in groundwater 1 The solid lines represent the CD-MUSIC modeling result
30
400
401
402
403
404
405
406
407
408409410
Table S75 Surface parameters and species used in the CD-MUSIC modeling in As(IIIV) removal under different GTiO2 dose in 01 M NaCl and groundwater 1 in Fig 2 and Fig S32
= exp(-FΨ1RT) P2 = exp(-FΨ2RT) F the Faraday constant (C mol-1) R the gas constant (J mol-1 K-1) T the absolute temperature (K)
Ψ0 Ψ1 Ψ2 the electrostatic potential (V) of 0- 1- and 2-plane respectively alogK for 01 M NaCl at 6 hours blogK for 01 M NaCl at 6 days clogK for groundwater 1 at 6 days
31
411412
413414415
32
416
Table S86 The charge distribution (f) of central As atom to TiO2 surface in simulating the effect of cations and anions on As adsorption in 01 M NaCl at pH 82 in Fig 4 BK Si HCO3 All
As(V) 022 017 012 016As(III) 040 020 058 056
Fig S43 Molar percentage () of As Ca Mg and Si on pristine and spent GTiO2
surfaces using EDX analysis The spent GTiO2 samples after field column experiments using groundwater 1 were identified with EBCT in min under x-axis The value of molar percentage of each element was averaged from randomly-chosen positions on the adsorbent surface
33
417
418
419420
421422
423
424
425
426
427
428
429
430
431
432
433434435436437438
439
440
441
As speciation analysis on spent GTiO2 using XANES
The spent GTiO2 samples were ground using a mortar and pestle and then the
ground powder was spread on Scotch tape The As k-edge XANES spectra were
collected at beamline 01C1 at the National Synchrotron Radiation Research Center
(NSRRC) Taiwan Spectra were acquired from -150 to 300 eV relative to the As K-
edge of 11867 eV at cryogenic temperature (77 K) using a cryostat to prevent the
oxidation of As(III) by X-rays The fluorescence signals were collected using a Lytle
detector Two to four scans were collected for each sample and averaged to improve
the signalnoise ratio The XANES analysis was performed with the Athena program
in the IFEFFIT computer package for linear combination fit (LCF) (Cui et al 2013
Ravel and Newville 2005)
34
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
PHREEQC modeling for As breakthrough curves in field column experiments
PHREEQC a geochemical model integrates macroscopic mass transfer
processes with a microscopic surface complexation model (Parkhurst and Appelo
2013) It can be applied in calculating solution complex speciation batch-reaction
and one-dimensional reactive-transport and inverse modeling In our study the one-
dimensional column was defined by four cells with the same length The cell length
was calculated to be one-fourth of the actual column length Time step (s) was
calculated according to equation Time step = Lcell(Q60A) where Lcell is the cell
length (cm) Q is flow velocity (mLmin) A is the effective column cross section area
(cm2) which is the column cross-sectional area multiplied by porosity (060) Total
shift number was calculated by dividing actual column operation time by the time
step The transport block was modeled by shifting the solute content from one cell to
the next one In each cell the aqueous solute was mixed and adsorbed on GTiO2
according to the equations In each cell the aqueous solute was mixed and assumed to
be in equilibration with GTiO2 The sequence of shifting mixing and equilibrium
adsorption was repeated for each cell until the total number of shifts was completed
The diffusion coefficient Dw in PHREEQC accounting for retardation was
calculated as Dw=x2
(36t) where x stands for the diffusion length (estimated as the
radius of the particle size) and t represents equilibrium time adopted from the batch
kinetic data (Mertens et al 2012)
For CD-MUSIC modeling in the PHREEQC take As(III) as an example to
explain the adsorption equation The As(III) adsorption is considered as a ligand
35
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
exchange reaction with the hydroxide group on GTiO2 (Surf_sOH-033) forming a
H3ArseniteO3 is the master species in groundwater at pH 82
(Surf_sO)2ArseniteOH-066 is the common adsorbed bidentate binuclear complex
evidenced by our previous reports(Pena et al 2006 Yan et al 2015) LogK is the
adsorption equilibrium constants Generally every adsorption equation under certain
experimental condition has a unique value of logK In the adsorption equation ldquo-2rdquo
represents the lost two hydrogens by Surf_sOH-033 after it adsorbs H3ArseniteO3 ldquo-
1rdquo represents the change in charge on Arsenite at 1 plane due to gaining one hydrogen
(+1) and one oxygen (-2) ldquo0rdquo represents no change in charge at the 2 plane ldquo066rdquo is
the fraction of the central ion (As) on GTiO2 surface that is associated with plane 0
ldquo3rdquo is the charge on the central ion As(III) Following this equation and the relevant
parameters As(III) adsorbed on GTiO2
The diffusion coefficient Dw in PHREEQC accounting for retardation was
calculated as Dw=x2(36t) where x stands for the diffusion length (estimated as the
radius of the particle size) and t represents equilibrium time adopted from the batch
kinetic data (Mertens et al 2012)
To well simulate the As breakthrough curve in columns four As(V) adsorption
reactions (Table 1) were employed Adsorption site density of 60 mmolg was
36
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
adopted from our previous study (Pena et al 2006) and the total adsorption sites were
calculated to be 1844 sitesnm2 The final optimized ratio of strong to weak sites was
51 The surface complexation constants were reasonably adjusted according to the
batch modeling results as the column reaction may not reach equilibrium in local
micro-interfacial areas due to much less contact time between As and GTiO2 than that
in batch experiments (Appelo and Postma 1999) In the modeling a stepwise
procedure was adopted to achieve a viable result An estimation of two thirds of the
surface site density being accessible for EBCT=011 min with large flow rate of 265
mLmin was optimized which could probably result from unavailable adsorption sites
due to fast transport through the column
The adsorbed As on GTiO2 in the column was calculated by mass balance
between the influent and effluent
where Asadsorbed is the adsorbed As on GTiO2 (mgg) n is the number of collected
samples Cin and Cout are influent and effluent As concentrations (mgL) respectively
Vi is volume (L) of groundwater passed through the column between sample i-1 and i
and m is the mass of GTiO2 (g)
Even though the oxidation of adsorbed As(III) occurred during filtration as
analyzed from XANES and mass balance analysis (Fig 7) no As(III) oxidation
reactions were considered in PHREEQC modeling which would not impact the
breakthrough of As(IIIV)
37
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
38
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
Fig S54 Effect of EBCT on Si Ca and Mg breakthrough curves using groundwater 1 The sample notation in panel c indicates field column experiments with EBCT in minutes
References
Appelo CAJ Postma D 1999 A consistent model for surface complexation on birnessite (MnO2) and its application to a column experiment Geochim Cosmochim Ac 63 (19-20) 3039-3048Badruzzaman M Westerhoff P Knappe DRU 2004 Intraparticle diffusion and adsorption of arsenate onto granular ferric hydroxide (GFH) Water Res 38 (18) 4002-4012Banerjee K Amy GL Prevost M Nour S Jekel M Gallagher PM Blumenschein CD 2008 Kinetic and thermodynamic aspects of adsorption of arsenic onto granular ferric hydroxide (GFH) Water Res 42 (13) 3371-3378Bang S Patel M Lippincott L Meng XG 2005 Removal of arsenic from groundwater by granular titanium dioxide adsorbent Chemosphere 60 (3) 389-397Bang S Pena ME Patel M Lippincott L Meng X Kim KW 2011 Removal of arsenate from water by adsorbents a comparative case study Environ Geochem Hlth 33 133-141Cui JL Shi JB Jiang GB Jing CY 2013 Arsenic levels and speciation from ingestion exposures to biomarkers in Shanxi China Implications for human health Environ Sci Technol 47 (10) 5419-5424Daus B Wennrich R Weiss H 2004 Sorption materials for arsenic removal from water A comparative study Water Res 38 (12) 2948-2954Dou XM Mohan D Pittman CU 2013 Arsenate adsorption on three types of granular schwertmannite Water Res 47 (9) 2938-2948Dou XM Zhang Y Yang M Pei YS Huang X Takayama T Kato S 2006 Occurrence of arsenic in groundwater in the suburbs of Beijing and its removal using an iron-cerium bimetal oxide adsorbent Water Qual Res J Can 41 (2) 140-146Gibbons MK Gagnon GA 2010 Adsorption of arsenic from a Nova Scotia groundwater onto water treatment residual solids Water Res 44 (19) 5740-5749Glocheux Y Mendez Pasarin M Albadarin AB Allen SJ Walker GM 2013 Removal of arsenic from groundwater by adsorption onto an acidified laterite by-product Chem Eng J 228 565-574Guan XH Wang JM Chusuei CC 2008 Removal of arsenic from water using granular ferric hydroxide Macroscopic and microscopic studies J Hazard Mater 156 (1-3) 178-185Gupta K Maity A Ghosh UC 2010 Manganese associated nanoparticles agglomerate of iron(III) oxide Synthesis characterization and arsenic(III) sorption behavior with mechanism J Hazard Mater 184 (1-3) 832-842Hao JM Han MJ Wang C Meng XG 2009 Enhanced removal of arsenite from water by a mesoporous hybrid material - Thiol-functionalized silica coated activated alumina Micropor Mesopor
Mat 124 (1-3) 1-7Hiemstra T Van Riemsdijk WH 2006 On the relationship between charge distribution surface hydration and the structure of the interface of metal hydroxides J Colloid Interf Sci 301 (1) 1-18Hristovski K Baumgardner A Westerhoff P 2007 Selecting metal oxide nanomaterials for arsenic removal in fixed bed columns From nanopowders to aggregated nanoparticle media J Hazard Mater 147 (1-2) 265-274Jang M Chen WF Cannon FS 2008 Preloading hydrous ferric oxide into granular activated carbon for arsenic removal Environ Sci Technol 42 (9) 3369-3374Jing CY Cui JL Huang YY Li AG 2012 Fabrication characterization and application of a composite adsorbent for simultaneous removal of arsenic and fluoride ACS Appl Mater Interfaces 4 (2) 714-720Kanematsu M Young TM Fukushi K Green PG Darby JL 2010 Extended triple layer modeling of arsenate and phosphate adsorption on a goethite-based granular porous adsorbent Environ Sci Technol 44 (9) 3388-3394Kong S Wang Y Zhan H Yuan S Liu M Zhou C 2013 Arsenite and Arsenate Removal from Contaminated Groundwater by Nanoscale Iron-Manganese Binary Oxides Column Studies Environmental Engineering Science 30 (11) 689-696Li Y Liu JR Jia SY Guo JW Zhuo J Na P 2012 TiO2 pillared montmorillonite as a photoactive adsorbent of arsenic under UV irradiation Chem Eng J 191 66-74Lin TF Wu JK 2001 Adsorption of arsenite and arsenate within activated alumina grains Equilibrium and kinetics Water Res 35 (8) 2049-2057Luo T Cui JL Hu S Huang YY Jing CY 2010 Arsenic removal and recovery from copper smelting wastewater using TiO2 Environ Sci Technol 44 (23) 9094-9098Maiti A Basu JK De S 2010a Development of a Treated Laterite for Arsenic Adsorption Effects of Treatment Parameters Industrial amp Engineering Chemistry Research 49 (10) 4873-4886Maiti A Basu JK De S 2010b Removal of Arsenic from Synthetic and Natural Groundwater Using Acid-Activated Laterite Environmental Progress amp Sustainable Energy 29 (4) 457-470Maiti A Basu JK De S 2012 Experimental and kinetic modeling of As(V) and As(III) adsorption on treated laterite using synthetic and contaminated groundwater Effects of phosphate silicate and carbonate ions Chem Eng J 191 1-12Maiti A Thakur BK Basu JK De S 2013a Comparison of treated laterite as arsenic adsorbent from different locations and performance of best filter under field conditions J Hazard Mater 262 1176-1186Maiti A Thakur BK Basu JK De S 2013b Comparison of treated laterite as arsenic adsorbent from different locations and performance of best filter under field conditions J Hazard Mater 262 (0) 1176-1186Maji SK Pal A Pal T 2008 Arsenic removal from real-life groundwater by adsorption on laterite soil J Hazard Mater 151 (2-3) 811-820Maji SK Kao YH Wang CJ Lu GS Wu JJ Liu CW 2012 Fixed bed adsorption of As(III) on iron-oxide-coated natural rock (IOCNR) and application to real arsenic-bearing groundwater Chem Eng J 203 285-293Mertens J Rose J Kagi R Chaurand P Plotze M Wehrli B Furrer G 2012 Adsorption of arsenic on polyaluminum granulate Environ Sci Technol 46 (13) 7310-7317Nguyen TV Vigneswaran S Ngo HH Pokhre D Viraraghavan T 2006 Iron-coated sponge as
effective media to remove arsenic from drinking water Water Qual Res J Can 41 (2) 164-170Parkhurst DL Appelo CAJ 2013 Description of input and examples for PHREEQC version 3-A computer program for speciation batch-reaction one-dimensional transport and inverse geochemical calculations US Geological SurveyPena M Meng XG Korfiatis GP Jing CY 2006 Adsorption mechanism of arsenic on nanocrystalline titanium dioxide Environ Sci Technol 40 (4) 1257-1262Ravel B Newville M 2005 ATHENA ARTEMIS HEPHAESTUS Data analysis for X-ray absorption spectroscopy using IFEFFIT J Synchrotron Radiat 12 537-541Saha B Bains R Greenwood F 2005 Physicochemical characterization of granular ferric hydroxide (GFH) for arsenic(V) sorption from water Separation Science and Technology 40 (14) 2909-2932Shan H Ma T Wang Y Zhao J Han H Deng Y He X Dong Y 2013 A cost-effective system for in-situ geological arsenic adsorption from groundwater J Contam Hydrol 154 1-9Stachowicz M Hiemstra T van Riemsdijk WH 2008 Multi-competitive interaction of As(III) and As(V) oxyanions with Ca2+ Mg2+ PO4
3- and CO32- ions on goethite J Colloid Interf Sci 320 (2) 400-
414Streat M Hellgardt K Newton NLR 2008 Hydrous ferric oxide as an adsorbent in water treatment - Part 3 Batch and mini-column adsorption of arsenic phosphorus fluorine and cadmium ions Process Safety and Environmental Protection 86 (B1) 21-30Thirunavukkarasu OS Viraraghavan T Subramanian KS 2003 Arsenic removal from drinking water using iron oxide-coated sand Water Air Soil Poll 142 (1-4) 95-111USEPA 2008 Assessing arsenic removal by metal (hydr)oxide adsorptive media using rapid small scale column tests Govenrnment Printing Office Washington DCWang J Xu W Chen L Huang X Liu J 2014 Preparation and evaluation of magnetic nanoparticles impregnated chitosan beads for arsenic removal from water Chem Eng J 251 25-34Westerhoff P Highfield D Badruzzaman M Yoon Y 2005 Rapid small-scale column tests for arsenate removal in iron oxide packed bed columns J Environ Eng-Asce 131 (2) 262-271Westerhoff P De Haan M Martindale A Badruzzaman M 2006 Arsenic adsorptive media technology selection strategies Water Qual Res J Can 41 (2) 171-184Yan L Huang Y Cui J Jing C 2015 Simultaneous As(III) and Cd removal from copper smelting wastewater using granular TiO2 columns Water Res 68 (0) 572-579Zhao K Guo HM 2014 Behavior and mechanism of arsenate adsorption on activated natural siderite Evidences from FTIR and XANES analysis Environ Sci Pollut Res 21 (3) 1944-1953Zhao K Guo H Zhou X 2014 Adsorption and heterogeneous oxidation of arsenite on modified granular natural siderite Characterization and behaviors Appl Geochem 48 184-192
Arsenite adsorption equation on GTiO2 surface H3ArseniteO3 is the primary species of As(III) at the groundwater pH 82 (Surf_sO)2ArseniteOH-066 is the adsorptive bidentate binuclear structure of As(III) on GTiO2
log_k 1635 The adsorptive reaction constant for As(III) on GTiO2 in
the current condition which could be changed with different experimental conditions
-cd_music -2 -1 0 066 3 CD-MUSIC model is integrated in the PHREEQC
modeling The numbers represent -2 the change in charge at the plane of Surf_sOH due to loss of two hydrogens -1 the change in charge at 1 plane due to gain of one hydrogen and one oxygen on Arsenite 0 the change in charge at the 2 plane usually caused by the outer sphere adsorption 066 the fraction of the central ion (As) charge that is associated with plane 0 which reflecting the charge distribution 3 the charge on the central ion (As)
Table S54 Parameters of Weber-Morris intraparticle model for As(IIIV) adsorption kinetics on GTiO2 using synthetic water Initial As concentration = 800 μgL adsorbent dose = 02 gL pH = 82 in synthetic groundwater
External film diffusion
Intraparticle diffusion
aRex2 bkp1
cb1aRin
2 bkp2cb 2
As(V) 0984 0497 0022 0976 01331878
As(III) 0970 0583
-0088 0981 0218
1105
aRex is WM external proportion fitting parameter while Rin is WM intraparticle proportion fitting parameterbk The unit of kp is mggh05 cb The unit of b is mgg
Table S6 Comparison of the adsorption capacities of As(III) and As(V) on GTiO2 and the representative granular adsorbents in similar experimental condition from the literature
AdsorbentParticle size (mm) As
qm
(mgg)Dose (gL) Experimental conditions Literature
GTiO2 018~025 As(III) 980 1 0~500 mgL at pH 82 01 M NaCl This studyGTiO2 018~025 As(V) 358 1 0~500 mgL at pH 82 01 M NaCl This study
Granular TiO2 015~06 As(III) 392 10~60 mgL As at pH 70 in simulated groundwater (100 mgL Ca 20 mgL Mg 50 mgL Na 200 mgL Cl-
)(Bang et al 2005)
Granular TiO2 015~06 As(V) 400 10~60 mgL As at pH 70 in simulated groundwater (100 mgL Ca 20 mgL Mg 50 mgL Na 200 mgL Cl-
)(Bang et al 2005)
E33 (FeOOH)0044~0075 As(V) 202 1 0~15 mgL at pH 70 in 001 M NaCl
(Kanematsu et al 2010)
E33 (FeOOH) 05~2 As(V) 180 1 0~50 mgL at pH 70 in 004 M NaClO4 (Jing et al 2012)
GFH 02~06 As(V) 650 10 0~2000 mgL at pH 8 in 01 M NaNO3
(Guan et al 2008)
GFH0009~0125 As(V) 23 025 0~07 μgL at pH 65 in DI water
(Banerjee et al 2008)
GFH0009~0125 As(V) 200 - 0~01 μgL at pH 70 in DI water
(Badruzzaman et al 2004)
GFH 050~065 As(V) 155 - 0~06 μgL at pH 70 in DI water (Saha et al 2005)
GHFO-NN 015~030 As(V) 330 0001 0~225 mgL at pH 8 in DI water(Streat et al 2008)
GHFO-VL 015~030 As(V) 360 0001 0~225 mgL at pH 8 in DI water(Streat et al 2008)
25
374375
Spherical schwertmannite 1~15 As(V) 36 05 0~5 mgL at pH 70 in DI water (Dou et al 2013)Cylindrical schwertmannite 1~25 As(V) 223 05
0~5 mgL at pH 70 in DI water(Dou et al 2013)
Irregular schwertmannite 10~16 As(V) 317 05 0~5 mgL at pH 70 in DI water (Dou et al 2013)Fe impregnated chitosan beads (MICB) 25 As(III) 117 1 0~05 mgL at pH 60 in DI water
(Wang et al 2014)
MICB 25 As(V) 191 1 0~1 mgL at pH 60 in DI water(Wang et al 2014)
MICB 25 As(III) 353 1 0~15 mgL at pH 60 in DI water(Wang et al 2014)
MICB 25 As(V) 357 1 0~16 mgL at pH 60 in DI water(Wang et al 2014)
Iron hydroxide granules (GIH) 3~4 As(V) 23 4
5~100 mgL at pH 70 in 10 mgL SO42-
14 mgL NH4Cl buffer solution (Daus et al 2004)
Activated Al2O3
0074~0149 As(V) 159 - 285~115 mgL at pH 52 in DI water
(Lin and Wu 2001)
Activated Al2O3
0074~0149 As(III) 35 - 079~490 mgL at pH 70 in DI water
(Lin and Wu 2001)
Activated Al2O3 ~20 As(V) 73 at pH 70 in 004 M NaClO4 (Jing et al 2012)
Activated natural siderite 05~10 As(V) 22 10 0 1~20 mgL at pH 7 in DI water(Zhao and Guo 2014)
Polyaluminum Granulate 1~3 As(III) 705 10 0~150 mgL at pH 51-56 in DI water(Mertens et al 2012)
Polyaluminum Granulate 1~3 As(V) 180 10 0~150 mgL at pH 51-56 in DI water (Mertens et al
26
2012)
Acidified laterite 1~12 As(III) 19 1 025~5 mgL at pH 7 in 100 mgL NaHCO3
(Glocheux et al 2013)
Acidified laterite 1~12 As(V) 13 1 025~5 mgL at pH 7 in 100 mgL NaHCO3
(Glocheux et al 2013)
Laterite 1~12 As(III) 07 1025~5 mgL at pH 7 in 100 mgL NaHCO3 (Glocheux et al
2013)
Laterite 1~12 As(V) 04 1025~5 mgL at pH 7 in 100 mgL NaHCO3 (Glocheux et al
2013)
Treated laterite 03-05 As(V) 216 05 02-20 mgL at pH 70 in DI water(Maiti et al 2012)
Treated laterite 03-05 As(III) 94 05 02-20 mgL at pH 70 in DI water(Maiti et al 2012)
Treated laterite03-05
As(V) 241 05 02-20 mgL at pH 70 in DI water(Maiti et al 2010a)
Treated laterite03-05
As(III) 81 05 02-20 mgL at pH 70 in DI water(Maiti et al 2010a)
Acid-activated laterite-103-07
As(III) 0633 50 02-10 mgL at pH 66-70 in DI water(Maiti et al 2010b)
Acid-activated laterite-203-07
As(III) 087650 02-10 mgL at pH 66-70 in DI water (Maiti et al
2010b)
Acid-activated laterite-303-07
As(III) 063450 02-10 mgL at pH 66-70 in DI water (Maiti et al
2010b)
Acid-activated laterite-103-07
As(V) 059850 02-10 mgL at pH 66-70 in DI water (Maiti et al
2010b)
27
Acid-activated laterite-203-07
As(V) 07550 02-10 mgL at pH 66-70 in DI water (Maiti et al
2010b)
Acid-activated laterite-303-07
As(V) 07550 02-10 mgL at pH 66-70 in DI water (Maiti et al
2010b)
Treated laterite-1 03-06 As(V) 019 20 0-20 mgL As at pH 72 in DI water(Maiti et al 2013b)
Treated laterite-1 03-06 As(III) 018 20 0-20 mgL As at pH 72 in DI water(Maiti et al 2013b)
Treated laterite-2 03-06 As(V) 004 20 0-20 mgL As at pH 72 in DI water(Maiti et al 2013b)
Treated laterite-2 03-06 As(III) 003 20 0-20 mgL As at pH 72 in DI water(Maiti et al 2013b)
Treated laterite-3 03-06 As(V) 007 20 0-20 mgL As at pH 72 in DI water(Maiti et al 2013b)
Treated laterite-3 03-06 As(III) 004 20 0-20 mgL As at pH 72 in DI water(Maiti et al 2013b)
28
376377
Charge distribution multi-site surface complexation (CD-MUSIC) modeling
The CD-MUSIC model with the 2-pK TPM adsorption option was used to
describe adsorption behaviors of As cations and anions on GTiO2 The CD-MUSIC
model incorporates the structural information of surfaces adsorbed species and the
double layers by distributing the charge of an adsorbate between the surface and
interfacial water (Hiemstra and Van Riemsdijk 2006) The CD-MUSIC model has
been successfully used in describing As adsorption in batch experiments (Pena et al
2006 Stachowicz et al 2008)
The adsorption constants of counter ions were set to -1 and the proton affinity
constant was set to the PZC of 58 for TiOH-13 (Luo et al 2010) The charge
distribution (CD) value shows the fraction (f) of the charge of the central As ion
attributed to the surface plane and the remaining part (1-f) was attributed to the other
ligands of the complex which were positioned toward the diffuse layer The CD value
for As surface complexes was obtained by fitting the experimental data The
calculation was performed using the chemical equilibrium program MINTEQ to
simulate the adsorption and the aqueous reactions
29
378379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
Fig S32 Adsorption of silicate (a) calcium and magnesium (b) as a function of GTiO2
dose in groundwater 1 The solid lines represent the CD-MUSIC modeling result
30
400
401
402
403
404
405
406
407
408409410
Table S75 Surface parameters and species used in the CD-MUSIC modeling in As(IIIV) removal under different GTiO2 dose in 01 M NaCl and groundwater 1 in Fig 2 and Fig S32
= exp(-FΨ1RT) P2 = exp(-FΨ2RT) F the Faraday constant (C mol-1) R the gas constant (J mol-1 K-1) T the absolute temperature (K)
Ψ0 Ψ1 Ψ2 the electrostatic potential (V) of 0- 1- and 2-plane respectively alogK for 01 M NaCl at 6 hours blogK for 01 M NaCl at 6 days clogK for groundwater 1 at 6 days
31
411412
413414415
32
416
Table S86 The charge distribution (f) of central As atom to TiO2 surface in simulating the effect of cations and anions on As adsorption in 01 M NaCl at pH 82 in Fig 4 BK Si HCO3 All
As(V) 022 017 012 016As(III) 040 020 058 056
Fig S43 Molar percentage () of As Ca Mg and Si on pristine and spent GTiO2
surfaces using EDX analysis The spent GTiO2 samples after field column experiments using groundwater 1 were identified with EBCT in min under x-axis The value of molar percentage of each element was averaged from randomly-chosen positions on the adsorbent surface
33
417
418
419420
421422
423
424
425
426
427
428
429
430
431
432
433434435436437438
439
440
441
As speciation analysis on spent GTiO2 using XANES
The spent GTiO2 samples were ground using a mortar and pestle and then the
ground powder was spread on Scotch tape The As k-edge XANES spectra were
collected at beamline 01C1 at the National Synchrotron Radiation Research Center
(NSRRC) Taiwan Spectra were acquired from -150 to 300 eV relative to the As K-
edge of 11867 eV at cryogenic temperature (77 K) using a cryostat to prevent the
oxidation of As(III) by X-rays The fluorescence signals were collected using a Lytle
detector Two to four scans were collected for each sample and averaged to improve
the signalnoise ratio The XANES analysis was performed with the Athena program
in the IFEFFIT computer package for linear combination fit (LCF) (Cui et al 2013
Ravel and Newville 2005)
34
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
PHREEQC modeling for As breakthrough curves in field column experiments
PHREEQC a geochemical model integrates macroscopic mass transfer
processes with a microscopic surface complexation model (Parkhurst and Appelo
2013) It can be applied in calculating solution complex speciation batch-reaction
and one-dimensional reactive-transport and inverse modeling In our study the one-
dimensional column was defined by four cells with the same length The cell length
was calculated to be one-fourth of the actual column length Time step (s) was
calculated according to equation Time step = Lcell(Q60A) where Lcell is the cell
length (cm) Q is flow velocity (mLmin) A is the effective column cross section area
(cm2) which is the column cross-sectional area multiplied by porosity (060) Total
shift number was calculated by dividing actual column operation time by the time
step The transport block was modeled by shifting the solute content from one cell to
the next one In each cell the aqueous solute was mixed and adsorbed on GTiO2
according to the equations In each cell the aqueous solute was mixed and assumed to
be in equilibration with GTiO2 The sequence of shifting mixing and equilibrium
adsorption was repeated for each cell until the total number of shifts was completed
The diffusion coefficient Dw in PHREEQC accounting for retardation was
calculated as Dw=x2
(36t) where x stands for the diffusion length (estimated as the
radius of the particle size) and t represents equilibrium time adopted from the batch
kinetic data (Mertens et al 2012)
For CD-MUSIC modeling in the PHREEQC take As(III) as an example to
explain the adsorption equation The As(III) adsorption is considered as a ligand
35
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
exchange reaction with the hydroxide group on GTiO2 (Surf_sOH-033) forming a
H3ArseniteO3 is the master species in groundwater at pH 82
(Surf_sO)2ArseniteOH-066 is the common adsorbed bidentate binuclear complex
evidenced by our previous reports(Pena et al 2006 Yan et al 2015) LogK is the
adsorption equilibrium constants Generally every adsorption equation under certain
experimental condition has a unique value of logK In the adsorption equation ldquo-2rdquo
represents the lost two hydrogens by Surf_sOH-033 after it adsorbs H3ArseniteO3 ldquo-
1rdquo represents the change in charge on Arsenite at 1 plane due to gaining one hydrogen
(+1) and one oxygen (-2) ldquo0rdquo represents no change in charge at the 2 plane ldquo066rdquo is
the fraction of the central ion (As) on GTiO2 surface that is associated with plane 0
ldquo3rdquo is the charge on the central ion As(III) Following this equation and the relevant
parameters As(III) adsorbed on GTiO2
The diffusion coefficient Dw in PHREEQC accounting for retardation was
calculated as Dw=x2(36t) where x stands for the diffusion length (estimated as the
radius of the particle size) and t represents equilibrium time adopted from the batch
kinetic data (Mertens et al 2012)
To well simulate the As breakthrough curve in columns four As(V) adsorption
reactions (Table 1) were employed Adsorption site density of 60 mmolg was
36
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
adopted from our previous study (Pena et al 2006) and the total adsorption sites were
calculated to be 1844 sitesnm2 The final optimized ratio of strong to weak sites was
51 The surface complexation constants were reasonably adjusted according to the
batch modeling results as the column reaction may not reach equilibrium in local
micro-interfacial areas due to much less contact time between As and GTiO2 than that
in batch experiments (Appelo and Postma 1999) In the modeling a stepwise
procedure was adopted to achieve a viable result An estimation of two thirds of the
surface site density being accessible for EBCT=011 min with large flow rate of 265
mLmin was optimized which could probably result from unavailable adsorption sites
due to fast transport through the column
The adsorbed As on GTiO2 in the column was calculated by mass balance
between the influent and effluent
where Asadsorbed is the adsorbed As on GTiO2 (mgg) n is the number of collected
samples Cin and Cout are influent and effluent As concentrations (mgL) respectively
Vi is volume (L) of groundwater passed through the column between sample i-1 and i
and m is the mass of GTiO2 (g)
Even though the oxidation of adsorbed As(III) occurred during filtration as
analyzed from XANES and mass balance analysis (Fig 7) no As(III) oxidation
reactions were considered in PHREEQC modeling which would not impact the
breakthrough of As(IIIV)
37
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
38
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
Fig S54 Effect of EBCT on Si Ca and Mg breakthrough curves using groundwater 1 The sample notation in panel c indicates field column experiments with EBCT in minutes
References
Appelo CAJ Postma D 1999 A consistent model for surface complexation on birnessite (MnO2) and its application to a column experiment Geochim Cosmochim Ac 63 (19-20) 3039-3048Badruzzaman M Westerhoff P Knappe DRU 2004 Intraparticle diffusion and adsorption of arsenate onto granular ferric hydroxide (GFH) Water Res 38 (18) 4002-4012Banerjee K Amy GL Prevost M Nour S Jekel M Gallagher PM Blumenschein CD 2008 Kinetic and thermodynamic aspects of adsorption of arsenic onto granular ferric hydroxide (GFH) Water Res 42 (13) 3371-3378Bang S Patel M Lippincott L Meng XG 2005 Removal of arsenic from groundwater by granular titanium dioxide adsorbent Chemosphere 60 (3) 389-397Bang S Pena ME Patel M Lippincott L Meng X Kim KW 2011 Removal of arsenate from water by adsorbents a comparative case study Environ Geochem Hlth 33 133-141Cui JL Shi JB Jiang GB Jing CY 2013 Arsenic levels and speciation from ingestion exposures to biomarkers in Shanxi China Implications for human health Environ Sci Technol 47 (10) 5419-5424Daus B Wennrich R Weiss H 2004 Sorption materials for arsenic removal from water A comparative study Water Res 38 (12) 2948-2954Dou XM Mohan D Pittman CU 2013 Arsenate adsorption on three types of granular schwertmannite Water Res 47 (9) 2938-2948Dou XM Zhang Y Yang M Pei YS Huang X Takayama T Kato S 2006 Occurrence of arsenic in groundwater in the suburbs of Beijing and its removal using an iron-cerium bimetal oxide adsorbent Water Qual Res J Can 41 (2) 140-146Gibbons MK Gagnon GA 2010 Adsorption of arsenic from a Nova Scotia groundwater onto water treatment residual solids Water Res 44 (19) 5740-5749Glocheux Y Mendez Pasarin M Albadarin AB Allen SJ Walker GM 2013 Removal of arsenic from groundwater by adsorption onto an acidified laterite by-product Chem Eng J 228 565-574Guan XH Wang JM Chusuei CC 2008 Removal of arsenic from water using granular ferric hydroxide Macroscopic and microscopic studies J Hazard Mater 156 (1-3) 178-185Gupta K Maity A Ghosh UC 2010 Manganese associated nanoparticles agglomerate of iron(III) oxide Synthesis characterization and arsenic(III) sorption behavior with mechanism J Hazard Mater 184 (1-3) 832-842Hao JM Han MJ Wang C Meng XG 2009 Enhanced removal of arsenite from water by a mesoporous hybrid material - Thiol-functionalized silica coated activated alumina Micropor Mesopor
Mat 124 (1-3) 1-7Hiemstra T Van Riemsdijk WH 2006 On the relationship between charge distribution surface hydration and the structure of the interface of metal hydroxides J Colloid Interf Sci 301 (1) 1-18Hristovski K Baumgardner A Westerhoff P 2007 Selecting metal oxide nanomaterials for arsenic removal in fixed bed columns From nanopowders to aggregated nanoparticle media J Hazard Mater 147 (1-2) 265-274Jang M Chen WF Cannon FS 2008 Preloading hydrous ferric oxide into granular activated carbon for arsenic removal Environ Sci Technol 42 (9) 3369-3374Jing CY Cui JL Huang YY Li AG 2012 Fabrication characterization and application of a composite adsorbent for simultaneous removal of arsenic and fluoride ACS Appl Mater Interfaces 4 (2) 714-720Kanematsu M Young TM Fukushi K Green PG Darby JL 2010 Extended triple layer modeling of arsenate and phosphate adsorption on a goethite-based granular porous adsorbent Environ Sci Technol 44 (9) 3388-3394Kong S Wang Y Zhan H Yuan S Liu M Zhou C 2013 Arsenite and Arsenate Removal from Contaminated Groundwater by Nanoscale Iron-Manganese Binary Oxides Column Studies Environmental Engineering Science 30 (11) 689-696Li Y Liu JR Jia SY Guo JW Zhuo J Na P 2012 TiO2 pillared montmorillonite as a photoactive adsorbent of arsenic under UV irradiation Chem Eng J 191 66-74Lin TF Wu JK 2001 Adsorption of arsenite and arsenate within activated alumina grains Equilibrium and kinetics Water Res 35 (8) 2049-2057Luo T Cui JL Hu S Huang YY Jing CY 2010 Arsenic removal and recovery from copper smelting wastewater using TiO2 Environ Sci Technol 44 (23) 9094-9098Maiti A Basu JK De S 2010a Development of a Treated Laterite for Arsenic Adsorption Effects of Treatment Parameters Industrial amp Engineering Chemistry Research 49 (10) 4873-4886Maiti A Basu JK De S 2010b Removal of Arsenic from Synthetic and Natural Groundwater Using Acid-Activated Laterite Environmental Progress amp Sustainable Energy 29 (4) 457-470Maiti A Basu JK De S 2012 Experimental and kinetic modeling of As(V) and As(III) adsorption on treated laterite using synthetic and contaminated groundwater Effects of phosphate silicate and carbonate ions Chem Eng J 191 1-12Maiti A Thakur BK Basu JK De S 2013a Comparison of treated laterite as arsenic adsorbent from different locations and performance of best filter under field conditions J Hazard Mater 262 1176-1186Maiti A Thakur BK Basu JK De S 2013b Comparison of treated laterite as arsenic adsorbent from different locations and performance of best filter under field conditions J Hazard Mater 262 (0) 1176-1186Maji SK Pal A Pal T 2008 Arsenic removal from real-life groundwater by adsorption on laterite soil J Hazard Mater 151 (2-3) 811-820Maji SK Kao YH Wang CJ Lu GS Wu JJ Liu CW 2012 Fixed bed adsorption of As(III) on iron-oxide-coated natural rock (IOCNR) and application to real arsenic-bearing groundwater Chem Eng J 203 285-293Mertens J Rose J Kagi R Chaurand P Plotze M Wehrli B Furrer G 2012 Adsorption of arsenic on polyaluminum granulate Environ Sci Technol 46 (13) 7310-7317Nguyen TV Vigneswaran S Ngo HH Pokhre D Viraraghavan T 2006 Iron-coated sponge as
effective media to remove arsenic from drinking water Water Qual Res J Can 41 (2) 164-170Parkhurst DL Appelo CAJ 2013 Description of input and examples for PHREEQC version 3-A computer program for speciation batch-reaction one-dimensional transport and inverse geochemical calculations US Geological SurveyPena M Meng XG Korfiatis GP Jing CY 2006 Adsorption mechanism of arsenic on nanocrystalline titanium dioxide Environ Sci Technol 40 (4) 1257-1262Ravel B Newville M 2005 ATHENA ARTEMIS HEPHAESTUS Data analysis for X-ray absorption spectroscopy using IFEFFIT J Synchrotron Radiat 12 537-541Saha B Bains R Greenwood F 2005 Physicochemical characterization of granular ferric hydroxide (GFH) for arsenic(V) sorption from water Separation Science and Technology 40 (14) 2909-2932Shan H Ma T Wang Y Zhao J Han H Deng Y He X Dong Y 2013 A cost-effective system for in-situ geological arsenic adsorption from groundwater J Contam Hydrol 154 1-9Stachowicz M Hiemstra T van Riemsdijk WH 2008 Multi-competitive interaction of As(III) and As(V) oxyanions with Ca2+ Mg2+ PO4
3- and CO32- ions on goethite J Colloid Interf Sci 320 (2) 400-
414Streat M Hellgardt K Newton NLR 2008 Hydrous ferric oxide as an adsorbent in water treatment - Part 3 Batch and mini-column adsorption of arsenic phosphorus fluorine and cadmium ions Process Safety and Environmental Protection 86 (B1) 21-30Thirunavukkarasu OS Viraraghavan T Subramanian KS 2003 Arsenic removal from drinking water using iron oxide-coated sand Water Air Soil Poll 142 (1-4) 95-111USEPA 2008 Assessing arsenic removal by metal (hydr)oxide adsorptive media using rapid small scale column tests Govenrnment Printing Office Washington DCWang J Xu W Chen L Huang X Liu J 2014 Preparation and evaluation of magnetic nanoparticles impregnated chitosan beads for arsenic removal from water Chem Eng J 251 25-34Westerhoff P Highfield D Badruzzaman M Yoon Y 2005 Rapid small-scale column tests for arsenate removal in iron oxide packed bed columns J Environ Eng-Asce 131 (2) 262-271Westerhoff P De Haan M Martindale A Badruzzaman M 2006 Arsenic adsorptive media technology selection strategies Water Qual Res J Can 41 (2) 171-184Yan L Huang Y Cui J Jing C 2015 Simultaneous As(III) and Cd removal from copper smelting wastewater using granular TiO2 columns Water Res 68 (0) 572-579Zhao K Guo HM 2014 Behavior and mechanism of arsenate adsorption on activated natural siderite Evidences from FTIR and XANES analysis Environ Sci Pollut Res 21 (3) 1944-1953Zhao K Guo H Zhou X 2014 Adsorption and heterogeneous oxidation of arsenite on modified granular natural siderite Characterization and behaviors Appl Geochem 48 184-192
Arsenite adsorption equation on GTiO2 surface H3ArseniteO3 is the primary species of As(III) at the groundwater pH 82 (Surf_sO)2ArseniteOH-066 is the adsorptive bidentate binuclear structure of As(III) on GTiO2
log_k 1635 The adsorptive reaction constant for As(III) on GTiO2 in
the current condition which could be changed with different experimental conditions
-cd_music -2 -1 0 066 3 CD-MUSIC model is integrated in the PHREEQC
modeling The numbers represent -2 the change in charge at the plane of Surf_sOH due to loss of two hydrogens -1 the change in charge at 1 plane due to gain of one hydrogen and one oxygen on Arsenite 0 the change in charge at the 2 plane usually caused by the outer sphere adsorption 066 the fraction of the central ion (As) charge that is associated with plane 0 which reflecting the charge distribution 3 the charge on the central ion (As)
Table S54 Parameters of Weber-Morris intraparticle model for As(IIIV) adsorption kinetics on GTiO2 using synthetic water Initial As concentration = 800 μgL adsorbent dose = 02 gL pH = 82 in synthetic groundwater
External film diffusion
Intraparticle diffusion
aRex2 bkp1
cb1aRin
2 bkp2cb 2
As(V) 0984 0497 0022 0976 01331878
As(III) 0970 0583
-0088 0981 0218
1105
aRex is WM external proportion fitting parameter while Rin is WM intraparticle proportion fitting parameterbk The unit of kp is mggh05 cb The unit of b is mgg
Table S6 Comparison of the adsorption capacities of As(III) and As(V) on GTiO2 and the representative granular adsorbents in similar experimental condition from the literature
AdsorbentParticle size (mm) As
qm
(mgg)Dose (gL) Experimental conditions Literature
GTiO2 018~025 As(III) 980 1 0~500 mgL at pH 82 01 M NaCl This studyGTiO2 018~025 As(V) 358 1 0~500 mgL at pH 82 01 M NaCl This study
Granular TiO2 015~06 As(III) 392 10~60 mgL As at pH 70 in simulated groundwater (100 mgL Ca 20 mgL Mg 50 mgL Na 200 mgL Cl-
)(Bang et al 2005)
Granular TiO2 015~06 As(V) 400 10~60 mgL As at pH 70 in simulated groundwater (100 mgL Ca 20 mgL Mg 50 mgL Na 200 mgL Cl-
)(Bang et al 2005)
E33 (FeOOH)0044~0075 As(V) 202 1 0~15 mgL at pH 70 in 001 M NaCl
(Kanematsu et al 2010)
E33 (FeOOH) 05~2 As(V) 180 1 0~50 mgL at pH 70 in 004 M NaClO4 (Jing et al 2012)
GFH 02~06 As(V) 650 10 0~2000 mgL at pH 8 in 01 M NaNO3
(Guan et al 2008)
GFH0009~0125 As(V) 23 025 0~07 μgL at pH 65 in DI water
(Banerjee et al 2008)
GFH0009~0125 As(V) 200 - 0~01 μgL at pH 70 in DI water
(Badruzzaman et al 2004)
GFH 050~065 As(V) 155 - 0~06 μgL at pH 70 in DI water (Saha et al 2005)
GHFO-NN 015~030 As(V) 330 0001 0~225 mgL at pH 8 in DI water(Streat et al 2008)
GHFO-VL 015~030 As(V) 360 0001 0~225 mgL at pH 8 in DI water(Streat et al 2008)
25
374375
Spherical schwertmannite 1~15 As(V) 36 05 0~5 mgL at pH 70 in DI water (Dou et al 2013)Cylindrical schwertmannite 1~25 As(V) 223 05
0~5 mgL at pH 70 in DI water(Dou et al 2013)
Irregular schwertmannite 10~16 As(V) 317 05 0~5 mgL at pH 70 in DI water (Dou et al 2013)Fe impregnated chitosan beads (MICB) 25 As(III) 117 1 0~05 mgL at pH 60 in DI water
(Wang et al 2014)
MICB 25 As(V) 191 1 0~1 mgL at pH 60 in DI water(Wang et al 2014)
MICB 25 As(III) 353 1 0~15 mgL at pH 60 in DI water(Wang et al 2014)
MICB 25 As(V) 357 1 0~16 mgL at pH 60 in DI water(Wang et al 2014)
Iron hydroxide granules (GIH) 3~4 As(V) 23 4
5~100 mgL at pH 70 in 10 mgL SO42-
14 mgL NH4Cl buffer solution (Daus et al 2004)
Activated Al2O3
0074~0149 As(V) 159 - 285~115 mgL at pH 52 in DI water
(Lin and Wu 2001)
Activated Al2O3
0074~0149 As(III) 35 - 079~490 mgL at pH 70 in DI water
(Lin and Wu 2001)
Activated Al2O3 ~20 As(V) 73 at pH 70 in 004 M NaClO4 (Jing et al 2012)
Activated natural siderite 05~10 As(V) 22 10 0 1~20 mgL at pH 7 in DI water(Zhao and Guo 2014)
Polyaluminum Granulate 1~3 As(III) 705 10 0~150 mgL at pH 51-56 in DI water(Mertens et al 2012)
Polyaluminum Granulate 1~3 As(V) 180 10 0~150 mgL at pH 51-56 in DI water (Mertens et al
26
2012)
Acidified laterite 1~12 As(III) 19 1 025~5 mgL at pH 7 in 100 mgL NaHCO3
(Glocheux et al 2013)
Acidified laterite 1~12 As(V) 13 1 025~5 mgL at pH 7 in 100 mgL NaHCO3
(Glocheux et al 2013)
Laterite 1~12 As(III) 07 1025~5 mgL at pH 7 in 100 mgL NaHCO3 (Glocheux et al
2013)
Laterite 1~12 As(V) 04 1025~5 mgL at pH 7 in 100 mgL NaHCO3 (Glocheux et al
2013)
Treated laterite 03-05 As(V) 216 05 02-20 mgL at pH 70 in DI water(Maiti et al 2012)
Treated laterite 03-05 As(III) 94 05 02-20 mgL at pH 70 in DI water(Maiti et al 2012)
Treated laterite03-05
As(V) 241 05 02-20 mgL at pH 70 in DI water(Maiti et al 2010a)
Treated laterite03-05
As(III) 81 05 02-20 mgL at pH 70 in DI water(Maiti et al 2010a)
Acid-activated laterite-103-07
As(III) 0633 50 02-10 mgL at pH 66-70 in DI water(Maiti et al 2010b)
Acid-activated laterite-203-07
As(III) 087650 02-10 mgL at pH 66-70 in DI water (Maiti et al
2010b)
Acid-activated laterite-303-07
As(III) 063450 02-10 mgL at pH 66-70 in DI water (Maiti et al
2010b)
Acid-activated laterite-103-07
As(V) 059850 02-10 mgL at pH 66-70 in DI water (Maiti et al
2010b)
27
Acid-activated laterite-203-07
As(V) 07550 02-10 mgL at pH 66-70 in DI water (Maiti et al
2010b)
Acid-activated laterite-303-07
As(V) 07550 02-10 mgL at pH 66-70 in DI water (Maiti et al
2010b)
Treated laterite-1 03-06 As(V) 019 20 0-20 mgL As at pH 72 in DI water(Maiti et al 2013b)
Treated laterite-1 03-06 As(III) 018 20 0-20 mgL As at pH 72 in DI water(Maiti et al 2013b)
Treated laterite-2 03-06 As(V) 004 20 0-20 mgL As at pH 72 in DI water(Maiti et al 2013b)
Treated laterite-2 03-06 As(III) 003 20 0-20 mgL As at pH 72 in DI water(Maiti et al 2013b)
Treated laterite-3 03-06 As(V) 007 20 0-20 mgL As at pH 72 in DI water(Maiti et al 2013b)
Treated laterite-3 03-06 As(III) 004 20 0-20 mgL As at pH 72 in DI water(Maiti et al 2013b)
28
376377
Charge distribution multi-site surface complexation (CD-MUSIC) modeling
The CD-MUSIC model with the 2-pK TPM adsorption option was used to
describe adsorption behaviors of As cations and anions on GTiO2 The CD-MUSIC
model incorporates the structural information of surfaces adsorbed species and the
double layers by distributing the charge of an adsorbate between the surface and
interfacial water (Hiemstra and Van Riemsdijk 2006) The CD-MUSIC model has
been successfully used in describing As adsorption in batch experiments (Pena et al
2006 Stachowicz et al 2008)
The adsorption constants of counter ions were set to -1 and the proton affinity
constant was set to the PZC of 58 for TiOH-13 (Luo et al 2010) The charge
distribution (CD) value shows the fraction (f) of the charge of the central As ion
attributed to the surface plane and the remaining part (1-f) was attributed to the other
ligands of the complex which were positioned toward the diffuse layer The CD value
for As surface complexes was obtained by fitting the experimental data The
calculation was performed using the chemical equilibrium program MINTEQ to
simulate the adsorption and the aqueous reactions
29
378379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
Fig S32 Adsorption of silicate (a) calcium and magnesium (b) as a function of GTiO2
dose in groundwater 1 The solid lines represent the CD-MUSIC modeling result
30
400
401
402
403
404
405
406
407
408409410
Table S75 Surface parameters and species used in the CD-MUSIC modeling in As(IIIV) removal under different GTiO2 dose in 01 M NaCl and groundwater 1 in Fig 2 and Fig S32
= exp(-FΨ1RT) P2 = exp(-FΨ2RT) F the Faraday constant (C mol-1) R the gas constant (J mol-1 K-1) T the absolute temperature (K)
Ψ0 Ψ1 Ψ2 the electrostatic potential (V) of 0- 1- and 2-plane respectively alogK for 01 M NaCl at 6 hours blogK for 01 M NaCl at 6 days clogK for groundwater 1 at 6 days
31
411412
413414415
32
416
Table S86 The charge distribution (f) of central As atom to TiO2 surface in simulating the effect of cations and anions on As adsorption in 01 M NaCl at pH 82 in Fig 4 BK Si HCO3 All
As(V) 022 017 012 016As(III) 040 020 058 056
Fig S43 Molar percentage () of As Ca Mg and Si on pristine and spent GTiO2
surfaces using EDX analysis The spent GTiO2 samples after field column experiments using groundwater 1 were identified with EBCT in min under x-axis The value of molar percentage of each element was averaged from randomly-chosen positions on the adsorbent surface
33
417
418
419420
421422
423
424
425
426
427
428
429
430
431
432
433434435436437438
439
440
441
As speciation analysis on spent GTiO2 using XANES
The spent GTiO2 samples were ground using a mortar and pestle and then the
ground powder was spread on Scotch tape The As k-edge XANES spectra were
collected at beamline 01C1 at the National Synchrotron Radiation Research Center
(NSRRC) Taiwan Spectra were acquired from -150 to 300 eV relative to the As K-
edge of 11867 eV at cryogenic temperature (77 K) using a cryostat to prevent the
oxidation of As(III) by X-rays The fluorescence signals were collected using a Lytle
detector Two to four scans were collected for each sample and averaged to improve
the signalnoise ratio The XANES analysis was performed with the Athena program
in the IFEFFIT computer package for linear combination fit (LCF) (Cui et al 2013
Ravel and Newville 2005)
34
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
PHREEQC modeling for As breakthrough curves in field column experiments
PHREEQC a geochemical model integrates macroscopic mass transfer
processes with a microscopic surface complexation model (Parkhurst and Appelo
2013) It can be applied in calculating solution complex speciation batch-reaction
and one-dimensional reactive-transport and inverse modeling In our study the one-
dimensional column was defined by four cells with the same length The cell length
was calculated to be one-fourth of the actual column length Time step (s) was
calculated according to equation Time step = Lcell(Q60A) where Lcell is the cell
length (cm) Q is flow velocity (mLmin) A is the effective column cross section area
(cm2) which is the column cross-sectional area multiplied by porosity (060) Total
shift number was calculated by dividing actual column operation time by the time
step The transport block was modeled by shifting the solute content from one cell to
the next one In each cell the aqueous solute was mixed and adsorbed on GTiO2
according to the equations In each cell the aqueous solute was mixed and assumed to
be in equilibration with GTiO2 The sequence of shifting mixing and equilibrium
adsorption was repeated for each cell until the total number of shifts was completed
The diffusion coefficient Dw in PHREEQC accounting for retardation was
calculated as Dw=x2
(36t) where x stands for the diffusion length (estimated as the
radius of the particle size) and t represents equilibrium time adopted from the batch
kinetic data (Mertens et al 2012)
For CD-MUSIC modeling in the PHREEQC take As(III) as an example to
explain the adsorption equation The As(III) adsorption is considered as a ligand
35
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
exchange reaction with the hydroxide group on GTiO2 (Surf_sOH-033) forming a
H3ArseniteO3 is the master species in groundwater at pH 82
(Surf_sO)2ArseniteOH-066 is the common adsorbed bidentate binuclear complex
evidenced by our previous reports(Pena et al 2006 Yan et al 2015) LogK is the
adsorption equilibrium constants Generally every adsorption equation under certain
experimental condition has a unique value of logK In the adsorption equation ldquo-2rdquo
represents the lost two hydrogens by Surf_sOH-033 after it adsorbs H3ArseniteO3 ldquo-
1rdquo represents the change in charge on Arsenite at 1 plane due to gaining one hydrogen
(+1) and one oxygen (-2) ldquo0rdquo represents no change in charge at the 2 plane ldquo066rdquo is
the fraction of the central ion (As) on GTiO2 surface that is associated with plane 0
ldquo3rdquo is the charge on the central ion As(III) Following this equation and the relevant
parameters As(III) adsorbed on GTiO2
The diffusion coefficient Dw in PHREEQC accounting for retardation was
calculated as Dw=x2(36t) where x stands for the diffusion length (estimated as the
radius of the particle size) and t represents equilibrium time adopted from the batch
kinetic data (Mertens et al 2012)
To well simulate the As breakthrough curve in columns four As(V) adsorption
reactions (Table 1) were employed Adsorption site density of 60 mmolg was
36
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
adopted from our previous study (Pena et al 2006) and the total adsorption sites were
calculated to be 1844 sitesnm2 The final optimized ratio of strong to weak sites was
51 The surface complexation constants were reasonably adjusted according to the
batch modeling results as the column reaction may not reach equilibrium in local
micro-interfacial areas due to much less contact time between As and GTiO2 than that
in batch experiments (Appelo and Postma 1999) In the modeling a stepwise
procedure was adopted to achieve a viable result An estimation of two thirds of the
surface site density being accessible for EBCT=011 min with large flow rate of 265
mLmin was optimized which could probably result from unavailable adsorption sites
due to fast transport through the column
The adsorbed As on GTiO2 in the column was calculated by mass balance
between the influent and effluent
where Asadsorbed is the adsorbed As on GTiO2 (mgg) n is the number of collected
samples Cin and Cout are influent and effluent As concentrations (mgL) respectively
Vi is volume (L) of groundwater passed through the column between sample i-1 and i
and m is the mass of GTiO2 (g)
Even though the oxidation of adsorbed As(III) occurred during filtration as
analyzed from XANES and mass balance analysis (Fig 7) no As(III) oxidation
reactions were considered in PHREEQC modeling which would not impact the
breakthrough of As(IIIV)
37
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
38
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
Fig S54 Effect of EBCT on Si Ca and Mg breakthrough curves using groundwater 1 The sample notation in panel c indicates field column experiments with EBCT in minutes
References
Appelo CAJ Postma D 1999 A consistent model for surface complexation on birnessite (MnO2) and its application to a column experiment Geochim Cosmochim Ac 63 (19-20) 3039-3048Badruzzaman M Westerhoff P Knappe DRU 2004 Intraparticle diffusion and adsorption of arsenate onto granular ferric hydroxide (GFH) Water Res 38 (18) 4002-4012Banerjee K Amy GL Prevost M Nour S Jekel M Gallagher PM Blumenschein CD 2008 Kinetic and thermodynamic aspects of adsorption of arsenic onto granular ferric hydroxide (GFH) Water Res 42 (13) 3371-3378Bang S Patel M Lippincott L Meng XG 2005 Removal of arsenic from groundwater by granular titanium dioxide adsorbent Chemosphere 60 (3) 389-397Bang S Pena ME Patel M Lippincott L Meng X Kim KW 2011 Removal of arsenate from water by adsorbents a comparative case study Environ Geochem Hlth 33 133-141Cui JL Shi JB Jiang GB Jing CY 2013 Arsenic levels and speciation from ingestion exposures to biomarkers in Shanxi China Implications for human health Environ Sci Technol 47 (10) 5419-5424Daus B Wennrich R Weiss H 2004 Sorption materials for arsenic removal from water A comparative study Water Res 38 (12) 2948-2954Dou XM Mohan D Pittman CU 2013 Arsenate adsorption on three types of granular schwertmannite Water Res 47 (9) 2938-2948Dou XM Zhang Y Yang M Pei YS Huang X Takayama T Kato S 2006 Occurrence of arsenic in groundwater in the suburbs of Beijing and its removal using an iron-cerium bimetal oxide adsorbent Water Qual Res J Can 41 (2) 140-146Gibbons MK Gagnon GA 2010 Adsorption of arsenic from a Nova Scotia groundwater onto water treatment residual solids Water Res 44 (19) 5740-5749Glocheux Y Mendez Pasarin M Albadarin AB Allen SJ Walker GM 2013 Removal of arsenic from groundwater by adsorption onto an acidified laterite by-product Chem Eng J 228 565-574Guan XH Wang JM Chusuei CC 2008 Removal of arsenic from water using granular ferric hydroxide Macroscopic and microscopic studies J Hazard Mater 156 (1-3) 178-185Gupta K Maity A Ghosh UC 2010 Manganese associated nanoparticles agglomerate of iron(III) oxide Synthesis characterization and arsenic(III) sorption behavior with mechanism J Hazard Mater 184 (1-3) 832-842Hao JM Han MJ Wang C Meng XG 2009 Enhanced removal of arsenite from water by a mesoporous hybrid material - Thiol-functionalized silica coated activated alumina Micropor Mesopor
Mat 124 (1-3) 1-7Hiemstra T Van Riemsdijk WH 2006 On the relationship between charge distribution surface hydration and the structure of the interface of metal hydroxides J Colloid Interf Sci 301 (1) 1-18Hristovski K Baumgardner A Westerhoff P 2007 Selecting metal oxide nanomaterials for arsenic removal in fixed bed columns From nanopowders to aggregated nanoparticle media J Hazard Mater 147 (1-2) 265-274Jang M Chen WF Cannon FS 2008 Preloading hydrous ferric oxide into granular activated carbon for arsenic removal Environ Sci Technol 42 (9) 3369-3374Jing CY Cui JL Huang YY Li AG 2012 Fabrication characterization and application of a composite adsorbent for simultaneous removal of arsenic and fluoride ACS Appl Mater Interfaces 4 (2) 714-720Kanematsu M Young TM Fukushi K Green PG Darby JL 2010 Extended triple layer modeling of arsenate and phosphate adsorption on a goethite-based granular porous adsorbent Environ Sci Technol 44 (9) 3388-3394Kong S Wang Y Zhan H Yuan S Liu M Zhou C 2013 Arsenite and Arsenate Removal from Contaminated Groundwater by Nanoscale Iron-Manganese Binary Oxides Column Studies Environmental Engineering Science 30 (11) 689-696Li Y Liu JR Jia SY Guo JW Zhuo J Na P 2012 TiO2 pillared montmorillonite as a photoactive adsorbent of arsenic under UV irradiation Chem Eng J 191 66-74Lin TF Wu JK 2001 Adsorption of arsenite and arsenate within activated alumina grains Equilibrium and kinetics Water Res 35 (8) 2049-2057Luo T Cui JL Hu S Huang YY Jing CY 2010 Arsenic removal and recovery from copper smelting wastewater using TiO2 Environ Sci Technol 44 (23) 9094-9098Maiti A Basu JK De S 2010a Development of a Treated Laterite for Arsenic Adsorption Effects of Treatment Parameters Industrial amp Engineering Chemistry Research 49 (10) 4873-4886Maiti A Basu JK De S 2010b Removal of Arsenic from Synthetic and Natural Groundwater Using Acid-Activated Laterite Environmental Progress amp Sustainable Energy 29 (4) 457-470Maiti A Basu JK De S 2012 Experimental and kinetic modeling of As(V) and As(III) adsorption on treated laterite using synthetic and contaminated groundwater Effects of phosphate silicate and carbonate ions Chem Eng J 191 1-12Maiti A Thakur BK Basu JK De S 2013a Comparison of treated laterite as arsenic adsorbent from different locations and performance of best filter under field conditions J Hazard Mater 262 1176-1186Maiti A Thakur BK Basu JK De S 2013b Comparison of treated laterite as arsenic adsorbent from different locations and performance of best filter under field conditions J Hazard Mater 262 (0) 1176-1186Maji SK Pal A Pal T 2008 Arsenic removal from real-life groundwater by adsorption on laterite soil J Hazard Mater 151 (2-3) 811-820Maji SK Kao YH Wang CJ Lu GS Wu JJ Liu CW 2012 Fixed bed adsorption of As(III) on iron-oxide-coated natural rock (IOCNR) and application to real arsenic-bearing groundwater Chem Eng J 203 285-293Mertens J Rose J Kagi R Chaurand P Plotze M Wehrli B Furrer G 2012 Adsorption of arsenic on polyaluminum granulate Environ Sci Technol 46 (13) 7310-7317Nguyen TV Vigneswaran S Ngo HH Pokhre D Viraraghavan T 2006 Iron-coated sponge as
effective media to remove arsenic from drinking water Water Qual Res J Can 41 (2) 164-170Parkhurst DL Appelo CAJ 2013 Description of input and examples for PHREEQC version 3-A computer program for speciation batch-reaction one-dimensional transport and inverse geochemical calculations US Geological SurveyPena M Meng XG Korfiatis GP Jing CY 2006 Adsorption mechanism of arsenic on nanocrystalline titanium dioxide Environ Sci Technol 40 (4) 1257-1262Ravel B Newville M 2005 ATHENA ARTEMIS HEPHAESTUS Data analysis for X-ray absorption spectroscopy using IFEFFIT J Synchrotron Radiat 12 537-541Saha B Bains R Greenwood F 2005 Physicochemical characterization of granular ferric hydroxide (GFH) for arsenic(V) sorption from water Separation Science and Technology 40 (14) 2909-2932Shan H Ma T Wang Y Zhao J Han H Deng Y He X Dong Y 2013 A cost-effective system for in-situ geological arsenic adsorption from groundwater J Contam Hydrol 154 1-9Stachowicz M Hiemstra T van Riemsdijk WH 2008 Multi-competitive interaction of As(III) and As(V) oxyanions with Ca2+ Mg2+ PO4
3- and CO32- ions on goethite J Colloid Interf Sci 320 (2) 400-
414Streat M Hellgardt K Newton NLR 2008 Hydrous ferric oxide as an adsorbent in water treatment - Part 3 Batch and mini-column adsorption of arsenic phosphorus fluorine and cadmium ions Process Safety and Environmental Protection 86 (B1) 21-30Thirunavukkarasu OS Viraraghavan T Subramanian KS 2003 Arsenic removal from drinking water using iron oxide-coated sand Water Air Soil Poll 142 (1-4) 95-111USEPA 2008 Assessing arsenic removal by metal (hydr)oxide adsorptive media using rapid small scale column tests Govenrnment Printing Office Washington DCWang J Xu W Chen L Huang X Liu J 2014 Preparation and evaluation of magnetic nanoparticles impregnated chitosan beads for arsenic removal from water Chem Eng J 251 25-34Westerhoff P Highfield D Badruzzaman M Yoon Y 2005 Rapid small-scale column tests for arsenate removal in iron oxide packed bed columns J Environ Eng-Asce 131 (2) 262-271Westerhoff P De Haan M Martindale A Badruzzaman M 2006 Arsenic adsorptive media technology selection strategies Water Qual Res J Can 41 (2) 171-184Yan L Huang Y Cui J Jing C 2015 Simultaneous As(III) and Cd removal from copper smelting wastewater using granular TiO2 columns Water Res 68 (0) 572-579Zhao K Guo HM 2014 Behavior and mechanism of arsenate adsorption on activated natural siderite Evidences from FTIR and XANES analysis Environ Sci Pollut Res 21 (3) 1944-1953Zhao K Guo H Zhou X 2014 Adsorption and heterogeneous oxidation of arsenite on modified granular natural siderite Characterization and behaviors Appl Geochem 48 184-192
Arsenite adsorption equation on GTiO2 surface H3ArseniteO3 is the primary species of As(III) at the groundwater pH 82 (Surf_sO)2ArseniteOH-066 is the adsorptive bidentate binuclear structure of As(III) on GTiO2
log_k 1635 The adsorptive reaction constant for As(III) on GTiO2 in
the current condition which could be changed with different experimental conditions
-cd_music -2 -1 0 066 3 CD-MUSIC model is integrated in the PHREEQC
modeling The numbers represent -2 the change in charge at the plane of Surf_sOH due to loss of two hydrogens -1 the change in charge at 1 plane due to gain of one hydrogen and one oxygen on Arsenite 0 the change in charge at the 2 plane usually caused by the outer sphere adsorption 066 the fraction of the central ion (As) charge that is associated with plane 0 which reflecting the charge distribution 3 the charge on the central ion (As)
Table S54 Parameters of Weber-Morris intraparticle model for As(IIIV) adsorption kinetics on GTiO2 using synthetic water Initial As concentration = 800 μgL adsorbent dose = 02 gL pH = 82 in synthetic groundwater
External film diffusion
Intraparticle diffusion
aRex2 bkp1
cb1aRin
2 bkp2cb 2
As(V) 0984 0497 0022 0976 01331878
As(III) 0970 0583
-0088 0981 0218
1105
aRex is WM external proportion fitting parameter while Rin is WM intraparticle proportion fitting parameterbk The unit of kp is mggh05 cb The unit of b is mgg
Table S6 Comparison of the adsorption capacities of As(III) and As(V) on GTiO2 and the representative granular adsorbents in similar experimental condition from the literature
AdsorbentParticle size (mm) As
qm
(mgg)Dose (gL) Experimental conditions Literature
GTiO2 018~025 As(III) 980 1 0~500 mgL at pH 82 01 M NaCl This studyGTiO2 018~025 As(V) 358 1 0~500 mgL at pH 82 01 M NaCl This study
Granular TiO2 015~06 As(III) 392 10~60 mgL As at pH 70 in simulated groundwater (100 mgL Ca 20 mgL Mg 50 mgL Na 200 mgL Cl-
)(Bang et al 2005)
Granular TiO2 015~06 As(V) 400 10~60 mgL As at pH 70 in simulated groundwater (100 mgL Ca 20 mgL Mg 50 mgL Na 200 mgL Cl-
)(Bang et al 2005)
E33 (FeOOH)0044~0075 As(V) 202 1 0~15 mgL at pH 70 in 001 M NaCl
(Kanematsu et al 2010)
E33 (FeOOH) 05~2 As(V) 180 1 0~50 mgL at pH 70 in 004 M NaClO4 (Jing et al 2012)
GFH 02~06 As(V) 650 10 0~2000 mgL at pH 8 in 01 M NaNO3
(Guan et al 2008)
GFH0009~0125 As(V) 23 025 0~07 μgL at pH 65 in DI water
(Banerjee et al 2008)
GFH0009~0125 As(V) 200 - 0~01 μgL at pH 70 in DI water
(Badruzzaman et al 2004)
GFH 050~065 As(V) 155 - 0~06 μgL at pH 70 in DI water (Saha et al 2005)
GHFO-NN 015~030 As(V) 330 0001 0~225 mgL at pH 8 in DI water(Streat et al 2008)
GHFO-VL 015~030 As(V) 360 0001 0~225 mgL at pH 8 in DI water(Streat et al 2008)
25
374375
Spherical schwertmannite 1~15 As(V) 36 05 0~5 mgL at pH 70 in DI water (Dou et al 2013)Cylindrical schwertmannite 1~25 As(V) 223 05
0~5 mgL at pH 70 in DI water(Dou et al 2013)
Irregular schwertmannite 10~16 As(V) 317 05 0~5 mgL at pH 70 in DI water (Dou et al 2013)Fe impregnated chitosan beads (MICB) 25 As(III) 117 1 0~05 mgL at pH 60 in DI water
(Wang et al 2014)
MICB 25 As(V) 191 1 0~1 mgL at pH 60 in DI water(Wang et al 2014)
MICB 25 As(III) 353 1 0~15 mgL at pH 60 in DI water(Wang et al 2014)
MICB 25 As(V) 357 1 0~16 mgL at pH 60 in DI water(Wang et al 2014)
Iron hydroxide granules (GIH) 3~4 As(V) 23 4
5~100 mgL at pH 70 in 10 mgL SO42-
14 mgL NH4Cl buffer solution (Daus et al 2004)
Activated Al2O3
0074~0149 As(V) 159 - 285~115 mgL at pH 52 in DI water
(Lin and Wu 2001)
Activated Al2O3
0074~0149 As(III) 35 - 079~490 mgL at pH 70 in DI water
(Lin and Wu 2001)
Activated Al2O3 ~20 As(V) 73 at pH 70 in 004 M NaClO4 (Jing et al 2012)
Activated natural siderite 05~10 As(V) 22 10 0 1~20 mgL at pH 7 in DI water(Zhao and Guo 2014)
Polyaluminum Granulate 1~3 As(III) 705 10 0~150 mgL at pH 51-56 in DI water(Mertens et al 2012)
Polyaluminum Granulate 1~3 As(V) 180 10 0~150 mgL at pH 51-56 in DI water (Mertens et al
26
2012)
Acidified laterite 1~12 As(III) 19 1 025~5 mgL at pH 7 in 100 mgL NaHCO3
(Glocheux et al 2013)
Acidified laterite 1~12 As(V) 13 1 025~5 mgL at pH 7 in 100 mgL NaHCO3
(Glocheux et al 2013)
Laterite 1~12 As(III) 07 1025~5 mgL at pH 7 in 100 mgL NaHCO3 (Glocheux et al
2013)
Laterite 1~12 As(V) 04 1025~5 mgL at pH 7 in 100 mgL NaHCO3 (Glocheux et al
2013)
Treated laterite 03-05 As(V) 216 05 02-20 mgL at pH 70 in DI water(Maiti et al 2012)
Treated laterite 03-05 As(III) 94 05 02-20 mgL at pH 70 in DI water(Maiti et al 2012)
Treated laterite03-05
As(V) 241 05 02-20 mgL at pH 70 in DI water(Maiti et al 2010a)
Treated laterite03-05
As(III) 81 05 02-20 mgL at pH 70 in DI water(Maiti et al 2010a)
Acid-activated laterite-103-07
As(III) 0633 50 02-10 mgL at pH 66-70 in DI water(Maiti et al 2010b)
Acid-activated laterite-203-07
As(III) 087650 02-10 mgL at pH 66-70 in DI water (Maiti et al
2010b)
Acid-activated laterite-303-07
As(III) 063450 02-10 mgL at pH 66-70 in DI water (Maiti et al
2010b)
Acid-activated laterite-103-07
As(V) 059850 02-10 mgL at pH 66-70 in DI water (Maiti et al
2010b)
27
Acid-activated laterite-203-07
As(V) 07550 02-10 mgL at pH 66-70 in DI water (Maiti et al
2010b)
Acid-activated laterite-303-07
As(V) 07550 02-10 mgL at pH 66-70 in DI water (Maiti et al
2010b)
Treated laterite-1 03-06 As(V) 019 20 0-20 mgL As at pH 72 in DI water(Maiti et al 2013b)
Treated laterite-1 03-06 As(III) 018 20 0-20 mgL As at pH 72 in DI water(Maiti et al 2013b)
Treated laterite-2 03-06 As(V) 004 20 0-20 mgL As at pH 72 in DI water(Maiti et al 2013b)
Treated laterite-2 03-06 As(III) 003 20 0-20 mgL As at pH 72 in DI water(Maiti et al 2013b)
Treated laterite-3 03-06 As(V) 007 20 0-20 mgL As at pH 72 in DI water(Maiti et al 2013b)
Treated laterite-3 03-06 As(III) 004 20 0-20 mgL As at pH 72 in DI water(Maiti et al 2013b)
28
376377
Charge distribution multi-site surface complexation (CD-MUSIC) modeling
The CD-MUSIC model with the 2-pK TPM adsorption option was used to
describe adsorption behaviors of As cations and anions on GTiO2 The CD-MUSIC
model incorporates the structural information of surfaces adsorbed species and the
double layers by distributing the charge of an adsorbate between the surface and
interfacial water (Hiemstra and Van Riemsdijk 2006) The CD-MUSIC model has
been successfully used in describing As adsorption in batch experiments (Pena et al
2006 Stachowicz et al 2008)
The adsorption constants of counter ions were set to -1 and the proton affinity
constant was set to the PZC of 58 for TiOH-13 (Luo et al 2010) The charge
distribution (CD) value shows the fraction (f) of the charge of the central As ion
attributed to the surface plane and the remaining part (1-f) was attributed to the other
ligands of the complex which were positioned toward the diffuse layer The CD value
for As surface complexes was obtained by fitting the experimental data The
calculation was performed using the chemical equilibrium program MINTEQ to
simulate the adsorption and the aqueous reactions
29
378379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
Fig S32 Adsorption of silicate (a) calcium and magnesium (b) as a function of GTiO2
dose in groundwater 1 The solid lines represent the CD-MUSIC modeling result
30
400
401
402
403
404
405
406
407
408409410
Table S75 Surface parameters and species used in the CD-MUSIC modeling in As(IIIV) removal under different GTiO2 dose in 01 M NaCl and groundwater 1 in Fig 2 and Fig S32
= exp(-FΨ1RT) P2 = exp(-FΨ2RT) F the Faraday constant (C mol-1) R the gas constant (J mol-1 K-1) T the absolute temperature (K)
Ψ0 Ψ1 Ψ2 the electrostatic potential (V) of 0- 1- and 2-plane respectively alogK for 01 M NaCl at 6 hours blogK for 01 M NaCl at 6 days clogK for groundwater 1 at 6 days
31
411412
413414415
32
416
Table S86 The charge distribution (f) of central As atom to TiO2 surface in simulating the effect of cations and anions on As adsorption in 01 M NaCl at pH 82 in Fig 4 BK Si HCO3 All
As(V) 022 017 012 016As(III) 040 020 058 056
Fig S43 Molar percentage () of As Ca Mg and Si on pristine and spent GTiO2
surfaces using EDX analysis The spent GTiO2 samples after field column experiments using groundwater 1 were identified with EBCT in min under x-axis The value of molar percentage of each element was averaged from randomly-chosen positions on the adsorbent surface
33
417
418
419420
421422
423
424
425
426
427
428
429
430
431
432
433434435436437438
439
440
441
As speciation analysis on spent GTiO2 using XANES
The spent GTiO2 samples were ground using a mortar and pestle and then the
ground powder was spread on Scotch tape The As k-edge XANES spectra were
collected at beamline 01C1 at the National Synchrotron Radiation Research Center
(NSRRC) Taiwan Spectra were acquired from -150 to 300 eV relative to the As K-
edge of 11867 eV at cryogenic temperature (77 K) using a cryostat to prevent the
oxidation of As(III) by X-rays The fluorescence signals were collected using a Lytle
detector Two to four scans were collected for each sample and averaged to improve
the signalnoise ratio The XANES analysis was performed with the Athena program
in the IFEFFIT computer package for linear combination fit (LCF) (Cui et al 2013
Ravel and Newville 2005)
34
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
PHREEQC modeling for As breakthrough curves in field column experiments
PHREEQC a geochemical model integrates macroscopic mass transfer
processes with a microscopic surface complexation model (Parkhurst and Appelo
2013) It can be applied in calculating solution complex speciation batch-reaction
and one-dimensional reactive-transport and inverse modeling In our study the one-
dimensional column was defined by four cells with the same length The cell length
was calculated to be one-fourth of the actual column length Time step (s) was
calculated according to equation Time step = Lcell(Q60A) where Lcell is the cell
length (cm) Q is flow velocity (mLmin) A is the effective column cross section area
(cm2) which is the column cross-sectional area multiplied by porosity (060) Total
shift number was calculated by dividing actual column operation time by the time
step The transport block was modeled by shifting the solute content from one cell to
the next one In each cell the aqueous solute was mixed and adsorbed on GTiO2
according to the equations In each cell the aqueous solute was mixed and assumed to
be in equilibration with GTiO2 The sequence of shifting mixing and equilibrium
adsorption was repeated for each cell until the total number of shifts was completed
The diffusion coefficient Dw in PHREEQC accounting for retardation was
calculated as Dw=x2
(36t) where x stands for the diffusion length (estimated as the
radius of the particle size) and t represents equilibrium time adopted from the batch
kinetic data (Mertens et al 2012)
For CD-MUSIC modeling in the PHREEQC take As(III) as an example to
explain the adsorption equation The As(III) adsorption is considered as a ligand
35
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
exchange reaction with the hydroxide group on GTiO2 (Surf_sOH-033) forming a
H3ArseniteO3 is the master species in groundwater at pH 82
(Surf_sO)2ArseniteOH-066 is the common adsorbed bidentate binuclear complex
evidenced by our previous reports(Pena et al 2006 Yan et al 2015) LogK is the
adsorption equilibrium constants Generally every adsorption equation under certain
experimental condition has a unique value of logK In the adsorption equation ldquo-2rdquo
represents the lost two hydrogens by Surf_sOH-033 after it adsorbs H3ArseniteO3 ldquo-
1rdquo represents the change in charge on Arsenite at 1 plane due to gaining one hydrogen
(+1) and one oxygen (-2) ldquo0rdquo represents no change in charge at the 2 plane ldquo066rdquo is
the fraction of the central ion (As) on GTiO2 surface that is associated with plane 0
ldquo3rdquo is the charge on the central ion As(III) Following this equation and the relevant
parameters As(III) adsorbed on GTiO2
The diffusion coefficient Dw in PHREEQC accounting for retardation was
calculated as Dw=x2(36t) where x stands for the diffusion length (estimated as the
radius of the particle size) and t represents equilibrium time adopted from the batch
kinetic data (Mertens et al 2012)
To well simulate the As breakthrough curve in columns four As(V) adsorption
reactions (Table 1) were employed Adsorption site density of 60 mmolg was
36
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
adopted from our previous study (Pena et al 2006) and the total adsorption sites were
calculated to be 1844 sitesnm2 The final optimized ratio of strong to weak sites was
51 The surface complexation constants were reasonably adjusted according to the
batch modeling results as the column reaction may not reach equilibrium in local
micro-interfacial areas due to much less contact time between As and GTiO2 than that
in batch experiments (Appelo and Postma 1999) In the modeling a stepwise
procedure was adopted to achieve a viable result An estimation of two thirds of the
surface site density being accessible for EBCT=011 min with large flow rate of 265
mLmin was optimized which could probably result from unavailable adsorption sites
due to fast transport through the column
The adsorbed As on GTiO2 in the column was calculated by mass balance
between the influent and effluent
where Asadsorbed is the adsorbed As on GTiO2 (mgg) n is the number of collected
samples Cin and Cout are influent and effluent As concentrations (mgL) respectively
Vi is volume (L) of groundwater passed through the column between sample i-1 and i
and m is the mass of GTiO2 (g)
Even though the oxidation of adsorbed As(III) occurred during filtration as
analyzed from XANES and mass balance analysis (Fig 7) no As(III) oxidation
reactions were considered in PHREEQC modeling which would not impact the
breakthrough of As(IIIV)
37
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
38
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
Fig S54 Effect of EBCT on Si Ca and Mg breakthrough curves using groundwater 1 The sample notation in panel c indicates field column experiments with EBCT in minutes
References
Appelo CAJ Postma D 1999 A consistent model for surface complexation on birnessite (MnO2) and its application to a column experiment Geochim Cosmochim Ac 63 (19-20) 3039-3048Badruzzaman M Westerhoff P Knappe DRU 2004 Intraparticle diffusion and adsorption of arsenate onto granular ferric hydroxide (GFH) Water Res 38 (18) 4002-4012Banerjee K Amy GL Prevost M Nour S Jekel M Gallagher PM Blumenschein CD 2008 Kinetic and thermodynamic aspects of adsorption of arsenic onto granular ferric hydroxide (GFH) Water Res 42 (13) 3371-3378Bang S Patel M Lippincott L Meng XG 2005 Removal of arsenic from groundwater by granular titanium dioxide adsorbent Chemosphere 60 (3) 389-397Bang S Pena ME Patel M Lippincott L Meng X Kim KW 2011 Removal of arsenate from water by adsorbents a comparative case study Environ Geochem Hlth 33 133-141Cui JL Shi JB Jiang GB Jing CY 2013 Arsenic levels and speciation from ingestion exposures to biomarkers in Shanxi China Implications for human health Environ Sci Technol 47 (10) 5419-5424Daus B Wennrich R Weiss H 2004 Sorption materials for arsenic removal from water A comparative study Water Res 38 (12) 2948-2954Dou XM Mohan D Pittman CU 2013 Arsenate adsorption on three types of granular schwertmannite Water Res 47 (9) 2938-2948Dou XM Zhang Y Yang M Pei YS Huang X Takayama T Kato S 2006 Occurrence of arsenic in groundwater in the suburbs of Beijing and its removal using an iron-cerium bimetal oxide adsorbent Water Qual Res J Can 41 (2) 140-146Gibbons MK Gagnon GA 2010 Adsorption of arsenic from a Nova Scotia groundwater onto water treatment residual solids Water Res 44 (19) 5740-5749Glocheux Y Mendez Pasarin M Albadarin AB Allen SJ Walker GM 2013 Removal of arsenic from groundwater by adsorption onto an acidified laterite by-product Chem Eng J 228 565-574Guan XH Wang JM Chusuei CC 2008 Removal of arsenic from water using granular ferric hydroxide Macroscopic and microscopic studies J Hazard Mater 156 (1-3) 178-185Gupta K Maity A Ghosh UC 2010 Manganese associated nanoparticles agglomerate of iron(III) oxide Synthesis characterization and arsenic(III) sorption behavior with mechanism J Hazard Mater 184 (1-3) 832-842Hao JM Han MJ Wang C Meng XG 2009 Enhanced removal of arsenite from water by a mesoporous hybrid material - Thiol-functionalized silica coated activated alumina Micropor Mesopor
Mat 124 (1-3) 1-7Hiemstra T Van Riemsdijk WH 2006 On the relationship between charge distribution surface hydration and the structure of the interface of metal hydroxides J Colloid Interf Sci 301 (1) 1-18Hristovski K Baumgardner A Westerhoff P 2007 Selecting metal oxide nanomaterials for arsenic removal in fixed bed columns From nanopowders to aggregated nanoparticle media J Hazard Mater 147 (1-2) 265-274Jang M Chen WF Cannon FS 2008 Preloading hydrous ferric oxide into granular activated carbon for arsenic removal Environ Sci Technol 42 (9) 3369-3374Jing CY Cui JL Huang YY Li AG 2012 Fabrication characterization and application of a composite adsorbent for simultaneous removal of arsenic and fluoride ACS Appl Mater Interfaces 4 (2) 714-720Kanematsu M Young TM Fukushi K Green PG Darby JL 2010 Extended triple layer modeling of arsenate and phosphate adsorption on a goethite-based granular porous adsorbent Environ Sci Technol 44 (9) 3388-3394Kong S Wang Y Zhan H Yuan S Liu M Zhou C 2013 Arsenite and Arsenate Removal from Contaminated Groundwater by Nanoscale Iron-Manganese Binary Oxides Column Studies Environmental Engineering Science 30 (11) 689-696Li Y Liu JR Jia SY Guo JW Zhuo J Na P 2012 TiO2 pillared montmorillonite as a photoactive adsorbent of arsenic under UV irradiation Chem Eng J 191 66-74Lin TF Wu JK 2001 Adsorption of arsenite and arsenate within activated alumina grains Equilibrium and kinetics Water Res 35 (8) 2049-2057Luo T Cui JL Hu S Huang YY Jing CY 2010 Arsenic removal and recovery from copper smelting wastewater using TiO2 Environ Sci Technol 44 (23) 9094-9098Maiti A Basu JK De S 2010a Development of a Treated Laterite for Arsenic Adsorption Effects of Treatment Parameters Industrial amp Engineering Chemistry Research 49 (10) 4873-4886Maiti A Basu JK De S 2010b Removal of Arsenic from Synthetic and Natural Groundwater Using Acid-Activated Laterite Environmental Progress amp Sustainable Energy 29 (4) 457-470Maiti A Basu JK De S 2012 Experimental and kinetic modeling of As(V) and As(III) adsorption on treated laterite using synthetic and contaminated groundwater Effects of phosphate silicate and carbonate ions Chem Eng J 191 1-12Maiti A Thakur BK Basu JK De S 2013a Comparison of treated laterite as arsenic adsorbent from different locations and performance of best filter under field conditions J Hazard Mater 262 1176-1186Maiti A Thakur BK Basu JK De S 2013b Comparison of treated laterite as arsenic adsorbent from different locations and performance of best filter under field conditions J Hazard Mater 262 (0) 1176-1186Maji SK Pal A Pal T 2008 Arsenic removal from real-life groundwater by adsorption on laterite soil J Hazard Mater 151 (2-3) 811-820Maji SK Kao YH Wang CJ Lu GS Wu JJ Liu CW 2012 Fixed bed adsorption of As(III) on iron-oxide-coated natural rock (IOCNR) and application to real arsenic-bearing groundwater Chem Eng J 203 285-293Mertens J Rose J Kagi R Chaurand P Plotze M Wehrli B Furrer G 2012 Adsorption of arsenic on polyaluminum granulate Environ Sci Technol 46 (13) 7310-7317Nguyen TV Vigneswaran S Ngo HH Pokhre D Viraraghavan T 2006 Iron-coated sponge as
effective media to remove arsenic from drinking water Water Qual Res J Can 41 (2) 164-170Parkhurst DL Appelo CAJ 2013 Description of input and examples for PHREEQC version 3-A computer program for speciation batch-reaction one-dimensional transport and inverse geochemical calculations US Geological SurveyPena M Meng XG Korfiatis GP Jing CY 2006 Adsorption mechanism of arsenic on nanocrystalline titanium dioxide Environ Sci Technol 40 (4) 1257-1262Ravel B Newville M 2005 ATHENA ARTEMIS HEPHAESTUS Data analysis for X-ray absorption spectroscopy using IFEFFIT J Synchrotron Radiat 12 537-541Saha B Bains R Greenwood F 2005 Physicochemical characterization of granular ferric hydroxide (GFH) for arsenic(V) sorption from water Separation Science and Technology 40 (14) 2909-2932Shan H Ma T Wang Y Zhao J Han H Deng Y He X Dong Y 2013 A cost-effective system for in-situ geological arsenic adsorption from groundwater J Contam Hydrol 154 1-9Stachowicz M Hiemstra T van Riemsdijk WH 2008 Multi-competitive interaction of As(III) and As(V) oxyanions with Ca2+ Mg2+ PO4
3- and CO32- ions on goethite J Colloid Interf Sci 320 (2) 400-
414Streat M Hellgardt K Newton NLR 2008 Hydrous ferric oxide as an adsorbent in water treatment - Part 3 Batch and mini-column adsorption of arsenic phosphorus fluorine and cadmium ions Process Safety and Environmental Protection 86 (B1) 21-30Thirunavukkarasu OS Viraraghavan T Subramanian KS 2003 Arsenic removal from drinking water using iron oxide-coated sand Water Air Soil Poll 142 (1-4) 95-111USEPA 2008 Assessing arsenic removal by metal (hydr)oxide adsorptive media using rapid small scale column tests Govenrnment Printing Office Washington DCWang J Xu W Chen L Huang X Liu J 2014 Preparation and evaluation of magnetic nanoparticles impregnated chitosan beads for arsenic removal from water Chem Eng J 251 25-34Westerhoff P Highfield D Badruzzaman M Yoon Y 2005 Rapid small-scale column tests for arsenate removal in iron oxide packed bed columns J Environ Eng-Asce 131 (2) 262-271Westerhoff P De Haan M Martindale A Badruzzaman M 2006 Arsenic adsorptive media technology selection strategies Water Qual Res J Can 41 (2) 171-184Yan L Huang Y Cui J Jing C 2015 Simultaneous As(III) and Cd removal from copper smelting wastewater using granular TiO2 columns Water Res 68 (0) 572-579Zhao K Guo HM 2014 Behavior and mechanism of arsenate adsorption on activated natural siderite Evidences from FTIR and XANES analysis Environ Sci Pollut Res 21 (3) 1944-1953Zhao K Guo H Zhou X 2014 Adsorption and heterogeneous oxidation of arsenite on modified granular natural siderite Characterization and behaviors Appl Geochem 48 184-192
Table S54 Parameters of Weber-Morris intraparticle model for As(IIIV) adsorption kinetics on GTiO2 using synthetic water Initial As concentration = 800 μgL adsorbent dose = 02 gL pH = 82 in synthetic groundwater
External film diffusion
Intraparticle diffusion
aRex2 bkp1
cb1aRin
2 bkp2cb 2
As(V) 0984 0497 0022 0976 01331878
As(III) 0970 0583
-0088 0981 0218
1105
aRex is WM external proportion fitting parameter while Rin is WM intraparticle proportion fitting parameterbk The unit of kp is mggh05 cb The unit of b is mgg
Table S6 Comparison of the adsorption capacities of As(III) and As(V) on GTiO2 and the representative granular adsorbents in similar experimental condition from the literature
AdsorbentParticle size (mm) As
qm
(mgg)Dose (gL) Experimental conditions Literature
GTiO2 018~025 As(III) 980 1 0~500 mgL at pH 82 01 M NaCl This studyGTiO2 018~025 As(V) 358 1 0~500 mgL at pH 82 01 M NaCl This study
Granular TiO2 015~06 As(III) 392 10~60 mgL As at pH 70 in simulated groundwater (100 mgL Ca 20 mgL Mg 50 mgL Na 200 mgL Cl-
)(Bang et al 2005)
Granular TiO2 015~06 As(V) 400 10~60 mgL As at pH 70 in simulated groundwater (100 mgL Ca 20 mgL Mg 50 mgL Na 200 mgL Cl-
)(Bang et al 2005)
E33 (FeOOH)0044~0075 As(V) 202 1 0~15 mgL at pH 70 in 001 M NaCl
(Kanematsu et al 2010)
E33 (FeOOH) 05~2 As(V) 180 1 0~50 mgL at pH 70 in 004 M NaClO4 (Jing et al 2012)
GFH 02~06 As(V) 650 10 0~2000 mgL at pH 8 in 01 M NaNO3
(Guan et al 2008)
GFH0009~0125 As(V) 23 025 0~07 μgL at pH 65 in DI water
(Banerjee et al 2008)
GFH0009~0125 As(V) 200 - 0~01 μgL at pH 70 in DI water
(Badruzzaman et al 2004)
GFH 050~065 As(V) 155 - 0~06 μgL at pH 70 in DI water (Saha et al 2005)
GHFO-NN 015~030 As(V) 330 0001 0~225 mgL at pH 8 in DI water(Streat et al 2008)
GHFO-VL 015~030 As(V) 360 0001 0~225 mgL at pH 8 in DI water(Streat et al 2008)
25
374375
Spherical schwertmannite 1~15 As(V) 36 05 0~5 mgL at pH 70 in DI water (Dou et al 2013)Cylindrical schwertmannite 1~25 As(V) 223 05
0~5 mgL at pH 70 in DI water(Dou et al 2013)
Irregular schwertmannite 10~16 As(V) 317 05 0~5 mgL at pH 70 in DI water (Dou et al 2013)Fe impregnated chitosan beads (MICB) 25 As(III) 117 1 0~05 mgL at pH 60 in DI water
(Wang et al 2014)
MICB 25 As(V) 191 1 0~1 mgL at pH 60 in DI water(Wang et al 2014)
MICB 25 As(III) 353 1 0~15 mgL at pH 60 in DI water(Wang et al 2014)
MICB 25 As(V) 357 1 0~16 mgL at pH 60 in DI water(Wang et al 2014)
Iron hydroxide granules (GIH) 3~4 As(V) 23 4
5~100 mgL at pH 70 in 10 mgL SO42-
14 mgL NH4Cl buffer solution (Daus et al 2004)
Activated Al2O3
0074~0149 As(V) 159 - 285~115 mgL at pH 52 in DI water
(Lin and Wu 2001)
Activated Al2O3
0074~0149 As(III) 35 - 079~490 mgL at pH 70 in DI water
(Lin and Wu 2001)
Activated Al2O3 ~20 As(V) 73 at pH 70 in 004 M NaClO4 (Jing et al 2012)
Activated natural siderite 05~10 As(V) 22 10 0 1~20 mgL at pH 7 in DI water(Zhao and Guo 2014)
Polyaluminum Granulate 1~3 As(III) 705 10 0~150 mgL at pH 51-56 in DI water(Mertens et al 2012)
Polyaluminum Granulate 1~3 As(V) 180 10 0~150 mgL at pH 51-56 in DI water (Mertens et al
26
2012)
Acidified laterite 1~12 As(III) 19 1 025~5 mgL at pH 7 in 100 mgL NaHCO3
(Glocheux et al 2013)
Acidified laterite 1~12 As(V) 13 1 025~5 mgL at pH 7 in 100 mgL NaHCO3
(Glocheux et al 2013)
Laterite 1~12 As(III) 07 1025~5 mgL at pH 7 in 100 mgL NaHCO3 (Glocheux et al
2013)
Laterite 1~12 As(V) 04 1025~5 mgL at pH 7 in 100 mgL NaHCO3 (Glocheux et al
2013)
Treated laterite 03-05 As(V) 216 05 02-20 mgL at pH 70 in DI water(Maiti et al 2012)
Treated laterite 03-05 As(III) 94 05 02-20 mgL at pH 70 in DI water(Maiti et al 2012)
Treated laterite03-05
As(V) 241 05 02-20 mgL at pH 70 in DI water(Maiti et al 2010a)
Treated laterite03-05
As(III) 81 05 02-20 mgL at pH 70 in DI water(Maiti et al 2010a)
Acid-activated laterite-103-07
As(III) 0633 50 02-10 mgL at pH 66-70 in DI water(Maiti et al 2010b)
Acid-activated laterite-203-07
As(III) 087650 02-10 mgL at pH 66-70 in DI water (Maiti et al
2010b)
Acid-activated laterite-303-07
As(III) 063450 02-10 mgL at pH 66-70 in DI water (Maiti et al
2010b)
Acid-activated laterite-103-07
As(V) 059850 02-10 mgL at pH 66-70 in DI water (Maiti et al
2010b)
27
Acid-activated laterite-203-07
As(V) 07550 02-10 mgL at pH 66-70 in DI water (Maiti et al
2010b)
Acid-activated laterite-303-07
As(V) 07550 02-10 mgL at pH 66-70 in DI water (Maiti et al
2010b)
Treated laterite-1 03-06 As(V) 019 20 0-20 mgL As at pH 72 in DI water(Maiti et al 2013b)
Treated laterite-1 03-06 As(III) 018 20 0-20 mgL As at pH 72 in DI water(Maiti et al 2013b)
Treated laterite-2 03-06 As(V) 004 20 0-20 mgL As at pH 72 in DI water(Maiti et al 2013b)
Treated laterite-2 03-06 As(III) 003 20 0-20 mgL As at pH 72 in DI water(Maiti et al 2013b)
Treated laterite-3 03-06 As(V) 007 20 0-20 mgL As at pH 72 in DI water(Maiti et al 2013b)
Treated laterite-3 03-06 As(III) 004 20 0-20 mgL As at pH 72 in DI water(Maiti et al 2013b)
28
376377
Charge distribution multi-site surface complexation (CD-MUSIC) modeling
The CD-MUSIC model with the 2-pK TPM adsorption option was used to
describe adsorption behaviors of As cations and anions on GTiO2 The CD-MUSIC
model incorporates the structural information of surfaces adsorbed species and the
double layers by distributing the charge of an adsorbate between the surface and
interfacial water (Hiemstra and Van Riemsdijk 2006) The CD-MUSIC model has
been successfully used in describing As adsorption in batch experiments (Pena et al
2006 Stachowicz et al 2008)
The adsorption constants of counter ions were set to -1 and the proton affinity
constant was set to the PZC of 58 for TiOH-13 (Luo et al 2010) The charge
distribution (CD) value shows the fraction (f) of the charge of the central As ion
attributed to the surface plane and the remaining part (1-f) was attributed to the other
ligands of the complex which were positioned toward the diffuse layer The CD value
for As surface complexes was obtained by fitting the experimental data The
calculation was performed using the chemical equilibrium program MINTEQ to
simulate the adsorption and the aqueous reactions
29
378379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
Fig S32 Adsorption of silicate (a) calcium and magnesium (b) as a function of GTiO2
dose in groundwater 1 The solid lines represent the CD-MUSIC modeling result
30
400
401
402
403
404
405
406
407
408409410
Table S75 Surface parameters and species used in the CD-MUSIC modeling in As(IIIV) removal under different GTiO2 dose in 01 M NaCl and groundwater 1 in Fig 2 and Fig S32
= exp(-FΨ1RT) P2 = exp(-FΨ2RT) F the Faraday constant (C mol-1) R the gas constant (J mol-1 K-1) T the absolute temperature (K)
Ψ0 Ψ1 Ψ2 the electrostatic potential (V) of 0- 1- and 2-plane respectively alogK for 01 M NaCl at 6 hours blogK for 01 M NaCl at 6 days clogK for groundwater 1 at 6 days
31
411412
413414415
32
416
Table S86 The charge distribution (f) of central As atom to TiO2 surface in simulating the effect of cations and anions on As adsorption in 01 M NaCl at pH 82 in Fig 4 BK Si HCO3 All
As(V) 022 017 012 016As(III) 040 020 058 056
Fig S43 Molar percentage () of As Ca Mg and Si on pristine and spent GTiO2
surfaces using EDX analysis The spent GTiO2 samples after field column experiments using groundwater 1 were identified with EBCT in min under x-axis The value of molar percentage of each element was averaged from randomly-chosen positions on the adsorbent surface
33
417
418
419420
421422
423
424
425
426
427
428
429
430
431
432
433434435436437438
439
440
441
As speciation analysis on spent GTiO2 using XANES
The spent GTiO2 samples were ground using a mortar and pestle and then the
ground powder was spread on Scotch tape The As k-edge XANES spectra were
collected at beamline 01C1 at the National Synchrotron Radiation Research Center
(NSRRC) Taiwan Spectra were acquired from -150 to 300 eV relative to the As K-
edge of 11867 eV at cryogenic temperature (77 K) using a cryostat to prevent the
oxidation of As(III) by X-rays The fluorescence signals were collected using a Lytle
detector Two to four scans were collected for each sample and averaged to improve
the signalnoise ratio The XANES analysis was performed with the Athena program
in the IFEFFIT computer package for linear combination fit (LCF) (Cui et al 2013
Ravel and Newville 2005)
34
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
PHREEQC modeling for As breakthrough curves in field column experiments
PHREEQC a geochemical model integrates macroscopic mass transfer
processes with a microscopic surface complexation model (Parkhurst and Appelo
2013) It can be applied in calculating solution complex speciation batch-reaction
and one-dimensional reactive-transport and inverse modeling In our study the one-
dimensional column was defined by four cells with the same length The cell length
was calculated to be one-fourth of the actual column length Time step (s) was
calculated according to equation Time step = Lcell(Q60A) where Lcell is the cell
length (cm) Q is flow velocity (mLmin) A is the effective column cross section area
(cm2) which is the column cross-sectional area multiplied by porosity (060) Total
shift number was calculated by dividing actual column operation time by the time
step The transport block was modeled by shifting the solute content from one cell to
the next one In each cell the aqueous solute was mixed and adsorbed on GTiO2
according to the equations In each cell the aqueous solute was mixed and assumed to
be in equilibration with GTiO2 The sequence of shifting mixing and equilibrium
adsorption was repeated for each cell until the total number of shifts was completed
The diffusion coefficient Dw in PHREEQC accounting for retardation was
calculated as Dw=x2
(36t) where x stands for the diffusion length (estimated as the
radius of the particle size) and t represents equilibrium time adopted from the batch
kinetic data (Mertens et al 2012)
For CD-MUSIC modeling in the PHREEQC take As(III) as an example to
explain the adsorption equation The As(III) adsorption is considered as a ligand
35
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
exchange reaction with the hydroxide group on GTiO2 (Surf_sOH-033) forming a
H3ArseniteO3 is the master species in groundwater at pH 82
(Surf_sO)2ArseniteOH-066 is the common adsorbed bidentate binuclear complex
evidenced by our previous reports(Pena et al 2006 Yan et al 2015) LogK is the
adsorption equilibrium constants Generally every adsorption equation under certain
experimental condition has a unique value of logK In the adsorption equation ldquo-2rdquo
represents the lost two hydrogens by Surf_sOH-033 after it adsorbs H3ArseniteO3 ldquo-
1rdquo represents the change in charge on Arsenite at 1 plane due to gaining one hydrogen
(+1) and one oxygen (-2) ldquo0rdquo represents no change in charge at the 2 plane ldquo066rdquo is
the fraction of the central ion (As) on GTiO2 surface that is associated with plane 0
ldquo3rdquo is the charge on the central ion As(III) Following this equation and the relevant
parameters As(III) adsorbed on GTiO2
The diffusion coefficient Dw in PHREEQC accounting for retardation was
calculated as Dw=x2(36t) where x stands for the diffusion length (estimated as the
radius of the particle size) and t represents equilibrium time adopted from the batch
kinetic data (Mertens et al 2012)
To well simulate the As breakthrough curve in columns four As(V) adsorption
reactions (Table 1) were employed Adsorption site density of 60 mmolg was
36
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
adopted from our previous study (Pena et al 2006) and the total adsorption sites were
calculated to be 1844 sitesnm2 The final optimized ratio of strong to weak sites was
51 The surface complexation constants were reasonably adjusted according to the
batch modeling results as the column reaction may not reach equilibrium in local
micro-interfacial areas due to much less contact time between As and GTiO2 than that
in batch experiments (Appelo and Postma 1999) In the modeling a stepwise
procedure was adopted to achieve a viable result An estimation of two thirds of the
surface site density being accessible for EBCT=011 min with large flow rate of 265
mLmin was optimized which could probably result from unavailable adsorption sites
due to fast transport through the column
The adsorbed As on GTiO2 in the column was calculated by mass balance
between the influent and effluent
where Asadsorbed is the adsorbed As on GTiO2 (mgg) n is the number of collected
samples Cin and Cout are influent and effluent As concentrations (mgL) respectively
Vi is volume (L) of groundwater passed through the column between sample i-1 and i
and m is the mass of GTiO2 (g)
Even though the oxidation of adsorbed As(III) occurred during filtration as
analyzed from XANES and mass balance analysis (Fig 7) no As(III) oxidation
reactions were considered in PHREEQC modeling which would not impact the
breakthrough of As(IIIV)
37
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
38
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
Fig S54 Effect of EBCT on Si Ca and Mg breakthrough curves using groundwater 1 The sample notation in panel c indicates field column experiments with EBCT in minutes
References
Appelo CAJ Postma D 1999 A consistent model for surface complexation on birnessite (MnO2) and its application to a column experiment Geochim Cosmochim Ac 63 (19-20) 3039-3048Badruzzaman M Westerhoff P Knappe DRU 2004 Intraparticle diffusion and adsorption of arsenate onto granular ferric hydroxide (GFH) Water Res 38 (18) 4002-4012Banerjee K Amy GL Prevost M Nour S Jekel M Gallagher PM Blumenschein CD 2008 Kinetic and thermodynamic aspects of adsorption of arsenic onto granular ferric hydroxide (GFH) Water Res 42 (13) 3371-3378Bang S Patel M Lippincott L Meng XG 2005 Removal of arsenic from groundwater by granular titanium dioxide adsorbent Chemosphere 60 (3) 389-397Bang S Pena ME Patel M Lippincott L Meng X Kim KW 2011 Removal of arsenate from water by adsorbents a comparative case study Environ Geochem Hlth 33 133-141Cui JL Shi JB Jiang GB Jing CY 2013 Arsenic levels and speciation from ingestion exposures to biomarkers in Shanxi China Implications for human health Environ Sci Technol 47 (10) 5419-5424Daus B Wennrich R Weiss H 2004 Sorption materials for arsenic removal from water A comparative study Water Res 38 (12) 2948-2954Dou XM Mohan D Pittman CU 2013 Arsenate adsorption on three types of granular schwertmannite Water Res 47 (9) 2938-2948Dou XM Zhang Y Yang M Pei YS Huang X Takayama T Kato S 2006 Occurrence of arsenic in groundwater in the suburbs of Beijing and its removal using an iron-cerium bimetal oxide adsorbent Water Qual Res J Can 41 (2) 140-146Gibbons MK Gagnon GA 2010 Adsorption of arsenic from a Nova Scotia groundwater onto water treatment residual solids Water Res 44 (19) 5740-5749Glocheux Y Mendez Pasarin M Albadarin AB Allen SJ Walker GM 2013 Removal of arsenic from groundwater by adsorption onto an acidified laterite by-product Chem Eng J 228 565-574Guan XH Wang JM Chusuei CC 2008 Removal of arsenic from water using granular ferric hydroxide Macroscopic and microscopic studies J Hazard Mater 156 (1-3) 178-185Gupta K Maity A Ghosh UC 2010 Manganese associated nanoparticles agglomerate of iron(III) oxide Synthesis characterization and arsenic(III) sorption behavior with mechanism J Hazard Mater 184 (1-3) 832-842Hao JM Han MJ Wang C Meng XG 2009 Enhanced removal of arsenite from water by a mesoporous hybrid material - Thiol-functionalized silica coated activated alumina Micropor Mesopor
Mat 124 (1-3) 1-7Hiemstra T Van Riemsdijk WH 2006 On the relationship between charge distribution surface hydration and the structure of the interface of metal hydroxides J Colloid Interf Sci 301 (1) 1-18Hristovski K Baumgardner A Westerhoff P 2007 Selecting metal oxide nanomaterials for arsenic removal in fixed bed columns From nanopowders to aggregated nanoparticle media J Hazard Mater 147 (1-2) 265-274Jang M Chen WF Cannon FS 2008 Preloading hydrous ferric oxide into granular activated carbon for arsenic removal Environ Sci Technol 42 (9) 3369-3374Jing CY Cui JL Huang YY Li AG 2012 Fabrication characterization and application of a composite adsorbent for simultaneous removal of arsenic and fluoride ACS Appl Mater Interfaces 4 (2) 714-720Kanematsu M Young TM Fukushi K Green PG Darby JL 2010 Extended triple layer modeling of arsenate and phosphate adsorption on a goethite-based granular porous adsorbent Environ Sci Technol 44 (9) 3388-3394Kong S Wang Y Zhan H Yuan S Liu M Zhou C 2013 Arsenite and Arsenate Removal from Contaminated Groundwater by Nanoscale Iron-Manganese Binary Oxides Column Studies Environmental Engineering Science 30 (11) 689-696Li Y Liu JR Jia SY Guo JW Zhuo J Na P 2012 TiO2 pillared montmorillonite as a photoactive adsorbent of arsenic under UV irradiation Chem Eng J 191 66-74Lin TF Wu JK 2001 Adsorption of arsenite and arsenate within activated alumina grains Equilibrium and kinetics Water Res 35 (8) 2049-2057Luo T Cui JL Hu S Huang YY Jing CY 2010 Arsenic removal and recovery from copper smelting wastewater using TiO2 Environ Sci Technol 44 (23) 9094-9098Maiti A Basu JK De S 2010a Development of a Treated Laterite for Arsenic Adsorption Effects of Treatment Parameters Industrial amp Engineering Chemistry Research 49 (10) 4873-4886Maiti A Basu JK De S 2010b Removal of Arsenic from Synthetic and Natural Groundwater Using Acid-Activated Laterite Environmental Progress amp Sustainable Energy 29 (4) 457-470Maiti A Basu JK De S 2012 Experimental and kinetic modeling of As(V) and As(III) adsorption on treated laterite using synthetic and contaminated groundwater Effects of phosphate silicate and carbonate ions Chem Eng J 191 1-12Maiti A Thakur BK Basu JK De S 2013a Comparison of treated laterite as arsenic adsorbent from different locations and performance of best filter under field conditions J Hazard Mater 262 1176-1186Maiti A Thakur BK Basu JK De S 2013b Comparison of treated laterite as arsenic adsorbent from different locations and performance of best filter under field conditions J Hazard Mater 262 (0) 1176-1186Maji SK Pal A Pal T 2008 Arsenic removal from real-life groundwater by adsorption on laterite soil J Hazard Mater 151 (2-3) 811-820Maji SK Kao YH Wang CJ Lu GS Wu JJ Liu CW 2012 Fixed bed adsorption of As(III) on iron-oxide-coated natural rock (IOCNR) and application to real arsenic-bearing groundwater Chem Eng J 203 285-293Mertens J Rose J Kagi R Chaurand P Plotze M Wehrli B Furrer G 2012 Adsorption of arsenic on polyaluminum granulate Environ Sci Technol 46 (13) 7310-7317Nguyen TV Vigneswaran S Ngo HH Pokhre D Viraraghavan T 2006 Iron-coated sponge as
effective media to remove arsenic from drinking water Water Qual Res J Can 41 (2) 164-170Parkhurst DL Appelo CAJ 2013 Description of input and examples for PHREEQC version 3-A computer program for speciation batch-reaction one-dimensional transport and inverse geochemical calculations US Geological SurveyPena M Meng XG Korfiatis GP Jing CY 2006 Adsorption mechanism of arsenic on nanocrystalline titanium dioxide Environ Sci Technol 40 (4) 1257-1262Ravel B Newville M 2005 ATHENA ARTEMIS HEPHAESTUS Data analysis for X-ray absorption spectroscopy using IFEFFIT J Synchrotron Radiat 12 537-541Saha B Bains R Greenwood F 2005 Physicochemical characterization of granular ferric hydroxide (GFH) for arsenic(V) sorption from water Separation Science and Technology 40 (14) 2909-2932Shan H Ma T Wang Y Zhao J Han H Deng Y He X Dong Y 2013 A cost-effective system for in-situ geological arsenic adsorption from groundwater J Contam Hydrol 154 1-9Stachowicz M Hiemstra T van Riemsdijk WH 2008 Multi-competitive interaction of As(III) and As(V) oxyanions with Ca2+ Mg2+ PO4
3- and CO32- ions on goethite J Colloid Interf Sci 320 (2) 400-
414Streat M Hellgardt K Newton NLR 2008 Hydrous ferric oxide as an adsorbent in water treatment - Part 3 Batch and mini-column adsorption of arsenic phosphorus fluorine and cadmium ions Process Safety and Environmental Protection 86 (B1) 21-30Thirunavukkarasu OS Viraraghavan T Subramanian KS 2003 Arsenic removal from drinking water using iron oxide-coated sand Water Air Soil Poll 142 (1-4) 95-111USEPA 2008 Assessing arsenic removal by metal (hydr)oxide adsorptive media using rapid small scale column tests Govenrnment Printing Office Washington DCWang J Xu W Chen L Huang X Liu J 2014 Preparation and evaluation of magnetic nanoparticles impregnated chitosan beads for arsenic removal from water Chem Eng J 251 25-34Westerhoff P Highfield D Badruzzaman M Yoon Y 2005 Rapid small-scale column tests for arsenate removal in iron oxide packed bed columns J Environ Eng-Asce 131 (2) 262-271Westerhoff P De Haan M Martindale A Badruzzaman M 2006 Arsenic adsorptive media technology selection strategies Water Qual Res J Can 41 (2) 171-184Yan L Huang Y Cui J Jing C 2015 Simultaneous As(III) and Cd removal from copper smelting wastewater using granular TiO2 columns Water Res 68 (0) 572-579Zhao K Guo HM 2014 Behavior and mechanism of arsenate adsorption on activated natural siderite Evidences from FTIR and XANES analysis Environ Sci Pollut Res 21 (3) 1944-1953Zhao K Guo H Zhou X 2014 Adsorption and heterogeneous oxidation of arsenite on modified granular natural siderite Characterization and behaviors Appl Geochem 48 184-192
Table S54 Parameters of Weber-Morris intraparticle model for As(IIIV) adsorption kinetics on GTiO2 using synthetic water Initial As concentration = 800 μgL adsorbent dose = 02 gL pH = 82 in synthetic groundwater
External film diffusion
Intraparticle diffusion
aRex2 bkp1
cb1aRin
2 bkp2cb 2
As(V) 0984 0497 0022 0976 01331878
As(III) 0970 0583
-0088 0981 0218
1105
aRex is WM external proportion fitting parameter while Rin is WM intraparticle proportion fitting parameterbk The unit of kp is mggh05 cb The unit of b is mgg
Table S6 Comparison of the adsorption capacities of As(III) and As(V) on GTiO2 and the representative granular adsorbents in similar experimental condition from the literature
AdsorbentParticle size (mm) As
qm
(mgg)Dose (gL) Experimental conditions Literature
GTiO2 018~025 As(III) 980 1 0~500 mgL at pH 82 01 M NaCl This studyGTiO2 018~025 As(V) 358 1 0~500 mgL at pH 82 01 M NaCl This study
Granular TiO2 015~06 As(III) 392 10~60 mgL As at pH 70 in simulated groundwater (100 mgL Ca 20 mgL Mg 50 mgL Na 200 mgL Cl-
)(Bang et al 2005)
Granular TiO2 015~06 As(V) 400 10~60 mgL As at pH 70 in simulated groundwater (100 mgL Ca 20 mgL Mg 50 mgL Na 200 mgL Cl-
)(Bang et al 2005)
E33 (FeOOH)0044~0075 As(V) 202 1 0~15 mgL at pH 70 in 001 M NaCl
(Kanematsu et al 2010)
E33 (FeOOH) 05~2 As(V) 180 1 0~50 mgL at pH 70 in 004 M NaClO4 (Jing et al 2012)
GFH 02~06 As(V) 650 10 0~2000 mgL at pH 8 in 01 M NaNO3
(Guan et al 2008)
GFH0009~0125 As(V) 23 025 0~07 μgL at pH 65 in DI water
(Banerjee et al 2008)
GFH0009~0125 As(V) 200 - 0~01 μgL at pH 70 in DI water
(Badruzzaman et al 2004)
GFH 050~065 As(V) 155 - 0~06 μgL at pH 70 in DI water (Saha et al 2005)
GHFO-NN 015~030 As(V) 330 0001 0~225 mgL at pH 8 in DI water(Streat et al 2008)
GHFO-VL 015~030 As(V) 360 0001 0~225 mgL at pH 8 in DI water(Streat et al 2008)
25
374375
Spherical schwertmannite 1~15 As(V) 36 05 0~5 mgL at pH 70 in DI water (Dou et al 2013)Cylindrical schwertmannite 1~25 As(V) 223 05
0~5 mgL at pH 70 in DI water(Dou et al 2013)
Irregular schwertmannite 10~16 As(V) 317 05 0~5 mgL at pH 70 in DI water (Dou et al 2013)Fe impregnated chitosan beads (MICB) 25 As(III) 117 1 0~05 mgL at pH 60 in DI water
(Wang et al 2014)
MICB 25 As(V) 191 1 0~1 mgL at pH 60 in DI water(Wang et al 2014)
MICB 25 As(III) 353 1 0~15 mgL at pH 60 in DI water(Wang et al 2014)
MICB 25 As(V) 357 1 0~16 mgL at pH 60 in DI water(Wang et al 2014)
Iron hydroxide granules (GIH) 3~4 As(V) 23 4
5~100 mgL at pH 70 in 10 mgL SO42-
14 mgL NH4Cl buffer solution (Daus et al 2004)
Activated Al2O3
0074~0149 As(V) 159 - 285~115 mgL at pH 52 in DI water
(Lin and Wu 2001)
Activated Al2O3
0074~0149 As(III) 35 - 079~490 mgL at pH 70 in DI water
(Lin and Wu 2001)
Activated Al2O3 ~20 As(V) 73 at pH 70 in 004 M NaClO4 (Jing et al 2012)
Activated natural siderite 05~10 As(V) 22 10 0 1~20 mgL at pH 7 in DI water(Zhao and Guo 2014)
Polyaluminum Granulate 1~3 As(III) 705 10 0~150 mgL at pH 51-56 in DI water(Mertens et al 2012)
Polyaluminum Granulate 1~3 As(V) 180 10 0~150 mgL at pH 51-56 in DI water (Mertens et al
26
2012)
Acidified laterite 1~12 As(III) 19 1 025~5 mgL at pH 7 in 100 mgL NaHCO3
(Glocheux et al 2013)
Acidified laterite 1~12 As(V) 13 1 025~5 mgL at pH 7 in 100 mgL NaHCO3
(Glocheux et al 2013)
Laterite 1~12 As(III) 07 1025~5 mgL at pH 7 in 100 mgL NaHCO3 (Glocheux et al
2013)
Laterite 1~12 As(V) 04 1025~5 mgL at pH 7 in 100 mgL NaHCO3 (Glocheux et al
2013)
Treated laterite 03-05 As(V) 216 05 02-20 mgL at pH 70 in DI water(Maiti et al 2012)
Treated laterite 03-05 As(III) 94 05 02-20 mgL at pH 70 in DI water(Maiti et al 2012)
Treated laterite03-05
As(V) 241 05 02-20 mgL at pH 70 in DI water(Maiti et al 2010a)
Treated laterite03-05
As(III) 81 05 02-20 mgL at pH 70 in DI water(Maiti et al 2010a)
Acid-activated laterite-103-07
As(III) 0633 50 02-10 mgL at pH 66-70 in DI water(Maiti et al 2010b)
Acid-activated laterite-203-07
As(III) 087650 02-10 mgL at pH 66-70 in DI water (Maiti et al
2010b)
Acid-activated laterite-303-07
As(III) 063450 02-10 mgL at pH 66-70 in DI water (Maiti et al
2010b)
Acid-activated laterite-103-07
As(V) 059850 02-10 mgL at pH 66-70 in DI water (Maiti et al
2010b)
27
Acid-activated laterite-203-07
As(V) 07550 02-10 mgL at pH 66-70 in DI water (Maiti et al
2010b)
Acid-activated laterite-303-07
As(V) 07550 02-10 mgL at pH 66-70 in DI water (Maiti et al
2010b)
Treated laterite-1 03-06 As(V) 019 20 0-20 mgL As at pH 72 in DI water(Maiti et al 2013b)
Treated laterite-1 03-06 As(III) 018 20 0-20 mgL As at pH 72 in DI water(Maiti et al 2013b)
Treated laterite-2 03-06 As(V) 004 20 0-20 mgL As at pH 72 in DI water(Maiti et al 2013b)
Treated laterite-2 03-06 As(III) 003 20 0-20 mgL As at pH 72 in DI water(Maiti et al 2013b)
Treated laterite-3 03-06 As(V) 007 20 0-20 mgL As at pH 72 in DI water(Maiti et al 2013b)
Treated laterite-3 03-06 As(III) 004 20 0-20 mgL As at pH 72 in DI water(Maiti et al 2013b)
28
376377
Charge distribution multi-site surface complexation (CD-MUSIC) modeling
The CD-MUSIC model with the 2-pK TPM adsorption option was used to
describe adsorption behaviors of As cations and anions on GTiO2 The CD-MUSIC
model incorporates the structural information of surfaces adsorbed species and the
double layers by distributing the charge of an adsorbate between the surface and
interfacial water (Hiemstra and Van Riemsdijk 2006) The CD-MUSIC model has
been successfully used in describing As adsorption in batch experiments (Pena et al
2006 Stachowicz et al 2008)
The adsorption constants of counter ions were set to -1 and the proton affinity
constant was set to the PZC of 58 for TiOH-13 (Luo et al 2010) The charge
distribution (CD) value shows the fraction (f) of the charge of the central As ion
attributed to the surface plane and the remaining part (1-f) was attributed to the other
ligands of the complex which were positioned toward the diffuse layer The CD value
for As surface complexes was obtained by fitting the experimental data The
calculation was performed using the chemical equilibrium program MINTEQ to
simulate the adsorption and the aqueous reactions
29
378379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
Fig S32 Adsorption of silicate (a) calcium and magnesium (b) as a function of GTiO2
dose in groundwater 1 The solid lines represent the CD-MUSIC modeling result
30
400
401
402
403
404
405
406
407
408409410
Table S75 Surface parameters and species used in the CD-MUSIC modeling in As(IIIV) removal under different GTiO2 dose in 01 M NaCl and groundwater 1 in Fig 2 and Fig S32
= exp(-FΨ1RT) P2 = exp(-FΨ2RT) F the Faraday constant (C mol-1) R the gas constant (J mol-1 K-1) T the absolute temperature (K)
Ψ0 Ψ1 Ψ2 the electrostatic potential (V) of 0- 1- and 2-plane respectively alogK for 01 M NaCl at 6 hours blogK for 01 M NaCl at 6 days clogK for groundwater 1 at 6 days
31
411412
413414415
32
416
Table S86 The charge distribution (f) of central As atom to TiO2 surface in simulating the effect of cations and anions on As adsorption in 01 M NaCl at pH 82 in Fig 4 BK Si HCO3 All
As(V) 022 017 012 016As(III) 040 020 058 056
Fig S43 Molar percentage () of As Ca Mg and Si on pristine and spent GTiO2
surfaces using EDX analysis The spent GTiO2 samples after field column experiments using groundwater 1 were identified with EBCT in min under x-axis The value of molar percentage of each element was averaged from randomly-chosen positions on the adsorbent surface
33
417
418
419420
421422
423
424
425
426
427
428
429
430
431
432
433434435436437438
439
440
441
As speciation analysis on spent GTiO2 using XANES
The spent GTiO2 samples were ground using a mortar and pestle and then the
ground powder was spread on Scotch tape The As k-edge XANES spectra were
collected at beamline 01C1 at the National Synchrotron Radiation Research Center
(NSRRC) Taiwan Spectra were acquired from -150 to 300 eV relative to the As K-
edge of 11867 eV at cryogenic temperature (77 K) using a cryostat to prevent the
oxidation of As(III) by X-rays The fluorescence signals were collected using a Lytle
detector Two to four scans were collected for each sample and averaged to improve
the signalnoise ratio The XANES analysis was performed with the Athena program
in the IFEFFIT computer package for linear combination fit (LCF) (Cui et al 2013
Ravel and Newville 2005)
34
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
PHREEQC modeling for As breakthrough curves in field column experiments
PHREEQC a geochemical model integrates macroscopic mass transfer
processes with a microscopic surface complexation model (Parkhurst and Appelo
2013) It can be applied in calculating solution complex speciation batch-reaction
and one-dimensional reactive-transport and inverse modeling In our study the one-
dimensional column was defined by four cells with the same length The cell length
was calculated to be one-fourth of the actual column length Time step (s) was
calculated according to equation Time step = Lcell(Q60A) where Lcell is the cell
length (cm) Q is flow velocity (mLmin) A is the effective column cross section area
(cm2) which is the column cross-sectional area multiplied by porosity (060) Total
shift number was calculated by dividing actual column operation time by the time
step The transport block was modeled by shifting the solute content from one cell to
the next one In each cell the aqueous solute was mixed and adsorbed on GTiO2
according to the equations In each cell the aqueous solute was mixed and assumed to
be in equilibration with GTiO2 The sequence of shifting mixing and equilibrium
adsorption was repeated for each cell until the total number of shifts was completed
The diffusion coefficient Dw in PHREEQC accounting for retardation was
calculated as Dw=x2
(36t) where x stands for the diffusion length (estimated as the
radius of the particle size) and t represents equilibrium time adopted from the batch
kinetic data (Mertens et al 2012)
For CD-MUSIC modeling in the PHREEQC take As(III) as an example to
explain the adsorption equation The As(III) adsorption is considered as a ligand
35
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
exchange reaction with the hydroxide group on GTiO2 (Surf_sOH-033) forming a
H3ArseniteO3 is the master species in groundwater at pH 82
(Surf_sO)2ArseniteOH-066 is the common adsorbed bidentate binuclear complex
evidenced by our previous reports(Pena et al 2006 Yan et al 2015) LogK is the
adsorption equilibrium constants Generally every adsorption equation under certain
experimental condition has a unique value of logK In the adsorption equation ldquo-2rdquo
represents the lost two hydrogens by Surf_sOH-033 after it adsorbs H3ArseniteO3 ldquo-
1rdquo represents the change in charge on Arsenite at 1 plane due to gaining one hydrogen
(+1) and one oxygen (-2) ldquo0rdquo represents no change in charge at the 2 plane ldquo066rdquo is
the fraction of the central ion (As) on GTiO2 surface that is associated with plane 0
ldquo3rdquo is the charge on the central ion As(III) Following this equation and the relevant
parameters As(III) adsorbed on GTiO2
The diffusion coefficient Dw in PHREEQC accounting for retardation was
calculated as Dw=x2(36t) where x stands for the diffusion length (estimated as the
radius of the particle size) and t represents equilibrium time adopted from the batch
kinetic data (Mertens et al 2012)
To well simulate the As breakthrough curve in columns four As(V) adsorption
reactions (Table 1) were employed Adsorption site density of 60 mmolg was
36
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
adopted from our previous study (Pena et al 2006) and the total adsorption sites were
calculated to be 1844 sitesnm2 The final optimized ratio of strong to weak sites was
51 The surface complexation constants were reasonably adjusted according to the
batch modeling results as the column reaction may not reach equilibrium in local
micro-interfacial areas due to much less contact time between As and GTiO2 than that
in batch experiments (Appelo and Postma 1999) In the modeling a stepwise
procedure was adopted to achieve a viable result An estimation of two thirds of the
surface site density being accessible for EBCT=011 min with large flow rate of 265
mLmin was optimized which could probably result from unavailable adsorption sites
due to fast transport through the column
The adsorbed As on GTiO2 in the column was calculated by mass balance
between the influent and effluent
where Asadsorbed is the adsorbed As on GTiO2 (mgg) n is the number of collected
samples Cin and Cout are influent and effluent As concentrations (mgL) respectively
Vi is volume (L) of groundwater passed through the column between sample i-1 and i
and m is the mass of GTiO2 (g)
Even though the oxidation of adsorbed As(III) occurred during filtration as
analyzed from XANES and mass balance analysis (Fig 7) no As(III) oxidation
reactions were considered in PHREEQC modeling which would not impact the
breakthrough of As(IIIV)
37
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
38
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
Fig S54 Effect of EBCT on Si Ca and Mg breakthrough curves using groundwater 1 The sample notation in panel c indicates field column experiments with EBCT in minutes
References
Appelo CAJ Postma D 1999 A consistent model for surface complexation on birnessite (MnO2) and its application to a column experiment Geochim Cosmochim Ac 63 (19-20) 3039-3048Badruzzaman M Westerhoff P Knappe DRU 2004 Intraparticle diffusion and adsorption of arsenate onto granular ferric hydroxide (GFH) Water Res 38 (18) 4002-4012Banerjee K Amy GL Prevost M Nour S Jekel M Gallagher PM Blumenschein CD 2008 Kinetic and thermodynamic aspects of adsorption of arsenic onto granular ferric hydroxide (GFH) Water Res 42 (13) 3371-3378Bang S Patel M Lippincott L Meng XG 2005 Removal of arsenic from groundwater by granular titanium dioxide adsorbent Chemosphere 60 (3) 389-397Bang S Pena ME Patel M Lippincott L Meng X Kim KW 2011 Removal of arsenate from water by adsorbents a comparative case study Environ Geochem Hlth 33 133-141Cui JL Shi JB Jiang GB Jing CY 2013 Arsenic levels and speciation from ingestion exposures to biomarkers in Shanxi China Implications for human health Environ Sci Technol 47 (10) 5419-5424Daus B Wennrich R Weiss H 2004 Sorption materials for arsenic removal from water A comparative study Water Res 38 (12) 2948-2954Dou XM Mohan D Pittman CU 2013 Arsenate adsorption on three types of granular schwertmannite Water Res 47 (9) 2938-2948Dou XM Zhang Y Yang M Pei YS Huang X Takayama T Kato S 2006 Occurrence of arsenic in groundwater in the suburbs of Beijing and its removal using an iron-cerium bimetal oxide adsorbent Water Qual Res J Can 41 (2) 140-146Gibbons MK Gagnon GA 2010 Adsorption of arsenic from a Nova Scotia groundwater onto water treatment residual solids Water Res 44 (19) 5740-5749Glocheux Y Mendez Pasarin M Albadarin AB Allen SJ Walker GM 2013 Removal of arsenic from groundwater by adsorption onto an acidified laterite by-product Chem Eng J 228 565-574Guan XH Wang JM Chusuei CC 2008 Removal of arsenic from water using granular ferric hydroxide Macroscopic and microscopic studies J Hazard Mater 156 (1-3) 178-185Gupta K Maity A Ghosh UC 2010 Manganese associated nanoparticles agglomerate of iron(III) oxide Synthesis characterization and arsenic(III) sorption behavior with mechanism J Hazard Mater 184 (1-3) 832-842Hao JM Han MJ Wang C Meng XG 2009 Enhanced removal of arsenite from water by a mesoporous hybrid material - Thiol-functionalized silica coated activated alumina Micropor Mesopor
Mat 124 (1-3) 1-7Hiemstra T Van Riemsdijk WH 2006 On the relationship between charge distribution surface hydration and the structure of the interface of metal hydroxides J Colloid Interf Sci 301 (1) 1-18Hristovski K Baumgardner A Westerhoff P 2007 Selecting metal oxide nanomaterials for arsenic removal in fixed bed columns From nanopowders to aggregated nanoparticle media J Hazard Mater 147 (1-2) 265-274Jang M Chen WF Cannon FS 2008 Preloading hydrous ferric oxide into granular activated carbon for arsenic removal Environ Sci Technol 42 (9) 3369-3374Jing CY Cui JL Huang YY Li AG 2012 Fabrication characterization and application of a composite adsorbent for simultaneous removal of arsenic and fluoride ACS Appl Mater Interfaces 4 (2) 714-720Kanematsu M Young TM Fukushi K Green PG Darby JL 2010 Extended triple layer modeling of arsenate and phosphate adsorption on a goethite-based granular porous adsorbent Environ Sci Technol 44 (9) 3388-3394Kong S Wang Y Zhan H Yuan S Liu M Zhou C 2013 Arsenite and Arsenate Removal from Contaminated Groundwater by Nanoscale Iron-Manganese Binary Oxides Column Studies Environmental Engineering Science 30 (11) 689-696Li Y Liu JR Jia SY Guo JW Zhuo J Na P 2012 TiO2 pillared montmorillonite as a photoactive adsorbent of arsenic under UV irradiation Chem Eng J 191 66-74Lin TF Wu JK 2001 Adsorption of arsenite and arsenate within activated alumina grains Equilibrium and kinetics Water Res 35 (8) 2049-2057Luo T Cui JL Hu S Huang YY Jing CY 2010 Arsenic removal and recovery from copper smelting wastewater using TiO2 Environ Sci Technol 44 (23) 9094-9098Maiti A Basu JK De S 2010a Development of a Treated Laterite for Arsenic Adsorption Effects of Treatment Parameters Industrial amp Engineering Chemistry Research 49 (10) 4873-4886Maiti A Basu JK De S 2010b Removal of Arsenic from Synthetic and Natural Groundwater Using Acid-Activated Laterite Environmental Progress amp Sustainable Energy 29 (4) 457-470Maiti A Basu JK De S 2012 Experimental and kinetic modeling of As(V) and As(III) adsorption on treated laterite using synthetic and contaminated groundwater Effects of phosphate silicate and carbonate ions Chem Eng J 191 1-12Maiti A Thakur BK Basu JK De S 2013a Comparison of treated laterite as arsenic adsorbent from different locations and performance of best filter under field conditions J Hazard Mater 262 1176-1186Maiti A Thakur BK Basu JK De S 2013b Comparison of treated laterite as arsenic adsorbent from different locations and performance of best filter under field conditions J Hazard Mater 262 (0) 1176-1186Maji SK Pal A Pal T 2008 Arsenic removal from real-life groundwater by adsorption on laterite soil J Hazard Mater 151 (2-3) 811-820Maji SK Kao YH Wang CJ Lu GS Wu JJ Liu CW 2012 Fixed bed adsorption of As(III) on iron-oxide-coated natural rock (IOCNR) and application to real arsenic-bearing groundwater Chem Eng J 203 285-293Mertens J Rose J Kagi R Chaurand P Plotze M Wehrli B Furrer G 2012 Adsorption of arsenic on polyaluminum granulate Environ Sci Technol 46 (13) 7310-7317Nguyen TV Vigneswaran S Ngo HH Pokhre D Viraraghavan T 2006 Iron-coated sponge as
effective media to remove arsenic from drinking water Water Qual Res J Can 41 (2) 164-170Parkhurst DL Appelo CAJ 2013 Description of input and examples for PHREEQC version 3-A computer program for speciation batch-reaction one-dimensional transport and inverse geochemical calculations US Geological SurveyPena M Meng XG Korfiatis GP Jing CY 2006 Adsorption mechanism of arsenic on nanocrystalline titanium dioxide Environ Sci Technol 40 (4) 1257-1262Ravel B Newville M 2005 ATHENA ARTEMIS HEPHAESTUS Data analysis for X-ray absorption spectroscopy using IFEFFIT J Synchrotron Radiat 12 537-541Saha B Bains R Greenwood F 2005 Physicochemical characterization of granular ferric hydroxide (GFH) for arsenic(V) sorption from water Separation Science and Technology 40 (14) 2909-2932Shan H Ma T Wang Y Zhao J Han H Deng Y He X Dong Y 2013 A cost-effective system for in-situ geological arsenic adsorption from groundwater J Contam Hydrol 154 1-9Stachowicz M Hiemstra T van Riemsdijk WH 2008 Multi-competitive interaction of As(III) and As(V) oxyanions with Ca2+ Mg2+ PO4
3- and CO32- ions on goethite J Colloid Interf Sci 320 (2) 400-
414Streat M Hellgardt K Newton NLR 2008 Hydrous ferric oxide as an adsorbent in water treatment - Part 3 Batch and mini-column adsorption of arsenic phosphorus fluorine and cadmium ions Process Safety and Environmental Protection 86 (B1) 21-30Thirunavukkarasu OS Viraraghavan T Subramanian KS 2003 Arsenic removal from drinking water using iron oxide-coated sand Water Air Soil Poll 142 (1-4) 95-111USEPA 2008 Assessing arsenic removal by metal (hydr)oxide adsorptive media using rapid small scale column tests Govenrnment Printing Office Washington DCWang J Xu W Chen L Huang X Liu J 2014 Preparation and evaluation of magnetic nanoparticles impregnated chitosan beads for arsenic removal from water Chem Eng J 251 25-34Westerhoff P Highfield D Badruzzaman M Yoon Y 2005 Rapid small-scale column tests for arsenate removal in iron oxide packed bed columns J Environ Eng-Asce 131 (2) 262-271Westerhoff P De Haan M Martindale A Badruzzaman M 2006 Arsenic adsorptive media technology selection strategies Water Qual Res J Can 41 (2) 171-184Yan L Huang Y Cui J Jing C 2015 Simultaneous As(III) and Cd removal from copper smelting wastewater using granular TiO2 columns Water Res 68 (0) 572-579Zhao K Guo HM 2014 Behavior and mechanism of arsenate adsorption on activated natural siderite Evidences from FTIR and XANES analysis Environ Sci Pollut Res 21 (3) 1944-1953Zhao K Guo H Zhou X 2014 Adsorption and heterogeneous oxidation of arsenite on modified granular natural siderite Characterization and behaviors Appl Geochem 48 184-192
Table S6 Comparison of the adsorption capacities of As(III) and As(V) on GTiO2 and the representative granular adsorbents in similar experimental condition from the literature
AdsorbentParticle size (mm) As
qm
(mgg)Dose (gL) Experimental conditions Literature
GTiO2 018~025 As(III) 980 1 0~500 mgL at pH 82 01 M NaCl This studyGTiO2 018~025 As(V) 358 1 0~500 mgL at pH 82 01 M NaCl This study
Granular TiO2 015~06 As(III) 392 10~60 mgL As at pH 70 in simulated groundwater (100 mgL Ca 20 mgL Mg 50 mgL Na 200 mgL Cl-
)(Bang et al 2005)
Granular TiO2 015~06 As(V) 400 10~60 mgL As at pH 70 in simulated groundwater (100 mgL Ca 20 mgL Mg 50 mgL Na 200 mgL Cl-
)(Bang et al 2005)
E33 (FeOOH)0044~0075 As(V) 202 1 0~15 mgL at pH 70 in 001 M NaCl
(Kanematsu et al 2010)
E33 (FeOOH) 05~2 As(V) 180 1 0~50 mgL at pH 70 in 004 M NaClO4 (Jing et al 2012)
GFH 02~06 As(V) 650 10 0~2000 mgL at pH 8 in 01 M NaNO3
(Guan et al 2008)
GFH0009~0125 As(V) 23 025 0~07 μgL at pH 65 in DI water
(Banerjee et al 2008)
GFH0009~0125 As(V) 200 - 0~01 μgL at pH 70 in DI water
(Badruzzaman et al 2004)
GFH 050~065 As(V) 155 - 0~06 μgL at pH 70 in DI water (Saha et al 2005)
GHFO-NN 015~030 As(V) 330 0001 0~225 mgL at pH 8 in DI water(Streat et al 2008)
GHFO-VL 015~030 As(V) 360 0001 0~225 mgL at pH 8 in DI water(Streat et al 2008)
25
374375
Spherical schwertmannite 1~15 As(V) 36 05 0~5 mgL at pH 70 in DI water (Dou et al 2013)Cylindrical schwertmannite 1~25 As(V) 223 05
0~5 mgL at pH 70 in DI water(Dou et al 2013)
Irregular schwertmannite 10~16 As(V) 317 05 0~5 mgL at pH 70 in DI water (Dou et al 2013)Fe impregnated chitosan beads (MICB) 25 As(III) 117 1 0~05 mgL at pH 60 in DI water
(Wang et al 2014)
MICB 25 As(V) 191 1 0~1 mgL at pH 60 in DI water(Wang et al 2014)
MICB 25 As(III) 353 1 0~15 mgL at pH 60 in DI water(Wang et al 2014)
MICB 25 As(V) 357 1 0~16 mgL at pH 60 in DI water(Wang et al 2014)
Iron hydroxide granules (GIH) 3~4 As(V) 23 4
5~100 mgL at pH 70 in 10 mgL SO42-
14 mgL NH4Cl buffer solution (Daus et al 2004)
Activated Al2O3
0074~0149 As(V) 159 - 285~115 mgL at pH 52 in DI water
(Lin and Wu 2001)
Activated Al2O3
0074~0149 As(III) 35 - 079~490 mgL at pH 70 in DI water
(Lin and Wu 2001)
Activated Al2O3 ~20 As(V) 73 at pH 70 in 004 M NaClO4 (Jing et al 2012)
Activated natural siderite 05~10 As(V) 22 10 0 1~20 mgL at pH 7 in DI water(Zhao and Guo 2014)
Polyaluminum Granulate 1~3 As(III) 705 10 0~150 mgL at pH 51-56 in DI water(Mertens et al 2012)
Polyaluminum Granulate 1~3 As(V) 180 10 0~150 mgL at pH 51-56 in DI water (Mertens et al
26
2012)
Acidified laterite 1~12 As(III) 19 1 025~5 mgL at pH 7 in 100 mgL NaHCO3
(Glocheux et al 2013)
Acidified laterite 1~12 As(V) 13 1 025~5 mgL at pH 7 in 100 mgL NaHCO3
(Glocheux et al 2013)
Laterite 1~12 As(III) 07 1025~5 mgL at pH 7 in 100 mgL NaHCO3 (Glocheux et al
2013)
Laterite 1~12 As(V) 04 1025~5 mgL at pH 7 in 100 mgL NaHCO3 (Glocheux et al
2013)
Treated laterite 03-05 As(V) 216 05 02-20 mgL at pH 70 in DI water(Maiti et al 2012)
Treated laterite 03-05 As(III) 94 05 02-20 mgL at pH 70 in DI water(Maiti et al 2012)
Treated laterite03-05
As(V) 241 05 02-20 mgL at pH 70 in DI water(Maiti et al 2010a)
Treated laterite03-05
As(III) 81 05 02-20 mgL at pH 70 in DI water(Maiti et al 2010a)
Acid-activated laterite-103-07
As(III) 0633 50 02-10 mgL at pH 66-70 in DI water(Maiti et al 2010b)
Acid-activated laterite-203-07
As(III) 087650 02-10 mgL at pH 66-70 in DI water (Maiti et al
2010b)
Acid-activated laterite-303-07
As(III) 063450 02-10 mgL at pH 66-70 in DI water (Maiti et al
2010b)
Acid-activated laterite-103-07
As(V) 059850 02-10 mgL at pH 66-70 in DI water (Maiti et al
2010b)
27
Acid-activated laterite-203-07
As(V) 07550 02-10 mgL at pH 66-70 in DI water (Maiti et al
2010b)
Acid-activated laterite-303-07
As(V) 07550 02-10 mgL at pH 66-70 in DI water (Maiti et al
2010b)
Treated laterite-1 03-06 As(V) 019 20 0-20 mgL As at pH 72 in DI water(Maiti et al 2013b)
Treated laterite-1 03-06 As(III) 018 20 0-20 mgL As at pH 72 in DI water(Maiti et al 2013b)
Treated laterite-2 03-06 As(V) 004 20 0-20 mgL As at pH 72 in DI water(Maiti et al 2013b)
Treated laterite-2 03-06 As(III) 003 20 0-20 mgL As at pH 72 in DI water(Maiti et al 2013b)
Treated laterite-3 03-06 As(V) 007 20 0-20 mgL As at pH 72 in DI water(Maiti et al 2013b)
Treated laterite-3 03-06 As(III) 004 20 0-20 mgL As at pH 72 in DI water(Maiti et al 2013b)
28
376377
Charge distribution multi-site surface complexation (CD-MUSIC) modeling
The CD-MUSIC model with the 2-pK TPM adsorption option was used to
describe adsorption behaviors of As cations and anions on GTiO2 The CD-MUSIC
model incorporates the structural information of surfaces adsorbed species and the
double layers by distributing the charge of an adsorbate between the surface and
interfacial water (Hiemstra and Van Riemsdijk 2006) The CD-MUSIC model has
been successfully used in describing As adsorption in batch experiments (Pena et al
2006 Stachowicz et al 2008)
The adsorption constants of counter ions were set to -1 and the proton affinity
constant was set to the PZC of 58 for TiOH-13 (Luo et al 2010) The charge
distribution (CD) value shows the fraction (f) of the charge of the central As ion
attributed to the surface plane and the remaining part (1-f) was attributed to the other
ligands of the complex which were positioned toward the diffuse layer The CD value
for As surface complexes was obtained by fitting the experimental data The
calculation was performed using the chemical equilibrium program MINTEQ to
simulate the adsorption and the aqueous reactions
29
378379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
Fig S32 Adsorption of silicate (a) calcium and magnesium (b) as a function of GTiO2
dose in groundwater 1 The solid lines represent the CD-MUSIC modeling result
30
400
401
402
403
404
405
406
407
408409410
Table S75 Surface parameters and species used in the CD-MUSIC modeling in As(IIIV) removal under different GTiO2 dose in 01 M NaCl and groundwater 1 in Fig 2 and Fig S32
= exp(-FΨ1RT) P2 = exp(-FΨ2RT) F the Faraday constant (C mol-1) R the gas constant (J mol-1 K-1) T the absolute temperature (K)
Ψ0 Ψ1 Ψ2 the electrostatic potential (V) of 0- 1- and 2-plane respectively alogK for 01 M NaCl at 6 hours blogK for 01 M NaCl at 6 days clogK for groundwater 1 at 6 days
31
411412
413414415
32
416
Table S86 The charge distribution (f) of central As atom to TiO2 surface in simulating the effect of cations and anions on As adsorption in 01 M NaCl at pH 82 in Fig 4 BK Si HCO3 All
As(V) 022 017 012 016As(III) 040 020 058 056
Fig S43 Molar percentage () of As Ca Mg and Si on pristine and spent GTiO2
surfaces using EDX analysis The spent GTiO2 samples after field column experiments using groundwater 1 were identified with EBCT in min under x-axis The value of molar percentage of each element was averaged from randomly-chosen positions on the adsorbent surface
33
417
418
419420
421422
423
424
425
426
427
428
429
430
431
432
433434435436437438
439
440
441
As speciation analysis on spent GTiO2 using XANES
The spent GTiO2 samples were ground using a mortar and pestle and then the
ground powder was spread on Scotch tape The As k-edge XANES spectra were
collected at beamline 01C1 at the National Synchrotron Radiation Research Center
(NSRRC) Taiwan Spectra were acquired from -150 to 300 eV relative to the As K-
edge of 11867 eV at cryogenic temperature (77 K) using a cryostat to prevent the
oxidation of As(III) by X-rays The fluorescence signals were collected using a Lytle
detector Two to four scans were collected for each sample and averaged to improve
the signalnoise ratio The XANES analysis was performed with the Athena program
in the IFEFFIT computer package for linear combination fit (LCF) (Cui et al 2013
Ravel and Newville 2005)
34
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
PHREEQC modeling for As breakthrough curves in field column experiments
PHREEQC a geochemical model integrates macroscopic mass transfer
processes with a microscopic surface complexation model (Parkhurst and Appelo
2013) It can be applied in calculating solution complex speciation batch-reaction
and one-dimensional reactive-transport and inverse modeling In our study the one-
dimensional column was defined by four cells with the same length The cell length
was calculated to be one-fourth of the actual column length Time step (s) was
calculated according to equation Time step = Lcell(Q60A) where Lcell is the cell
length (cm) Q is flow velocity (mLmin) A is the effective column cross section area
(cm2) which is the column cross-sectional area multiplied by porosity (060) Total
shift number was calculated by dividing actual column operation time by the time
step The transport block was modeled by shifting the solute content from one cell to
the next one In each cell the aqueous solute was mixed and adsorbed on GTiO2
according to the equations In each cell the aqueous solute was mixed and assumed to
be in equilibration with GTiO2 The sequence of shifting mixing and equilibrium
adsorption was repeated for each cell until the total number of shifts was completed
The diffusion coefficient Dw in PHREEQC accounting for retardation was
calculated as Dw=x2
(36t) where x stands for the diffusion length (estimated as the
radius of the particle size) and t represents equilibrium time adopted from the batch
kinetic data (Mertens et al 2012)
For CD-MUSIC modeling in the PHREEQC take As(III) as an example to
explain the adsorption equation The As(III) adsorption is considered as a ligand
35
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
exchange reaction with the hydroxide group on GTiO2 (Surf_sOH-033) forming a
H3ArseniteO3 is the master species in groundwater at pH 82
(Surf_sO)2ArseniteOH-066 is the common adsorbed bidentate binuclear complex
evidenced by our previous reports(Pena et al 2006 Yan et al 2015) LogK is the
adsorption equilibrium constants Generally every adsorption equation under certain
experimental condition has a unique value of logK In the adsorption equation ldquo-2rdquo
represents the lost two hydrogens by Surf_sOH-033 after it adsorbs H3ArseniteO3 ldquo-
1rdquo represents the change in charge on Arsenite at 1 plane due to gaining one hydrogen
(+1) and one oxygen (-2) ldquo0rdquo represents no change in charge at the 2 plane ldquo066rdquo is
the fraction of the central ion (As) on GTiO2 surface that is associated with plane 0
ldquo3rdquo is the charge on the central ion As(III) Following this equation and the relevant
parameters As(III) adsorbed on GTiO2
The diffusion coefficient Dw in PHREEQC accounting for retardation was
calculated as Dw=x2(36t) where x stands for the diffusion length (estimated as the
radius of the particle size) and t represents equilibrium time adopted from the batch
kinetic data (Mertens et al 2012)
To well simulate the As breakthrough curve in columns four As(V) adsorption
reactions (Table 1) were employed Adsorption site density of 60 mmolg was
36
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
adopted from our previous study (Pena et al 2006) and the total adsorption sites were
calculated to be 1844 sitesnm2 The final optimized ratio of strong to weak sites was
51 The surface complexation constants were reasonably adjusted according to the
batch modeling results as the column reaction may not reach equilibrium in local
micro-interfacial areas due to much less contact time between As and GTiO2 than that
in batch experiments (Appelo and Postma 1999) In the modeling a stepwise
procedure was adopted to achieve a viable result An estimation of two thirds of the
surface site density being accessible for EBCT=011 min with large flow rate of 265
mLmin was optimized which could probably result from unavailable adsorption sites
due to fast transport through the column
The adsorbed As on GTiO2 in the column was calculated by mass balance
between the influent and effluent
where Asadsorbed is the adsorbed As on GTiO2 (mgg) n is the number of collected
samples Cin and Cout are influent and effluent As concentrations (mgL) respectively
Vi is volume (L) of groundwater passed through the column between sample i-1 and i
and m is the mass of GTiO2 (g)
Even though the oxidation of adsorbed As(III) occurred during filtration as
analyzed from XANES and mass balance analysis (Fig 7) no As(III) oxidation
reactions were considered in PHREEQC modeling which would not impact the
breakthrough of As(IIIV)
37
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
38
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
Fig S54 Effect of EBCT on Si Ca and Mg breakthrough curves using groundwater 1 The sample notation in panel c indicates field column experiments with EBCT in minutes
References
Appelo CAJ Postma D 1999 A consistent model for surface complexation on birnessite (MnO2) and its application to a column experiment Geochim Cosmochim Ac 63 (19-20) 3039-3048Badruzzaman M Westerhoff P Knappe DRU 2004 Intraparticle diffusion and adsorption of arsenate onto granular ferric hydroxide (GFH) Water Res 38 (18) 4002-4012Banerjee K Amy GL Prevost M Nour S Jekel M Gallagher PM Blumenschein CD 2008 Kinetic and thermodynamic aspects of adsorption of arsenic onto granular ferric hydroxide (GFH) Water Res 42 (13) 3371-3378Bang S Patel M Lippincott L Meng XG 2005 Removal of arsenic from groundwater by granular titanium dioxide adsorbent Chemosphere 60 (3) 389-397Bang S Pena ME Patel M Lippincott L Meng X Kim KW 2011 Removal of arsenate from water by adsorbents a comparative case study Environ Geochem Hlth 33 133-141Cui JL Shi JB Jiang GB Jing CY 2013 Arsenic levels and speciation from ingestion exposures to biomarkers in Shanxi China Implications for human health Environ Sci Technol 47 (10) 5419-5424Daus B Wennrich R Weiss H 2004 Sorption materials for arsenic removal from water A comparative study Water Res 38 (12) 2948-2954Dou XM Mohan D Pittman CU 2013 Arsenate adsorption on three types of granular schwertmannite Water Res 47 (9) 2938-2948Dou XM Zhang Y Yang M Pei YS Huang X Takayama T Kato S 2006 Occurrence of arsenic in groundwater in the suburbs of Beijing and its removal using an iron-cerium bimetal oxide adsorbent Water Qual Res J Can 41 (2) 140-146Gibbons MK Gagnon GA 2010 Adsorption of arsenic from a Nova Scotia groundwater onto water treatment residual solids Water Res 44 (19) 5740-5749Glocheux Y Mendez Pasarin M Albadarin AB Allen SJ Walker GM 2013 Removal of arsenic from groundwater by adsorption onto an acidified laterite by-product Chem Eng J 228 565-574Guan XH Wang JM Chusuei CC 2008 Removal of arsenic from water using granular ferric hydroxide Macroscopic and microscopic studies J Hazard Mater 156 (1-3) 178-185Gupta K Maity A Ghosh UC 2010 Manganese associated nanoparticles agglomerate of iron(III) oxide Synthesis characterization and arsenic(III) sorption behavior with mechanism J Hazard Mater 184 (1-3) 832-842Hao JM Han MJ Wang C Meng XG 2009 Enhanced removal of arsenite from water by a mesoporous hybrid material - Thiol-functionalized silica coated activated alumina Micropor Mesopor
Mat 124 (1-3) 1-7Hiemstra T Van Riemsdijk WH 2006 On the relationship between charge distribution surface hydration and the structure of the interface of metal hydroxides J Colloid Interf Sci 301 (1) 1-18Hristovski K Baumgardner A Westerhoff P 2007 Selecting metal oxide nanomaterials for arsenic removal in fixed bed columns From nanopowders to aggregated nanoparticle media J Hazard Mater 147 (1-2) 265-274Jang M Chen WF Cannon FS 2008 Preloading hydrous ferric oxide into granular activated carbon for arsenic removal Environ Sci Technol 42 (9) 3369-3374Jing CY Cui JL Huang YY Li AG 2012 Fabrication characterization and application of a composite adsorbent for simultaneous removal of arsenic and fluoride ACS Appl Mater Interfaces 4 (2) 714-720Kanematsu M Young TM Fukushi K Green PG Darby JL 2010 Extended triple layer modeling of arsenate and phosphate adsorption on a goethite-based granular porous adsorbent Environ Sci Technol 44 (9) 3388-3394Kong S Wang Y Zhan H Yuan S Liu M Zhou C 2013 Arsenite and Arsenate Removal from Contaminated Groundwater by Nanoscale Iron-Manganese Binary Oxides Column Studies Environmental Engineering Science 30 (11) 689-696Li Y Liu JR Jia SY Guo JW Zhuo J Na P 2012 TiO2 pillared montmorillonite as a photoactive adsorbent of arsenic under UV irradiation Chem Eng J 191 66-74Lin TF Wu JK 2001 Adsorption of arsenite and arsenate within activated alumina grains Equilibrium and kinetics Water Res 35 (8) 2049-2057Luo T Cui JL Hu S Huang YY Jing CY 2010 Arsenic removal and recovery from copper smelting wastewater using TiO2 Environ Sci Technol 44 (23) 9094-9098Maiti A Basu JK De S 2010a Development of a Treated Laterite for Arsenic Adsorption Effects of Treatment Parameters Industrial amp Engineering Chemistry Research 49 (10) 4873-4886Maiti A Basu JK De S 2010b Removal of Arsenic from Synthetic and Natural Groundwater Using Acid-Activated Laterite Environmental Progress amp Sustainable Energy 29 (4) 457-470Maiti A Basu JK De S 2012 Experimental and kinetic modeling of As(V) and As(III) adsorption on treated laterite using synthetic and contaminated groundwater Effects of phosphate silicate and carbonate ions Chem Eng J 191 1-12Maiti A Thakur BK Basu JK De S 2013a Comparison of treated laterite as arsenic adsorbent from different locations and performance of best filter under field conditions J Hazard Mater 262 1176-1186Maiti A Thakur BK Basu JK De S 2013b Comparison of treated laterite as arsenic adsorbent from different locations and performance of best filter under field conditions J Hazard Mater 262 (0) 1176-1186Maji SK Pal A Pal T 2008 Arsenic removal from real-life groundwater by adsorption on laterite soil J Hazard Mater 151 (2-3) 811-820Maji SK Kao YH Wang CJ Lu GS Wu JJ Liu CW 2012 Fixed bed adsorption of As(III) on iron-oxide-coated natural rock (IOCNR) and application to real arsenic-bearing groundwater Chem Eng J 203 285-293Mertens J Rose J Kagi R Chaurand P Plotze M Wehrli B Furrer G 2012 Adsorption of arsenic on polyaluminum granulate Environ Sci Technol 46 (13) 7310-7317Nguyen TV Vigneswaran S Ngo HH Pokhre D Viraraghavan T 2006 Iron-coated sponge as
effective media to remove arsenic from drinking water Water Qual Res J Can 41 (2) 164-170Parkhurst DL Appelo CAJ 2013 Description of input and examples for PHREEQC version 3-A computer program for speciation batch-reaction one-dimensional transport and inverse geochemical calculations US Geological SurveyPena M Meng XG Korfiatis GP Jing CY 2006 Adsorption mechanism of arsenic on nanocrystalline titanium dioxide Environ Sci Technol 40 (4) 1257-1262Ravel B Newville M 2005 ATHENA ARTEMIS HEPHAESTUS Data analysis for X-ray absorption spectroscopy using IFEFFIT J Synchrotron Radiat 12 537-541Saha B Bains R Greenwood F 2005 Physicochemical characterization of granular ferric hydroxide (GFH) for arsenic(V) sorption from water Separation Science and Technology 40 (14) 2909-2932Shan H Ma T Wang Y Zhao J Han H Deng Y He X Dong Y 2013 A cost-effective system for in-situ geological arsenic adsorption from groundwater J Contam Hydrol 154 1-9Stachowicz M Hiemstra T van Riemsdijk WH 2008 Multi-competitive interaction of As(III) and As(V) oxyanions with Ca2+ Mg2+ PO4
3- and CO32- ions on goethite J Colloid Interf Sci 320 (2) 400-
414Streat M Hellgardt K Newton NLR 2008 Hydrous ferric oxide as an adsorbent in water treatment - Part 3 Batch and mini-column adsorption of arsenic phosphorus fluorine and cadmium ions Process Safety and Environmental Protection 86 (B1) 21-30Thirunavukkarasu OS Viraraghavan T Subramanian KS 2003 Arsenic removal from drinking water using iron oxide-coated sand Water Air Soil Poll 142 (1-4) 95-111USEPA 2008 Assessing arsenic removal by metal (hydr)oxide adsorptive media using rapid small scale column tests Govenrnment Printing Office Washington DCWang J Xu W Chen L Huang X Liu J 2014 Preparation and evaluation of magnetic nanoparticles impregnated chitosan beads for arsenic removal from water Chem Eng J 251 25-34Westerhoff P Highfield D Badruzzaman M Yoon Y 2005 Rapid small-scale column tests for arsenate removal in iron oxide packed bed columns J Environ Eng-Asce 131 (2) 262-271Westerhoff P De Haan M Martindale A Badruzzaman M 2006 Arsenic adsorptive media technology selection strategies Water Qual Res J Can 41 (2) 171-184Yan L Huang Y Cui J Jing C 2015 Simultaneous As(III) and Cd removal from copper smelting wastewater using granular TiO2 columns Water Res 68 (0) 572-579Zhao K Guo HM 2014 Behavior and mechanism of arsenate adsorption on activated natural siderite Evidences from FTIR and XANES analysis Environ Sci Pollut Res 21 (3) 1944-1953Zhao K Guo H Zhou X 2014 Adsorption and heterogeneous oxidation of arsenite on modified granular natural siderite Characterization and behaviors Appl Geochem 48 184-192
Table S6 Comparison of the adsorption capacities of As(III) and As(V) on GTiO2 and the representative granular adsorbents in similar experimental condition from the literature
AdsorbentParticle size (mm) As
qm
(mgg)Dose (gL) Experimental conditions Literature
GTiO2 018~025 As(III) 980 1 0~500 mgL at pH 82 01 M NaCl This studyGTiO2 018~025 As(V) 358 1 0~500 mgL at pH 82 01 M NaCl This study
Granular TiO2 015~06 As(III) 392 10~60 mgL As at pH 70 in simulated groundwater (100 mgL Ca 20 mgL Mg 50 mgL Na 200 mgL Cl-
)(Bang et al 2005)
Granular TiO2 015~06 As(V) 400 10~60 mgL As at pH 70 in simulated groundwater (100 mgL Ca 20 mgL Mg 50 mgL Na 200 mgL Cl-
)(Bang et al 2005)
E33 (FeOOH)0044~0075 As(V) 202 1 0~15 mgL at pH 70 in 001 M NaCl
(Kanematsu et al 2010)
E33 (FeOOH) 05~2 As(V) 180 1 0~50 mgL at pH 70 in 004 M NaClO4 (Jing et al 2012)
GFH 02~06 As(V) 650 10 0~2000 mgL at pH 8 in 01 M NaNO3
(Guan et al 2008)
GFH0009~0125 As(V) 23 025 0~07 μgL at pH 65 in DI water
(Banerjee et al 2008)
GFH0009~0125 As(V) 200 - 0~01 μgL at pH 70 in DI water
(Badruzzaman et al 2004)
GFH 050~065 As(V) 155 - 0~06 μgL at pH 70 in DI water (Saha et al 2005)
GHFO-NN 015~030 As(V) 330 0001 0~225 mgL at pH 8 in DI water(Streat et al 2008)
GHFO-VL 015~030 As(V) 360 0001 0~225 mgL at pH 8 in DI water(Streat et al 2008)
25
374375
Spherical schwertmannite 1~15 As(V) 36 05 0~5 mgL at pH 70 in DI water (Dou et al 2013)Cylindrical schwertmannite 1~25 As(V) 223 05
0~5 mgL at pH 70 in DI water(Dou et al 2013)
Irregular schwertmannite 10~16 As(V) 317 05 0~5 mgL at pH 70 in DI water (Dou et al 2013)Fe impregnated chitosan beads (MICB) 25 As(III) 117 1 0~05 mgL at pH 60 in DI water
(Wang et al 2014)
MICB 25 As(V) 191 1 0~1 mgL at pH 60 in DI water(Wang et al 2014)
MICB 25 As(III) 353 1 0~15 mgL at pH 60 in DI water(Wang et al 2014)
MICB 25 As(V) 357 1 0~16 mgL at pH 60 in DI water(Wang et al 2014)
Iron hydroxide granules (GIH) 3~4 As(V) 23 4
5~100 mgL at pH 70 in 10 mgL SO42-
14 mgL NH4Cl buffer solution (Daus et al 2004)
Activated Al2O3
0074~0149 As(V) 159 - 285~115 mgL at pH 52 in DI water
(Lin and Wu 2001)
Activated Al2O3
0074~0149 As(III) 35 - 079~490 mgL at pH 70 in DI water
(Lin and Wu 2001)
Activated Al2O3 ~20 As(V) 73 at pH 70 in 004 M NaClO4 (Jing et al 2012)
Activated natural siderite 05~10 As(V) 22 10 0 1~20 mgL at pH 7 in DI water(Zhao and Guo 2014)
Polyaluminum Granulate 1~3 As(III) 705 10 0~150 mgL at pH 51-56 in DI water(Mertens et al 2012)
Polyaluminum Granulate 1~3 As(V) 180 10 0~150 mgL at pH 51-56 in DI water (Mertens et al
26
2012)
Acidified laterite 1~12 As(III) 19 1 025~5 mgL at pH 7 in 100 mgL NaHCO3
(Glocheux et al 2013)
Acidified laterite 1~12 As(V) 13 1 025~5 mgL at pH 7 in 100 mgL NaHCO3
(Glocheux et al 2013)
Laterite 1~12 As(III) 07 1025~5 mgL at pH 7 in 100 mgL NaHCO3 (Glocheux et al
2013)
Laterite 1~12 As(V) 04 1025~5 mgL at pH 7 in 100 mgL NaHCO3 (Glocheux et al
2013)
Treated laterite 03-05 As(V) 216 05 02-20 mgL at pH 70 in DI water(Maiti et al 2012)
Treated laterite 03-05 As(III) 94 05 02-20 mgL at pH 70 in DI water(Maiti et al 2012)
Treated laterite03-05
As(V) 241 05 02-20 mgL at pH 70 in DI water(Maiti et al 2010a)
Treated laterite03-05
As(III) 81 05 02-20 mgL at pH 70 in DI water(Maiti et al 2010a)
Acid-activated laterite-103-07
As(III) 0633 50 02-10 mgL at pH 66-70 in DI water(Maiti et al 2010b)
Acid-activated laterite-203-07
As(III) 087650 02-10 mgL at pH 66-70 in DI water (Maiti et al
2010b)
Acid-activated laterite-303-07
As(III) 063450 02-10 mgL at pH 66-70 in DI water (Maiti et al
2010b)
Acid-activated laterite-103-07
As(V) 059850 02-10 mgL at pH 66-70 in DI water (Maiti et al
2010b)
27
Acid-activated laterite-203-07
As(V) 07550 02-10 mgL at pH 66-70 in DI water (Maiti et al
2010b)
Acid-activated laterite-303-07
As(V) 07550 02-10 mgL at pH 66-70 in DI water (Maiti et al
2010b)
Treated laterite-1 03-06 As(V) 019 20 0-20 mgL As at pH 72 in DI water(Maiti et al 2013b)
Treated laterite-1 03-06 As(III) 018 20 0-20 mgL As at pH 72 in DI water(Maiti et al 2013b)
Treated laterite-2 03-06 As(V) 004 20 0-20 mgL As at pH 72 in DI water(Maiti et al 2013b)
Treated laterite-2 03-06 As(III) 003 20 0-20 mgL As at pH 72 in DI water(Maiti et al 2013b)
Treated laterite-3 03-06 As(V) 007 20 0-20 mgL As at pH 72 in DI water(Maiti et al 2013b)
Treated laterite-3 03-06 As(III) 004 20 0-20 mgL As at pH 72 in DI water(Maiti et al 2013b)
28
376377
Charge distribution multi-site surface complexation (CD-MUSIC) modeling
The CD-MUSIC model with the 2-pK TPM adsorption option was used to
describe adsorption behaviors of As cations and anions on GTiO2 The CD-MUSIC
model incorporates the structural information of surfaces adsorbed species and the
double layers by distributing the charge of an adsorbate between the surface and
interfacial water (Hiemstra and Van Riemsdijk 2006) The CD-MUSIC model has
been successfully used in describing As adsorption in batch experiments (Pena et al
2006 Stachowicz et al 2008)
The adsorption constants of counter ions were set to -1 and the proton affinity
constant was set to the PZC of 58 for TiOH-13 (Luo et al 2010) The charge
distribution (CD) value shows the fraction (f) of the charge of the central As ion
attributed to the surface plane and the remaining part (1-f) was attributed to the other
ligands of the complex which were positioned toward the diffuse layer The CD value
for As surface complexes was obtained by fitting the experimental data The
calculation was performed using the chemical equilibrium program MINTEQ to
simulate the adsorption and the aqueous reactions
29
378379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
Fig S32 Adsorption of silicate (a) calcium and magnesium (b) as a function of GTiO2
dose in groundwater 1 The solid lines represent the CD-MUSIC modeling result
30
400
401
402
403
404
405
406
407
408409410
Table S75 Surface parameters and species used in the CD-MUSIC modeling in As(IIIV) removal under different GTiO2 dose in 01 M NaCl and groundwater 1 in Fig 2 and Fig S32
= exp(-FΨ1RT) P2 = exp(-FΨ2RT) F the Faraday constant (C mol-1) R the gas constant (J mol-1 K-1) T the absolute temperature (K)
Ψ0 Ψ1 Ψ2 the electrostatic potential (V) of 0- 1- and 2-plane respectively alogK for 01 M NaCl at 6 hours blogK for 01 M NaCl at 6 days clogK for groundwater 1 at 6 days
31
411412
413414415
32
416
Table S86 The charge distribution (f) of central As atom to TiO2 surface in simulating the effect of cations and anions on As adsorption in 01 M NaCl at pH 82 in Fig 4 BK Si HCO3 All
As(V) 022 017 012 016As(III) 040 020 058 056
Fig S43 Molar percentage () of As Ca Mg and Si on pristine and spent GTiO2
surfaces using EDX analysis The spent GTiO2 samples after field column experiments using groundwater 1 were identified with EBCT in min under x-axis The value of molar percentage of each element was averaged from randomly-chosen positions on the adsorbent surface
33
417
418
419420
421422
423
424
425
426
427
428
429
430
431
432
433434435436437438
439
440
441
As speciation analysis on spent GTiO2 using XANES
The spent GTiO2 samples were ground using a mortar and pestle and then the
ground powder was spread on Scotch tape The As k-edge XANES spectra were
collected at beamline 01C1 at the National Synchrotron Radiation Research Center
(NSRRC) Taiwan Spectra were acquired from -150 to 300 eV relative to the As K-
edge of 11867 eV at cryogenic temperature (77 K) using a cryostat to prevent the
oxidation of As(III) by X-rays The fluorescence signals were collected using a Lytle
detector Two to four scans were collected for each sample and averaged to improve
the signalnoise ratio The XANES analysis was performed with the Athena program
in the IFEFFIT computer package for linear combination fit (LCF) (Cui et al 2013
Ravel and Newville 2005)
34
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
PHREEQC modeling for As breakthrough curves in field column experiments
PHREEQC a geochemical model integrates macroscopic mass transfer
processes with a microscopic surface complexation model (Parkhurst and Appelo
2013) It can be applied in calculating solution complex speciation batch-reaction
and one-dimensional reactive-transport and inverse modeling In our study the one-
dimensional column was defined by four cells with the same length The cell length
was calculated to be one-fourth of the actual column length Time step (s) was
calculated according to equation Time step = Lcell(Q60A) where Lcell is the cell
length (cm) Q is flow velocity (mLmin) A is the effective column cross section area
(cm2) which is the column cross-sectional area multiplied by porosity (060) Total
shift number was calculated by dividing actual column operation time by the time
step The transport block was modeled by shifting the solute content from one cell to
the next one In each cell the aqueous solute was mixed and adsorbed on GTiO2
according to the equations In each cell the aqueous solute was mixed and assumed to
be in equilibration with GTiO2 The sequence of shifting mixing and equilibrium
adsorption was repeated for each cell until the total number of shifts was completed
The diffusion coefficient Dw in PHREEQC accounting for retardation was
calculated as Dw=x2
(36t) where x stands for the diffusion length (estimated as the
radius of the particle size) and t represents equilibrium time adopted from the batch
kinetic data (Mertens et al 2012)
For CD-MUSIC modeling in the PHREEQC take As(III) as an example to
explain the adsorption equation The As(III) adsorption is considered as a ligand
35
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
exchange reaction with the hydroxide group on GTiO2 (Surf_sOH-033) forming a
H3ArseniteO3 is the master species in groundwater at pH 82
(Surf_sO)2ArseniteOH-066 is the common adsorbed bidentate binuclear complex
evidenced by our previous reports(Pena et al 2006 Yan et al 2015) LogK is the
adsorption equilibrium constants Generally every adsorption equation under certain
experimental condition has a unique value of logK In the adsorption equation ldquo-2rdquo
represents the lost two hydrogens by Surf_sOH-033 after it adsorbs H3ArseniteO3 ldquo-
1rdquo represents the change in charge on Arsenite at 1 plane due to gaining one hydrogen
(+1) and one oxygen (-2) ldquo0rdquo represents no change in charge at the 2 plane ldquo066rdquo is
the fraction of the central ion (As) on GTiO2 surface that is associated with plane 0
ldquo3rdquo is the charge on the central ion As(III) Following this equation and the relevant
parameters As(III) adsorbed on GTiO2
The diffusion coefficient Dw in PHREEQC accounting for retardation was
calculated as Dw=x2(36t) where x stands for the diffusion length (estimated as the
radius of the particle size) and t represents equilibrium time adopted from the batch
kinetic data (Mertens et al 2012)
To well simulate the As breakthrough curve in columns four As(V) adsorption
reactions (Table 1) were employed Adsorption site density of 60 mmolg was
36
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
adopted from our previous study (Pena et al 2006) and the total adsorption sites were
calculated to be 1844 sitesnm2 The final optimized ratio of strong to weak sites was
51 The surface complexation constants were reasonably adjusted according to the
batch modeling results as the column reaction may not reach equilibrium in local
micro-interfacial areas due to much less contact time between As and GTiO2 than that
in batch experiments (Appelo and Postma 1999) In the modeling a stepwise
procedure was adopted to achieve a viable result An estimation of two thirds of the
surface site density being accessible for EBCT=011 min with large flow rate of 265
mLmin was optimized which could probably result from unavailable adsorption sites
due to fast transport through the column
The adsorbed As on GTiO2 in the column was calculated by mass balance
between the influent and effluent
where Asadsorbed is the adsorbed As on GTiO2 (mgg) n is the number of collected
samples Cin and Cout are influent and effluent As concentrations (mgL) respectively
Vi is volume (L) of groundwater passed through the column between sample i-1 and i
and m is the mass of GTiO2 (g)
Even though the oxidation of adsorbed As(III) occurred during filtration as
analyzed from XANES and mass balance analysis (Fig 7) no As(III) oxidation
reactions were considered in PHREEQC modeling which would not impact the
breakthrough of As(IIIV)
37
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
38
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
Fig S54 Effect of EBCT on Si Ca and Mg breakthrough curves using groundwater 1 The sample notation in panel c indicates field column experiments with EBCT in minutes
References
Appelo CAJ Postma D 1999 A consistent model for surface complexation on birnessite (MnO2) and its application to a column experiment Geochim Cosmochim Ac 63 (19-20) 3039-3048Badruzzaman M Westerhoff P Knappe DRU 2004 Intraparticle diffusion and adsorption of arsenate onto granular ferric hydroxide (GFH) Water Res 38 (18) 4002-4012Banerjee K Amy GL Prevost M Nour S Jekel M Gallagher PM Blumenschein CD 2008 Kinetic and thermodynamic aspects of adsorption of arsenic onto granular ferric hydroxide (GFH) Water Res 42 (13) 3371-3378Bang S Patel M Lippincott L Meng XG 2005 Removal of arsenic from groundwater by granular titanium dioxide adsorbent Chemosphere 60 (3) 389-397Bang S Pena ME Patel M Lippincott L Meng X Kim KW 2011 Removal of arsenate from water by adsorbents a comparative case study Environ Geochem Hlth 33 133-141Cui JL Shi JB Jiang GB Jing CY 2013 Arsenic levels and speciation from ingestion exposures to biomarkers in Shanxi China Implications for human health Environ Sci Technol 47 (10) 5419-5424Daus B Wennrich R Weiss H 2004 Sorption materials for arsenic removal from water A comparative study Water Res 38 (12) 2948-2954Dou XM Mohan D Pittman CU 2013 Arsenate adsorption on three types of granular schwertmannite Water Res 47 (9) 2938-2948Dou XM Zhang Y Yang M Pei YS Huang X Takayama T Kato S 2006 Occurrence of arsenic in groundwater in the suburbs of Beijing and its removal using an iron-cerium bimetal oxide adsorbent Water Qual Res J Can 41 (2) 140-146Gibbons MK Gagnon GA 2010 Adsorption of arsenic from a Nova Scotia groundwater onto water treatment residual solids Water Res 44 (19) 5740-5749Glocheux Y Mendez Pasarin M Albadarin AB Allen SJ Walker GM 2013 Removal of arsenic from groundwater by adsorption onto an acidified laterite by-product Chem Eng J 228 565-574Guan XH Wang JM Chusuei CC 2008 Removal of arsenic from water using granular ferric hydroxide Macroscopic and microscopic studies J Hazard Mater 156 (1-3) 178-185Gupta K Maity A Ghosh UC 2010 Manganese associated nanoparticles agglomerate of iron(III) oxide Synthesis characterization and arsenic(III) sorption behavior with mechanism J Hazard Mater 184 (1-3) 832-842Hao JM Han MJ Wang C Meng XG 2009 Enhanced removal of arsenite from water by a mesoporous hybrid material - Thiol-functionalized silica coated activated alumina Micropor Mesopor
Mat 124 (1-3) 1-7Hiemstra T Van Riemsdijk WH 2006 On the relationship between charge distribution surface hydration and the structure of the interface of metal hydroxides J Colloid Interf Sci 301 (1) 1-18Hristovski K Baumgardner A Westerhoff P 2007 Selecting metal oxide nanomaterials for arsenic removal in fixed bed columns From nanopowders to aggregated nanoparticle media J Hazard Mater 147 (1-2) 265-274Jang M Chen WF Cannon FS 2008 Preloading hydrous ferric oxide into granular activated carbon for arsenic removal Environ Sci Technol 42 (9) 3369-3374Jing CY Cui JL Huang YY Li AG 2012 Fabrication characterization and application of a composite adsorbent for simultaneous removal of arsenic and fluoride ACS Appl Mater Interfaces 4 (2) 714-720Kanematsu M Young TM Fukushi K Green PG Darby JL 2010 Extended triple layer modeling of arsenate and phosphate adsorption on a goethite-based granular porous adsorbent Environ Sci Technol 44 (9) 3388-3394Kong S Wang Y Zhan H Yuan S Liu M Zhou C 2013 Arsenite and Arsenate Removal from Contaminated Groundwater by Nanoscale Iron-Manganese Binary Oxides Column Studies Environmental Engineering Science 30 (11) 689-696Li Y Liu JR Jia SY Guo JW Zhuo J Na P 2012 TiO2 pillared montmorillonite as a photoactive adsorbent of arsenic under UV irradiation Chem Eng J 191 66-74Lin TF Wu JK 2001 Adsorption of arsenite and arsenate within activated alumina grains Equilibrium and kinetics Water Res 35 (8) 2049-2057Luo T Cui JL Hu S Huang YY Jing CY 2010 Arsenic removal and recovery from copper smelting wastewater using TiO2 Environ Sci Technol 44 (23) 9094-9098Maiti A Basu JK De S 2010a Development of a Treated Laterite for Arsenic Adsorption Effects of Treatment Parameters Industrial amp Engineering Chemistry Research 49 (10) 4873-4886Maiti A Basu JK De S 2010b Removal of Arsenic from Synthetic and Natural Groundwater Using Acid-Activated Laterite Environmental Progress amp Sustainable Energy 29 (4) 457-470Maiti A Basu JK De S 2012 Experimental and kinetic modeling of As(V) and As(III) adsorption on treated laterite using synthetic and contaminated groundwater Effects of phosphate silicate and carbonate ions Chem Eng J 191 1-12Maiti A Thakur BK Basu JK De S 2013a Comparison of treated laterite as arsenic adsorbent from different locations and performance of best filter under field conditions J Hazard Mater 262 1176-1186Maiti A Thakur BK Basu JK De S 2013b Comparison of treated laterite as arsenic adsorbent from different locations and performance of best filter under field conditions J Hazard Mater 262 (0) 1176-1186Maji SK Pal A Pal T 2008 Arsenic removal from real-life groundwater by adsorption on laterite soil J Hazard Mater 151 (2-3) 811-820Maji SK Kao YH Wang CJ Lu GS Wu JJ Liu CW 2012 Fixed bed adsorption of As(III) on iron-oxide-coated natural rock (IOCNR) and application to real arsenic-bearing groundwater Chem Eng J 203 285-293Mertens J Rose J Kagi R Chaurand P Plotze M Wehrli B Furrer G 2012 Adsorption of arsenic on polyaluminum granulate Environ Sci Technol 46 (13) 7310-7317Nguyen TV Vigneswaran S Ngo HH Pokhre D Viraraghavan T 2006 Iron-coated sponge as
effective media to remove arsenic from drinking water Water Qual Res J Can 41 (2) 164-170Parkhurst DL Appelo CAJ 2013 Description of input and examples for PHREEQC version 3-A computer program for speciation batch-reaction one-dimensional transport and inverse geochemical calculations US Geological SurveyPena M Meng XG Korfiatis GP Jing CY 2006 Adsorption mechanism of arsenic on nanocrystalline titanium dioxide Environ Sci Technol 40 (4) 1257-1262Ravel B Newville M 2005 ATHENA ARTEMIS HEPHAESTUS Data analysis for X-ray absorption spectroscopy using IFEFFIT J Synchrotron Radiat 12 537-541Saha B Bains R Greenwood F 2005 Physicochemical characterization of granular ferric hydroxide (GFH) for arsenic(V) sorption from water Separation Science and Technology 40 (14) 2909-2932Shan H Ma T Wang Y Zhao J Han H Deng Y He X Dong Y 2013 A cost-effective system for in-situ geological arsenic adsorption from groundwater J Contam Hydrol 154 1-9Stachowicz M Hiemstra T van Riemsdijk WH 2008 Multi-competitive interaction of As(III) and As(V) oxyanions with Ca2+ Mg2+ PO4
3- and CO32- ions on goethite J Colloid Interf Sci 320 (2) 400-
414Streat M Hellgardt K Newton NLR 2008 Hydrous ferric oxide as an adsorbent in water treatment - Part 3 Batch and mini-column adsorption of arsenic phosphorus fluorine and cadmium ions Process Safety and Environmental Protection 86 (B1) 21-30Thirunavukkarasu OS Viraraghavan T Subramanian KS 2003 Arsenic removal from drinking water using iron oxide-coated sand Water Air Soil Poll 142 (1-4) 95-111USEPA 2008 Assessing arsenic removal by metal (hydr)oxide adsorptive media using rapid small scale column tests Govenrnment Printing Office Washington DCWang J Xu W Chen L Huang X Liu J 2014 Preparation and evaluation of magnetic nanoparticles impregnated chitosan beads for arsenic removal from water Chem Eng J 251 25-34Westerhoff P Highfield D Badruzzaman M Yoon Y 2005 Rapid small-scale column tests for arsenate removal in iron oxide packed bed columns J Environ Eng-Asce 131 (2) 262-271Westerhoff P De Haan M Martindale A Badruzzaman M 2006 Arsenic adsorptive media technology selection strategies Water Qual Res J Can 41 (2) 171-184Yan L Huang Y Cui J Jing C 2015 Simultaneous As(III) and Cd removal from copper smelting wastewater using granular TiO2 columns Water Res 68 (0) 572-579Zhao K Guo HM 2014 Behavior and mechanism of arsenate adsorption on activated natural siderite Evidences from FTIR and XANES analysis Environ Sci Pollut Res 21 (3) 1944-1953Zhao K Guo H Zhou X 2014 Adsorption and heterogeneous oxidation of arsenite on modified granular natural siderite Characterization and behaviors Appl Geochem 48 184-192
Spherical schwertmannite 1~15 As(V) 36 05 0~5 mgL at pH 70 in DI water (Dou et al 2013)Cylindrical schwertmannite 1~25 As(V) 223 05
0~5 mgL at pH 70 in DI water(Dou et al 2013)
Irregular schwertmannite 10~16 As(V) 317 05 0~5 mgL at pH 70 in DI water (Dou et al 2013)Fe impregnated chitosan beads (MICB) 25 As(III) 117 1 0~05 mgL at pH 60 in DI water
(Wang et al 2014)
MICB 25 As(V) 191 1 0~1 mgL at pH 60 in DI water(Wang et al 2014)
MICB 25 As(III) 353 1 0~15 mgL at pH 60 in DI water(Wang et al 2014)
MICB 25 As(V) 357 1 0~16 mgL at pH 60 in DI water(Wang et al 2014)
Iron hydroxide granules (GIH) 3~4 As(V) 23 4
5~100 mgL at pH 70 in 10 mgL SO42-
14 mgL NH4Cl buffer solution (Daus et al 2004)
Activated Al2O3
0074~0149 As(V) 159 - 285~115 mgL at pH 52 in DI water
(Lin and Wu 2001)
Activated Al2O3
0074~0149 As(III) 35 - 079~490 mgL at pH 70 in DI water
(Lin and Wu 2001)
Activated Al2O3 ~20 As(V) 73 at pH 70 in 004 M NaClO4 (Jing et al 2012)
Activated natural siderite 05~10 As(V) 22 10 0 1~20 mgL at pH 7 in DI water(Zhao and Guo 2014)
Polyaluminum Granulate 1~3 As(III) 705 10 0~150 mgL at pH 51-56 in DI water(Mertens et al 2012)
Polyaluminum Granulate 1~3 As(V) 180 10 0~150 mgL at pH 51-56 in DI water (Mertens et al
26
2012)
Acidified laterite 1~12 As(III) 19 1 025~5 mgL at pH 7 in 100 mgL NaHCO3
(Glocheux et al 2013)
Acidified laterite 1~12 As(V) 13 1 025~5 mgL at pH 7 in 100 mgL NaHCO3
(Glocheux et al 2013)
Laterite 1~12 As(III) 07 1025~5 mgL at pH 7 in 100 mgL NaHCO3 (Glocheux et al
2013)
Laterite 1~12 As(V) 04 1025~5 mgL at pH 7 in 100 mgL NaHCO3 (Glocheux et al
2013)
Treated laterite 03-05 As(V) 216 05 02-20 mgL at pH 70 in DI water(Maiti et al 2012)
Treated laterite 03-05 As(III) 94 05 02-20 mgL at pH 70 in DI water(Maiti et al 2012)
Treated laterite03-05
As(V) 241 05 02-20 mgL at pH 70 in DI water(Maiti et al 2010a)
Treated laterite03-05
As(III) 81 05 02-20 mgL at pH 70 in DI water(Maiti et al 2010a)
Acid-activated laterite-103-07
As(III) 0633 50 02-10 mgL at pH 66-70 in DI water(Maiti et al 2010b)
Acid-activated laterite-203-07
As(III) 087650 02-10 mgL at pH 66-70 in DI water (Maiti et al
2010b)
Acid-activated laterite-303-07
As(III) 063450 02-10 mgL at pH 66-70 in DI water (Maiti et al
2010b)
Acid-activated laterite-103-07
As(V) 059850 02-10 mgL at pH 66-70 in DI water (Maiti et al
2010b)
27
Acid-activated laterite-203-07
As(V) 07550 02-10 mgL at pH 66-70 in DI water (Maiti et al
2010b)
Acid-activated laterite-303-07
As(V) 07550 02-10 mgL at pH 66-70 in DI water (Maiti et al
2010b)
Treated laterite-1 03-06 As(V) 019 20 0-20 mgL As at pH 72 in DI water(Maiti et al 2013b)
Treated laterite-1 03-06 As(III) 018 20 0-20 mgL As at pH 72 in DI water(Maiti et al 2013b)
Treated laterite-2 03-06 As(V) 004 20 0-20 mgL As at pH 72 in DI water(Maiti et al 2013b)
Treated laterite-2 03-06 As(III) 003 20 0-20 mgL As at pH 72 in DI water(Maiti et al 2013b)
Treated laterite-3 03-06 As(V) 007 20 0-20 mgL As at pH 72 in DI water(Maiti et al 2013b)
Treated laterite-3 03-06 As(III) 004 20 0-20 mgL As at pH 72 in DI water(Maiti et al 2013b)
28
376377
Charge distribution multi-site surface complexation (CD-MUSIC) modeling
The CD-MUSIC model with the 2-pK TPM adsorption option was used to
describe adsorption behaviors of As cations and anions on GTiO2 The CD-MUSIC
model incorporates the structural information of surfaces adsorbed species and the
double layers by distributing the charge of an adsorbate between the surface and
interfacial water (Hiemstra and Van Riemsdijk 2006) The CD-MUSIC model has
been successfully used in describing As adsorption in batch experiments (Pena et al
2006 Stachowicz et al 2008)
The adsorption constants of counter ions were set to -1 and the proton affinity
constant was set to the PZC of 58 for TiOH-13 (Luo et al 2010) The charge
distribution (CD) value shows the fraction (f) of the charge of the central As ion
attributed to the surface plane and the remaining part (1-f) was attributed to the other
ligands of the complex which were positioned toward the diffuse layer The CD value
for As surface complexes was obtained by fitting the experimental data The
calculation was performed using the chemical equilibrium program MINTEQ to
simulate the adsorption and the aqueous reactions
29
378379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
Fig S32 Adsorption of silicate (a) calcium and magnesium (b) as a function of GTiO2
dose in groundwater 1 The solid lines represent the CD-MUSIC modeling result
30
400
401
402
403
404
405
406
407
408409410
Table S75 Surface parameters and species used in the CD-MUSIC modeling in As(IIIV) removal under different GTiO2 dose in 01 M NaCl and groundwater 1 in Fig 2 and Fig S32
= exp(-FΨ1RT) P2 = exp(-FΨ2RT) F the Faraday constant (C mol-1) R the gas constant (J mol-1 K-1) T the absolute temperature (K)
Ψ0 Ψ1 Ψ2 the electrostatic potential (V) of 0- 1- and 2-plane respectively alogK for 01 M NaCl at 6 hours blogK for 01 M NaCl at 6 days clogK for groundwater 1 at 6 days
31
411412
413414415
32
416
Table S86 The charge distribution (f) of central As atom to TiO2 surface in simulating the effect of cations and anions on As adsorption in 01 M NaCl at pH 82 in Fig 4 BK Si HCO3 All
As(V) 022 017 012 016As(III) 040 020 058 056
Fig S43 Molar percentage () of As Ca Mg and Si on pristine and spent GTiO2
surfaces using EDX analysis The spent GTiO2 samples after field column experiments using groundwater 1 were identified with EBCT in min under x-axis The value of molar percentage of each element was averaged from randomly-chosen positions on the adsorbent surface
33
417
418
419420
421422
423
424
425
426
427
428
429
430
431
432
433434435436437438
439
440
441
As speciation analysis on spent GTiO2 using XANES
The spent GTiO2 samples were ground using a mortar and pestle and then the
ground powder was spread on Scotch tape The As k-edge XANES spectra were
collected at beamline 01C1 at the National Synchrotron Radiation Research Center
(NSRRC) Taiwan Spectra were acquired from -150 to 300 eV relative to the As K-
edge of 11867 eV at cryogenic temperature (77 K) using a cryostat to prevent the
oxidation of As(III) by X-rays The fluorescence signals were collected using a Lytle
detector Two to four scans were collected for each sample and averaged to improve
the signalnoise ratio The XANES analysis was performed with the Athena program
in the IFEFFIT computer package for linear combination fit (LCF) (Cui et al 2013
Ravel and Newville 2005)
34
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
PHREEQC modeling for As breakthrough curves in field column experiments
PHREEQC a geochemical model integrates macroscopic mass transfer
processes with a microscopic surface complexation model (Parkhurst and Appelo
2013) It can be applied in calculating solution complex speciation batch-reaction
and one-dimensional reactive-transport and inverse modeling In our study the one-
dimensional column was defined by four cells with the same length The cell length
was calculated to be one-fourth of the actual column length Time step (s) was
calculated according to equation Time step = Lcell(Q60A) where Lcell is the cell
length (cm) Q is flow velocity (mLmin) A is the effective column cross section area
(cm2) which is the column cross-sectional area multiplied by porosity (060) Total
shift number was calculated by dividing actual column operation time by the time
step The transport block was modeled by shifting the solute content from one cell to
the next one In each cell the aqueous solute was mixed and adsorbed on GTiO2
according to the equations In each cell the aqueous solute was mixed and assumed to
be in equilibration with GTiO2 The sequence of shifting mixing and equilibrium
adsorption was repeated for each cell until the total number of shifts was completed
The diffusion coefficient Dw in PHREEQC accounting for retardation was
calculated as Dw=x2
(36t) where x stands for the diffusion length (estimated as the
radius of the particle size) and t represents equilibrium time adopted from the batch
kinetic data (Mertens et al 2012)
For CD-MUSIC modeling in the PHREEQC take As(III) as an example to
explain the adsorption equation The As(III) adsorption is considered as a ligand
35
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
exchange reaction with the hydroxide group on GTiO2 (Surf_sOH-033) forming a
H3ArseniteO3 is the master species in groundwater at pH 82
(Surf_sO)2ArseniteOH-066 is the common adsorbed bidentate binuclear complex
evidenced by our previous reports(Pena et al 2006 Yan et al 2015) LogK is the
adsorption equilibrium constants Generally every adsorption equation under certain
experimental condition has a unique value of logK In the adsorption equation ldquo-2rdquo
represents the lost two hydrogens by Surf_sOH-033 after it adsorbs H3ArseniteO3 ldquo-
1rdquo represents the change in charge on Arsenite at 1 plane due to gaining one hydrogen
(+1) and one oxygen (-2) ldquo0rdquo represents no change in charge at the 2 plane ldquo066rdquo is
the fraction of the central ion (As) on GTiO2 surface that is associated with plane 0
ldquo3rdquo is the charge on the central ion As(III) Following this equation and the relevant
parameters As(III) adsorbed on GTiO2
The diffusion coefficient Dw in PHREEQC accounting for retardation was
calculated as Dw=x2(36t) where x stands for the diffusion length (estimated as the
radius of the particle size) and t represents equilibrium time adopted from the batch
kinetic data (Mertens et al 2012)
To well simulate the As breakthrough curve in columns four As(V) adsorption
reactions (Table 1) were employed Adsorption site density of 60 mmolg was
36
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
adopted from our previous study (Pena et al 2006) and the total adsorption sites were
calculated to be 1844 sitesnm2 The final optimized ratio of strong to weak sites was
51 The surface complexation constants were reasonably adjusted according to the
batch modeling results as the column reaction may not reach equilibrium in local
micro-interfacial areas due to much less contact time between As and GTiO2 than that
in batch experiments (Appelo and Postma 1999) In the modeling a stepwise
procedure was adopted to achieve a viable result An estimation of two thirds of the
surface site density being accessible for EBCT=011 min with large flow rate of 265
mLmin was optimized which could probably result from unavailable adsorption sites
due to fast transport through the column
The adsorbed As on GTiO2 in the column was calculated by mass balance
between the influent and effluent
where Asadsorbed is the adsorbed As on GTiO2 (mgg) n is the number of collected
samples Cin and Cout are influent and effluent As concentrations (mgL) respectively
Vi is volume (L) of groundwater passed through the column between sample i-1 and i
and m is the mass of GTiO2 (g)
Even though the oxidation of adsorbed As(III) occurred during filtration as
analyzed from XANES and mass balance analysis (Fig 7) no As(III) oxidation
reactions were considered in PHREEQC modeling which would not impact the
breakthrough of As(IIIV)
37
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
38
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
Fig S54 Effect of EBCT on Si Ca and Mg breakthrough curves using groundwater 1 The sample notation in panel c indicates field column experiments with EBCT in minutes
References
Appelo CAJ Postma D 1999 A consistent model for surface complexation on birnessite (MnO2) and its application to a column experiment Geochim Cosmochim Ac 63 (19-20) 3039-3048Badruzzaman M Westerhoff P Knappe DRU 2004 Intraparticle diffusion and adsorption of arsenate onto granular ferric hydroxide (GFH) Water Res 38 (18) 4002-4012Banerjee K Amy GL Prevost M Nour S Jekel M Gallagher PM Blumenschein CD 2008 Kinetic and thermodynamic aspects of adsorption of arsenic onto granular ferric hydroxide (GFH) Water Res 42 (13) 3371-3378Bang S Patel M Lippincott L Meng XG 2005 Removal of arsenic from groundwater by granular titanium dioxide adsorbent Chemosphere 60 (3) 389-397Bang S Pena ME Patel M Lippincott L Meng X Kim KW 2011 Removal of arsenate from water by adsorbents a comparative case study Environ Geochem Hlth 33 133-141Cui JL Shi JB Jiang GB Jing CY 2013 Arsenic levels and speciation from ingestion exposures to biomarkers in Shanxi China Implications for human health Environ Sci Technol 47 (10) 5419-5424Daus B Wennrich R Weiss H 2004 Sorption materials for arsenic removal from water A comparative study Water Res 38 (12) 2948-2954Dou XM Mohan D Pittman CU 2013 Arsenate adsorption on three types of granular schwertmannite Water Res 47 (9) 2938-2948Dou XM Zhang Y Yang M Pei YS Huang X Takayama T Kato S 2006 Occurrence of arsenic in groundwater in the suburbs of Beijing and its removal using an iron-cerium bimetal oxide adsorbent Water Qual Res J Can 41 (2) 140-146Gibbons MK Gagnon GA 2010 Adsorption of arsenic from a Nova Scotia groundwater onto water treatment residual solids Water Res 44 (19) 5740-5749Glocheux Y Mendez Pasarin M Albadarin AB Allen SJ Walker GM 2013 Removal of arsenic from groundwater by adsorption onto an acidified laterite by-product Chem Eng J 228 565-574Guan XH Wang JM Chusuei CC 2008 Removal of arsenic from water using granular ferric hydroxide Macroscopic and microscopic studies J Hazard Mater 156 (1-3) 178-185Gupta K Maity A Ghosh UC 2010 Manganese associated nanoparticles agglomerate of iron(III) oxide Synthesis characterization and arsenic(III) sorption behavior with mechanism J Hazard Mater 184 (1-3) 832-842Hao JM Han MJ Wang C Meng XG 2009 Enhanced removal of arsenite from water by a mesoporous hybrid material - Thiol-functionalized silica coated activated alumina Micropor Mesopor
Mat 124 (1-3) 1-7Hiemstra T Van Riemsdijk WH 2006 On the relationship between charge distribution surface hydration and the structure of the interface of metal hydroxides J Colloid Interf Sci 301 (1) 1-18Hristovski K Baumgardner A Westerhoff P 2007 Selecting metal oxide nanomaterials for arsenic removal in fixed bed columns From nanopowders to aggregated nanoparticle media J Hazard Mater 147 (1-2) 265-274Jang M Chen WF Cannon FS 2008 Preloading hydrous ferric oxide into granular activated carbon for arsenic removal Environ Sci Technol 42 (9) 3369-3374Jing CY Cui JL Huang YY Li AG 2012 Fabrication characterization and application of a composite adsorbent for simultaneous removal of arsenic and fluoride ACS Appl Mater Interfaces 4 (2) 714-720Kanematsu M Young TM Fukushi K Green PG Darby JL 2010 Extended triple layer modeling of arsenate and phosphate adsorption on a goethite-based granular porous adsorbent Environ Sci Technol 44 (9) 3388-3394Kong S Wang Y Zhan H Yuan S Liu M Zhou C 2013 Arsenite and Arsenate Removal from Contaminated Groundwater by Nanoscale Iron-Manganese Binary Oxides Column Studies Environmental Engineering Science 30 (11) 689-696Li Y Liu JR Jia SY Guo JW Zhuo J Na P 2012 TiO2 pillared montmorillonite as a photoactive adsorbent of arsenic under UV irradiation Chem Eng J 191 66-74Lin TF Wu JK 2001 Adsorption of arsenite and arsenate within activated alumina grains Equilibrium and kinetics Water Res 35 (8) 2049-2057Luo T Cui JL Hu S Huang YY Jing CY 2010 Arsenic removal and recovery from copper smelting wastewater using TiO2 Environ Sci Technol 44 (23) 9094-9098Maiti A Basu JK De S 2010a Development of a Treated Laterite for Arsenic Adsorption Effects of Treatment Parameters Industrial amp Engineering Chemistry Research 49 (10) 4873-4886Maiti A Basu JK De S 2010b Removal of Arsenic from Synthetic and Natural Groundwater Using Acid-Activated Laterite Environmental Progress amp Sustainable Energy 29 (4) 457-470Maiti A Basu JK De S 2012 Experimental and kinetic modeling of As(V) and As(III) adsorption on treated laterite using synthetic and contaminated groundwater Effects of phosphate silicate and carbonate ions Chem Eng J 191 1-12Maiti A Thakur BK Basu JK De S 2013a Comparison of treated laterite as arsenic adsorbent from different locations and performance of best filter under field conditions J Hazard Mater 262 1176-1186Maiti A Thakur BK Basu JK De S 2013b Comparison of treated laterite as arsenic adsorbent from different locations and performance of best filter under field conditions J Hazard Mater 262 (0) 1176-1186Maji SK Pal A Pal T 2008 Arsenic removal from real-life groundwater by adsorption on laterite soil J Hazard Mater 151 (2-3) 811-820Maji SK Kao YH Wang CJ Lu GS Wu JJ Liu CW 2012 Fixed bed adsorption of As(III) on iron-oxide-coated natural rock (IOCNR) and application to real arsenic-bearing groundwater Chem Eng J 203 285-293Mertens J Rose J Kagi R Chaurand P Plotze M Wehrli B Furrer G 2012 Adsorption of arsenic on polyaluminum granulate Environ Sci Technol 46 (13) 7310-7317Nguyen TV Vigneswaran S Ngo HH Pokhre D Viraraghavan T 2006 Iron-coated sponge as
effective media to remove arsenic from drinking water Water Qual Res J Can 41 (2) 164-170Parkhurst DL Appelo CAJ 2013 Description of input and examples for PHREEQC version 3-A computer program for speciation batch-reaction one-dimensional transport and inverse geochemical calculations US Geological SurveyPena M Meng XG Korfiatis GP Jing CY 2006 Adsorption mechanism of arsenic on nanocrystalline titanium dioxide Environ Sci Technol 40 (4) 1257-1262Ravel B Newville M 2005 ATHENA ARTEMIS HEPHAESTUS Data analysis for X-ray absorption spectroscopy using IFEFFIT J Synchrotron Radiat 12 537-541Saha B Bains R Greenwood F 2005 Physicochemical characterization of granular ferric hydroxide (GFH) for arsenic(V) sorption from water Separation Science and Technology 40 (14) 2909-2932Shan H Ma T Wang Y Zhao J Han H Deng Y He X Dong Y 2013 A cost-effective system for in-situ geological arsenic adsorption from groundwater J Contam Hydrol 154 1-9Stachowicz M Hiemstra T van Riemsdijk WH 2008 Multi-competitive interaction of As(III) and As(V) oxyanions with Ca2+ Mg2+ PO4
3- and CO32- ions on goethite J Colloid Interf Sci 320 (2) 400-
414Streat M Hellgardt K Newton NLR 2008 Hydrous ferric oxide as an adsorbent in water treatment - Part 3 Batch and mini-column adsorption of arsenic phosphorus fluorine and cadmium ions Process Safety and Environmental Protection 86 (B1) 21-30Thirunavukkarasu OS Viraraghavan T Subramanian KS 2003 Arsenic removal from drinking water using iron oxide-coated sand Water Air Soil Poll 142 (1-4) 95-111USEPA 2008 Assessing arsenic removal by metal (hydr)oxide adsorptive media using rapid small scale column tests Govenrnment Printing Office Washington DCWang J Xu W Chen L Huang X Liu J 2014 Preparation and evaluation of magnetic nanoparticles impregnated chitosan beads for arsenic removal from water Chem Eng J 251 25-34Westerhoff P Highfield D Badruzzaman M Yoon Y 2005 Rapid small-scale column tests for arsenate removal in iron oxide packed bed columns J Environ Eng-Asce 131 (2) 262-271Westerhoff P De Haan M Martindale A Badruzzaman M 2006 Arsenic adsorptive media technology selection strategies Water Qual Res J Can 41 (2) 171-184Yan L Huang Y Cui J Jing C 2015 Simultaneous As(III) and Cd removal from copper smelting wastewater using granular TiO2 columns Water Res 68 (0) 572-579Zhao K Guo HM 2014 Behavior and mechanism of arsenate adsorption on activated natural siderite Evidences from FTIR and XANES analysis Environ Sci Pollut Res 21 (3) 1944-1953Zhao K Guo H Zhou X 2014 Adsorption and heterogeneous oxidation of arsenite on modified granular natural siderite Characterization and behaviors Appl Geochem 48 184-192
Acidified laterite 1~12 As(III) 19 1 025~5 mgL at pH 7 in 100 mgL NaHCO3
(Glocheux et al 2013)
Acidified laterite 1~12 As(V) 13 1 025~5 mgL at pH 7 in 100 mgL NaHCO3
(Glocheux et al 2013)
Laterite 1~12 As(III) 07 1025~5 mgL at pH 7 in 100 mgL NaHCO3 (Glocheux et al
2013)
Laterite 1~12 As(V) 04 1025~5 mgL at pH 7 in 100 mgL NaHCO3 (Glocheux et al
2013)
Treated laterite 03-05 As(V) 216 05 02-20 mgL at pH 70 in DI water(Maiti et al 2012)
Treated laterite 03-05 As(III) 94 05 02-20 mgL at pH 70 in DI water(Maiti et al 2012)
Treated laterite03-05
As(V) 241 05 02-20 mgL at pH 70 in DI water(Maiti et al 2010a)
Treated laterite03-05
As(III) 81 05 02-20 mgL at pH 70 in DI water(Maiti et al 2010a)
Acid-activated laterite-103-07
As(III) 0633 50 02-10 mgL at pH 66-70 in DI water(Maiti et al 2010b)
Acid-activated laterite-203-07
As(III) 087650 02-10 mgL at pH 66-70 in DI water (Maiti et al
2010b)
Acid-activated laterite-303-07
As(III) 063450 02-10 mgL at pH 66-70 in DI water (Maiti et al
2010b)
Acid-activated laterite-103-07
As(V) 059850 02-10 mgL at pH 66-70 in DI water (Maiti et al
2010b)
27
Acid-activated laterite-203-07
As(V) 07550 02-10 mgL at pH 66-70 in DI water (Maiti et al
2010b)
Acid-activated laterite-303-07
As(V) 07550 02-10 mgL at pH 66-70 in DI water (Maiti et al
2010b)
Treated laterite-1 03-06 As(V) 019 20 0-20 mgL As at pH 72 in DI water(Maiti et al 2013b)
Treated laterite-1 03-06 As(III) 018 20 0-20 mgL As at pH 72 in DI water(Maiti et al 2013b)
Treated laterite-2 03-06 As(V) 004 20 0-20 mgL As at pH 72 in DI water(Maiti et al 2013b)
Treated laterite-2 03-06 As(III) 003 20 0-20 mgL As at pH 72 in DI water(Maiti et al 2013b)
Treated laterite-3 03-06 As(V) 007 20 0-20 mgL As at pH 72 in DI water(Maiti et al 2013b)
Treated laterite-3 03-06 As(III) 004 20 0-20 mgL As at pH 72 in DI water(Maiti et al 2013b)
28
376377
Charge distribution multi-site surface complexation (CD-MUSIC) modeling
The CD-MUSIC model with the 2-pK TPM adsorption option was used to
describe adsorption behaviors of As cations and anions on GTiO2 The CD-MUSIC
model incorporates the structural information of surfaces adsorbed species and the
double layers by distributing the charge of an adsorbate between the surface and
interfacial water (Hiemstra and Van Riemsdijk 2006) The CD-MUSIC model has
been successfully used in describing As adsorption in batch experiments (Pena et al
2006 Stachowicz et al 2008)
The adsorption constants of counter ions were set to -1 and the proton affinity
constant was set to the PZC of 58 for TiOH-13 (Luo et al 2010) The charge
distribution (CD) value shows the fraction (f) of the charge of the central As ion
attributed to the surface plane and the remaining part (1-f) was attributed to the other
ligands of the complex which were positioned toward the diffuse layer The CD value
for As surface complexes was obtained by fitting the experimental data The
calculation was performed using the chemical equilibrium program MINTEQ to
simulate the adsorption and the aqueous reactions
29
378379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
Fig S32 Adsorption of silicate (a) calcium and magnesium (b) as a function of GTiO2
dose in groundwater 1 The solid lines represent the CD-MUSIC modeling result
30
400
401
402
403
404
405
406
407
408409410
Table S75 Surface parameters and species used in the CD-MUSIC modeling in As(IIIV) removal under different GTiO2 dose in 01 M NaCl and groundwater 1 in Fig 2 and Fig S32
= exp(-FΨ1RT) P2 = exp(-FΨ2RT) F the Faraday constant (C mol-1) R the gas constant (J mol-1 K-1) T the absolute temperature (K)
Ψ0 Ψ1 Ψ2 the electrostatic potential (V) of 0- 1- and 2-plane respectively alogK for 01 M NaCl at 6 hours blogK for 01 M NaCl at 6 days clogK for groundwater 1 at 6 days
31
411412
413414415
32
416
Table S86 The charge distribution (f) of central As atom to TiO2 surface in simulating the effect of cations and anions on As adsorption in 01 M NaCl at pH 82 in Fig 4 BK Si HCO3 All
As(V) 022 017 012 016As(III) 040 020 058 056
Fig S43 Molar percentage () of As Ca Mg and Si on pristine and spent GTiO2
surfaces using EDX analysis The spent GTiO2 samples after field column experiments using groundwater 1 were identified with EBCT in min under x-axis The value of molar percentage of each element was averaged from randomly-chosen positions on the adsorbent surface
33
417
418
419420
421422
423
424
425
426
427
428
429
430
431
432
433434435436437438
439
440
441
As speciation analysis on spent GTiO2 using XANES
The spent GTiO2 samples were ground using a mortar and pestle and then the
ground powder was spread on Scotch tape The As k-edge XANES spectra were
collected at beamline 01C1 at the National Synchrotron Radiation Research Center
(NSRRC) Taiwan Spectra were acquired from -150 to 300 eV relative to the As K-
edge of 11867 eV at cryogenic temperature (77 K) using a cryostat to prevent the
oxidation of As(III) by X-rays The fluorescence signals were collected using a Lytle
detector Two to four scans were collected for each sample and averaged to improve
the signalnoise ratio The XANES analysis was performed with the Athena program
in the IFEFFIT computer package for linear combination fit (LCF) (Cui et al 2013
Ravel and Newville 2005)
34
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
PHREEQC modeling for As breakthrough curves in field column experiments
PHREEQC a geochemical model integrates macroscopic mass transfer
processes with a microscopic surface complexation model (Parkhurst and Appelo
2013) It can be applied in calculating solution complex speciation batch-reaction
and one-dimensional reactive-transport and inverse modeling In our study the one-
dimensional column was defined by four cells with the same length The cell length
was calculated to be one-fourth of the actual column length Time step (s) was
calculated according to equation Time step = Lcell(Q60A) where Lcell is the cell
length (cm) Q is flow velocity (mLmin) A is the effective column cross section area
(cm2) which is the column cross-sectional area multiplied by porosity (060) Total
shift number was calculated by dividing actual column operation time by the time
step The transport block was modeled by shifting the solute content from one cell to
the next one In each cell the aqueous solute was mixed and adsorbed on GTiO2
according to the equations In each cell the aqueous solute was mixed and assumed to
be in equilibration with GTiO2 The sequence of shifting mixing and equilibrium
adsorption was repeated for each cell until the total number of shifts was completed
The diffusion coefficient Dw in PHREEQC accounting for retardation was
calculated as Dw=x2
(36t) where x stands for the diffusion length (estimated as the
radius of the particle size) and t represents equilibrium time adopted from the batch
kinetic data (Mertens et al 2012)
For CD-MUSIC modeling in the PHREEQC take As(III) as an example to
explain the adsorption equation The As(III) adsorption is considered as a ligand
35
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
exchange reaction with the hydroxide group on GTiO2 (Surf_sOH-033) forming a
H3ArseniteO3 is the master species in groundwater at pH 82
(Surf_sO)2ArseniteOH-066 is the common adsorbed bidentate binuclear complex
evidenced by our previous reports(Pena et al 2006 Yan et al 2015) LogK is the
adsorption equilibrium constants Generally every adsorption equation under certain
experimental condition has a unique value of logK In the adsorption equation ldquo-2rdquo
represents the lost two hydrogens by Surf_sOH-033 after it adsorbs H3ArseniteO3 ldquo-
1rdquo represents the change in charge on Arsenite at 1 plane due to gaining one hydrogen
(+1) and one oxygen (-2) ldquo0rdquo represents no change in charge at the 2 plane ldquo066rdquo is
the fraction of the central ion (As) on GTiO2 surface that is associated with plane 0
ldquo3rdquo is the charge on the central ion As(III) Following this equation and the relevant
parameters As(III) adsorbed on GTiO2
The diffusion coefficient Dw in PHREEQC accounting for retardation was
calculated as Dw=x2(36t) where x stands for the diffusion length (estimated as the
radius of the particle size) and t represents equilibrium time adopted from the batch
kinetic data (Mertens et al 2012)
To well simulate the As breakthrough curve in columns four As(V) adsorption
reactions (Table 1) were employed Adsorption site density of 60 mmolg was
36
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
adopted from our previous study (Pena et al 2006) and the total adsorption sites were
calculated to be 1844 sitesnm2 The final optimized ratio of strong to weak sites was
51 The surface complexation constants were reasonably adjusted according to the
batch modeling results as the column reaction may not reach equilibrium in local
micro-interfacial areas due to much less contact time between As and GTiO2 than that
in batch experiments (Appelo and Postma 1999) In the modeling a stepwise
procedure was adopted to achieve a viable result An estimation of two thirds of the
surface site density being accessible for EBCT=011 min with large flow rate of 265
mLmin was optimized which could probably result from unavailable adsorption sites
due to fast transport through the column
The adsorbed As on GTiO2 in the column was calculated by mass balance
between the influent and effluent
where Asadsorbed is the adsorbed As on GTiO2 (mgg) n is the number of collected
samples Cin and Cout are influent and effluent As concentrations (mgL) respectively
Vi is volume (L) of groundwater passed through the column between sample i-1 and i
and m is the mass of GTiO2 (g)
Even though the oxidation of adsorbed As(III) occurred during filtration as
analyzed from XANES and mass balance analysis (Fig 7) no As(III) oxidation
reactions were considered in PHREEQC modeling which would not impact the
breakthrough of As(IIIV)
37
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
38
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
Fig S54 Effect of EBCT on Si Ca and Mg breakthrough curves using groundwater 1 The sample notation in panel c indicates field column experiments with EBCT in minutes
References
Appelo CAJ Postma D 1999 A consistent model for surface complexation on birnessite (MnO2) and its application to a column experiment Geochim Cosmochim Ac 63 (19-20) 3039-3048Badruzzaman M Westerhoff P Knappe DRU 2004 Intraparticle diffusion and adsorption of arsenate onto granular ferric hydroxide (GFH) Water Res 38 (18) 4002-4012Banerjee K Amy GL Prevost M Nour S Jekel M Gallagher PM Blumenschein CD 2008 Kinetic and thermodynamic aspects of adsorption of arsenic onto granular ferric hydroxide (GFH) Water Res 42 (13) 3371-3378Bang S Patel M Lippincott L Meng XG 2005 Removal of arsenic from groundwater by granular titanium dioxide adsorbent Chemosphere 60 (3) 389-397Bang S Pena ME Patel M Lippincott L Meng X Kim KW 2011 Removal of arsenate from water by adsorbents a comparative case study Environ Geochem Hlth 33 133-141Cui JL Shi JB Jiang GB Jing CY 2013 Arsenic levels and speciation from ingestion exposures to biomarkers in Shanxi China Implications for human health Environ Sci Technol 47 (10) 5419-5424Daus B Wennrich R Weiss H 2004 Sorption materials for arsenic removal from water A comparative study Water Res 38 (12) 2948-2954Dou XM Mohan D Pittman CU 2013 Arsenate adsorption on three types of granular schwertmannite Water Res 47 (9) 2938-2948Dou XM Zhang Y Yang M Pei YS Huang X Takayama T Kato S 2006 Occurrence of arsenic in groundwater in the suburbs of Beijing and its removal using an iron-cerium bimetal oxide adsorbent Water Qual Res J Can 41 (2) 140-146Gibbons MK Gagnon GA 2010 Adsorption of arsenic from a Nova Scotia groundwater onto water treatment residual solids Water Res 44 (19) 5740-5749Glocheux Y Mendez Pasarin M Albadarin AB Allen SJ Walker GM 2013 Removal of arsenic from groundwater by adsorption onto an acidified laterite by-product Chem Eng J 228 565-574Guan XH Wang JM Chusuei CC 2008 Removal of arsenic from water using granular ferric hydroxide Macroscopic and microscopic studies J Hazard Mater 156 (1-3) 178-185Gupta K Maity A Ghosh UC 2010 Manganese associated nanoparticles agglomerate of iron(III) oxide Synthesis characterization and arsenic(III) sorption behavior with mechanism J Hazard Mater 184 (1-3) 832-842Hao JM Han MJ Wang C Meng XG 2009 Enhanced removal of arsenite from water by a mesoporous hybrid material - Thiol-functionalized silica coated activated alumina Micropor Mesopor
Mat 124 (1-3) 1-7Hiemstra T Van Riemsdijk WH 2006 On the relationship between charge distribution surface hydration and the structure of the interface of metal hydroxides J Colloid Interf Sci 301 (1) 1-18Hristovski K Baumgardner A Westerhoff P 2007 Selecting metal oxide nanomaterials for arsenic removal in fixed bed columns From nanopowders to aggregated nanoparticle media J Hazard Mater 147 (1-2) 265-274Jang M Chen WF Cannon FS 2008 Preloading hydrous ferric oxide into granular activated carbon for arsenic removal Environ Sci Technol 42 (9) 3369-3374Jing CY Cui JL Huang YY Li AG 2012 Fabrication characterization and application of a composite adsorbent for simultaneous removal of arsenic and fluoride ACS Appl Mater Interfaces 4 (2) 714-720Kanematsu M Young TM Fukushi K Green PG Darby JL 2010 Extended triple layer modeling of arsenate and phosphate adsorption on a goethite-based granular porous adsorbent Environ Sci Technol 44 (9) 3388-3394Kong S Wang Y Zhan H Yuan S Liu M Zhou C 2013 Arsenite and Arsenate Removal from Contaminated Groundwater by Nanoscale Iron-Manganese Binary Oxides Column Studies Environmental Engineering Science 30 (11) 689-696Li Y Liu JR Jia SY Guo JW Zhuo J Na P 2012 TiO2 pillared montmorillonite as a photoactive adsorbent of arsenic under UV irradiation Chem Eng J 191 66-74Lin TF Wu JK 2001 Adsorption of arsenite and arsenate within activated alumina grains Equilibrium and kinetics Water Res 35 (8) 2049-2057Luo T Cui JL Hu S Huang YY Jing CY 2010 Arsenic removal and recovery from copper smelting wastewater using TiO2 Environ Sci Technol 44 (23) 9094-9098Maiti A Basu JK De S 2010a Development of a Treated Laterite for Arsenic Adsorption Effects of Treatment Parameters Industrial amp Engineering Chemistry Research 49 (10) 4873-4886Maiti A Basu JK De S 2010b Removal of Arsenic from Synthetic and Natural Groundwater Using Acid-Activated Laterite Environmental Progress amp Sustainable Energy 29 (4) 457-470Maiti A Basu JK De S 2012 Experimental and kinetic modeling of As(V) and As(III) adsorption on treated laterite using synthetic and contaminated groundwater Effects of phosphate silicate and carbonate ions Chem Eng J 191 1-12Maiti A Thakur BK Basu JK De S 2013a Comparison of treated laterite as arsenic adsorbent from different locations and performance of best filter under field conditions J Hazard Mater 262 1176-1186Maiti A Thakur BK Basu JK De S 2013b Comparison of treated laterite as arsenic adsorbent from different locations and performance of best filter under field conditions J Hazard Mater 262 (0) 1176-1186Maji SK Pal A Pal T 2008 Arsenic removal from real-life groundwater by adsorption on laterite soil J Hazard Mater 151 (2-3) 811-820Maji SK Kao YH Wang CJ Lu GS Wu JJ Liu CW 2012 Fixed bed adsorption of As(III) on iron-oxide-coated natural rock (IOCNR) and application to real arsenic-bearing groundwater Chem Eng J 203 285-293Mertens J Rose J Kagi R Chaurand P Plotze M Wehrli B Furrer G 2012 Adsorption of arsenic on polyaluminum granulate Environ Sci Technol 46 (13) 7310-7317Nguyen TV Vigneswaran S Ngo HH Pokhre D Viraraghavan T 2006 Iron-coated sponge as
effective media to remove arsenic from drinking water Water Qual Res J Can 41 (2) 164-170Parkhurst DL Appelo CAJ 2013 Description of input and examples for PHREEQC version 3-A computer program for speciation batch-reaction one-dimensional transport and inverse geochemical calculations US Geological SurveyPena M Meng XG Korfiatis GP Jing CY 2006 Adsorption mechanism of arsenic on nanocrystalline titanium dioxide Environ Sci Technol 40 (4) 1257-1262Ravel B Newville M 2005 ATHENA ARTEMIS HEPHAESTUS Data analysis for X-ray absorption spectroscopy using IFEFFIT J Synchrotron Radiat 12 537-541Saha B Bains R Greenwood F 2005 Physicochemical characterization of granular ferric hydroxide (GFH) for arsenic(V) sorption from water Separation Science and Technology 40 (14) 2909-2932Shan H Ma T Wang Y Zhao J Han H Deng Y He X Dong Y 2013 A cost-effective system for in-situ geological arsenic adsorption from groundwater J Contam Hydrol 154 1-9Stachowicz M Hiemstra T van Riemsdijk WH 2008 Multi-competitive interaction of As(III) and As(V) oxyanions with Ca2+ Mg2+ PO4
3- and CO32- ions on goethite J Colloid Interf Sci 320 (2) 400-
414Streat M Hellgardt K Newton NLR 2008 Hydrous ferric oxide as an adsorbent in water treatment - Part 3 Batch and mini-column adsorption of arsenic phosphorus fluorine and cadmium ions Process Safety and Environmental Protection 86 (B1) 21-30Thirunavukkarasu OS Viraraghavan T Subramanian KS 2003 Arsenic removal from drinking water using iron oxide-coated sand Water Air Soil Poll 142 (1-4) 95-111USEPA 2008 Assessing arsenic removal by metal (hydr)oxide adsorptive media using rapid small scale column tests Govenrnment Printing Office Washington DCWang J Xu W Chen L Huang X Liu J 2014 Preparation and evaluation of magnetic nanoparticles impregnated chitosan beads for arsenic removal from water Chem Eng J 251 25-34Westerhoff P Highfield D Badruzzaman M Yoon Y 2005 Rapid small-scale column tests for arsenate removal in iron oxide packed bed columns J Environ Eng-Asce 131 (2) 262-271Westerhoff P De Haan M Martindale A Badruzzaman M 2006 Arsenic adsorptive media technology selection strategies Water Qual Res J Can 41 (2) 171-184Yan L Huang Y Cui J Jing C 2015 Simultaneous As(III) and Cd removal from copper smelting wastewater using granular TiO2 columns Water Res 68 (0) 572-579Zhao K Guo HM 2014 Behavior and mechanism of arsenate adsorption on activated natural siderite Evidences from FTIR and XANES analysis Environ Sci Pollut Res 21 (3) 1944-1953Zhao K Guo H Zhou X 2014 Adsorption and heterogeneous oxidation of arsenite on modified granular natural siderite Characterization and behaviors Appl Geochem 48 184-192
As(V) 07550 02-10 mgL at pH 66-70 in DI water (Maiti et al
2010b)
Acid-activated laterite-303-07
As(V) 07550 02-10 mgL at pH 66-70 in DI water (Maiti et al
2010b)
Treated laterite-1 03-06 As(V) 019 20 0-20 mgL As at pH 72 in DI water(Maiti et al 2013b)
Treated laterite-1 03-06 As(III) 018 20 0-20 mgL As at pH 72 in DI water(Maiti et al 2013b)
Treated laterite-2 03-06 As(V) 004 20 0-20 mgL As at pH 72 in DI water(Maiti et al 2013b)
Treated laterite-2 03-06 As(III) 003 20 0-20 mgL As at pH 72 in DI water(Maiti et al 2013b)
Treated laterite-3 03-06 As(V) 007 20 0-20 mgL As at pH 72 in DI water(Maiti et al 2013b)
Treated laterite-3 03-06 As(III) 004 20 0-20 mgL As at pH 72 in DI water(Maiti et al 2013b)
28
376377
Charge distribution multi-site surface complexation (CD-MUSIC) modeling
The CD-MUSIC model with the 2-pK TPM adsorption option was used to
describe adsorption behaviors of As cations and anions on GTiO2 The CD-MUSIC
model incorporates the structural information of surfaces adsorbed species and the
double layers by distributing the charge of an adsorbate between the surface and
interfacial water (Hiemstra and Van Riemsdijk 2006) The CD-MUSIC model has
been successfully used in describing As adsorption in batch experiments (Pena et al
2006 Stachowicz et al 2008)
The adsorption constants of counter ions were set to -1 and the proton affinity
constant was set to the PZC of 58 for TiOH-13 (Luo et al 2010) The charge
distribution (CD) value shows the fraction (f) of the charge of the central As ion
attributed to the surface plane and the remaining part (1-f) was attributed to the other
ligands of the complex which were positioned toward the diffuse layer The CD value
for As surface complexes was obtained by fitting the experimental data The
calculation was performed using the chemical equilibrium program MINTEQ to
simulate the adsorption and the aqueous reactions
29
378379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
Fig S32 Adsorption of silicate (a) calcium and magnesium (b) as a function of GTiO2
dose in groundwater 1 The solid lines represent the CD-MUSIC modeling result
30
400
401
402
403
404
405
406
407
408409410
Table S75 Surface parameters and species used in the CD-MUSIC modeling in As(IIIV) removal under different GTiO2 dose in 01 M NaCl and groundwater 1 in Fig 2 and Fig S32
= exp(-FΨ1RT) P2 = exp(-FΨ2RT) F the Faraday constant (C mol-1) R the gas constant (J mol-1 K-1) T the absolute temperature (K)
Ψ0 Ψ1 Ψ2 the electrostatic potential (V) of 0- 1- and 2-plane respectively alogK for 01 M NaCl at 6 hours blogK for 01 M NaCl at 6 days clogK for groundwater 1 at 6 days
31
411412
413414415
32
416
Table S86 The charge distribution (f) of central As atom to TiO2 surface in simulating the effect of cations and anions on As adsorption in 01 M NaCl at pH 82 in Fig 4 BK Si HCO3 All
As(V) 022 017 012 016As(III) 040 020 058 056
Fig S43 Molar percentage () of As Ca Mg and Si on pristine and spent GTiO2
surfaces using EDX analysis The spent GTiO2 samples after field column experiments using groundwater 1 were identified with EBCT in min under x-axis The value of molar percentage of each element was averaged from randomly-chosen positions on the adsorbent surface
33
417
418
419420
421422
423
424
425
426
427
428
429
430
431
432
433434435436437438
439
440
441
As speciation analysis on spent GTiO2 using XANES
The spent GTiO2 samples were ground using a mortar and pestle and then the
ground powder was spread on Scotch tape The As k-edge XANES spectra were
collected at beamline 01C1 at the National Synchrotron Radiation Research Center
(NSRRC) Taiwan Spectra were acquired from -150 to 300 eV relative to the As K-
edge of 11867 eV at cryogenic temperature (77 K) using a cryostat to prevent the
oxidation of As(III) by X-rays The fluorescence signals were collected using a Lytle
detector Two to four scans were collected for each sample and averaged to improve
the signalnoise ratio The XANES analysis was performed with the Athena program
in the IFEFFIT computer package for linear combination fit (LCF) (Cui et al 2013
Ravel and Newville 2005)
34
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
PHREEQC modeling for As breakthrough curves in field column experiments
PHREEQC a geochemical model integrates macroscopic mass transfer
processes with a microscopic surface complexation model (Parkhurst and Appelo
2013) It can be applied in calculating solution complex speciation batch-reaction
and one-dimensional reactive-transport and inverse modeling In our study the one-
dimensional column was defined by four cells with the same length The cell length
was calculated to be one-fourth of the actual column length Time step (s) was
calculated according to equation Time step = Lcell(Q60A) where Lcell is the cell
length (cm) Q is flow velocity (mLmin) A is the effective column cross section area
(cm2) which is the column cross-sectional area multiplied by porosity (060) Total
shift number was calculated by dividing actual column operation time by the time
step The transport block was modeled by shifting the solute content from one cell to
the next one In each cell the aqueous solute was mixed and adsorbed on GTiO2
according to the equations In each cell the aqueous solute was mixed and assumed to
be in equilibration with GTiO2 The sequence of shifting mixing and equilibrium
adsorption was repeated for each cell until the total number of shifts was completed
The diffusion coefficient Dw in PHREEQC accounting for retardation was
calculated as Dw=x2
(36t) where x stands for the diffusion length (estimated as the
radius of the particle size) and t represents equilibrium time adopted from the batch
kinetic data (Mertens et al 2012)
For CD-MUSIC modeling in the PHREEQC take As(III) as an example to
explain the adsorption equation The As(III) adsorption is considered as a ligand
35
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
exchange reaction with the hydroxide group on GTiO2 (Surf_sOH-033) forming a
H3ArseniteO3 is the master species in groundwater at pH 82
(Surf_sO)2ArseniteOH-066 is the common adsorbed bidentate binuclear complex
evidenced by our previous reports(Pena et al 2006 Yan et al 2015) LogK is the
adsorption equilibrium constants Generally every adsorption equation under certain
experimental condition has a unique value of logK In the adsorption equation ldquo-2rdquo
represents the lost two hydrogens by Surf_sOH-033 after it adsorbs H3ArseniteO3 ldquo-
1rdquo represents the change in charge on Arsenite at 1 plane due to gaining one hydrogen
(+1) and one oxygen (-2) ldquo0rdquo represents no change in charge at the 2 plane ldquo066rdquo is
the fraction of the central ion (As) on GTiO2 surface that is associated with plane 0
ldquo3rdquo is the charge on the central ion As(III) Following this equation and the relevant
parameters As(III) adsorbed on GTiO2
The diffusion coefficient Dw in PHREEQC accounting for retardation was
calculated as Dw=x2(36t) where x stands for the diffusion length (estimated as the
radius of the particle size) and t represents equilibrium time adopted from the batch
kinetic data (Mertens et al 2012)
To well simulate the As breakthrough curve in columns four As(V) adsorption
reactions (Table 1) were employed Adsorption site density of 60 mmolg was
36
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
adopted from our previous study (Pena et al 2006) and the total adsorption sites were
calculated to be 1844 sitesnm2 The final optimized ratio of strong to weak sites was
51 The surface complexation constants were reasonably adjusted according to the
batch modeling results as the column reaction may not reach equilibrium in local
micro-interfacial areas due to much less contact time between As and GTiO2 than that
in batch experiments (Appelo and Postma 1999) In the modeling a stepwise
procedure was adopted to achieve a viable result An estimation of two thirds of the
surface site density being accessible for EBCT=011 min with large flow rate of 265
mLmin was optimized which could probably result from unavailable adsorption sites
due to fast transport through the column
The adsorbed As on GTiO2 in the column was calculated by mass balance
between the influent and effluent
where Asadsorbed is the adsorbed As on GTiO2 (mgg) n is the number of collected
samples Cin and Cout are influent and effluent As concentrations (mgL) respectively
Vi is volume (L) of groundwater passed through the column between sample i-1 and i
and m is the mass of GTiO2 (g)
Even though the oxidation of adsorbed As(III) occurred during filtration as
analyzed from XANES and mass balance analysis (Fig 7) no As(III) oxidation
reactions were considered in PHREEQC modeling which would not impact the
breakthrough of As(IIIV)
37
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
38
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
Fig S54 Effect of EBCT on Si Ca and Mg breakthrough curves using groundwater 1 The sample notation in panel c indicates field column experiments with EBCT in minutes
References
Appelo CAJ Postma D 1999 A consistent model for surface complexation on birnessite (MnO2) and its application to a column experiment Geochim Cosmochim Ac 63 (19-20) 3039-3048Badruzzaman M Westerhoff P Knappe DRU 2004 Intraparticle diffusion and adsorption of arsenate onto granular ferric hydroxide (GFH) Water Res 38 (18) 4002-4012Banerjee K Amy GL Prevost M Nour S Jekel M Gallagher PM Blumenschein CD 2008 Kinetic and thermodynamic aspects of adsorption of arsenic onto granular ferric hydroxide (GFH) Water Res 42 (13) 3371-3378Bang S Patel M Lippincott L Meng XG 2005 Removal of arsenic from groundwater by granular titanium dioxide adsorbent Chemosphere 60 (3) 389-397Bang S Pena ME Patel M Lippincott L Meng X Kim KW 2011 Removal of arsenate from water by adsorbents a comparative case study Environ Geochem Hlth 33 133-141Cui JL Shi JB Jiang GB Jing CY 2013 Arsenic levels and speciation from ingestion exposures to biomarkers in Shanxi China Implications for human health Environ Sci Technol 47 (10) 5419-5424Daus B Wennrich R Weiss H 2004 Sorption materials for arsenic removal from water A comparative study Water Res 38 (12) 2948-2954Dou XM Mohan D Pittman CU 2013 Arsenate adsorption on three types of granular schwertmannite Water Res 47 (9) 2938-2948Dou XM Zhang Y Yang M Pei YS Huang X Takayama T Kato S 2006 Occurrence of arsenic in groundwater in the suburbs of Beijing and its removal using an iron-cerium bimetal oxide adsorbent Water Qual Res J Can 41 (2) 140-146Gibbons MK Gagnon GA 2010 Adsorption of arsenic from a Nova Scotia groundwater onto water treatment residual solids Water Res 44 (19) 5740-5749Glocheux Y Mendez Pasarin M Albadarin AB Allen SJ Walker GM 2013 Removal of arsenic from groundwater by adsorption onto an acidified laterite by-product Chem Eng J 228 565-574Guan XH Wang JM Chusuei CC 2008 Removal of arsenic from water using granular ferric hydroxide Macroscopic and microscopic studies J Hazard Mater 156 (1-3) 178-185Gupta K Maity A Ghosh UC 2010 Manganese associated nanoparticles agglomerate of iron(III) oxide Synthesis characterization and arsenic(III) sorption behavior with mechanism J Hazard Mater 184 (1-3) 832-842Hao JM Han MJ Wang C Meng XG 2009 Enhanced removal of arsenite from water by a mesoporous hybrid material - Thiol-functionalized silica coated activated alumina Micropor Mesopor
Mat 124 (1-3) 1-7Hiemstra T Van Riemsdijk WH 2006 On the relationship between charge distribution surface hydration and the structure of the interface of metal hydroxides J Colloid Interf Sci 301 (1) 1-18Hristovski K Baumgardner A Westerhoff P 2007 Selecting metal oxide nanomaterials for arsenic removal in fixed bed columns From nanopowders to aggregated nanoparticle media J Hazard Mater 147 (1-2) 265-274Jang M Chen WF Cannon FS 2008 Preloading hydrous ferric oxide into granular activated carbon for arsenic removal Environ Sci Technol 42 (9) 3369-3374Jing CY Cui JL Huang YY Li AG 2012 Fabrication characterization and application of a composite adsorbent for simultaneous removal of arsenic and fluoride ACS Appl Mater Interfaces 4 (2) 714-720Kanematsu M Young TM Fukushi K Green PG Darby JL 2010 Extended triple layer modeling of arsenate and phosphate adsorption on a goethite-based granular porous adsorbent Environ Sci Technol 44 (9) 3388-3394Kong S Wang Y Zhan H Yuan S Liu M Zhou C 2013 Arsenite and Arsenate Removal from Contaminated Groundwater by Nanoscale Iron-Manganese Binary Oxides Column Studies Environmental Engineering Science 30 (11) 689-696Li Y Liu JR Jia SY Guo JW Zhuo J Na P 2012 TiO2 pillared montmorillonite as a photoactive adsorbent of arsenic under UV irradiation Chem Eng J 191 66-74Lin TF Wu JK 2001 Adsorption of arsenite and arsenate within activated alumina grains Equilibrium and kinetics Water Res 35 (8) 2049-2057Luo T Cui JL Hu S Huang YY Jing CY 2010 Arsenic removal and recovery from copper smelting wastewater using TiO2 Environ Sci Technol 44 (23) 9094-9098Maiti A Basu JK De S 2010a Development of a Treated Laterite for Arsenic Adsorption Effects of Treatment Parameters Industrial amp Engineering Chemistry Research 49 (10) 4873-4886Maiti A Basu JK De S 2010b Removal of Arsenic from Synthetic and Natural Groundwater Using Acid-Activated Laterite Environmental Progress amp Sustainable Energy 29 (4) 457-470Maiti A Basu JK De S 2012 Experimental and kinetic modeling of As(V) and As(III) adsorption on treated laterite using synthetic and contaminated groundwater Effects of phosphate silicate and carbonate ions Chem Eng J 191 1-12Maiti A Thakur BK Basu JK De S 2013a Comparison of treated laterite as arsenic adsorbent from different locations and performance of best filter under field conditions J Hazard Mater 262 1176-1186Maiti A Thakur BK Basu JK De S 2013b Comparison of treated laterite as arsenic adsorbent from different locations and performance of best filter under field conditions J Hazard Mater 262 (0) 1176-1186Maji SK Pal A Pal T 2008 Arsenic removal from real-life groundwater by adsorption on laterite soil J Hazard Mater 151 (2-3) 811-820Maji SK Kao YH Wang CJ Lu GS Wu JJ Liu CW 2012 Fixed bed adsorption of As(III) on iron-oxide-coated natural rock (IOCNR) and application to real arsenic-bearing groundwater Chem Eng J 203 285-293Mertens J Rose J Kagi R Chaurand P Plotze M Wehrli B Furrer G 2012 Adsorption of arsenic on polyaluminum granulate Environ Sci Technol 46 (13) 7310-7317Nguyen TV Vigneswaran S Ngo HH Pokhre D Viraraghavan T 2006 Iron-coated sponge as
effective media to remove arsenic from drinking water Water Qual Res J Can 41 (2) 164-170Parkhurst DL Appelo CAJ 2013 Description of input and examples for PHREEQC version 3-A computer program for speciation batch-reaction one-dimensional transport and inverse geochemical calculations US Geological SurveyPena M Meng XG Korfiatis GP Jing CY 2006 Adsorption mechanism of arsenic on nanocrystalline titanium dioxide Environ Sci Technol 40 (4) 1257-1262Ravel B Newville M 2005 ATHENA ARTEMIS HEPHAESTUS Data analysis for X-ray absorption spectroscopy using IFEFFIT J Synchrotron Radiat 12 537-541Saha B Bains R Greenwood F 2005 Physicochemical characterization of granular ferric hydroxide (GFH) for arsenic(V) sorption from water Separation Science and Technology 40 (14) 2909-2932Shan H Ma T Wang Y Zhao J Han H Deng Y He X Dong Y 2013 A cost-effective system for in-situ geological arsenic adsorption from groundwater J Contam Hydrol 154 1-9Stachowicz M Hiemstra T van Riemsdijk WH 2008 Multi-competitive interaction of As(III) and As(V) oxyanions with Ca2+ Mg2+ PO4
3- and CO32- ions on goethite J Colloid Interf Sci 320 (2) 400-
414Streat M Hellgardt K Newton NLR 2008 Hydrous ferric oxide as an adsorbent in water treatment - Part 3 Batch and mini-column adsorption of arsenic phosphorus fluorine and cadmium ions Process Safety and Environmental Protection 86 (B1) 21-30Thirunavukkarasu OS Viraraghavan T Subramanian KS 2003 Arsenic removal from drinking water using iron oxide-coated sand Water Air Soil Poll 142 (1-4) 95-111USEPA 2008 Assessing arsenic removal by metal (hydr)oxide adsorptive media using rapid small scale column tests Govenrnment Printing Office Washington DCWang J Xu W Chen L Huang X Liu J 2014 Preparation and evaluation of magnetic nanoparticles impregnated chitosan beads for arsenic removal from water Chem Eng J 251 25-34Westerhoff P Highfield D Badruzzaman M Yoon Y 2005 Rapid small-scale column tests for arsenate removal in iron oxide packed bed columns J Environ Eng-Asce 131 (2) 262-271Westerhoff P De Haan M Martindale A Badruzzaman M 2006 Arsenic adsorptive media technology selection strategies Water Qual Res J Can 41 (2) 171-184Yan L Huang Y Cui J Jing C 2015 Simultaneous As(III) and Cd removal from copper smelting wastewater using granular TiO2 columns Water Res 68 (0) 572-579Zhao K Guo HM 2014 Behavior and mechanism of arsenate adsorption on activated natural siderite Evidences from FTIR and XANES analysis Environ Sci Pollut Res 21 (3) 1944-1953Zhao K Guo H Zhou X 2014 Adsorption and heterogeneous oxidation of arsenite on modified granular natural siderite Characterization and behaviors Appl Geochem 48 184-192
Charge distribution multi-site surface complexation (CD-MUSIC) modeling
The CD-MUSIC model with the 2-pK TPM adsorption option was used to
describe adsorption behaviors of As cations and anions on GTiO2 The CD-MUSIC
model incorporates the structural information of surfaces adsorbed species and the
double layers by distributing the charge of an adsorbate between the surface and
interfacial water (Hiemstra and Van Riemsdijk 2006) The CD-MUSIC model has
been successfully used in describing As adsorption in batch experiments (Pena et al
2006 Stachowicz et al 2008)
The adsorption constants of counter ions were set to -1 and the proton affinity
constant was set to the PZC of 58 for TiOH-13 (Luo et al 2010) The charge
distribution (CD) value shows the fraction (f) of the charge of the central As ion
attributed to the surface plane and the remaining part (1-f) was attributed to the other
ligands of the complex which were positioned toward the diffuse layer The CD value
for As surface complexes was obtained by fitting the experimental data The
calculation was performed using the chemical equilibrium program MINTEQ to
simulate the adsorption and the aqueous reactions
29
378379
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386
387
388
389
390
391
392
393
394
395
396
397
398
399
Fig S32 Adsorption of silicate (a) calcium and magnesium (b) as a function of GTiO2
dose in groundwater 1 The solid lines represent the CD-MUSIC modeling result
30
400
401
402
403
404
405
406
407
408409410
Table S75 Surface parameters and species used in the CD-MUSIC modeling in As(IIIV) removal under different GTiO2 dose in 01 M NaCl and groundwater 1 in Fig 2 and Fig S32
= exp(-FΨ1RT) P2 = exp(-FΨ2RT) F the Faraday constant (C mol-1) R the gas constant (J mol-1 K-1) T the absolute temperature (K)
Ψ0 Ψ1 Ψ2 the electrostatic potential (V) of 0- 1- and 2-plane respectively alogK for 01 M NaCl at 6 hours blogK for 01 M NaCl at 6 days clogK for groundwater 1 at 6 days
31
411412
413414415
32
416
Table S86 The charge distribution (f) of central As atom to TiO2 surface in simulating the effect of cations and anions on As adsorption in 01 M NaCl at pH 82 in Fig 4 BK Si HCO3 All
As(V) 022 017 012 016As(III) 040 020 058 056
Fig S43 Molar percentage () of As Ca Mg and Si on pristine and spent GTiO2
surfaces using EDX analysis The spent GTiO2 samples after field column experiments using groundwater 1 were identified with EBCT in min under x-axis The value of molar percentage of each element was averaged from randomly-chosen positions on the adsorbent surface
33
417
418
419420
421422
423
424
425
426
427
428
429
430
431
432
433434435436437438
439
440
441
As speciation analysis on spent GTiO2 using XANES
The spent GTiO2 samples were ground using a mortar and pestle and then the
ground powder was spread on Scotch tape The As k-edge XANES spectra were
collected at beamline 01C1 at the National Synchrotron Radiation Research Center
(NSRRC) Taiwan Spectra were acquired from -150 to 300 eV relative to the As K-
edge of 11867 eV at cryogenic temperature (77 K) using a cryostat to prevent the
oxidation of As(III) by X-rays The fluorescence signals were collected using a Lytle
detector Two to four scans were collected for each sample and averaged to improve
the signalnoise ratio The XANES analysis was performed with the Athena program
in the IFEFFIT computer package for linear combination fit (LCF) (Cui et al 2013
Ravel and Newville 2005)
34
442
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451
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460
461
462
463
PHREEQC modeling for As breakthrough curves in field column experiments
PHREEQC a geochemical model integrates macroscopic mass transfer
processes with a microscopic surface complexation model (Parkhurst and Appelo
2013) It can be applied in calculating solution complex speciation batch-reaction
and one-dimensional reactive-transport and inverse modeling In our study the one-
dimensional column was defined by four cells with the same length The cell length
was calculated to be one-fourth of the actual column length Time step (s) was
calculated according to equation Time step = Lcell(Q60A) where Lcell is the cell
length (cm) Q is flow velocity (mLmin) A is the effective column cross section area
(cm2) which is the column cross-sectional area multiplied by porosity (060) Total
shift number was calculated by dividing actual column operation time by the time
step The transport block was modeled by shifting the solute content from one cell to
the next one In each cell the aqueous solute was mixed and adsorbed on GTiO2
according to the equations In each cell the aqueous solute was mixed and assumed to
be in equilibration with GTiO2 The sequence of shifting mixing and equilibrium
adsorption was repeated for each cell until the total number of shifts was completed
The diffusion coefficient Dw in PHREEQC accounting for retardation was
calculated as Dw=x2
(36t) where x stands for the diffusion length (estimated as the
radius of the particle size) and t represents equilibrium time adopted from the batch
kinetic data (Mertens et al 2012)
For CD-MUSIC modeling in the PHREEQC take As(III) as an example to
explain the adsorption equation The As(III) adsorption is considered as a ligand
35
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469
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471
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481
482
483
484
485
exchange reaction with the hydroxide group on GTiO2 (Surf_sOH-033) forming a
H3ArseniteO3 is the master species in groundwater at pH 82
(Surf_sO)2ArseniteOH-066 is the common adsorbed bidentate binuclear complex
evidenced by our previous reports(Pena et al 2006 Yan et al 2015) LogK is the
adsorption equilibrium constants Generally every adsorption equation under certain
experimental condition has a unique value of logK In the adsorption equation ldquo-2rdquo
represents the lost two hydrogens by Surf_sOH-033 after it adsorbs H3ArseniteO3 ldquo-
1rdquo represents the change in charge on Arsenite at 1 plane due to gaining one hydrogen
(+1) and one oxygen (-2) ldquo0rdquo represents no change in charge at the 2 plane ldquo066rdquo is
the fraction of the central ion (As) on GTiO2 surface that is associated with plane 0
ldquo3rdquo is the charge on the central ion As(III) Following this equation and the relevant
parameters As(III) adsorbed on GTiO2
The diffusion coefficient Dw in PHREEQC accounting for retardation was
calculated as Dw=x2(36t) where x stands for the diffusion length (estimated as the
radius of the particle size) and t represents equilibrium time adopted from the batch
kinetic data (Mertens et al 2012)
To well simulate the As breakthrough curve in columns four As(V) adsorption
reactions (Table 1) were employed Adsorption site density of 60 mmolg was
36
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491
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506
507
adopted from our previous study (Pena et al 2006) and the total adsorption sites were
calculated to be 1844 sitesnm2 The final optimized ratio of strong to weak sites was
51 The surface complexation constants were reasonably adjusted according to the
batch modeling results as the column reaction may not reach equilibrium in local
micro-interfacial areas due to much less contact time between As and GTiO2 than that
in batch experiments (Appelo and Postma 1999) In the modeling a stepwise
procedure was adopted to achieve a viable result An estimation of two thirds of the
surface site density being accessible for EBCT=011 min with large flow rate of 265
mLmin was optimized which could probably result from unavailable adsorption sites
due to fast transport through the column
The adsorbed As on GTiO2 in the column was calculated by mass balance
between the influent and effluent
where Asadsorbed is the adsorbed As on GTiO2 (mgg) n is the number of collected
samples Cin and Cout are influent and effluent As concentrations (mgL) respectively
Vi is volume (L) of groundwater passed through the column between sample i-1 and i
and m is the mass of GTiO2 (g)
Even though the oxidation of adsorbed As(III) occurred during filtration as
analyzed from XANES and mass balance analysis (Fig 7) no As(III) oxidation
reactions were considered in PHREEQC modeling which would not impact the
breakthrough of As(IIIV)
37
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
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38
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531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
Fig S54 Effect of EBCT on Si Ca and Mg breakthrough curves using groundwater 1 The sample notation in panel c indicates field column experiments with EBCT in minutes
References
Appelo CAJ Postma D 1999 A consistent model for surface complexation on birnessite (MnO2) and its application to a column experiment Geochim Cosmochim Ac 63 (19-20) 3039-3048Badruzzaman M Westerhoff P Knappe DRU 2004 Intraparticle diffusion and adsorption of arsenate onto granular ferric hydroxide (GFH) Water Res 38 (18) 4002-4012Banerjee K Amy GL Prevost M Nour S Jekel M Gallagher PM Blumenschein CD 2008 Kinetic and thermodynamic aspects of adsorption of arsenic onto granular ferric hydroxide (GFH) Water Res 42 (13) 3371-3378Bang S Patel M Lippincott L Meng XG 2005 Removal of arsenic from groundwater by granular titanium dioxide adsorbent Chemosphere 60 (3) 389-397Bang S Pena ME Patel M Lippincott L Meng X Kim KW 2011 Removal of arsenate from water by adsorbents a comparative case study Environ Geochem Hlth 33 133-141Cui JL Shi JB Jiang GB Jing CY 2013 Arsenic levels and speciation from ingestion exposures to biomarkers in Shanxi China Implications for human health Environ Sci Technol 47 (10) 5419-5424Daus B Wennrich R Weiss H 2004 Sorption materials for arsenic removal from water A comparative study Water Res 38 (12) 2948-2954Dou XM Mohan D Pittman CU 2013 Arsenate adsorption on three types of granular schwertmannite Water Res 47 (9) 2938-2948Dou XM Zhang Y Yang M Pei YS Huang X Takayama T Kato S 2006 Occurrence of arsenic in groundwater in the suburbs of Beijing and its removal using an iron-cerium bimetal oxide adsorbent Water Qual Res J Can 41 (2) 140-146Gibbons MK Gagnon GA 2010 Adsorption of arsenic from a Nova Scotia groundwater onto water treatment residual solids Water Res 44 (19) 5740-5749Glocheux Y Mendez Pasarin M Albadarin AB Allen SJ Walker GM 2013 Removal of arsenic from groundwater by adsorption onto an acidified laterite by-product Chem Eng J 228 565-574Guan XH Wang JM Chusuei CC 2008 Removal of arsenic from water using granular ferric hydroxide Macroscopic and microscopic studies J Hazard Mater 156 (1-3) 178-185Gupta K Maity A Ghosh UC 2010 Manganese associated nanoparticles agglomerate of iron(III) oxide Synthesis characterization and arsenic(III) sorption behavior with mechanism J Hazard Mater 184 (1-3) 832-842Hao JM Han MJ Wang C Meng XG 2009 Enhanced removal of arsenite from water by a mesoporous hybrid material - Thiol-functionalized silica coated activated alumina Micropor Mesopor
Mat 124 (1-3) 1-7Hiemstra T Van Riemsdijk WH 2006 On the relationship between charge distribution surface hydration and the structure of the interface of metal hydroxides J Colloid Interf Sci 301 (1) 1-18Hristovski K Baumgardner A Westerhoff P 2007 Selecting metal oxide nanomaterials for arsenic removal in fixed bed columns From nanopowders to aggregated nanoparticle media J Hazard Mater 147 (1-2) 265-274Jang M Chen WF Cannon FS 2008 Preloading hydrous ferric oxide into granular activated carbon for arsenic removal Environ Sci Technol 42 (9) 3369-3374Jing CY Cui JL Huang YY Li AG 2012 Fabrication characterization and application of a composite adsorbent for simultaneous removal of arsenic and fluoride ACS Appl Mater Interfaces 4 (2) 714-720Kanematsu M Young TM Fukushi K Green PG Darby JL 2010 Extended triple layer modeling of arsenate and phosphate adsorption on a goethite-based granular porous adsorbent Environ Sci Technol 44 (9) 3388-3394Kong S Wang Y Zhan H Yuan S Liu M Zhou C 2013 Arsenite and Arsenate Removal from Contaminated Groundwater by Nanoscale Iron-Manganese Binary Oxides Column Studies Environmental Engineering Science 30 (11) 689-696Li Y Liu JR Jia SY Guo JW Zhuo J Na P 2012 TiO2 pillared montmorillonite as a photoactive adsorbent of arsenic under UV irradiation Chem Eng J 191 66-74Lin TF Wu JK 2001 Adsorption of arsenite and arsenate within activated alumina grains Equilibrium and kinetics Water Res 35 (8) 2049-2057Luo T Cui JL Hu S Huang YY Jing CY 2010 Arsenic removal and recovery from copper smelting wastewater using TiO2 Environ Sci Technol 44 (23) 9094-9098Maiti A Basu JK De S 2010a Development of a Treated Laterite for Arsenic Adsorption Effects of Treatment Parameters Industrial amp Engineering Chemistry Research 49 (10) 4873-4886Maiti A Basu JK De S 2010b Removal of Arsenic from Synthetic and Natural Groundwater Using Acid-Activated Laterite Environmental Progress amp Sustainable Energy 29 (4) 457-470Maiti A Basu JK De S 2012 Experimental and kinetic modeling of As(V) and As(III) adsorption on treated laterite using synthetic and contaminated groundwater Effects of phosphate silicate and carbonate ions Chem Eng J 191 1-12Maiti A Thakur BK Basu JK De S 2013a Comparison of treated laterite as arsenic adsorbent from different locations and performance of best filter under field conditions J Hazard Mater 262 1176-1186Maiti A Thakur BK Basu JK De S 2013b Comparison of treated laterite as arsenic adsorbent from different locations and performance of best filter under field conditions J Hazard Mater 262 (0) 1176-1186Maji SK Pal A Pal T 2008 Arsenic removal from real-life groundwater by adsorption on laterite soil J Hazard Mater 151 (2-3) 811-820Maji SK Kao YH Wang CJ Lu GS Wu JJ Liu CW 2012 Fixed bed adsorption of As(III) on iron-oxide-coated natural rock (IOCNR) and application to real arsenic-bearing groundwater Chem Eng J 203 285-293Mertens J Rose J Kagi R Chaurand P Plotze M Wehrli B Furrer G 2012 Adsorption of arsenic on polyaluminum granulate Environ Sci Technol 46 (13) 7310-7317Nguyen TV Vigneswaran S Ngo HH Pokhre D Viraraghavan T 2006 Iron-coated sponge as
effective media to remove arsenic from drinking water Water Qual Res J Can 41 (2) 164-170Parkhurst DL Appelo CAJ 2013 Description of input and examples for PHREEQC version 3-A computer program for speciation batch-reaction one-dimensional transport and inverse geochemical calculations US Geological SurveyPena M Meng XG Korfiatis GP Jing CY 2006 Adsorption mechanism of arsenic on nanocrystalline titanium dioxide Environ Sci Technol 40 (4) 1257-1262Ravel B Newville M 2005 ATHENA ARTEMIS HEPHAESTUS Data analysis for X-ray absorption spectroscopy using IFEFFIT J Synchrotron Radiat 12 537-541Saha B Bains R Greenwood F 2005 Physicochemical characterization of granular ferric hydroxide (GFH) for arsenic(V) sorption from water Separation Science and Technology 40 (14) 2909-2932Shan H Ma T Wang Y Zhao J Han H Deng Y He X Dong Y 2013 A cost-effective system for in-situ geological arsenic adsorption from groundwater J Contam Hydrol 154 1-9Stachowicz M Hiemstra T van Riemsdijk WH 2008 Multi-competitive interaction of As(III) and As(V) oxyanions with Ca2+ Mg2+ PO4
3- and CO32- ions on goethite J Colloid Interf Sci 320 (2) 400-
414Streat M Hellgardt K Newton NLR 2008 Hydrous ferric oxide as an adsorbent in water treatment - Part 3 Batch and mini-column adsorption of arsenic phosphorus fluorine and cadmium ions Process Safety and Environmental Protection 86 (B1) 21-30Thirunavukkarasu OS Viraraghavan T Subramanian KS 2003 Arsenic removal from drinking water using iron oxide-coated sand Water Air Soil Poll 142 (1-4) 95-111USEPA 2008 Assessing arsenic removal by metal (hydr)oxide adsorptive media using rapid small scale column tests Govenrnment Printing Office Washington DCWang J Xu W Chen L Huang X Liu J 2014 Preparation and evaluation of magnetic nanoparticles impregnated chitosan beads for arsenic removal from water Chem Eng J 251 25-34Westerhoff P Highfield D Badruzzaman M Yoon Y 2005 Rapid small-scale column tests for arsenate removal in iron oxide packed bed columns J Environ Eng-Asce 131 (2) 262-271Westerhoff P De Haan M Martindale A Badruzzaman M 2006 Arsenic adsorptive media technology selection strategies Water Qual Res J Can 41 (2) 171-184Yan L Huang Y Cui J Jing C 2015 Simultaneous As(III) and Cd removal from copper smelting wastewater using granular TiO2 columns Water Res 68 (0) 572-579Zhao K Guo HM 2014 Behavior and mechanism of arsenate adsorption on activated natural siderite Evidences from FTIR and XANES analysis Environ Sci Pollut Res 21 (3) 1944-1953Zhao K Guo H Zhou X 2014 Adsorption and heterogeneous oxidation of arsenite on modified granular natural siderite Characterization and behaviors Appl Geochem 48 184-192
Fig S32 Adsorption of silicate (a) calcium and magnesium (b) as a function of GTiO2
dose in groundwater 1 The solid lines represent the CD-MUSIC modeling result
30
400
401
402
403
404
405
406
407
408409410
Table S75 Surface parameters and species used in the CD-MUSIC modeling in As(IIIV) removal under different GTiO2 dose in 01 M NaCl and groundwater 1 in Fig 2 and Fig S32
= exp(-FΨ1RT) P2 = exp(-FΨ2RT) F the Faraday constant (C mol-1) R the gas constant (J mol-1 K-1) T the absolute temperature (K)
Ψ0 Ψ1 Ψ2 the electrostatic potential (V) of 0- 1- and 2-plane respectively alogK for 01 M NaCl at 6 hours blogK for 01 M NaCl at 6 days clogK for groundwater 1 at 6 days
31
411412
413414415
32
416
Table S86 The charge distribution (f) of central As atom to TiO2 surface in simulating the effect of cations and anions on As adsorption in 01 M NaCl at pH 82 in Fig 4 BK Si HCO3 All
As(V) 022 017 012 016As(III) 040 020 058 056
Fig S43 Molar percentage () of As Ca Mg and Si on pristine and spent GTiO2
surfaces using EDX analysis The spent GTiO2 samples after field column experiments using groundwater 1 were identified with EBCT in min under x-axis The value of molar percentage of each element was averaged from randomly-chosen positions on the adsorbent surface
33
417
418
419420
421422
423
424
425
426
427
428
429
430
431
432
433434435436437438
439
440
441
As speciation analysis on spent GTiO2 using XANES
The spent GTiO2 samples were ground using a mortar and pestle and then the
ground powder was spread on Scotch tape The As k-edge XANES spectra were
collected at beamline 01C1 at the National Synchrotron Radiation Research Center
(NSRRC) Taiwan Spectra were acquired from -150 to 300 eV relative to the As K-
edge of 11867 eV at cryogenic temperature (77 K) using a cryostat to prevent the
oxidation of As(III) by X-rays The fluorescence signals were collected using a Lytle
detector Two to four scans were collected for each sample and averaged to improve
the signalnoise ratio The XANES analysis was performed with the Athena program
in the IFEFFIT computer package for linear combination fit (LCF) (Cui et al 2013
Ravel and Newville 2005)
34
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
PHREEQC modeling for As breakthrough curves in field column experiments
PHREEQC a geochemical model integrates macroscopic mass transfer
processes with a microscopic surface complexation model (Parkhurst and Appelo
2013) It can be applied in calculating solution complex speciation batch-reaction
and one-dimensional reactive-transport and inverse modeling In our study the one-
dimensional column was defined by four cells with the same length The cell length
was calculated to be one-fourth of the actual column length Time step (s) was
calculated according to equation Time step = Lcell(Q60A) where Lcell is the cell
length (cm) Q is flow velocity (mLmin) A is the effective column cross section area
(cm2) which is the column cross-sectional area multiplied by porosity (060) Total
shift number was calculated by dividing actual column operation time by the time
step The transport block was modeled by shifting the solute content from one cell to
the next one In each cell the aqueous solute was mixed and adsorbed on GTiO2
according to the equations In each cell the aqueous solute was mixed and assumed to
be in equilibration with GTiO2 The sequence of shifting mixing and equilibrium
adsorption was repeated for each cell until the total number of shifts was completed
The diffusion coefficient Dw in PHREEQC accounting for retardation was
calculated as Dw=x2
(36t) where x stands for the diffusion length (estimated as the
radius of the particle size) and t represents equilibrium time adopted from the batch
kinetic data (Mertens et al 2012)
For CD-MUSIC modeling in the PHREEQC take As(III) as an example to
explain the adsorption equation The As(III) adsorption is considered as a ligand
35
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
exchange reaction with the hydroxide group on GTiO2 (Surf_sOH-033) forming a
H3ArseniteO3 is the master species in groundwater at pH 82
(Surf_sO)2ArseniteOH-066 is the common adsorbed bidentate binuclear complex
evidenced by our previous reports(Pena et al 2006 Yan et al 2015) LogK is the
adsorption equilibrium constants Generally every adsorption equation under certain
experimental condition has a unique value of logK In the adsorption equation ldquo-2rdquo
represents the lost two hydrogens by Surf_sOH-033 after it adsorbs H3ArseniteO3 ldquo-
1rdquo represents the change in charge on Arsenite at 1 plane due to gaining one hydrogen
(+1) and one oxygen (-2) ldquo0rdquo represents no change in charge at the 2 plane ldquo066rdquo is
the fraction of the central ion (As) on GTiO2 surface that is associated with plane 0
ldquo3rdquo is the charge on the central ion As(III) Following this equation and the relevant
parameters As(III) adsorbed on GTiO2
The diffusion coefficient Dw in PHREEQC accounting for retardation was
calculated as Dw=x2(36t) where x stands for the diffusion length (estimated as the
radius of the particle size) and t represents equilibrium time adopted from the batch
kinetic data (Mertens et al 2012)
To well simulate the As breakthrough curve in columns four As(V) adsorption
reactions (Table 1) were employed Adsorption site density of 60 mmolg was
36
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
adopted from our previous study (Pena et al 2006) and the total adsorption sites were
calculated to be 1844 sitesnm2 The final optimized ratio of strong to weak sites was
51 The surface complexation constants were reasonably adjusted according to the
batch modeling results as the column reaction may not reach equilibrium in local
micro-interfacial areas due to much less contact time between As and GTiO2 than that
in batch experiments (Appelo and Postma 1999) In the modeling a stepwise
procedure was adopted to achieve a viable result An estimation of two thirds of the
surface site density being accessible for EBCT=011 min with large flow rate of 265
mLmin was optimized which could probably result from unavailable adsorption sites
due to fast transport through the column
The adsorbed As on GTiO2 in the column was calculated by mass balance
between the influent and effluent
where Asadsorbed is the adsorbed As on GTiO2 (mgg) n is the number of collected
samples Cin and Cout are influent and effluent As concentrations (mgL) respectively
Vi is volume (L) of groundwater passed through the column between sample i-1 and i
and m is the mass of GTiO2 (g)
Even though the oxidation of adsorbed As(III) occurred during filtration as
analyzed from XANES and mass balance analysis (Fig 7) no As(III) oxidation
reactions were considered in PHREEQC modeling which would not impact the
breakthrough of As(IIIV)
37
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
38
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
Fig S54 Effect of EBCT on Si Ca and Mg breakthrough curves using groundwater 1 The sample notation in panel c indicates field column experiments with EBCT in minutes
References
Appelo CAJ Postma D 1999 A consistent model for surface complexation on birnessite (MnO2) and its application to a column experiment Geochim Cosmochim Ac 63 (19-20) 3039-3048Badruzzaman M Westerhoff P Knappe DRU 2004 Intraparticle diffusion and adsorption of arsenate onto granular ferric hydroxide (GFH) Water Res 38 (18) 4002-4012Banerjee K Amy GL Prevost M Nour S Jekel M Gallagher PM Blumenschein CD 2008 Kinetic and thermodynamic aspects of adsorption of arsenic onto granular ferric hydroxide (GFH) Water Res 42 (13) 3371-3378Bang S Patel M Lippincott L Meng XG 2005 Removal of arsenic from groundwater by granular titanium dioxide adsorbent Chemosphere 60 (3) 389-397Bang S Pena ME Patel M Lippincott L Meng X Kim KW 2011 Removal of arsenate from water by adsorbents a comparative case study Environ Geochem Hlth 33 133-141Cui JL Shi JB Jiang GB Jing CY 2013 Arsenic levels and speciation from ingestion exposures to biomarkers in Shanxi China Implications for human health Environ Sci Technol 47 (10) 5419-5424Daus B Wennrich R Weiss H 2004 Sorption materials for arsenic removal from water A comparative study Water Res 38 (12) 2948-2954Dou XM Mohan D Pittman CU 2013 Arsenate adsorption on three types of granular schwertmannite Water Res 47 (9) 2938-2948Dou XM Zhang Y Yang M Pei YS Huang X Takayama T Kato S 2006 Occurrence of arsenic in groundwater in the suburbs of Beijing and its removal using an iron-cerium bimetal oxide adsorbent Water Qual Res J Can 41 (2) 140-146Gibbons MK Gagnon GA 2010 Adsorption of arsenic from a Nova Scotia groundwater onto water treatment residual solids Water Res 44 (19) 5740-5749Glocheux Y Mendez Pasarin M Albadarin AB Allen SJ Walker GM 2013 Removal of arsenic from groundwater by adsorption onto an acidified laterite by-product Chem Eng J 228 565-574Guan XH Wang JM Chusuei CC 2008 Removal of arsenic from water using granular ferric hydroxide Macroscopic and microscopic studies J Hazard Mater 156 (1-3) 178-185Gupta K Maity A Ghosh UC 2010 Manganese associated nanoparticles agglomerate of iron(III) oxide Synthesis characterization and arsenic(III) sorption behavior with mechanism J Hazard Mater 184 (1-3) 832-842Hao JM Han MJ Wang C Meng XG 2009 Enhanced removal of arsenite from water by a mesoporous hybrid material - Thiol-functionalized silica coated activated alumina Micropor Mesopor
Mat 124 (1-3) 1-7Hiemstra T Van Riemsdijk WH 2006 On the relationship between charge distribution surface hydration and the structure of the interface of metal hydroxides J Colloid Interf Sci 301 (1) 1-18Hristovski K Baumgardner A Westerhoff P 2007 Selecting metal oxide nanomaterials for arsenic removal in fixed bed columns From nanopowders to aggregated nanoparticle media J Hazard Mater 147 (1-2) 265-274Jang M Chen WF Cannon FS 2008 Preloading hydrous ferric oxide into granular activated carbon for arsenic removal Environ Sci Technol 42 (9) 3369-3374Jing CY Cui JL Huang YY Li AG 2012 Fabrication characterization and application of a composite adsorbent for simultaneous removal of arsenic and fluoride ACS Appl Mater Interfaces 4 (2) 714-720Kanematsu M Young TM Fukushi K Green PG Darby JL 2010 Extended triple layer modeling of arsenate and phosphate adsorption on a goethite-based granular porous adsorbent Environ Sci Technol 44 (9) 3388-3394Kong S Wang Y Zhan H Yuan S Liu M Zhou C 2013 Arsenite and Arsenate Removal from Contaminated Groundwater by Nanoscale Iron-Manganese Binary Oxides Column Studies Environmental Engineering Science 30 (11) 689-696Li Y Liu JR Jia SY Guo JW Zhuo J Na P 2012 TiO2 pillared montmorillonite as a photoactive adsorbent of arsenic under UV irradiation Chem Eng J 191 66-74Lin TF Wu JK 2001 Adsorption of arsenite and arsenate within activated alumina grains Equilibrium and kinetics Water Res 35 (8) 2049-2057Luo T Cui JL Hu S Huang YY Jing CY 2010 Arsenic removal and recovery from copper smelting wastewater using TiO2 Environ Sci Technol 44 (23) 9094-9098Maiti A Basu JK De S 2010a Development of a Treated Laterite for Arsenic Adsorption Effects of Treatment Parameters Industrial amp Engineering Chemistry Research 49 (10) 4873-4886Maiti A Basu JK De S 2010b Removal of Arsenic from Synthetic and Natural Groundwater Using Acid-Activated Laterite Environmental Progress amp Sustainable Energy 29 (4) 457-470Maiti A Basu JK De S 2012 Experimental and kinetic modeling of As(V) and As(III) adsorption on treated laterite using synthetic and contaminated groundwater Effects of phosphate silicate and carbonate ions Chem Eng J 191 1-12Maiti A Thakur BK Basu JK De S 2013a Comparison of treated laterite as arsenic adsorbent from different locations and performance of best filter under field conditions J Hazard Mater 262 1176-1186Maiti A Thakur BK Basu JK De S 2013b Comparison of treated laterite as arsenic adsorbent from different locations and performance of best filter under field conditions J Hazard Mater 262 (0) 1176-1186Maji SK Pal A Pal T 2008 Arsenic removal from real-life groundwater by adsorption on laterite soil J Hazard Mater 151 (2-3) 811-820Maji SK Kao YH Wang CJ Lu GS Wu JJ Liu CW 2012 Fixed bed adsorption of As(III) on iron-oxide-coated natural rock (IOCNR) and application to real arsenic-bearing groundwater Chem Eng J 203 285-293Mertens J Rose J Kagi R Chaurand P Plotze M Wehrli B Furrer G 2012 Adsorption of arsenic on polyaluminum granulate Environ Sci Technol 46 (13) 7310-7317Nguyen TV Vigneswaran S Ngo HH Pokhre D Viraraghavan T 2006 Iron-coated sponge as
effective media to remove arsenic from drinking water Water Qual Res J Can 41 (2) 164-170Parkhurst DL Appelo CAJ 2013 Description of input and examples for PHREEQC version 3-A computer program for speciation batch-reaction one-dimensional transport and inverse geochemical calculations US Geological SurveyPena M Meng XG Korfiatis GP Jing CY 2006 Adsorption mechanism of arsenic on nanocrystalline titanium dioxide Environ Sci Technol 40 (4) 1257-1262Ravel B Newville M 2005 ATHENA ARTEMIS HEPHAESTUS Data analysis for X-ray absorption spectroscopy using IFEFFIT J Synchrotron Radiat 12 537-541Saha B Bains R Greenwood F 2005 Physicochemical characterization of granular ferric hydroxide (GFH) for arsenic(V) sorption from water Separation Science and Technology 40 (14) 2909-2932Shan H Ma T Wang Y Zhao J Han H Deng Y He X Dong Y 2013 A cost-effective system for in-situ geological arsenic adsorption from groundwater J Contam Hydrol 154 1-9Stachowicz M Hiemstra T van Riemsdijk WH 2008 Multi-competitive interaction of As(III) and As(V) oxyanions with Ca2+ Mg2+ PO4
3- and CO32- ions on goethite J Colloid Interf Sci 320 (2) 400-
414Streat M Hellgardt K Newton NLR 2008 Hydrous ferric oxide as an adsorbent in water treatment - Part 3 Batch and mini-column adsorption of arsenic phosphorus fluorine and cadmium ions Process Safety and Environmental Protection 86 (B1) 21-30Thirunavukkarasu OS Viraraghavan T Subramanian KS 2003 Arsenic removal from drinking water using iron oxide-coated sand Water Air Soil Poll 142 (1-4) 95-111USEPA 2008 Assessing arsenic removal by metal (hydr)oxide adsorptive media using rapid small scale column tests Govenrnment Printing Office Washington DCWang J Xu W Chen L Huang X Liu J 2014 Preparation and evaluation of magnetic nanoparticles impregnated chitosan beads for arsenic removal from water Chem Eng J 251 25-34Westerhoff P Highfield D Badruzzaman M Yoon Y 2005 Rapid small-scale column tests for arsenate removal in iron oxide packed bed columns J Environ Eng-Asce 131 (2) 262-271Westerhoff P De Haan M Martindale A Badruzzaman M 2006 Arsenic adsorptive media technology selection strategies Water Qual Res J Can 41 (2) 171-184Yan L Huang Y Cui J Jing C 2015 Simultaneous As(III) and Cd removal from copper smelting wastewater using granular TiO2 columns Water Res 68 (0) 572-579Zhao K Guo HM 2014 Behavior and mechanism of arsenate adsorption on activated natural siderite Evidences from FTIR and XANES analysis Environ Sci Pollut Res 21 (3) 1944-1953Zhao K Guo H Zhou X 2014 Adsorption and heterogeneous oxidation of arsenite on modified granular natural siderite Characterization and behaviors Appl Geochem 48 184-192
Table S75 Surface parameters and species used in the CD-MUSIC modeling in As(IIIV) removal under different GTiO2 dose in 01 M NaCl and groundwater 1 in Fig 2 and Fig S32
= exp(-FΨ1RT) P2 = exp(-FΨ2RT) F the Faraday constant (C mol-1) R the gas constant (J mol-1 K-1) T the absolute temperature (K)
Ψ0 Ψ1 Ψ2 the electrostatic potential (V) of 0- 1- and 2-plane respectively alogK for 01 M NaCl at 6 hours blogK for 01 M NaCl at 6 days clogK for groundwater 1 at 6 days
31
411412
413414415
32
416
Table S86 The charge distribution (f) of central As atom to TiO2 surface in simulating the effect of cations and anions on As adsorption in 01 M NaCl at pH 82 in Fig 4 BK Si HCO3 All
As(V) 022 017 012 016As(III) 040 020 058 056
Fig S43 Molar percentage () of As Ca Mg and Si on pristine and spent GTiO2
surfaces using EDX analysis The spent GTiO2 samples after field column experiments using groundwater 1 were identified with EBCT in min under x-axis The value of molar percentage of each element was averaged from randomly-chosen positions on the adsorbent surface
33
417
418
419420
421422
423
424
425
426
427
428
429
430
431
432
433434435436437438
439
440
441
As speciation analysis on spent GTiO2 using XANES
The spent GTiO2 samples were ground using a mortar and pestle and then the
ground powder was spread on Scotch tape The As k-edge XANES spectra were
collected at beamline 01C1 at the National Synchrotron Radiation Research Center
(NSRRC) Taiwan Spectra were acquired from -150 to 300 eV relative to the As K-
edge of 11867 eV at cryogenic temperature (77 K) using a cryostat to prevent the
oxidation of As(III) by X-rays The fluorescence signals were collected using a Lytle
detector Two to four scans were collected for each sample and averaged to improve
the signalnoise ratio The XANES analysis was performed with the Athena program
in the IFEFFIT computer package for linear combination fit (LCF) (Cui et al 2013
Ravel and Newville 2005)
34
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
PHREEQC modeling for As breakthrough curves in field column experiments
PHREEQC a geochemical model integrates macroscopic mass transfer
processes with a microscopic surface complexation model (Parkhurst and Appelo
2013) It can be applied in calculating solution complex speciation batch-reaction
and one-dimensional reactive-transport and inverse modeling In our study the one-
dimensional column was defined by four cells with the same length The cell length
was calculated to be one-fourth of the actual column length Time step (s) was
calculated according to equation Time step = Lcell(Q60A) where Lcell is the cell
length (cm) Q is flow velocity (mLmin) A is the effective column cross section area
(cm2) which is the column cross-sectional area multiplied by porosity (060) Total
shift number was calculated by dividing actual column operation time by the time
step The transport block was modeled by shifting the solute content from one cell to
the next one In each cell the aqueous solute was mixed and adsorbed on GTiO2
according to the equations In each cell the aqueous solute was mixed and assumed to
be in equilibration with GTiO2 The sequence of shifting mixing and equilibrium
adsorption was repeated for each cell until the total number of shifts was completed
The diffusion coefficient Dw in PHREEQC accounting for retardation was
calculated as Dw=x2
(36t) where x stands for the diffusion length (estimated as the
radius of the particle size) and t represents equilibrium time adopted from the batch
kinetic data (Mertens et al 2012)
For CD-MUSIC modeling in the PHREEQC take As(III) as an example to
explain the adsorption equation The As(III) adsorption is considered as a ligand
35
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
exchange reaction with the hydroxide group on GTiO2 (Surf_sOH-033) forming a
H3ArseniteO3 is the master species in groundwater at pH 82
(Surf_sO)2ArseniteOH-066 is the common adsorbed bidentate binuclear complex
evidenced by our previous reports(Pena et al 2006 Yan et al 2015) LogK is the
adsorption equilibrium constants Generally every adsorption equation under certain
experimental condition has a unique value of logK In the adsorption equation ldquo-2rdquo
represents the lost two hydrogens by Surf_sOH-033 after it adsorbs H3ArseniteO3 ldquo-
1rdquo represents the change in charge on Arsenite at 1 plane due to gaining one hydrogen
(+1) and one oxygen (-2) ldquo0rdquo represents no change in charge at the 2 plane ldquo066rdquo is
the fraction of the central ion (As) on GTiO2 surface that is associated with plane 0
ldquo3rdquo is the charge on the central ion As(III) Following this equation and the relevant
parameters As(III) adsorbed on GTiO2
The diffusion coefficient Dw in PHREEQC accounting for retardation was
calculated as Dw=x2(36t) where x stands for the diffusion length (estimated as the
radius of the particle size) and t represents equilibrium time adopted from the batch
kinetic data (Mertens et al 2012)
To well simulate the As breakthrough curve in columns four As(V) adsorption
reactions (Table 1) were employed Adsorption site density of 60 mmolg was
36
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
adopted from our previous study (Pena et al 2006) and the total adsorption sites were
calculated to be 1844 sitesnm2 The final optimized ratio of strong to weak sites was
51 The surface complexation constants were reasonably adjusted according to the
batch modeling results as the column reaction may not reach equilibrium in local
micro-interfacial areas due to much less contact time between As and GTiO2 than that
in batch experiments (Appelo and Postma 1999) In the modeling a stepwise
procedure was adopted to achieve a viable result An estimation of two thirds of the
surface site density being accessible for EBCT=011 min with large flow rate of 265
mLmin was optimized which could probably result from unavailable adsorption sites
due to fast transport through the column
The adsorbed As on GTiO2 in the column was calculated by mass balance
between the influent and effluent
where Asadsorbed is the adsorbed As on GTiO2 (mgg) n is the number of collected
samples Cin and Cout are influent and effluent As concentrations (mgL) respectively
Vi is volume (L) of groundwater passed through the column between sample i-1 and i
and m is the mass of GTiO2 (g)
Even though the oxidation of adsorbed As(III) occurred during filtration as
analyzed from XANES and mass balance analysis (Fig 7) no As(III) oxidation
reactions were considered in PHREEQC modeling which would not impact the
breakthrough of As(IIIV)
37
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
38
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
Fig S54 Effect of EBCT on Si Ca and Mg breakthrough curves using groundwater 1 The sample notation in panel c indicates field column experiments with EBCT in minutes
References
Appelo CAJ Postma D 1999 A consistent model for surface complexation on birnessite (MnO2) and its application to a column experiment Geochim Cosmochim Ac 63 (19-20) 3039-3048Badruzzaman M Westerhoff P Knappe DRU 2004 Intraparticle diffusion and adsorption of arsenate onto granular ferric hydroxide (GFH) Water Res 38 (18) 4002-4012Banerjee K Amy GL Prevost M Nour S Jekel M Gallagher PM Blumenschein CD 2008 Kinetic and thermodynamic aspects of adsorption of arsenic onto granular ferric hydroxide (GFH) Water Res 42 (13) 3371-3378Bang S Patel M Lippincott L Meng XG 2005 Removal of arsenic from groundwater by granular titanium dioxide adsorbent Chemosphere 60 (3) 389-397Bang S Pena ME Patel M Lippincott L Meng X Kim KW 2011 Removal of arsenate from water by adsorbents a comparative case study Environ Geochem Hlth 33 133-141Cui JL Shi JB Jiang GB Jing CY 2013 Arsenic levels and speciation from ingestion exposures to biomarkers in Shanxi China Implications for human health Environ Sci Technol 47 (10) 5419-5424Daus B Wennrich R Weiss H 2004 Sorption materials for arsenic removal from water A comparative study Water Res 38 (12) 2948-2954Dou XM Mohan D Pittman CU 2013 Arsenate adsorption on three types of granular schwertmannite Water Res 47 (9) 2938-2948Dou XM Zhang Y Yang M Pei YS Huang X Takayama T Kato S 2006 Occurrence of arsenic in groundwater in the suburbs of Beijing and its removal using an iron-cerium bimetal oxide adsorbent Water Qual Res J Can 41 (2) 140-146Gibbons MK Gagnon GA 2010 Adsorption of arsenic from a Nova Scotia groundwater onto water treatment residual solids Water Res 44 (19) 5740-5749Glocheux Y Mendez Pasarin M Albadarin AB Allen SJ Walker GM 2013 Removal of arsenic from groundwater by adsorption onto an acidified laterite by-product Chem Eng J 228 565-574Guan XH Wang JM Chusuei CC 2008 Removal of arsenic from water using granular ferric hydroxide Macroscopic and microscopic studies J Hazard Mater 156 (1-3) 178-185Gupta K Maity A Ghosh UC 2010 Manganese associated nanoparticles agglomerate of iron(III) oxide Synthesis characterization and arsenic(III) sorption behavior with mechanism J Hazard Mater 184 (1-3) 832-842Hao JM Han MJ Wang C Meng XG 2009 Enhanced removal of arsenite from water by a mesoporous hybrid material - Thiol-functionalized silica coated activated alumina Micropor Mesopor
Mat 124 (1-3) 1-7Hiemstra T Van Riemsdijk WH 2006 On the relationship between charge distribution surface hydration and the structure of the interface of metal hydroxides J Colloid Interf Sci 301 (1) 1-18Hristovski K Baumgardner A Westerhoff P 2007 Selecting metal oxide nanomaterials for arsenic removal in fixed bed columns From nanopowders to aggregated nanoparticle media J Hazard Mater 147 (1-2) 265-274Jang M Chen WF Cannon FS 2008 Preloading hydrous ferric oxide into granular activated carbon for arsenic removal Environ Sci Technol 42 (9) 3369-3374Jing CY Cui JL Huang YY Li AG 2012 Fabrication characterization and application of a composite adsorbent for simultaneous removal of arsenic and fluoride ACS Appl Mater Interfaces 4 (2) 714-720Kanematsu M Young TM Fukushi K Green PG Darby JL 2010 Extended triple layer modeling of arsenate and phosphate adsorption on a goethite-based granular porous adsorbent Environ Sci Technol 44 (9) 3388-3394Kong S Wang Y Zhan H Yuan S Liu M Zhou C 2013 Arsenite and Arsenate Removal from Contaminated Groundwater by Nanoscale Iron-Manganese Binary Oxides Column Studies Environmental Engineering Science 30 (11) 689-696Li Y Liu JR Jia SY Guo JW Zhuo J Na P 2012 TiO2 pillared montmorillonite as a photoactive adsorbent of arsenic under UV irradiation Chem Eng J 191 66-74Lin TF Wu JK 2001 Adsorption of arsenite and arsenate within activated alumina grains Equilibrium and kinetics Water Res 35 (8) 2049-2057Luo T Cui JL Hu S Huang YY Jing CY 2010 Arsenic removal and recovery from copper smelting wastewater using TiO2 Environ Sci Technol 44 (23) 9094-9098Maiti A Basu JK De S 2010a Development of a Treated Laterite for Arsenic Adsorption Effects of Treatment Parameters Industrial amp Engineering Chemistry Research 49 (10) 4873-4886Maiti A Basu JK De S 2010b Removal of Arsenic from Synthetic and Natural Groundwater Using Acid-Activated Laterite Environmental Progress amp Sustainable Energy 29 (4) 457-470Maiti A Basu JK De S 2012 Experimental and kinetic modeling of As(V) and As(III) adsorption on treated laterite using synthetic and contaminated groundwater Effects of phosphate silicate and carbonate ions Chem Eng J 191 1-12Maiti A Thakur BK Basu JK De S 2013a Comparison of treated laterite as arsenic adsorbent from different locations and performance of best filter under field conditions J Hazard Mater 262 1176-1186Maiti A Thakur BK Basu JK De S 2013b Comparison of treated laterite as arsenic adsorbent from different locations and performance of best filter under field conditions J Hazard Mater 262 (0) 1176-1186Maji SK Pal A Pal T 2008 Arsenic removal from real-life groundwater by adsorption on laterite soil J Hazard Mater 151 (2-3) 811-820Maji SK Kao YH Wang CJ Lu GS Wu JJ Liu CW 2012 Fixed bed adsorption of As(III) on iron-oxide-coated natural rock (IOCNR) and application to real arsenic-bearing groundwater Chem Eng J 203 285-293Mertens J Rose J Kagi R Chaurand P Plotze M Wehrli B Furrer G 2012 Adsorption of arsenic on polyaluminum granulate Environ Sci Technol 46 (13) 7310-7317Nguyen TV Vigneswaran S Ngo HH Pokhre D Viraraghavan T 2006 Iron-coated sponge as
effective media to remove arsenic from drinking water Water Qual Res J Can 41 (2) 164-170Parkhurst DL Appelo CAJ 2013 Description of input and examples for PHREEQC version 3-A computer program for speciation batch-reaction one-dimensional transport and inverse geochemical calculations US Geological SurveyPena M Meng XG Korfiatis GP Jing CY 2006 Adsorption mechanism of arsenic on nanocrystalline titanium dioxide Environ Sci Technol 40 (4) 1257-1262Ravel B Newville M 2005 ATHENA ARTEMIS HEPHAESTUS Data analysis for X-ray absorption spectroscopy using IFEFFIT J Synchrotron Radiat 12 537-541Saha B Bains R Greenwood F 2005 Physicochemical characterization of granular ferric hydroxide (GFH) for arsenic(V) sorption from water Separation Science and Technology 40 (14) 2909-2932Shan H Ma T Wang Y Zhao J Han H Deng Y He X Dong Y 2013 A cost-effective system for in-situ geological arsenic adsorption from groundwater J Contam Hydrol 154 1-9Stachowicz M Hiemstra T van Riemsdijk WH 2008 Multi-competitive interaction of As(III) and As(V) oxyanions with Ca2+ Mg2+ PO4
3- and CO32- ions on goethite J Colloid Interf Sci 320 (2) 400-
414Streat M Hellgardt K Newton NLR 2008 Hydrous ferric oxide as an adsorbent in water treatment - Part 3 Batch and mini-column adsorption of arsenic phosphorus fluorine and cadmium ions Process Safety and Environmental Protection 86 (B1) 21-30Thirunavukkarasu OS Viraraghavan T Subramanian KS 2003 Arsenic removal from drinking water using iron oxide-coated sand Water Air Soil Poll 142 (1-4) 95-111USEPA 2008 Assessing arsenic removal by metal (hydr)oxide adsorptive media using rapid small scale column tests Govenrnment Printing Office Washington DCWang J Xu W Chen L Huang X Liu J 2014 Preparation and evaluation of magnetic nanoparticles impregnated chitosan beads for arsenic removal from water Chem Eng J 251 25-34Westerhoff P Highfield D Badruzzaman M Yoon Y 2005 Rapid small-scale column tests for arsenate removal in iron oxide packed bed columns J Environ Eng-Asce 131 (2) 262-271Westerhoff P De Haan M Martindale A Badruzzaman M 2006 Arsenic adsorptive media technology selection strategies Water Qual Res J Can 41 (2) 171-184Yan L Huang Y Cui J Jing C 2015 Simultaneous As(III) and Cd removal from copper smelting wastewater using granular TiO2 columns Water Res 68 (0) 572-579Zhao K Guo HM 2014 Behavior and mechanism of arsenate adsorption on activated natural siderite Evidences from FTIR and XANES analysis Environ Sci Pollut Res 21 (3) 1944-1953Zhao K Guo H Zhou X 2014 Adsorption and heterogeneous oxidation of arsenite on modified granular natural siderite Characterization and behaviors Appl Geochem 48 184-192
Table S86 The charge distribution (f) of central As atom to TiO2 surface in simulating the effect of cations and anions on As adsorption in 01 M NaCl at pH 82 in Fig 4 BK Si HCO3 All
As(V) 022 017 012 016As(III) 040 020 058 056
Fig S43 Molar percentage () of As Ca Mg and Si on pristine and spent GTiO2
surfaces using EDX analysis The spent GTiO2 samples after field column experiments using groundwater 1 were identified with EBCT in min under x-axis The value of molar percentage of each element was averaged from randomly-chosen positions on the adsorbent surface
33
417
418
419420
421422
423
424
425
426
427
428
429
430
431
432
433434435436437438
439
440
441
As speciation analysis on spent GTiO2 using XANES
The spent GTiO2 samples were ground using a mortar and pestle and then the
ground powder was spread on Scotch tape The As k-edge XANES spectra were
collected at beamline 01C1 at the National Synchrotron Radiation Research Center
(NSRRC) Taiwan Spectra were acquired from -150 to 300 eV relative to the As K-
edge of 11867 eV at cryogenic temperature (77 K) using a cryostat to prevent the
oxidation of As(III) by X-rays The fluorescence signals were collected using a Lytle
detector Two to four scans were collected for each sample and averaged to improve
the signalnoise ratio The XANES analysis was performed with the Athena program
in the IFEFFIT computer package for linear combination fit (LCF) (Cui et al 2013
Ravel and Newville 2005)
34
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
PHREEQC modeling for As breakthrough curves in field column experiments
PHREEQC a geochemical model integrates macroscopic mass transfer
processes with a microscopic surface complexation model (Parkhurst and Appelo
2013) It can be applied in calculating solution complex speciation batch-reaction
and one-dimensional reactive-transport and inverse modeling In our study the one-
dimensional column was defined by four cells with the same length The cell length
was calculated to be one-fourth of the actual column length Time step (s) was
calculated according to equation Time step = Lcell(Q60A) where Lcell is the cell
length (cm) Q is flow velocity (mLmin) A is the effective column cross section area
(cm2) which is the column cross-sectional area multiplied by porosity (060) Total
shift number was calculated by dividing actual column operation time by the time
step The transport block was modeled by shifting the solute content from one cell to
the next one In each cell the aqueous solute was mixed and adsorbed on GTiO2
according to the equations In each cell the aqueous solute was mixed and assumed to
be in equilibration with GTiO2 The sequence of shifting mixing and equilibrium
adsorption was repeated for each cell until the total number of shifts was completed
The diffusion coefficient Dw in PHREEQC accounting for retardation was
calculated as Dw=x2
(36t) where x stands for the diffusion length (estimated as the
radius of the particle size) and t represents equilibrium time adopted from the batch
kinetic data (Mertens et al 2012)
For CD-MUSIC modeling in the PHREEQC take As(III) as an example to
explain the adsorption equation The As(III) adsorption is considered as a ligand
35
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
exchange reaction with the hydroxide group on GTiO2 (Surf_sOH-033) forming a
H3ArseniteO3 is the master species in groundwater at pH 82
(Surf_sO)2ArseniteOH-066 is the common adsorbed bidentate binuclear complex
evidenced by our previous reports(Pena et al 2006 Yan et al 2015) LogK is the
adsorption equilibrium constants Generally every adsorption equation under certain
experimental condition has a unique value of logK In the adsorption equation ldquo-2rdquo
represents the lost two hydrogens by Surf_sOH-033 after it adsorbs H3ArseniteO3 ldquo-
1rdquo represents the change in charge on Arsenite at 1 plane due to gaining one hydrogen
(+1) and one oxygen (-2) ldquo0rdquo represents no change in charge at the 2 plane ldquo066rdquo is
the fraction of the central ion (As) on GTiO2 surface that is associated with plane 0
ldquo3rdquo is the charge on the central ion As(III) Following this equation and the relevant
parameters As(III) adsorbed on GTiO2
The diffusion coefficient Dw in PHREEQC accounting for retardation was
calculated as Dw=x2(36t) where x stands for the diffusion length (estimated as the
radius of the particle size) and t represents equilibrium time adopted from the batch
kinetic data (Mertens et al 2012)
To well simulate the As breakthrough curve in columns four As(V) adsorption
reactions (Table 1) were employed Adsorption site density of 60 mmolg was
36
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
adopted from our previous study (Pena et al 2006) and the total adsorption sites were
calculated to be 1844 sitesnm2 The final optimized ratio of strong to weak sites was
51 The surface complexation constants were reasonably adjusted according to the
batch modeling results as the column reaction may not reach equilibrium in local
micro-interfacial areas due to much less contact time between As and GTiO2 than that
in batch experiments (Appelo and Postma 1999) In the modeling a stepwise
procedure was adopted to achieve a viable result An estimation of two thirds of the
surface site density being accessible for EBCT=011 min with large flow rate of 265
mLmin was optimized which could probably result from unavailable adsorption sites
due to fast transport through the column
The adsorbed As on GTiO2 in the column was calculated by mass balance
between the influent and effluent
where Asadsorbed is the adsorbed As on GTiO2 (mgg) n is the number of collected
samples Cin and Cout are influent and effluent As concentrations (mgL) respectively
Vi is volume (L) of groundwater passed through the column between sample i-1 and i
and m is the mass of GTiO2 (g)
Even though the oxidation of adsorbed As(III) occurred during filtration as
analyzed from XANES and mass balance analysis (Fig 7) no As(III) oxidation
reactions were considered in PHREEQC modeling which would not impact the
breakthrough of As(IIIV)
37
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
38
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
Fig S54 Effect of EBCT on Si Ca and Mg breakthrough curves using groundwater 1 The sample notation in panel c indicates field column experiments with EBCT in minutes
References
Appelo CAJ Postma D 1999 A consistent model for surface complexation on birnessite (MnO2) and its application to a column experiment Geochim Cosmochim Ac 63 (19-20) 3039-3048Badruzzaman M Westerhoff P Knappe DRU 2004 Intraparticle diffusion and adsorption of arsenate onto granular ferric hydroxide (GFH) Water Res 38 (18) 4002-4012Banerjee K Amy GL Prevost M Nour S Jekel M Gallagher PM Blumenschein CD 2008 Kinetic and thermodynamic aspects of adsorption of arsenic onto granular ferric hydroxide (GFH) Water Res 42 (13) 3371-3378Bang S Patel M Lippincott L Meng XG 2005 Removal of arsenic from groundwater by granular titanium dioxide adsorbent Chemosphere 60 (3) 389-397Bang S Pena ME Patel M Lippincott L Meng X Kim KW 2011 Removal of arsenate from water by adsorbents a comparative case study Environ Geochem Hlth 33 133-141Cui JL Shi JB Jiang GB Jing CY 2013 Arsenic levels and speciation from ingestion exposures to biomarkers in Shanxi China Implications for human health Environ Sci Technol 47 (10) 5419-5424Daus B Wennrich R Weiss H 2004 Sorption materials for arsenic removal from water A comparative study Water Res 38 (12) 2948-2954Dou XM Mohan D Pittman CU 2013 Arsenate adsorption on three types of granular schwertmannite Water Res 47 (9) 2938-2948Dou XM Zhang Y Yang M Pei YS Huang X Takayama T Kato S 2006 Occurrence of arsenic in groundwater in the suburbs of Beijing and its removal using an iron-cerium bimetal oxide adsorbent Water Qual Res J Can 41 (2) 140-146Gibbons MK Gagnon GA 2010 Adsorption of arsenic from a Nova Scotia groundwater onto water treatment residual solids Water Res 44 (19) 5740-5749Glocheux Y Mendez Pasarin M Albadarin AB Allen SJ Walker GM 2013 Removal of arsenic from groundwater by adsorption onto an acidified laterite by-product Chem Eng J 228 565-574Guan XH Wang JM Chusuei CC 2008 Removal of arsenic from water using granular ferric hydroxide Macroscopic and microscopic studies J Hazard Mater 156 (1-3) 178-185Gupta K Maity A Ghosh UC 2010 Manganese associated nanoparticles agglomerate of iron(III) oxide Synthesis characterization and arsenic(III) sorption behavior with mechanism J Hazard Mater 184 (1-3) 832-842Hao JM Han MJ Wang C Meng XG 2009 Enhanced removal of arsenite from water by a mesoporous hybrid material - Thiol-functionalized silica coated activated alumina Micropor Mesopor
Mat 124 (1-3) 1-7Hiemstra T Van Riemsdijk WH 2006 On the relationship between charge distribution surface hydration and the structure of the interface of metal hydroxides J Colloid Interf Sci 301 (1) 1-18Hristovski K Baumgardner A Westerhoff P 2007 Selecting metal oxide nanomaterials for arsenic removal in fixed bed columns From nanopowders to aggregated nanoparticle media J Hazard Mater 147 (1-2) 265-274Jang M Chen WF Cannon FS 2008 Preloading hydrous ferric oxide into granular activated carbon for arsenic removal Environ Sci Technol 42 (9) 3369-3374Jing CY Cui JL Huang YY Li AG 2012 Fabrication characterization and application of a composite adsorbent for simultaneous removal of arsenic and fluoride ACS Appl Mater Interfaces 4 (2) 714-720Kanematsu M Young TM Fukushi K Green PG Darby JL 2010 Extended triple layer modeling of arsenate and phosphate adsorption on a goethite-based granular porous adsorbent Environ Sci Technol 44 (9) 3388-3394Kong S Wang Y Zhan H Yuan S Liu M Zhou C 2013 Arsenite and Arsenate Removal from Contaminated Groundwater by Nanoscale Iron-Manganese Binary Oxides Column Studies Environmental Engineering Science 30 (11) 689-696Li Y Liu JR Jia SY Guo JW Zhuo J Na P 2012 TiO2 pillared montmorillonite as a photoactive adsorbent of arsenic under UV irradiation Chem Eng J 191 66-74Lin TF Wu JK 2001 Adsorption of arsenite and arsenate within activated alumina grains Equilibrium and kinetics Water Res 35 (8) 2049-2057Luo T Cui JL Hu S Huang YY Jing CY 2010 Arsenic removal and recovery from copper smelting wastewater using TiO2 Environ Sci Technol 44 (23) 9094-9098Maiti A Basu JK De S 2010a Development of a Treated Laterite for Arsenic Adsorption Effects of Treatment Parameters Industrial amp Engineering Chemistry Research 49 (10) 4873-4886Maiti A Basu JK De S 2010b Removal of Arsenic from Synthetic and Natural Groundwater Using Acid-Activated Laterite Environmental Progress amp Sustainable Energy 29 (4) 457-470Maiti A Basu JK De S 2012 Experimental and kinetic modeling of As(V) and As(III) adsorption on treated laterite using synthetic and contaminated groundwater Effects of phosphate silicate and carbonate ions Chem Eng J 191 1-12Maiti A Thakur BK Basu JK De S 2013a Comparison of treated laterite as arsenic adsorbent from different locations and performance of best filter under field conditions J Hazard Mater 262 1176-1186Maiti A Thakur BK Basu JK De S 2013b Comparison of treated laterite as arsenic adsorbent from different locations and performance of best filter under field conditions J Hazard Mater 262 (0) 1176-1186Maji SK Pal A Pal T 2008 Arsenic removal from real-life groundwater by adsorption on laterite soil J Hazard Mater 151 (2-3) 811-820Maji SK Kao YH Wang CJ Lu GS Wu JJ Liu CW 2012 Fixed bed adsorption of As(III) on iron-oxide-coated natural rock (IOCNR) and application to real arsenic-bearing groundwater Chem Eng J 203 285-293Mertens J Rose J Kagi R Chaurand P Plotze M Wehrli B Furrer G 2012 Adsorption of arsenic on polyaluminum granulate Environ Sci Technol 46 (13) 7310-7317Nguyen TV Vigneswaran S Ngo HH Pokhre D Viraraghavan T 2006 Iron-coated sponge as
effective media to remove arsenic from drinking water Water Qual Res J Can 41 (2) 164-170Parkhurst DL Appelo CAJ 2013 Description of input and examples for PHREEQC version 3-A computer program for speciation batch-reaction one-dimensional transport and inverse geochemical calculations US Geological SurveyPena M Meng XG Korfiatis GP Jing CY 2006 Adsorption mechanism of arsenic on nanocrystalline titanium dioxide Environ Sci Technol 40 (4) 1257-1262Ravel B Newville M 2005 ATHENA ARTEMIS HEPHAESTUS Data analysis for X-ray absorption spectroscopy using IFEFFIT J Synchrotron Radiat 12 537-541Saha B Bains R Greenwood F 2005 Physicochemical characterization of granular ferric hydroxide (GFH) for arsenic(V) sorption from water Separation Science and Technology 40 (14) 2909-2932Shan H Ma T Wang Y Zhao J Han H Deng Y He X Dong Y 2013 A cost-effective system for in-situ geological arsenic adsorption from groundwater J Contam Hydrol 154 1-9Stachowicz M Hiemstra T van Riemsdijk WH 2008 Multi-competitive interaction of As(III) and As(V) oxyanions with Ca2+ Mg2+ PO4
3- and CO32- ions on goethite J Colloid Interf Sci 320 (2) 400-
414Streat M Hellgardt K Newton NLR 2008 Hydrous ferric oxide as an adsorbent in water treatment - Part 3 Batch and mini-column adsorption of arsenic phosphorus fluorine and cadmium ions Process Safety and Environmental Protection 86 (B1) 21-30Thirunavukkarasu OS Viraraghavan T Subramanian KS 2003 Arsenic removal from drinking water using iron oxide-coated sand Water Air Soil Poll 142 (1-4) 95-111USEPA 2008 Assessing arsenic removal by metal (hydr)oxide adsorptive media using rapid small scale column tests Govenrnment Printing Office Washington DCWang J Xu W Chen L Huang X Liu J 2014 Preparation and evaluation of magnetic nanoparticles impregnated chitosan beads for arsenic removal from water Chem Eng J 251 25-34Westerhoff P Highfield D Badruzzaman M Yoon Y 2005 Rapid small-scale column tests for arsenate removal in iron oxide packed bed columns J Environ Eng-Asce 131 (2) 262-271Westerhoff P De Haan M Martindale A Badruzzaman M 2006 Arsenic adsorptive media technology selection strategies Water Qual Res J Can 41 (2) 171-184Yan L Huang Y Cui J Jing C 2015 Simultaneous As(III) and Cd removal from copper smelting wastewater using granular TiO2 columns Water Res 68 (0) 572-579Zhao K Guo HM 2014 Behavior and mechanism of arsenate adsorption on activated natural siderite Evidences from FTIR and XANES analysis Environ Sci Pollut Res 21 (3) 1944-1953Zhao K Guo H Zhou X 2014 Adsorption and heterogeneous oxidation of arsenite on modified granular natural siderite Characterization and behaviors Appl Geochem 48 184-192
Table S86 The charge distribution (f) of central As atom to TiO2 surface in simulating the effect of cations and anions on As adsorption in 01 M NaCl at pH 82 in Fig 4 BK Si HCO3 All
As(V) 022 017 012 016As(III) 040 020 058 056
Fig S43 Molar percentage () of As Ca Mg and Si on pristine and spent GTiO2
surfaces using EDX analysis The spent GTiO2 samples after field column experiments using groundwater 1 were identified with EBCT in min under x-axis The value of molar percentage of each element was averaged from randomly-chosen positions on the adsorbent surface
33
417
418
419420
421422
423
424
425
426
427
428
429
430
431
432
433434435436437438
439
440
441
As speciation analysis on spent GTiO2 using XANES
The spent GTiO2 samples were ground using a mortar and pestle and then the
ground powder was spread on Scotch tape The As k-edge XANES spectra were
collected at beamline 01C1 at the National Synchrotron Radiation Research Center
(NSRRC) Taiwan Spectra were acquired from -150 to 300 eV relative to the As K-
edge of 11867 eV at cryogenic temperature (77 K) using a cryostat to prevent the
oxidation of As(III) by X-rays The fluorescence signals were collected using a Lytle
detector Two to four scans were collected for each sample and averaged to improve
the signalnoise ratio The XANES analysis was performed with the Athena program
in the IFEFFIT computer package for linear combination fit (LCF) (Cui et al 2013
Ravel and Newville 2005)
34
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
PHREEQC modeling for As breakthrough curves in field column experiments
PHREEQC a geochemical model integrates macroscopic mass transfer
processes with a microscopic surface complexation model (Parkhurst and Appelo
2013) It can be applied in calculating solution complex speciation batch-reaction
and one-dimensional reactive-transport and inverse modeling In our study the one-
dimensional column was defined by four cells with the same length The cell length
was calculated to be one-fourth of the actual column length Time step (s) was
calculated according to equation Time step = Lcell(Q60A) where Lcell is the cell
length (cm) Q is flow velocity (mLmin) A is the effective column cross section area
(cm2) which is the column cross-sectional area multiplied by porosity (060) Total
shift number was calculated by dividing actual column operation time by the time
step The transport block was modeled by shifting the solute content from one cell to
the next one In each cell the aqueous solute was mixed and adsorbed on GTiO2
according to the equations In each cell the aqueous solute was mixed and assumed to
be in equilibration with GTiO2 The sequence of shifting mixing and equilibrium
adsorption was repeated for each cell until the total number of shifts was completed
The diffusion coefficient Dw in PHREEQC accounting for retardation was
calculated as Dw=x2
(36t) where x stands for the diffusion length (estimated as the
radius of the particle size) and t represents equilibrium time adopted from the batch
kinetic data (Mertens et al 2012)
For CD-MUSIC modeling in the PHREEQC take As(III) as an example to
explain the adsorption equation The As(III) adsorption is considered as a ligand
35
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
exchange reaction with the hydroxide group on GTiO2 (Surf_sOH-033) forming a
H3ArseniteO3 is the master species in groundwater at pH 82
(Surf_sO)2ArseniteOH-066 is the common adsorbed bidentate binuclear complex
evidenced by our previous reports(Pena et al 2006 Yan et al 2015) LogK is the
adsorption equilibrium constants Generally every adsorption equation under certain
experimental condition has a unique value of logK In the adsorption equation ldquo-2rdquo
represents the lost two hydrogens by Surf_sOH-033 after it adsorbs H3ArseniteO3 ldquo-
1rdquo represents the change in charge on Arsenite at 1 plane due to gaining one hydrogen
(+1) and one oxygen (-2) ldquo0rdquo represents no change in charge at the 2 plane ldquo066rdquo is
the fraction of the central ion (As) on GTiO2 surface that is associated with plane 0
ldquo3rdquo is the charge on the central ion As(III) Following this equation and the relevant
parameters As(III) adsorbed on GTiO2
The diffusion coefficient Dw in PHREEQC accounting for retardation was
calculated as Dw=x2(36t) where x stands for the diffusion length (estimated as the
radius of the particle size) and t represents equilibrium time adopted from the batch
kinetic data (Mertens et al 2012)
To well simulate the As breakthrough curve in columns four As(V) adsorption
reactions (Table 1) were employed Adsorption site density of 60 mmolg was
36
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
adopted from our previous study (Pena et al 2006) and the total adsorption sites were
calculated to be 1844 sitesnm2 The final optimized ratio of strong to weak sites was
51 The surface complexation constants were reasonably adjusted according to the
batch modeling results as the column reaction may not reach equilibrium in local
micro-interfacial areas due to much less contact time between As and GTiO2 than that
in batch experiments (Appelo and Postma 1999) In the modeling a stepwise
procedure was adopted to achieve a viable result An estimation of two thirds of the
surface site density being accessible for EBCT=011 min with large flow rate of 265
mLmin was optimized which could probably result from unavailable adsorption sites
due to fast transport through the column
The adsorbed As on GTiO2 in the column was calculated by mass balance
between the influent and effluent
where Asadsorbed is the adsorbed As on GTiO2 (mgg) n is the number of collected
samples Cin and Cout are influent and effluent As concentrations (mgL) respectively
Vi is volume (L) of groundwater passed through the column between sample i-1 and i
and m is the mass of GTiO2 (g)
Even though the oxidation of adsorbed As(III) occurred during filtration as
analyzed from XANES and mass balance analysis (Fig 7) no As(III) oxidation
reactions were considered in PHREEQC modeling which would not impact the
breakthrough of As(IIIV)
37
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
38
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
Fig S54 Effect of EBCT on Si Ca and Mg breakthrough curves using groundwater 1 The sample notation in panel c indicates field column experiments with EBCT in minutes
References
Appelo CAJ Postma D 1999 A consistent model for surface complexation on birnessite (MnO2) and its application to a column experiment Geochim Cosmochim Ac 63 (19-20) 3039-3048Badruzzaman M Westerhoff P Knappe DRU 2004 Intraparticle diffusion and adsorption of arsenate onto granular ferric hydroxide (GFH) Water Res 38 (18) 4002-4012Banerjee K Amy GL Prevost M Nour S Jekel M Gallagher PM Blumenschein CD 2008 Kinetic and thermodynamic aspects of adsorption of arsenic onto granular ferric hydroxide (GFH) Water Res 42 (13) 3371-3378Bang S Patel M Lippincott L Meng XG 2005 Removal of arsenic from groundwater by granular titanium dioxide adsorbent Chemosphere 60 (3) 389-397Bang S Pena ME Patel M Lippincott L Meng X Kim KW 2011 Removal of arsenate from water by adsorbents a comparative case study Environ Geochem Hlth 33 133-141Cui JL Shi JB Jiang GB Jing CY 2013 Arsenic levels and speciation from ingestion exposures to biomarkers in Shanxi China Implications for human health Environ Sci Technol 47 (10) 5419-5424Daus B Wennrich R Weiss H 2004 Sorption materials for arsenic removal from water A comparative study Water Res 38 (12) 2948-2954Dou XM Mohan D Pittman CU 2013 Arsenate adsorption on three types of granular schwertmannite Water Res 47 (9) 2938-2948Dou XM Zhang Y Yang M Pei YS Huang X Takayama T Kato S 2006 Occurrence of arsenic in groundwater in the suburbs of Beijing and its removal using an iron-cerium bimetal oxide adsorbent Water Qual Res J Can 41 (2) 140-146Gibbons MK Gagnon GA 2010 Adsorption of arsenic from a Nova Scotia groundwater onto water treatment residual solids Water Res 44 (19) 5740-5749Glocheux Y Mendez Pasarin M Albadarin AB Allen SJ Walker GM 2013 Removal of arsenic from groundwater by adsorption onto an acidified laterite by-product Chem Eng J 228 565-574Guan XH Wang JM Chusuei CC 2008 Removal of arsenic from water using granular ferric hydroxide Macroscopic and microscopic studies J Hazard Mater 156 (1-3) 178-185Gupta K Maity A Ghosh UC 2010 Manganese associated nanoparticles agglomerate of iron(III) oxide Synthesis characterization and arsenic(III) sorption behavior with mechanism J Hazard Mater 184 (1-3) 832-842Hao JM Han MJ Wang C Meng XG 2009 Enhanced removal of arsenite from water by a mesoporous hybrid material - Thiol-functionalized silica coated activated alumina Micropor Mesopor
Mat 124 (1-3) 1-7Hiemstra T Van Riemsdijk WH 2006 On the relationship between charge distribution surface hydration and the structure of the interface of metal hydroxides J Colloid Interf Sci 301 (1) 1-18Hristovski K Baumgardner A Westerhoff P 2007 Selecting metal oxide nanomaterials for arsenic removal in fixed bed columns From nanopowders to aggregated nanoparticle media J Hazard Mater 147 (1-2) 265-274Jang M Chen WF Cannon FS 2008 Preloading hydrous ferric oxide into granular activated carbon for arsenic removal Environ Sci Technol 42 (9) 3369-3374Jing CY Cui JL Huang YY Li AG 2012 Fabrication characterization and application of a composite adsorbent for simultaneous removal of arsenic and fluoride ACS Appl Mater Interfaces 4 (2) 714-720Kanematsu M Young TM Fukushi K Green PG Darby JL 2010 Extended triple layer modeling of arsenate and phosphate adsorption on a goethite-based granular porous adsorbent Environ Sci Technol 44 (9) 3388-3394Kong S Wang Y Zhan H Yuan S Liu M Zhou C 2013 Arsenite and Arsenate Removal from Contaminated Groundwater by Nanoscale Iron-Manganese Binary Oxides Column Studies Environmental Engineering Science 30 (11) 689-696Li Y Liu JR Jia SY Guo JW Zhuo J Na P 2012 TiO2 pillared montmorillonite as a photoactive adsorbent of arsenic under UV irradiation Chem Eng J 191 66-74Lin TF Wu JK 2001 Adsorption of arsenite and arsenate within activated alumina grains Equilibrium and kinetics Water Res 35 (8) 2049-2057Luo T Cui JL Hu S Huang YY Jing CY 2010 Arsenic removal and recovery from copper smelting wastewater using TiO2 Environ Sci Technol 44 (23) 9094-9098Maiti A Basu JK De S 2010a Development of a Treated Laterite for Arsenic Adsorption Effects of Treatment Parameters Industrial amp Engineering Chemistry Research 49 (10) 4873-4886Maiti A Basu JK De S 2010b Removal of Arsenic from Synthetic and Natural Groundwater Using Acid-Activated Laterite Environmental Progress amp Sustainable Energy 29 (4) 457-470Maiti A Basu JK De S 2012 Experimental and kinetic modeling of As(V) and As(III) adsorption on treated laterite using synthetic and contaminated groundwater Effects of phosphate silicate and carbonate ions Chem Eng J 191 1-12Maiti A Thakur BK Basu JK De S 2013a Comparison of treated laterite as arsenic adsorbent from different locations and performance of best filter under field conditions J Hazard Mater 262 1176-1186Maiti A Thakur BK Basu JK De S 2013b Comparison of treated laterite as arsenic adsorbent from different locations and performance of best filter under field conditions J Hazard Mater 262 (0) 1176-1186Maji SK Pal A Pal T 2008 Arsenic removal from real-life groundwater by adsorption on laterite soil J Hazard Mater 151 (2-3) 811-820Maji SK Kao YH Wang CJ Lu GS Wu JJ Liu CW 2012 Fixed bed adsorption of As(III) on iron-oxide-coated natural rock (IOCNR) and application to real arsenic-bearing groundwater Chem Eng J 203 285-293Mertens J Rose J Kagi R Chaurand P Plotze M Wehrli B Furrer G 2012 Adsorption of arsenic on polyaluminum granulate Environ Sci Technol 46 (13) 7310-7317Nguyen TV Vigneswaran S Ngo HH Pokhre D Viraraghavan T 2006 Iron-coated sponge as
effective media to remove arsenic from drinking water Water Qual Res J Can 41 (2) 164-170Parkhurst DL Appelo CAJ 2013 Description of input and examples for PHREEQC version 3-A computer program for speciation batch-reaction one-dimensional transport and inverse geochemical calculations US Geological SurveyPena M Meng XG Korfiatis GP Jing CY 2006 Adsorption mechanism of arsenic on nanocrystalline titanium dioxide Environ Sci Technol 40 (4) 1257-1262Ravel B Newville M 2005 ATHENA ARTEMIS HEPHAESTUS Data analysis for X-ray absorption spectroscopy using IFEFFIT J Synchrotron Radiat 12 537-541Saha B Bains R Greenwood F 2005 Physicochemical characterization of granular ferric hydroxide (GFH) for arsenic(V) sorption from water Separation Science and Technology 40 (14) 2909-2932Shan H Ma T Wang Y Zhao J Han H Deng Y He X Dong Y 2013 A cost-effective system for in-situ geological arsenic adsorption from groundwater J Contam Hydrol 154 1-9Stachowicz M Hiemstra T van Riemsdijk WH 2008 Multi-competitive interaction of As(III) and As(V) oxyanions with Ca2+ Mg2+ PO4
3- and CO32- ions on goethite J Colloid Interf Sci 320 (2) 400-
414Streat M Hellgardt K Newton NLR 2008 Hydrous ferric oxide as an adsorbent in water treatment - Part 3 Batch and mini-column adsorption of arsenic phosphorus fluorine and cadmium ions Process Safety and Environmental Protection 86 (B1) 21-30Thirunavukkarasu OS Viraraghavan T Subramanian KS 2003 Arsenic removal from drinking water using iron oxide-coated sand Water Air Soil Poll 142 (1-4) 95-111USEPA 2008 Assessing arsenic removal by metal (hydr)oxide adsorptive media using rapid small scale column tests Govenrnment Printing Office Washington DCWang J Xu W Chen L Huang X Liu J 2014 Preparation and evaluation of magnetic nanoparticles impregnated chitosan beads for arsenic removal from water Chem Eng J 251 25-34Westerhoff P Highfield D Badruzzaman M Yoon Y 2005 Rapid small-scale column tests for arsenate removal in iron oxide packed bed columns J Environ Eng-Asce 131 (2) 262-271Westerhoff P De Haan M Martindale A Badruzzaman M 2006 Arsenic adsorptive media technology selection strategies Water Qual Res J Can 41 (2) 171-184Yan L Huang Y Cui J Jing C 2015 Simultaneous As(III) and Cd removal from copper smelting wastewater using granular TiO2 columns Water Res 68 (0) 572-579Zhao K Guo HM 2014 Behavior and mechanism of arsenate adsorption on activated natural siderite Evidences from FTIR and XANES analysis Environ Sci Pollut Res 21 (3) 1944-1953Zhao K Guo H Zhou X 2014 Adsorption and heterogeneous oxidation of arsenite on modified granular natural siderite Characterization and behaviors Appl Geochem 48 184-192
H3ArseniteO3 is the master species in groundwater at pH 82
(Surf_sO)2ArseniteOH-066 is the common adsorbed bidentate binuclear complex
evidenced by our previous reports(Pena et al 2006 Yan et al 2015) LogK is the
adsorption equilibrium constants Generally every adsorption equation under certain
experimental condition has a unique value of logK In the adsorption equation ldquo-2rdquo
represents the lost two hydrogens by Surf_sOH-033 after it adsorbs H3ArseniteO3 ldquo-
1rdquo represents the change in charge on Arsenite at 1 plane due to gaining one hydrogen
(+1) and one oxygen (-2) ldquo0rdquo represents no change in charge at the 2 plane ldquo066rdquo is
the fraction of the central ion (As) on GTiO2 surface that is associated with plane 0
ldquo3rdquo is the charge on the central ion As(III) Following this equation and the relevant
parameters As(III) adsorbed on GTiO2
The diffusion coefficient Dw in PHREEQC accounting for retardation was
calculated as Dw=x2(36t) where x stands for the diffusion length (estimated as the
radius of the particle size) and t represents equilibrium time adopted from the batch
kinetic data (Mertens et al 2012)
To well simulate the As breakthrough curve in columns four As(V) adsorption
reactions (Table 1) were employed Adsorption site density of 60 mmolg was
36
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
adopted from our previous study (Pena et al 2006) and the total adsorption sites were
calculated to be 1844 sitesnm2 The final optimized ratio of strong to weak sites was
51 The surface complexation constants were reasonably adjusted according to the
batch modeling results as the column reaction may not reach equilibrium in local
micro-interfacial areas due to much less contact time between As and GTiO2 than that
in batch experiments (Appelo and Postma 1999) In the modeling a stepwise
procedure was adopted to achieve a viable result An estimation of two thirds of the
surface site density being accessible for EBCT=011 min with large flow rate of 265
mLmin was optimized which could probably result from unavailable adsorption sites
due to fast transport through the column
The adsorbed As on GTiO2 in the column was calculated by mass balance
between the influent and effluent
where Asadsorbed is the adsorbed As on GTiO2 (mgg) n is the number of collected
samples Cin and Cout are influent and effluent As concentrations (mgL) respectively
Vi is volume (L) of groundwater passed through the column between sample i-1 and i
and m is the mass of GTiO2 (g)
Even though the oxidation of adsorbed As(III) occurred during filtration as
analyzed from XANES and mass balance analysis (Fig 7) no As(III) oxidation
reactions were considered in PHREEQC modeling which would not impact the
breakthrough of As(IIIV)
37
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
38
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
Fig S54 Effect of EBCT on Si Ca and Mg breakthrough curves using groundwater 1 The sample notation in panel c indicates field column experiments with EBCT in minutes
References
Appelo CAJ Postma D 1999 A consistent model for surface complexation on birnessite (MnO2) and its application to a column experiment Geochim Cosmochim Ac 63 (19-20) 3039-3048Badruzzaman M Westerhoff P Knappe DRU 2004 Intraparticle diffusion and adsorption of arsenate onto granular ferric hydroxide (GFH) Water Res 38 (18) 4002-4012Banerjee K Amy GL Prevost M Nour S Jekel M Gallagher PM Blumenschein CD 2008 Kinetic and thermodynamic aspects of adsorption of arsenic onto granular ferric hydroxide (GFH) Water Res 42 (13) 3371-3378Bang S Patel M Lippincott L Meng XG 2005 Removal of arsenic from groundwater by granular titanium dioxide adsorbent Chemosphere 60 (3) 389-397Bang S Pena ME Patel M Lippincott L Meng X Kim KW 2011 Removal of arsenate from water by adsorbents a comparative case study Environ Geochem Hlth 33 133-141Cui JL Shi JB Jiang GB Jing CY 2013 Arsenic levels and speciation from ingestion exposures to biomarkers in Shanxi China Implications for human health Environ Sci Technol 47 (10) 5419-5424Daus B Wennrich R Weiss H 2004 Sorption materials for arsenic removal from water A comparative study Water Res 38 (12) 2948-2954Dou XM Mohan D Pittman CU 2013 Arsenate adsorption on three types of granular schwertmannite Water Res 47 (9) 2938-2948Dou XM Zhang Y Yang M Pei YS Huang X Takayama T Kato S 2006 Occurrence of arsenic in groundwater in the suburbs of Beijing and its removal using an iron-cerium bimetal oxide adsorbent Water Qual Res J Can 41 (2) 140-146Gibbons MK Gagnon GA 2010 Adsorption of arsenic from a Nova Scotia groundwater onto water treatment residual solids Water Res 44 (19) 5740-5749Glocheux Y Mendez Pasarin M Albadarin AB Allen SJ Walker GM 2013 Removal of arsenic from groundwater by adsorption onto an acidified laterite by-product Chem Eng J 228 565-574Guan XH Wang JM Chusuei CC 2008 Removal of arsenic from water using granular ferric hydroxide Macroscopic and microscopic studies J Hazard Mater 156 (1-3) 178-185Gupta K Maity A Ghosh UC 2010 Manganese associated nanoparticles agglomerate of iron(III) oxide Synthesis characterization and arsenic(III) sorption behavior with mechanism J Hazard Mater 184 (1-3) 832-842Hao JM Han MJ Wang C Meng XG 2009 Enhanced removal of arsenite from water by a mesoporous hybrid material - Thiol-functionalized silica coated activated alumina Micropor Mesopor
Mat 124 (1-3) 1-7Hiemstra T Van Riemsdijk WH 2006 On the relationship between charge distribution surface hydration and the structure of the interface of metal hydroxides J Colloid Interf Sci 301 (1) 1-18Hristovski K Baumgardner A Westerhoff P 2007 Selecting metal oxide nanomaterials for arsenic removal in fixed bed columns From nanopowders to aggregated nanoparticle media J Hazard Mater 147 (1-2) 265-274Jang M Chen WF Cannon FS 2008 Preloading hydrous ferric oxide into granular activated carbon for arsenic removal Environ Sci Technol 42 (9) 3369-3374Jing CY Cui JL Huang YY Li AG 2012 Fabrication characterization and application of a composite adsorbent for simultaneous removal of arsenic and fluoride ACS Appl Mater Interfaces 4 (2) 714-720Kanematsu M Young TM Fukushi K Green PG Darby JL 2010 Extended triple layer modeling of arsenate and phosphate adsorption on a goethite-based granular porous adsorbent Environ Sci Technol 44 (9) 3388-3394Kong S Wang Y Zhan H Yuan S Liu M Zhou C 2013 Arsenite and Arsenate Removal from Contaminated Groundwater by Nanoscale Iron-Manganese Binary Oxides Column Studies Environmental Engineering Science 30 (11) 689-696Li Y Liu JR Jia SY Guo JW Zhuo J Na P 2012 TiO2 pillared montmorillonite as a photoactive adsorbent of arsenic under UV irradiation Chem Eng J 191 66-74Lin TF Wu JK 2001 Adsorption of arsenite and arsenate within activated alumina grains Equilibrium and kinetics Water Res 35 (8) 2049-2057Luo T Cui JL Hu S Huang YY Jing CY 2010 Arsenic removal and recovery from copper smelting wastewater using TiO2 Environ Sci Technol 44 (23) 9094-9098Maiti A Basu JK De S 2010a Development of a Treated Laterite for Arsenic Adsorption Effects of Treatment Parameters Industrial amp Engineering Chemistry Research 49 (10) 4873-4886Maiti A Basu JK De S 2010b Removal of Arsenic from Synthetic and Natural Groundwater Using Acid-Activated Laterite Environmental Progress amp Sustainable Energy 29 (4) 457-470Maiti A Basu JK De S 2012 Experimental and kinetic modeling of As(V) and As(III) adsorption on treated laterite using synthetic and contaminated groundwater Effects of phosphate silicate and carbonate ions Chem Eng J 191 1-12Maiti A Thakur BK Basu JK De S 2013a Comparison of treated laterite as arsenic adsorbent from different locations and performance of best filter under field conditions J Hazard Mater 262 1176-1186Maiti A Thakur BK Basu JK De S 2013b Comparison of treated laterite as arsenic adsorbent from different locations and performance of best filter under field conditions J Hazard Mater 262 (0) 1176-1186Maji SK Pal A Pal T 2008 Arsenic removal from real-life groundwater by adsorption on laterite soil J Hazard Mater 151 (2-3) 811-820Maji SK Kao YH Wang CJ Lu GS Wu JJ Liu CW 2012 Fixed bed adsorption of As(III) on iron-oxide-coated natural rock (IOCNR) and application to real arsenic-bearing groundwater Chem Eng J 203 285-293Mertens J Rose J Kagi R Chaurand P Plotze M Wehrli B Furrer G 2012 Adsorption of arsenic on polyaluminum granulate Environ Sci Technol 46 (13) 7310-7317Nguyen TV Vigneswaran S Ngo HH Pokhre D Viraraghavan T 2006 Iron-coated sponge as
effective media to remove arsenic from drinking water Water Qual Res J Can 41 (2) 164-170Parkhurst DL Appelo CAJ 2013 Description of input and examples for PHREEQC version 3-A computer program for speciation batch-reaction one-dimensional transport and inverse geochemical calculations US Geological SurveyPena M Meng XG Korfiatis GP Jing CY 2006 Adsorption mechanism of arsenic on nanocrystalline titanium dioxide Environ Sci Technol 40 (4) 1257-1262Ravel B Newville M 2005 ATHENA ARTEMIS HEPHAESTUS Data analysis for X-ray absorption spectroscopy using IFEFFIT J Synchrotron Radiat 12 537-541Saha B Bains R Greenwood F 2005 Physicochemical characterization of granular ferric hydroxide (GFH) for arsenic(V) sorption from water Separation Science and Technology 40 (14) 2909-2932Shan H Ma T Wang Y Zhao J Han H Deng Y He X Dong Y 2013 A cost-effective system for in-situ geological arsenic adsorption from groundwater J Contam Hydrol 154 1-9Stachowicz M Hiemstra T van Riemsdijk WH 2008 Multi-competitive interaction of As(III) and As(V) oxyanions with Ca2+ Mg2+ PO4
3- and CO32- ions on goethite J Colloid Interf Sci 320 (2) 400-
414Streat M Hellgardt K Newton NLR 2008 Hydrous ferric oxide as an adsorbent in water treatment - Part 3 Batch and mini-column adsorption of arsenic phosphorus fluorine and cadmium ions Process Safety and Environmental Protection 86 (B1) 21-30Thirunavukkarasu OS Viraraghavan T Subramanian KS 2003 Arsenic removal from drinking water using iron oxide-coated sand Water Air Soil Poll 142 (1-4) 95-111USEPA 2008 Assessing arsenic removal by metal (hydr)oxide adsorptive media using rapid small scale column tests Govenrnment Printing Office Washington DCWang J Xu W Chen L Huang X Liu J 2014 Preparation and evaluation of magnetic nanoparticles impregnated chitosan beads for arsenic removal from water Chem Eng J 251 25-34Westerhoff P Highfield D Badruzzaman M Yoon Y 2005 Rapid small-scale column tests for arsenate removal in iron oxide packed bed columns J Environ Eng-Asce 131 (2) 262-271Westerhoff P De Haan M Martindale A Badruzzaman M 2006 Arsenic adsorptive media technology selection strategies Water Qual Res J Can 41 (2) 171-184Yan L Huang Y Cui J Jing C 2015 Simultaneous As(III) and Cd removal from copper smelting wastewater using granular TiO2 columns Water Res 68 (0) 572-579Zhao K Guo HM 2014 Behavior and mechanism of arsenate adsorption on activated natural siderite Evidences from FTIR and XANES analysis Environ Sci Pollut Res 21 (3) 1944-1953Zhao K Guo H Zhou X 2014 Adsorption and heterogeneous oxidation of arsenite on modified granular natural siderite Characterization and behaviors Appl Geochem 48 184-192
H3ArseniteO3 is the master species in groundwater at pH 82
(Surf_sO)2ArseniteOH-066 is the common adsorbed bidentate binuclear complex
evidenced by our previous reports(Pena et al 2006 Yan et al 2015) LogK is the
adsorption equilibrium constants Generally every adsorption equation under certain
experimental condition has a unique value of logK In the adsorption equation ldquo-2rdquo
represents the lost two hydrogens by Surf_sOH-033 after it adsorbs H3ArseniteO3 ldquo-
1rdquo represents the change in charge on Arsenite at 1 plane due to gaining one hydrogen
(+1) and one oxygen (-2) ldquo0rdquo represents no change in charge at the 2 plane ldquo066rdquo is
the fraction of the central ion (As) on GTiO2 surface that is associated with plane 0
ldquo3rdquo is the charge on the central ion As(III) Following this equation and the relevant
parameters As(III) adsorbed on GTiO2
The diffusion coefficient Dw in PHREEQC accounting for retardation was
calculated as Dw=x2(36t) where x stands for the diffusion length (estimated as the
radius of the particle size) and t represents equilibrium time adopted from the batch
kinetic data (Mertens et al 2012)
To well simulate the As breakthrough curve in columns four As(V) adsorption
reactions (Table 1) were employed Adsorption site density of 60 mmolg was
36
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
adopted from our previous study (Pena et al 2006) and the total adsorption sites were
calculated to be 1844 sitesnm2 The final optimized ratio of strong to weak sites was
51 The surface complexation constants were reasonably adjusted according to the
batch modeling results as the column reaction may not reach equilibrium in local
micro-interfacial areas due to much less contact time between As and GTiO2 than that
in batch experiments (Appelo and Postma 1999) In the modeling a stepwise
procedure was adopted to achieve a viable result An estimation of two thirds of the
surface site density being accessible for EBCT=011 min with large flow rate of 265
mLmin was optimized which could probably result from unavailable adsorption sites
due to fast transport through the column
The adsorbed As on GTiO2 in the column was calculated by mass balance
between the influent and effluent
where Asadsorbed is the adsorbed As on GTiO2 (mgg) n is the number of collected
samples Cin and Cout are influent and effluent As concentrations (mgL) respectively
Vi is volume (L) of groundwater passed through the column between sample i-1 and i
and m is the mass of GTiO2 (g)
Even though the oxidation of adsorbed As(III) occurred during filtration as
analyzed from XANES and mass balance analysis (Fig 7) no As(III) oxidation
reactions were considered in PHREEQC modeling which would not impact the
breakthrough of As(IIIV)
37
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
38
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
Fig S54 Effect of EBCT on Si Ca and Mg breakthrough curves using groundwater 1 The sample notation in panel c indicates field column experiments with EBCT in minutes
References
Appelo CAJ Postma D 1999 A consistent model for surface complexation on birnessite (MnO2) and its application to a column experiment Geochim Cosmochim Ac 63 (19-20) 3039-3048Badruzzaman M Westerhoff P Knappe DRU 2004 Intraparticle diffusion and adsorption of arsenate onto granular ferric hydroxide (GFH) Water Res 38 (18) 4002-4012Banerjee K Amy GL Prevost M Nour S Jekel M Gallagher PM Blumenschein CD 2008 Kinetic and thermodynamic aspects of adsorption of arsenic onto granular ferric hydroxide (GFH) Water Res 42 (13) 3371-3378Bang S Patel M Lippincott L Meng XG 2005 Removal of arsenic from groundwater by granular titanium dioxide adsorbent Chemosphere 60 (3) 389-397Bang S Pena ME Patel M Lippincott L Meng X Kim KW 2011 Removal of arsenate from water by adsorbents a comparative case study Environ Geochem Hlth 33 133-141Cui JL Shi JB Jiang GB Jing CY 2013 Arsenic levels and speciation from ingestion exposures to biomarkers in Shanxi China Implications for human health Environ Sci Technol 47 (10) 5419-5424Daus B Wennrich R Weiss H 2004 Sorption materials for arsenic removal from water A comparative study Water Res 38 (12) 2948-2954Dou XM Mohan D Pittman CU 2013 Arsenate adsorption on three types of granular schwertmannite Water Res 47 (9) 2938-2948Dou XM Zhang Y Yang M Pei YS Huang X Takayama T Kato S 2006 Occurrence of arsenic in groundwater in the suburbs of Beijing and its removal using an iron-cerium bimetal oxide adsorbent Water Qual Res J Can 41 (2) 140-146Gibbons MK Gagnon GA 2010 Adsorption of arsenic from a Nova Scotia groundwater onto water treatment residual solids Water Res 44 (19) 5740-5749Glocheux Y Mendez Pasarin M Albadarin AB Allen SJ Walker GM 2013 Removal of arsenic from groundwater by adsorption onto an acidified laterite by-product Chem Eng J 228 565-574Guan XH Wang JM Chusuei CC 2008 Removal of arsenic from water using granular ferric hydroxide Macroscopic and microscopic studies J Hazard Mater 156 (1-3) 178-185Gupta K Maity A Ghosh UC 2010 Manganese associated nanoparticles agglomerate of iron(III) oxide Synthesis characterization and arsenic(III) sorption behavior with mechanism J Hazard Mater 184 (1-3) 832-842Hao JM Han MJ Wang C Meng XG 2009 Enhanced removal of arsenite from water by a mesoporous hybrid material - Thiol-functionalized silica coated activated alumina Micropor Mesopor
Mat 124 (1-3) 1-7Hiemstra T Van Riemsdijk WH 2006 On the relationship between charge distribution surface hydration and the structure of the interface of metal hydroxides J Colloid Interf Sci 301 (1) 1-18Hristovski K Baumgardner A Westerhoff P 2007 Selecting metal oxide nanomaterials for arsenic removal in fixed bed columns From nanopowders to aggregated nanoparticle media J Hazard Mater 147 (1-2) 265-274Jang M Chen WF Cannon FS 2008 Preloading hydrous ferric oxide into granular activated carbon for arsenic removal Environ Sci Technol 42 (9) 3369-3374Jing CY Cui JL Huang YY Li AG 2012 Fabrication characterization and application of a composite adsorbent for simultaneous removal of arsenic and fluoride ACS Appl Mater Interfaces 4 (2) 714-720Kanematsu M Young TM Fukushi K Green PG Darby JL 2010 Extended triple layer modeling of arsenate and phosphate adsorption on a goethite-based granular porous adsorbent Environ Sci Technol 44 (9) 3388-3394Kong S Wang Y Zhan H Yuan S Liu M Zhou C 2013 Arsenite and Arsenate Removal from Contaminated Groundwater by Nanoscale Iron-Manganese Binary Oxides Column Studies Environmental Engineering Science 30 (11) 689-696Li Y Liu JR Jia SY Guo JW Zhuo J Na P 2012 TiO2 pillared montmorillonite as a photoactive adsorbent of arsenic under UV irradiation Chem Eng J 191 66-74Lin TF Wu JK 2001 Adsorption of arsenite and arsenate within activated alumina grains Equilibrium and kinetics Water Res 35 (8) 2049-2057Luo T Cui JL Hu S Huang YY Jing CY 2010 Arsenic removal and recovery from copper smelting wastewater using TiO2 Environ Sci Technol 44 (23) 9094-9098Maiti A Basu JK De S 2010a Development of a Treated Laterite for Arsenic Adsorption Effects of Treatment Parameters Industrial amp Engineering Chemistry Research 49 (10) 4873-4886Maiti A Basu JK De S 2010b Removal of Arsenic from Synthetic and Natural Groundwater Using Acid-Activated Laterite Environmental Progress amp Sustainable Energy 29 (4) 457-470Maiti A Basu JK De S 2012 Experimental and kinetic modeling of As(V) and As(III) adsorption on treated laterite using synthetic and contaminated groundwater Effects of phosphate silicate and carbonate ions Chem Eng J 191 1-12Maiti A Thakur BK Basu JK De S 2013a Comparison of treated laterite as arsenic adsorbent from different locations and performance of best filter under field conditions J Hazard Mater 262 1176-1186Maiti A Thakur BK Basu JK De S 2013b Comparison of treated laterite as arsenic adsorbent from different locations and performance of best filter under field conditions J Hazard Mater 262 (0) 1176-1186Maji SK Pal A Pal T 2008 Arsenic removal from real-life groundwater by adsorption on laterite soil J Hazard Mater 151 (2-3) 811-820Maji SK Kao YH Wang CJ Lu GS Wu JJ Liu CW 2012 Fixed bed adsorption of As(III) on iron-oxide-coated natural rock (IOCNR) and application to real arsenic-bearing groundwater Chem Eng J 203 285-293Mertens J Rose J Kagi R Chaurand P Plotze M Wehrli B Furrer G 2012 Adsorption of arsenic on polyaluminum granulate Environ Sci Technol 46 (13) 7310-7317Nguyen TV Vigneswaran S Ngo HH Pokhre D Viraraghavan T 2006 Iron-coated sponge as
effective media to remove arsenic from drinking water Water Qual Res J Can 41 (2) 164-170Parkhurst DL Appelo CAJ 2013 Description of input and examples for PHREEQC version 3-A computer program for speciation batch-reaction one-dimensional transport and inverse geochemical calculations US Geological SurveyPena M Meng XG Korfiatis GP Jing CY 2006 Adsorption mechanism of arsenic on nanocrystalline titanium dioxide Environ Sci Technol 40 (4) 1257-1262Ravel B Newville M 2005 ATHENA ARTEMIS HEPHAESTUS Data analysis for X-ray absorption spectroscopy using IFEFFIT J Synchrotron Radiat 12 537-541Saha B Bains R Greenwood F 2005 Physicochemical characterization of granular ferric hydroxide (GFH) for arsenic(V) sorption from water Separation Science and Technology 40 (14) 2909-2932Shan H Ma T Wang Y Zhao J Han H Deng Y He X Dong Y 2013 A cost-effective system for in-situ geological arsenic adsorption from groundwater J Contam Hydrol 154 1-9Stachowicz M Hiemstra T van Riemsdijk WH 2008 Multi-competitive interaction of As(III) and As(V) oxyanions with Ca2+ Mg2+ PO4
3- and CO32- ions on goethite J Colloid Interf Sci 320 (2) 400-
414Streat M Hellgardt K Newton NLR 2008 Hydrous ferric oxide as an adsorbent in water treatment - Part 3 Batch and mini-column adsorption of arsenic phosphorus fluorine and cadmium ions Process Safety and Environmental Protection 86 (B1) 21-30Thirunavukkarasu OS Viraraghavan T Subramanian KS 2003 Arsenic removal from drinking water using iron oxide-coated sand Water Air Soil Poll 142 (1-4) 95-111USEPA 2008 Assessing arsenic removal by metal (hydr)oxide adsorptive media using rapid small scale column tests Govenrnment Printing Office Washington DCWang J Xu W Chen L Huang X Liu J 2014 Preparation and evaluation of magnetic nanoparticles impregnated chitosan beads for arsenic removal from water Chem Eng J 251 25-34Westerhoff P Highfield D Badruzzaman M Yoon Y 2005 Rapid small-scale column tests for arsenate removal in iron oxide packed bed columns J Environ Eng-Asce 131 (2) 262-271Westerhoff P De Haan M Martindale A Badruzzaman M 2006 Arsenic adsorptive media technology selection strategies Water Qual Res J Can 41 (2) 171-184Yan L Huang Y Cui J Jing C 2015 Simultaneous As(III) and Cd removal from copper smelting wastewater using granular TiO2 columns Water Res 68 (0) 572-579Zhao K Guo HM 2014 Behavior and mechanism of arsenate adsorption on activated natural siderite Evidences from FTIR and XANES analysis Environ Sci Pollut Res 21 (3) 1944-1953Zhao K Guo H Zhou X 2014 Adsorption and heterogeneous oxidation of arsenite on modified granular natural siderite Characterization and behaviors Appl Geochem 48 184-192
H3ArseniteO3 is the master species in groundwater at pH 82
(Surf_sO)2ArseniteOH-066 is the common adsorbed bidentate binuclear complex
evidenced by our previous reports(Pena et al 2006 Yan et al 2015) LogK is the
adsorption equilibrium constants Generally every adsorption equation under certain
experimental condition has a unique value of logK In the adsorption equation ldquo-2rdquo
represents the lost two hydrogens by Surf_sOH-033 after it adsorbs H3ArseniteO3 ldquo-
1rdquo represents the change in charge on Arsenite at 1 plane due to gaining one hydrogen
(+1) and one oxygen (-2) ldquo0rdquo represents no change in charge at the 2 plane ldquo066rdquo is
the fraction of the central ion (As) on GTiO2 surface that is associated with plane 0
ldquo3rdquo is the charge on the central ion As(III) Following this equation and the relevant
parameters As(III) adsorbed on GTiO2
The diffusion coefficient Dw in PHREEQC accounting for retardation was
calculated as Dw=x2(36t) where x stands for the diffusion length (estimated as the
radius of the particle size) and t represents equilibrium time adopted from the batch
kinetic data (Mertens et al 2012)
To well simulate the As breakthrough curve in columns four As(V) adsorption
reactions (Table 1) were employed Adsorption site density of 60 mmolg was
36
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
adopted from our previous study (Pena et al 2006) and the total adsorption sites were
calculated to be 1844 sitesnm2 The final optimized ratio of strong to weak sites was
51 The surface complexation constants were reasonably adjusted according to the
batch modeling results as the column reaction may not reach equilibrium in local
micro-interfacial areas due to much less contact time between As and GTiO2 than that
in batch experiments (Appelo and Postma 1999) In the modeling a stepwise
procedure was adopted to achieve a viable result An estimation of two thirds of the
surface site density being accessible for EBCT=011 min with large flow rate of 265
mLmin was optimized which could probably result from unavailable adsorption sites
due to fast transport through the column
The adsorbed As on GTiO2 in the column was calculated by mass balance
between the influent and effluent
where Asadsorbed is the adsorbed As on GTiO2 (mgg) n is the number of collected
samples Cin and Cout are influent and effluent As concentrations (mgL) respectively
Vi is volume (L) of groundwater passed through the column between sample i-1 and i
and m is the mass of GTiO2 (g)
Even though the oxidation of adsorbed As(III) occurred during filtration as
analyzed from XANES and mass balance analysis (Fig 7) no As(III) oxidation
reactions were considered in PHREEQC modeling which would not impact the
breakthrough of As(IIIV)
37
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
38
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
Fig S54 Effect of EBCT on Si Ca and Mg breakthrough curves using groundwater 1 The sample notation in panel c indicates field column experiments with EBCT in minutes
References
Appelo CAJ Postma D 1999 A consistent model for surface complexation on birnessite (MnO2) and its application to a column experiment Geochim Cosmochim Ac 63 (19-20) 3039-3048Badruzzaman M Westerhoff P Knappe DRU 2004 Intraparticle diffusion and adsorption of arsenate onto granular ferric hydroxide (GFH) Water Res 38 (18) 4002-4012Banerjee K Amy GL Prevost M Nour S Jekel M Gallagher PM Blumenschein CD 2008 Kinetic and thermodynamic aspects of adsorption of arsenic onto granular ferric hydroxide (GFH) Water Res 42 (13) 3371-3378Bang S Patel M Lippincott L Meng XG 2005 Removal of arsenic from groundwater by granular titanium dioxide adsorbent Chemosphere 60 (3) 389-397Bang S Pena ME Patel M Lippincott L Meng X Kim KW 2011 Removal of arsenate from water by adsorbents a comparative case study Environ Geochem Hlth 33 133-141Cui JL Shi JB Jiang GB Jing CY 2013 Arsenic levels and speciation from ingestion exposures to biomarkers in Shanxi China Implications for human health Environ Sci Technol 47 (10) 5419-5424Daus B Wennrich R Weiss H 2004 Sorption materials for arsenic removal from water A comparative study Water Res 38 (12) 2948-2954Dou XM Mohan D Pittman CU 2013 Arsenate adsorption on three types of granular schwertmannite Water Res 47 (9) 2938-2948Dou XM Zhang Y Yang M Pei YS Huang X Takayama T Kato S 2006 Occurrence of arsenic in groundwater in the suburbs of Beijing and its removal using an iron-cerium bimetal oxide adsorbent Water Qual Res J Can 41 (2) 140-146Gibbons MK Gagnon GA 2010 Adsorption of arsenic from a Nova Scotia groundwater onto water treatment residual solids Water Res 44 (19) 5740-5749Glocheux Y Mendez Pasarin M Albadarin AB Allen SJ Walker GM 2013 Removal of arsenic from groundwater by adsorption onto an acidified laterite by-product Chem Eng J 228 565-574Guan XH Wang JM Chusuei CC 2008 Removal of arsenic from water using granular ferric hydroxide Macroscopic and microscopic studies J Hazard Mater 156 (1-3) 178-185Gupta K Maity A Ghosh UC 2010 Manganese associated nanoparticles agglomerate of iron(III) oxide Synthesis characterization and arsenic(III) sorption behavior with mechanism J Hazard Mater 184 (1-3) 832-842Hao JM Han MJ Wang C Meng XG 2009 Enhanced removal of arsenite from water by a mesoporous hybrid material - Thiol-functionalized silica coated activated alumina Micropor Mesopor
Mat 124 (1-3) 1-7Hiemstra T Van Riemsdijk WH 2006 On the relationship between charge distribution surface hydration and the structure of the interface of metal hydroxides J Colloid Interf Sci 301 (1) 1-18Hristovski K Baumgardner A Westerhoff P 2007 Selecting metal oxide nanomaterials for arsenic removal in fixed bed columns From nanopowders to aggregated nanoparticle media J Hazard Mater 147 (1-2) 265-274Jang M Chen WF Cannon FS 2008 Preloading hydrous ferric oxide into granular activated carbon for arsenic removal Environ Sci Technol 42 (9) 3369-3374Jing CY Cui JL Huang YY Li AG 2012 Fabrication characterization and application of a composite adsorbent for simultaneous removal of arsenic and fluoride ACS Appl Mater Interfaces 4 (2) 714-720Kanematsu M Young TM Fukushi K Green PG Darby JL 2010 Extended triple layer modeling of arsenate and phosphate adsorption on a goethite-based granular porous adsorbent Environ Sci Technol 44 (9) 3388-3394Kong S Wang Y Zhan H Yuan S Liu M Zhou C 2013 Arsenite and Arsenate Removal from Contaminated Groundwater by Nanoscale Iron-Manganese Binary Oxides Column Studies Environmental Engineering Science 30 (11) 689-696Li Y Liu JR Jia SY Guo JW Zhuo J Na P 2012 TiO2 pillared montmorillonite as a photoactive adsorbent of arsenic under UV irradiation Chem Eng J 191 66-74Lin TF Wu JK 2001 Adsorption of arsenite and arsenate within activated alumina grains Equilibrium and kinetics Water Res 35 (8) 2049-2057Luo T Cui JL Hu S Huang YY Jing CY 2010 Arsenic removal and recovery from copper smelting wastewater using TiO2 Environ Sci Technol 44 (23) 9094-9098Maiti A Basu JK De S 2010a Development of a Treated Laterite for Arsenic Adsorption Effects of Treatment Parameters Industrial amp Engineering Chemistry Research 49 (10) 4873-4886Maiti A Basu JK De S 2010b Removal of Arsenic from Synthetic and Natural Groundwater Using Acid-Activated Laterite Environmental Progress amp Sustainable Energy 29 (4) 457-470Maiti A Basu JK De S 2012 Experimental and kinetic modeling of As(V) and As(III) adsorption on treated laterite using synthetic and contaminated groundwater Effects of phosphate silicate and carbonate ions Chem Eng J 191 1-12Maiti A Thakur BK Basu JK De S 2013a Comparison of treated laterite as arsenic adsorbent from different locations and performance of best filter under field conditions J Hazard Mater 262 1176-1186Maiti A Thakur BK Basu JK De S 2013b Comparison of treated laterite as arsenic adsorbent from different locations and performance of best filter under field conditions J Hazard Mater 262 (0) 1176-1186Maji SK Pal A Pal T 2008 Arsenic removal from real-life groundwater by adsorption on laterite soil J Hazard Mater 151 (2-3) 811-820Maji SK Kao YH Wang CJ Lu GS Wu JJ Liu CW 2012 Fixed bed adsorption of As(III) on iron-oxide-coated natural rock (IOCNR) and application to real arsenic-bearing groundwater Chem Eng J 203 285-293Mertens J Rose J Kagi R Chaurand P Plotze M Wehrli B Furrer G 2012 Adsorption of arsenic on polyaluminum granulate Environ Sci Technol 46 (13) 7310-7317Nguyen TV Vigneswaran S Ngo HH Pokhre D Viraraghavan T 2006 Iron-coated sponge as
effective media to remove arsenic from drinking water Water Qual Res J Can 41 (2) 164-170Parkhurst DL Appelo CAJ 2013 Description of input and examples for PHREEQC version 3-A computer program for speciation batch-reaction one-dimensional transport and inverse geochemical calculations US Geological SurveyPena M Meng XG Korfiatis GP Jing CY 2006 Adsorption mechanism of arsenic on nanocrystalline titanium dioxide Environ Sci Technol 40 (4) 1257-1262Ravel B Newville M 2005 ATHENA ARTEMIS HEPHAESTUS Data analysis for X-ray absorption spectroscopy using IFEFFIT J Synchrotron Radiat 12 537-541Saha B Bains R Greenwood F 2005 Physicochemical characterization of granular ferric hydroxide (GFH) for arsenic(V) sorption from water Separation Science and Technology 40 (14) 2909-2932Shan H Ma T Wang Y Zhao J Han H Deng Y He X Dong Y 2013 A cost-effective system for in-situ geological arsenic adsorption from groundwater J Contam Hydrol 154 1-9Stachowicz M Hiemstra T van Riemsdijk WH 2008 Multi-competitive interaction of As(III) and As(V) oxyanions with Ca2+ Mg2+ PO4
3- and CO32- ions on goethite J Colloid Interf Sci 320 (2) 400-
414Streat M Hellgardt K Newton NLR 2008 Hydrous ferric oxide as an adsorbent in water treatment - Part 3 Batch and mini-column adsorption of arsenic phosphorus fluorine and cadmium ions Process Safety and Environmental Protection 86 (B1) 21-30Thirunavukkarasu OS Viraraghavan T Subramanian KS 2003 Arsenic removal from drinking water using iron oxide-coated sand Water Air Soil Poll 142 (1-4) 95-111USEPA 2008 Assessing arsenic removal by metal (hydr)oxide adsorptive media using rapid small scale column tests Govenrnment Printing Office Washington DCWang J Xu W Chen L Huang X Liu J 2014 Preparation and evaluation of magnetic nanoparticles impregnated chitosan beads for arsenic removal from water Chem Eng J 251 25-34Westerhoff P Highfield D Badruzzaman M Yoon Y 2005 Rapid small-scale column tests for arsenate removal in iron oxide packed bed columns J Environ Eng-Asce 131 (2) 262-271Westerhoff P De Haan M Martindale A Badruzzaman M 2006 Arsenic adsorptive media technology selection strategies Water Qual Res J Can 41 (2) 171-184Yan L Huang Y Cui J Jing C 2015 Simultaneous As(III) and Cd removal from copper smelting wastewater using granular TiO2 columns Water Res 68 (0) 572-579Zhao K Guo HM 2014 Behavior and mechanism of arsenate adsorption on activated natural siderite Evidences from FTIR and XANES analysis Environ Sci Pollut Res 21 (3) 1944-1953Zhao K Guo H Zhou X 2014 Adsorption and heterogeneous oxidation of arsenite on modified granular natural siderite Characterization and behaviors Appl Geochem 48 184-192
adopted from our previous study (Pena et al 2006) and the total adsorption sites were
calculated to be 1844 sitesnm2 The final optimized ratio of strong to weak sites was
51 The surface complexation constants were reasonably adjusted according to the
batch modeling results as the column reaction may not reach equilibrium in local
micro-interfacial areas due to much less contact time between As and GTiO2 than that
in batch experiments (Appelo and Postma 1999) In the modeling a stepwise
procedure was adopted to achieve a viable result An estimation of two thirds of the
surface site density being accessible for EBCT=011 min with large flow rate of 265
mLmin was optimized which could probably result from unavailable adsorption sites
due to fast transport through the column
The adsorbed As on GTiO2 in the column was calculated by mass balance
between the influent and effluent
where Asadsorbed is the adsorbed As on GTiO2 (mgg) n is the number of collected
samples Cin and Cout are influent and effluent As concentrations (mgL) respectively
Vi is volume (L) of groundwater passed through the column between sample i-1 and i
and m is the mass of GTiO2 (g)
Even though the oxidation of adsorbed As(III) occurred during filtration as
analyzed from XANES and mass balance analysis (Fig 7) no As(III) oxidation
reactions were considered in PHREEQC modeling which would not impact the
breakthrough of As(IIIV)
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Fig S54 Effect of EBCT on Si Ca and Mg breakthrough curves using groundwater 1 The sample notation in panel c indicates field column experiments with EBCT in minutes
References
Appelo CAJ Postma D 1999 A consistent model for surface complexation on birnessite (MnO2) and its application to a column experiment Geochim Cosmochim Ac 63 (19-20) 3039-3048Badruzzaman M Westerhoff P Knappe DRU 2004 Intraparticle diffusion and adsorption of arsenate onto granular ferric hydroxide (GFH) Water Res 38 (18) 4002-4012Banerjee K Amy GL Prevost M Nour S Jekel M Gallagher PM Blumenschein CD 2008 Kinetic and thermodynamic aspects of adsorption of arsenic onto granular ferric hydroxide (GFH) Water Res 42 (13) 3371-3378Bang S Patel M Lippincott L Meng XG 2005 Removal of arsenic from groundwater by granular titanium dioxide adsorbent Chemosphere 60 (3) 389-397Bang S Pena ME Patel M Lippincott L Meng X Kim KW 2011 Removal of arsenate from water by adsorbents a comparative case study Environ Geochem Hlth 33 133-141Cui JL Shi JB Jiang GB Jing CY 2013 Arsenic levels and speciation from ingestion exposures to biomarkers in Shanxi China Implications for human health Environ Sci Technol 47 (10) 5419-5424Daus B Wennrich R Weiss H 2004 Sorption materials for arsenic removal from water A comparative study Water Res 38 (12) 2948-2954Dou XM Mohan D Pittman CU 2013 Arsenate adsorption on three types of granular schwertmannite Water Res 47 (9) 2938-2948Dou XM Zhang Y Yang M Pei YS Huang X Takayama T Kato S 2006 Occurrence of arsenic in groundwater in the suburbs of Beijing and its removal using an iron-cerium bimetal oxide adsorbent Water Qual Res J Can 41 (2) 140-146Gibbons MK Gagnon GA 2010 Adsorption of arsenic from a Nova Scotia groundwater onto water treatment residual solids Water Res 44 (19) 5740-5749Glocheux Y Mendez Pasarin M Albadarin AB Allen SJ Walker GM 2013 Removal of arsenic from groundwater by adsorption onto an acidified laterite by-product Chem Eng J 228 565-574Guan XH Wang JM Chusuei CC 2008 Removal of arsenic from water using granular ferric hydroxide Macroscopic and microscopic studies J Hazard Mater 156 (1-3) 178-185Gupta K Maity A Ghosh UC 2010 Manganese associated nanoparticles agglomerate of iron(III) oxide Synthesis characterization and arsenic(III) sorption behavior with mechanism J Hazard Mater 184 (1-3) 832-842Hao JM Han MJ Wang C Meng XG 2009 Enhanced removal of arsenite from water by a mesoporous hybrid material - Thiol-functionalized silica coated activated alumina Micropor Mesopor
Mat 124 (1-3) 1-7Hiemstra T Van Riemsdijk WH 2006 On the relationship between charge distribution surface hydration and the structure of the interface of metal hydroxides J Colloid Interf Sci 301 (1) 1-18Hristovski K Baumgardner A Westerhoff P 2007 Selecting metal oxide nanomaterials for arsenic removal in fixed bed columns From nanopowders to aggregated nanoparticle media J Hazard Mater 147 (1-2) 265-274Jang M Chen WF Cannon FS 2008 Preloading hydrous ferric oxide into granular activated carbon for arsenic removal Environ Sci Technol 42 (9) 3369-3374Jing CY Cui JL Huang YY Li AG 2012 Fabrication characterization and application of a composite adsorbent for simultaneous removal of arsenic and fluoride ACS Appl Mater Interfaces 4 (2) 714-720Kanematsu M Young TM Fukushi K Green PG Darby JL 2010 Extended triple layer modeling of arsenate and phosphate adsorption on a goethite-based granular porous adsorbent Environ Sci Technol 44 (9) 3388-3394Kong S Wang Y Zhan H Yuan S Liu M Zhou C 2013 Arsenite and Arsenate Removal from Contaminated Groundwater by Nanoscale Iron-Manganese Binary Oxides Column Studies Environmental Engineering Science 30 (11) 689-696Li Y Liu JR Jia SY Guo JW Zhuo J Na P 2012 TiO2 pillared montmorillonite as a photoactive adsorbent of arsenic under UV irradiation Chem Eng J 191 66-74Lin TF Wu JK 2001 Adsorption of arsenite and arsenate within activated alumina grains Equilibrium and kinetics Water Res 35 (8) 2049-2057Luo T Cui JL Hu S Huang YY Jing CY 2010 Arsenic removal and recovery from copper smelting wastewater using TiO2 Environ Sci Technol 44 (23) 9094-9098Maiti A Basu JK De S 2010a Development of a Treated Laterite for Arsenic Adsorption Effects of Treatment Parameters Industrial amp Engineering Chemistry Research 49 (10) 4873-4886Maiti A Basu JK De S 2010b Removal of Arsenic from Synthetic and Natural Groundwater Using Acid-Activated Laterite Environmental Progress amp Sustainable Energy 29 (4) 457-470Maiti A Basu JK De S 2012 Experimental and kinetic modeling of As(V) and As(III) adsorption on treated laterite using synthetic and contaminated groundwater Effects of phosphate silicate and carbonate ions Chem Eng J 191 1-12Maiti A Thakur BK Basu JK De S 2013a Comparison of treated laterite as arsenic adsorbent from different locations and performance of best filter under field conditions J Hazard Mater 262 1176-1186Maiti A Thakur BK Basu JK De S 2013b Comparison of treated laterite as arsenic adsorbent from different locations and performance of best filter under field conditions J Hazard Mater 262 (0) 1176-1186Maji SK Pal A Pal T 2008 Arsenic removal from real-life groundwater by adsorption on laterite soil J Hazard Mater 151 (2-3) 811-820Maji SK Kao YH Wang CJ Lu GS Wu JJ Liu CW 2012 Fixed bed adsorption of As(III) on iron-oxide-coated natural rock (IOCNR) and application to real arsenic-bearing groundwater Chem Eng J 203 285-293Mertens J Rose J Kagi R Chaurand P Plotze M Wehrli B Furrer G 2012 Adsorption of arsenic on polyaluminum granulate Environ Sci Technol 46 (13) 7310-7317Nguyen TV Vigneswaran S Ngo HH Pokhre D Viraraghavan T 2006 Iron-coated sponge as
effective media to remove arsenic from drinking water Water Qual Res J Can 41 (2) 164-170Parkhurst DL Appelo CAJ 2013 Description of input and examples for PHREEQC version 3-A computer program for speciation batch-reaction one-dimensional transport and inverse geochemical calculations US Geological SurveyPena M Meng XG Korfiatis GP Jing CY 2006 Adsorption mechanism of arsenic on nanocrystalline titanium dioxide Environ Sci Technol 40 (4) 1257-1262Ravel B Newville M 2005 ATHENA ARTEMIS HEPHAESTUS Data analysis for X-ray absorption spectroscopy using IFEFFIT J Synchrotron Radiat 12 537-541Saha B Bains R Greenwood F 2005 Physicochemical characterization of granular ferric hydroxide (GFH) for arsenic(V) sorption from water Separation Science and Technology 40 (14) 2909-2932Shan H Ma T Wang Y Zhao J Han H Deng Y He X Dong Y 2013 A cost-effective system for in-situ geological arsenic adsorption from groundwater J Contam Hydrol 154 1-9Stachowicz M Hiemstra T van Riemsdijk WH 2008 Multi-competitive interaction of As(III) and As(V) oxyanions with Ca2+ Mg2+ PO4
3- and CO32- ions on goethite J Colloid Interf Sci 320 (2) 400-
414Streat M Hellgardt K Newton NLR 2008 Hydrous ferric oxide as an adsorbent in water treatment - Part 3 Batch and mini-column adsorption of arsenic phosphorus fluorine and cadmium ions Process Safety and Environmental Protection 86 (B1) 21-30Thirunavukkarasu OS Viraraghavan T Subramanian KS 2003 Arsenic removal from drinking water using iron oxide-coated sand Water Air Soil Poll 142 (1-4) 95-111USEPA 2008 Assessing arsenic removal by metal (hydr)oxide adsorptive media using rapid small scale column tests Govenrnment Printing Office Washington DCWang J Xu W Chen L Huang X Liu J 2014 Preparation and evaluation of magnetic nanoparticles impregnated chitosan beads for arsenic removal from water Chem Eng J 251 25-34Westerhoff P Highfield D Badruzzaman M Yoon Y 2005 Rapid small-scale column tests for arsenate removal in iron oxide packed bed columns J Environ Eng-Asce 131 (2) 262-271Westerhoff P De Haan M Martindale A Badruzzaman M 2006 Arsenic adsorptive media technology selection strategies Water Qual Res J Can 41 (2) 171-184Yan L Huang Y Cui J Jing C 2015 Simultaneous As(III) and Cd removal from copper smelting wastewater using granular TiO2 columns Water Res 68 (0) 572-579Zhao K Guo HM 2014 Behavior and mechanism of arsenate adsorption on activated natural siderite Evidences from FTIR and XANES analysis Environ Sci Pollut Res 21 (3) 1944-1953Zhao K Guo H Zhou X 2014 Adsorption and heterogeneous oxidation of arsenite on modified granular natural siderite Characterization and behaviors Appl Geochem 48 184-192
Fig S54 Effect of EBCT on Si Ca and Mg breakthrough curves using groundwater 1 The sample notation in panel c indicates field column experiments with EBCT in minutes
References
Appelo CAJ Postma D 1999 A consistent model for surface complexation on birnessite (MnO2) and its application to a column experiment Geochim Cosmochim Ac 63 (19-20) 3039-3048Badruzzaman M Westerhoff P Knappe DRU 2004 Intraparticle diffusion and adsorption of arsenate onto granular ferric hydroxide (GFH) Water Res 38 (18) 4002-4012Banerjee K Amy GL Prevost M Nour S Jekel M Gallagher PM Blumenschein CD 2008 Kinetic and thermodynamic aspects of adsorption of arsenic onto granular ferric hydroxide (GFH) Water Res 42 (13) 3371-3378Bang S Patel M Lippincott L Meng XG 2005 Removal of arsenic from groundwater by granular titanium dioxide adsorbent Chemosphere 60 (3) 389-397Bang S Pena ME Patel M Lippincott L Meng X Kim KW 2011 Removal of arsenate from water by adsorbents a comparative case study Environ Geochem Hlth 33 133-141Cui JL Shi JB Jiang GB Jing CY 2013 Arsenic levels and speciation from ingestion exposures to biomarkers in Shanxi China Implications for human health Environ Sci Technol 47 (10) 5419-5424Daus B Wennrich R Weiss H 2004 Sorption materials for arsenic removal from water A comparative study Water Res 38 (12) 2948-2954Dou XM Mohan D Pittman CU 2013 Arsenate adsorption on three types of granular schwertmannite Water Res 47 (9) 2938-2948Dou XM Zhang Y Yang M Pei YS Huang X Takayama T Kato S 2006 Occurrence of arsenic in groundwater in the suburbs of Beijing and its removal using an iron-cerium bimetal oxide adsorbent Water Qual Res J Can 41 (2) 140-146Gibbons MK Gagnon GA 2010 Adsorption of arsenic from a Nova Scotia groundwater onto water treatment residual solids Water Res 44 (19) 5740-5749Glocheux Y Mendez Pasarin M Albadarin AB Allen SJ Walker GM 2013 Removal of arsenic from groundwater by adsorption onto an acidified laterite by-product Chem Eng J 228 565-574Guan XH Wang JM Chusuei CC 2008 Removal of arsenic from water using granular ferric hydroxide Macroscopic and microscopic studies J Hazard Mater 156 (1-3) 178-185Gupta K Maity A Ghosh UC 2010 Manganese associated nanoparticles agglomerate of iron(III) oxide Synthesis characterization and arsenic(III) sorption behavior with mechanism J Hazard Mater 184 (1-3) 832-842Hao JM Han MJ Wang C Meng XG 2009 Enhanced removal of arsenite from water by a mesoporous hybrid material - Thiol-functionalized silica coated activated alumina Micropor Mesopor
Mat 124 (1-3) 1-7Hiemstra T Van Riemsdijk WH 2006 On the relationship between charge distribution surface hydration and the structure of the interface of metal hydroxides J Colloid Interf Sci 301 (1) 1-18Hristovski K Baumgardner A Westerhoff P 2007 Selecting metal oxide nanomaterials for arsenic removal in fixed bed columns From nanopowders to aggregated nanoparticle media J Hazard Mater 147 (1-2) 265-274Jang M Chen WF Cannon FS 2008 Preloading hydrous ferric oxide into granular activated carbon for arsenic removal Environ Sci Technol 42 (9) 3369-3374Jing CY Cui JL Huang YY Li AG 2012 Fabrication characterization and application of a composite adsorbent for simultaneous removal of arsenic and fluoride ACS Appl Mater Interfaces 4 (2) 714-720Kanematsu M Young TM Fukushi K Green PG Darby JL 2010 Extended triple layer modeling of arsenate and phosphate adsorption on a goethite-based granular porous adsorbent Environ Sci Technol 44 (9) 3388-3394Kong S Wang Y Zhan H Yuan S Liu M Zhou C 2013 Arsenite and Arsenate Removal from Contaminated Groundwater by Nanoscale Iron-Manganese Binary Oxides Column Studies Environmental Engineering Science 30 (11) 689-696Li Y Liu JR Jia SY Guo JW Zhuo J Na P 2012 TiO2 pillared montmorillonite as a photoactive adsorbent of arsenic under UV irradiation Chem Eng J 191 66-74Lin TF Wu JK 2001 Adsorption of arsenite and arsenate within activated alumina grains Equilibrium and kinetics Water Res 35 (8) 2049-2057Luo T Cui JL Hu S Huang YY Jing CY 2010 Arsenic removal and recovery from copper smelting wastewater using TiO2 Environ Sci Technol 44 (23) 9094-9098Maiti A Basu JK De S 2010a Development of a Treated Laterite for Arsenic Adsorption Effects of Treatment Parameters Industrial amp Engineering Chemistry Research 49 (10) 4873-4886Maiti A Basu JK De S 2010b Removal of Arsenic from Synthetic and Natural Groundwater Using Acid-Activated Laterite Environmental Progress amp Sustainable Energy 29 (4) 457-470Maiti A Basu JK De S 2012 Experimental and kinetic modeling of As(V) and As(III) adsorption on treated laterite using synthetic and contaminated groundwater Effects of phosphate silicate and carbonate ions Chem Eng J 191 1-12Maiti A Thakur BK Basu JK De S 2013a Comparison of treated laterite as arsenic adsorbent from different locations and performance of best filter under field conditions J Hazard Mater 262 1176-1186Maiti A Thakur BK Basu JK De S 2013b Comparison of treated laterite as arsenic adsorbent from different locations and performance of best filter under field conditions J Hazard Mater 262 (0) 1176-1186Maji SK Pal A Pal T 2008 Arsenic removal from real-life groundwater by adsorption on laterite soil J Hazard Mater 151 (2-3) 811-820Maji SK Kao YH Wang CJ Lu GS Wu JJ Liu CW 2012 Fixed bed adsorption of As(III) on iron-oxide-coated natural rock (IOCNR) and application to real arsenic-bearing groundwater Chem Eng J 203 285-293Mertens J Rose J Kagi R Chaurand P Plotze M Wehrli B Furrer G 2012 Adsorption of arsenic on polyaluminum granulate Environ Sci Technol 46 (13) 7310-7317Nguyen TV Vigneswaran S Ngo HH Pokhre D Viraraghavan T 2006 Iron-coated sponge as
effective media to remove arsenic from drinking water Water Qual Res J Can 41 (2) 164-170Parkhurst DL Appelo CAJ 2013 Description of input and examples for PHREEQC version 3-A computer program for speciation batch-reaction one-dimensional transport and inverse geochemical calculations US Geological SurveyPena M Meng XG Korfiatis GP Jing CY 2006 Adsorption mechanism of arsenic on nanocrystalline titanium dioxide Environ Sci Technol 40 (4) 1257-1262Ravel B Newville M 2005 ATHENA ARTEMIS HEPHAESTUS Data analysis for X-ray absorption spectroscopy using IFEFFIT J Synchrotron Radiat 12 537-541Saha B Bains R Greenwood F 2005 Physicochemical characterization of granular ferric hydroxide (GFH) for arsenic(V) sorption from water Separation Science and Technology 40 (14) 2909-2932Shan H Ma T Wang Y Zhao J Han H Deng Y He X Dong Y 2013 A cost-effective system for in-situ geological arsenic adsorption from groundwater J Contam Hydrol 154 1-9Stachowicz M Hiemstra T van Riemsdijk WH 2008 Multi-competitive interaction of As(III) and As(V) oxyanions with Ca2+ Mg2+ PO4
3- and CO32- ions on goethite J Colloid Interf Sci 320 (2) 400-
414Streat M Hellgardt K Newton NLR 2008 Hydrous ferric oxide as an adsorbent in water treatment - Part 3 Batch and mini-column adsorption of arsenic phosphorus fluorine and cadmium ions Process Safety and Environmental Protection 86 (B1) 21-30Thirunavukkarasu OS Viraraghavan T Subramanian KS 2003 Arsenic removal from drinking water using iron oxide-coated sand Water Air Soil Poll 142 (1-4) 95-111USEPA 2008 Assessing arsenic removal by metal (hydr)oxide adsorptive media using rapid small scale column tests Govenrnment Printing Office Washington DCWang J Xu W Chen L Huang X Liu J 2014 Preparation and evaluation of magnetic nanoparticles impregnated chitosan beads for arsenic removal from water Chem Eng J 251 25-34Westerhoff P Highfield D Badruzzaman M Yoon Y 2005 Rapid small-scale column tests for arsenate removal in iron oxide packed bed columns J Environ Eng-Asce 131 (2) 262-271Westerhoff P De Haan M Martindale A Badruzzaman M 2006 Arsenic adsorptive media technology selection strategies Water Qual Res J Can 41 (2) 171-184Yan L Huang Y Cui J Jing C 2015 Simultaneous As(III) and Cd removal from copper smelting wastewater using granular TiO2 columns Water Res 68 (0) 572-579Zhao K Guo HM 2014 Behavior and mechanism of arsenate adsorption on activated natural siderite Evidences from FTIR and XANES analysis Environ Sci Pollut Res 21 (3) 1944-1953Zhao K Guo H Zhou X 2014 Adsorption and heterogeneous oxidation of arsenite on modified granular natural siderite Characterization and behaviors Appl Geochem 48 184-192
Fig S54 Effect of EBCT on Si Ca and Mg breakthrough curves using groundwater 1 The sample notation in panel c indicates field column experiments with EBCT in minutes
References
Appelo CAJ Postma D 1999 A consistent model for surface complexation on birnessite (MnO2) and its application to a column experiment Geochim Cosmochim Ac 63 (19-20) 3039-3048Badruzzaman M Westerhoff P Knappe DRU 2004 Intraparticle diffusion and adsorption of arsenate onto granular ferric hydroxide (GFH) Water Res 38 (18) 4002-4012Banerjee K Amy GL Prevost M Nour S Jekel M Gallagher PM Blumenschein CD 2008 Kinetic and thermodynamic aspects of adsorption of arsenic onto granular ferric hydroxide (GFH) Water Res 42 (13) 3371-3378Bang S Patel M Lippincott L Meng XG 2005 Removal of arsenic from groundwater by granular titanium dioxide adsorbent Chemosphere 60 (3) 389-397Bang S Pena ME Patel M Lippincott L Meng X Kim KW 2011 Removal of arsenate from water by adsorbents a comparative case study Environ Geochem Hlth 33 133-141Cui JL Shi JB Jiang GB Jing CY 2013 Arsenic levels and speciation from ingestion exposures to biomarkers in Shanxi China Implications for human health Environ Sci Technol 47 (10) 5419-5424Daus B Wennrich R Weiss H 2004 Sorption materials for arsenic removal from water A comparative study Water Res 38 (12) 2948-2954Dou XM Mohan D Pittman CU 2013 Arsenate adsorption on three types of granular schwertmannite Water Res 47 (9) 2938-2948Dou XM Zhang Y Yang M Pei YS Huang X Takayama T Kato S 2006 Occurrence of arsenic in groundwater in the suburbs of Beijing and its removal using an iron-cerium bimetal oxide adsorbent Water Qual Res J Can 41 (2) 140-146Gibbons MK Gagnon GA 2010 Adsorption of arsenic from a Nova Scotia groundwater onto water treatment residual solids Water Res 44 (19) 5740-5749Glocheux Y Mendez Pasarin M Albadarin AB Allen SJ Walker GM 2013 Removal of arsenic from groundwater by adsorption onto an acidified laterite by-product Chem Eng J 228 565-574Guan XH Wang JM Chusuei CC 2008 Removal of arsenic from water using granular ferric hydroxide Macroscopic and microscopic studies J Hazard Mater 156 (1-3) 178-185Gupta K Maity A Ghosh UC 2010 Manganese associated nanoparticles agglomerate of iron(III) oxide Synthesis characterization and arsenic(III) sorption behavior with mechanism J Hazard Mater 184 (1-3) 832-842Hao JM Han MJ Wang C Meng XG 2009 Enhanced removal of arsenite from water by a mesoporous hybrid material - Thiol-functionalized silica coated activated alumina Micropor Mesopor
Mat 124 (1-3) 1-7Hiemstra T Van Riemsdijk WH 2006 On the relationship between charge distribution surface hydration and the structure of the interface of metal hydroxides J Colloid Interf Sci 301 (1) 1-18Hristovski K Baumgardner A Westerhoff P 2007 Selecting metal oxide nanomaterials for arsenic removal in fixed bed columns From nanopowders to aggregated nanoparticle media J Hazard Mater 147 (1-2) 265-274Jang M Chen WF Cannon FS 2008 Preloading hydrous ferric oxide into granular activated carbon for arsenic removal Environ Sci Technol 42 (9) 3369-3374Jing CY Cui JL Huang YY Li AG 2012 Fabrication characterization and application of a composite adsorbent for simultaneous removal of arsenic and fluoride ACS Appl Mater Interfaces 4 (2) 714-720Kanematsu M Young TM Fukushi K Green PG Darby JL 2010 Extended triple layer modeling of arsenate and phosphate adsorption on a goethite-based granular porous adsorbent Environ Sci Technol 44 (9) 3388-3394Kong S Wang Y Zhan H Yuan S Liu M Zhou C 2013 Arsenite and Arsenate Removal from Contaminated Groundwater by Nanoscale Iron-Manganese Binary Oxides Column Studies Environmental Engineering Science 30 (11) 689-696Li Y Liu JR Jia SY Guo JW Zhuo J Na P 2012 TiO2 pillared montmorillonite as a photoactive adsorbent of arsenic under UV irradiation Chem Eng J 191 66-74Lin TF Wu JK 2001 Adsorption of arsenite and arsenate within activated alumina grains Equilibrium and kinetics Water Res 35 (8) 2049-2057Luo T Cui JL Hu S Huang YY Jing CY 2010 Arsenic removal and recovery from copper smelting wastewater using TiO2 Environ Sci Technol 44 (23) 9094-9098Maiti A Basu JK De S 2010a Development of a Treated Laterite for Arsenic Adsorption Effects of Treatment Parameters Industrial amp Engineering Chemistry Research 49 (10) 4873-4886Maiti A Basu JK De S 2010b Removal of Arsenic from Synthetic and Natural Groundwater Using Acid-Activated Laterite Environmental Progress amp Sustainable Energy 29 (4) 457-470Maiti A Basu JK De S 2012 Experimental and kinetic modeling of As(V) and As(III) adsorption on treated laterite using synthetic and contaminated groundwater Effects of phosphate silicate and carbonate ions Chem Eng J 191 1-12Maiti A Thakur BK Basu JK De S 2013a Comparison of treated laterite as arsenic adsorbent from different locations and performance of best filter under field conditions J Hazard Mater 262 1176-1186Maiti A Thakur BK Basu JK De S 2013b Comparison of treated laterite as arsenic adsorbent from different locations and performance of best filter under field conditions J Hazard Mater 262 (0) 1176-1186Maji SK Pal A Pal T 2008 Arsenic removal from real-life groundwater by adsorption on laterite soil J Hazard Mater 151 (2-3) 811-820Maji SK Kao YH Wang CJ Lu GS Wu JJ Liu CW 2012 Fixed bed adsorption of As(III) on iron-oxide-coated natural rock (IOCNR) and application to real arsenic-bearing groundwater Chem Eng J 203 285-293Mertens J Rose J Kagi R Chaurand P Plotze M Wehrli B Furrer G 2012 Adsorption of arsenic on polyaluminum granulate Environ Sci Technol 46 (13) 7310-7317Nguyen TV Vigneswaran S Ngo HH Pokhre D Viraraghavan T 2006 Iron-coated sponge as
effective media to remove arsenic from drinking water Water Qual Res J Can 41 (2) 164-170Parkhurst DL Appelo CAJ 2013 Description of input and examples for PHREEQC version 3-A computer program for speciation batch-reaction one-dimensional transport and inverse geochemical calculations US Geological SurveyPena M Meng XG Korfiatis GP Jing CY 2006 Adsorption mechanism of arsenic on nanocrystalline titanium dioxide Environ Sci Technol 40 (4) 1257-1262Ravel B Newville M 2005 ATHENA ARTEMIS HEPHAESTUS Data analysis for X-ray absorption spectroscopy using IFEFFIT J Synchrotron Radiat 12 537-541Saha B Bains R Greenwood F 2005 Physicochemical characterization of granular ferric hydroxide (GFH) for arsenic(V) sorption from water Separation Science and Technology 40 (14) 2909-2932Shan H Ma T Wang Y Zhao J Han H Deng Y He X Dong Y 2013 A cost-effective system for in-situ geological arsenic adsorption from groundwater J Contam Hydrol 154 1-9Stachowicz M Hiemstra T van Riemsdijk WH 2008 Multi-competitive interaction of As(III) and As(V) oxyanions with Ca2+ Mg2+ PO4
3- and CO32- ions on goethite J Colloid Interf Sci 320 (2) 400-
414Streat M Hellgardt K Newton NLR 2008 Hydrous ferric oxide as an adsorbent in water treatment - Part 3 Batch and mini-column adsorption of arsenic phosphorus fluorine and cadmium ions Process Safety and Environmental Protection 86 (B1) 21-30Thirunavukkarasu OS Viraraghavan T Subramanian KS 2003 Arsenic removal from drinking water using iron oxide-coated sand Water Air Soil Poll 142 (1-4) 95-111USEPA 2008 Assessing arsenic removal by metal (hydr)oxide adsorptive media using rapid small scale column tests Govenrnment Printing Office Washington DCWang J Xu W Chen L Huang X Liu J 2014 Preparation and evaluation of magnetic nanoparticles impregnated chitosan beads for arsenic removal from water Chem Eng J 251 25-34Westerhoff P Highfield D Badruzzaman M Yoon Y 2005 Rapid small-scale column tests for arsenate removal in iron oxide packed bed columns J Environ Eng-Asce 131 (2) 262-271Westerhoff P De Haan M Martindale A Badruzzaman M 2006 Arsenic adsorptive media technology selection strategies Water Qual Res J Can 41 (2) 171-184Yan L Huang Y Cui J Jing C 2015 Simultaneous As(III) and Cd removal from copper smelting wastewater using granular TiO2 columns Water Res 68 (0) 572-579Zhao K Guo HM 2014 Behavior and mechanism of arsenate adsorption on activated natural siderite Evidences from FTIR and XANES analysis Environ Sci Pollut Res 21 (3) 1944-1953Zhao K Guo H Zhou X 2014 Adsorption and heterogeneous oxidation of arsenite on modified granular natural siderite Characterization and behaviors Appl Geochem 48 184-192
Mat 124 (1-3) 1-7Hiemstra T Van Riemsdijk WH 2006 On the relationship between charge distribution surface hydration and the structure of the interface of metal hydroxides J Colloid Interf Sci 301 (1) 1-18Hristovski K Baumgardner A Westerhoff P 2007 Selecting metal oxide nanomaterials for arsenic removal in fixed bed columns From nanopowders to aggregated nanoparticle media J Hazard Mater 147 (1-2) 265-274Jang M Chen WF Cannon FS 2008 Preloading hydrous ferric oxide into granular activated carbon for arsenic removal Environ Sci Technol 42 (9) 3369-3374Jing CY Cui JL Huang YY Li AG 2012 Fabrication characterization and application of a composite adsorbent for simultaneous removal of arsenic and fluoride ACS Appl Mater Interfaces 4 (2) 714-720Kanematsu M Young TM Fukushi K Green PG Darby JL 2010 Extended triple layer modeling of arsenate and phosphate adsorption on a goethite-based granular porous adsorbent Environ Sci Technol 44 (9) 3388-3394Kong S Wang Y Zhan H Yuan S Liu M Zhou C 2013 Arsenite and Arsenate Removal from Contaminated Groundwater by Nanoscale Iron-Manganese Binary Oxides Column Studies Environmental Engineering Science 30 (11) 689-696Li Y Liu JR Jia SY Guo JW Zhuo J Na P 2012 TiO2 pillared montmorillonite as a photoactive adsorbent of arsenic under UV irradiation Chem Eng J 191 66-74Lin TF Wu JK 2001 Adsorption of arsenite and arsenate within activated alumina grains Equilibrium and kinetics Water Res 35 (8) 2049-2057Luo T Cui JL Hu S Huang YY Jing CY 2010 Arsenic removal and recovery from copper smelting wastewater using TiO2 Environ Sci Technol 44 (23) 9094-9098Maiti A Basu JK De S 2010a Development of a Treated Laterite for Arsenic Adsorption Effects of Treatment Parameters Industrial amp Engineering Chemistry Research 49 (10) 4873-4886Maiti A Basu JK De S 2010b Removal of Arsenic from Synthetic and Natural Groundwater Using Acid-Activated Laterite Environmental Progress amp Sustainable Energy 29 (4) 457-470Maiti A Basu JK De S 2012 Experimental and kinetic modeling of As(V) and As(III) adsorption on treated laterite using synthetic and contaminated groundwater Effects of phosphate silicate and carbonate ions Chem Eng J 191 1-12Maiti A Thakur BK Basu JK De S 2013a Comparison of treated laterite as arsenic adsorbent from different locations and performance of best filter under field conditions J Hazard Mater 262 1176-1186Maiti A Thakur BK Basu JK De S 2013b Comparison of treated laterite as arsenic adsorbent from different locations and performance of best filter under field conditions J Hazard Mater 262 (0) 1176-1186Maji SK Pal A Pal T 2008 Arsenic removal from real-life groundwater by adsorption on laterite soil J Hazard Mater 151 (2-3) 811-820Maji SK Kao YH Wang CJ Lu GS Wu JJ Liu CW 2012 Fixed bed adsorption of As(III) on iron-oxide-coated natural rock (IOCNR) and application to real arsenic-bearing groundwater Chem Eng J 203 285-293Mertens J Rose J Kagi R Chaurand P Plotze M Wehrli B Furrer G 2012 Adsorption of arsenic on polyaluminum granulate Environ Sci Technol 46 (13) 7310-7317Nguyen TV Vigneswaran S Ngo HH Pokhre D Viraraghavan T 2006 Iron-coated sponge as
effective media to remove arsenic from drinking water Water Qual Res J Can 41 (2) 164-170Parkhurst DL Appelo CAJ 2013 Description of input and examples for PHREEQC version 3-A computer program for speciation batch-reaction one-dimensional transport and inverse geochemical calculations US Geological SurveyPena M Meng XG Korfiatis GP Jing CY 2006 Adsorption mechanism of arsenic on nanocrystalline titanium dioxide Environ Sci Technol 40 (4) 1257-1262Ravel B Newville M 2005 ATHENA ARTEMIS HEPHAESTUS Data analysis for X-ray absorption spectroscopy using IFEFFIT J Synchrotron Radiat 12 537-541Saha B Bains R Greenwood F 2005 Physicochemical characterization of granular ferric hydroxide (GFH) for arsenic(V) sorption from water Separation Science and Technology 40 (14) 2909-2932Shan H Ma T Wang Y Zhao J Han H Deng Y He X Dong Y 2013 A cost-effective system for in-situ geological arsenic adsorption from groundwater J Contam Hydrol 154 1-9Stachowicz M Hiemstra T van Riemsdijk WH 2008 Multi-competitive interaction of As(III) and As(V) oxyanions with Ca2+ Mg2+ PO4
3- and CO32- ions on goethite J Colloid Interf Sci 320 (2) 400-
414Streat M Hellgardt K Newton NLR 2008 Hydrous ferric oxide as an adsorbent in water treatment - Part 3 Batch and mini-column adsorption of arsenic phosphorus fluorine and cadmium ions Process Safety and Environmental Protection 86 (B1) 21-30Thirunavukkarasu OS Viraraghavan T Subramanian KS 2003 Arsenic removal from drinking water using iron oxide-coated sand Water Air Soil Poll 142 (1-4) 95-111USEPA 2008 Assessing arsenic removal by metal (hydr)oxide adsorptive media using rapid small scale column tests Govenrnment Printing Office Washington DCWang J Xu W Chen L Huang X Liu J 2014 Preparation and evaluation of magnetic nanoparticles impregnated chitosan beads for arsenic removal from water Chem Eng J 251 25-34Westerhoff P Highfield D Badruzzaman M Yoon Y 2005 Rapid small-scale column tests for arsenate removal in iron oxide packed bed columns J Environ Eng-Asce 131 (2) 262-271Westerhoff P De Haan M Martindale A Badruzzaman M 2006 Arsenic adsorptive media technology selection strategies Water Qual Res J Can 41 (2) 171-184Yan L Huang Y Cui J Jing C 2015 Simultaneous As(III) and Cd removal from copper smelting wastewater using granular TiO2 columns Water Res 68 (0) 572-579Zhao K Guo HM 2014 Behavior and mechanism of arsenate adsorption on activated natural siderite Evidences from FTIR and XANES analysis Environ Sci Pollut Res 21 (3) 1944-1953Zhao K Guo H Zhou X 2014 Adsorption and heterogeneous oxidation of arsenite on modified granular natural siderite Characterization and behaviors Appl Geochem 48 184-192
effective media to remove arsenic from drinking water Water Qual Res J Can 41 (2) 164-170Parkhurst DL Appelo CAJ 2013 Description of input and examples for PHREEQC version 3-A computer program for speciation batch-reaction one-dimensional transport and inverse geochemical calculations US Geological SurveyPena M Meng XG Korfiatis GP Jing CY 2006 Adsorption mechanism of arsenic on nanocrystalline titanium dioxide Environ Sci Technol 40 (4) 1257-1262Ravel B Newville M 2005 ATHENA ARTEMIS HEPHAESTUS Data analysis for X-ray absorption spectroscopy using IFEFFIT J Synchrotron Radiat 12 537-541Saha B Bains R Greenwood F 2005 Physicochemical characterization of granular ferric hydroxide (GFH) for arsenic(V) sorption from water Separation Science and Technology 40 (14) 2909-2932Shan H Ma T Wang Y Zhao J Han H Deng Y He X Dong Y 2013 A cost-effective system for in-situ geological arsenic adsorption from groundwater J Contam Hydrol 154 1-9Stachowicz M Hiemstra T van Riemsdijk WH 2008 Multi-competitive interaction of As(III) and As(V) oxyanions with Ca2+ Mg2+ PO4
3- and CO32- ions on goethite J Colloid Interf Sci 320 (2) 400-
414Streat M Hellgardt K Newton NLR 2008 Hydrous ferric oxide as an adsorbent in water treatment - Part 3 Batch and mini-column adsorption of arsenic phosphorus fluorine and cadmium ions Process Safety and Environmental Protection 86 (B1) 21-30Thirunavukkarasu OS Viraraghavan T Subramanian KS 2003 Arsenic removal from drinking water using iron oxide-coated sand Water Air Soil Poll 142 (1-4) 95-111USEPA 2008 Assessing arsenic removal by metal (hydr)oxide adsorptive media using rapid small scale column tests Govenrnment Printing Office Washington DCWang J Xu W Chen L Huang X Liu J 2014 Preparation and evaluation of magnetic nanoparticles impregnated chitosan beads for arsenic removal from water Chem Eng J 251 25-34Westerhoff P Highfield D Badruzzaman M Yoon Y 2005 Rapid small-scale column tests for arsenate removal in iron oxide packed bed columns J Environ Eng-Asce 131 (2) 262-271Westerhoff P De Haan M Martindale A Badruzzaman M 2006 Arsenic adsorptive media technology selection strategies Water Qual Res J Can 41 (2) 171-184Yan L Huang Y Cui J Jing C 2015 Simultaneous As(III) and Cd removal from copper smelting wastewater using granular TiO2 columns Water Res 68 (0) 572-579Zhao K Guo HM 2014 Behavior and mechanism of arsenate adsorption on activated natural siderite Evidences from FTIR and XANES analysis Environ Sci Pollut Res 21 (3) 1944-1953Zhao K Guo H Zhou X 2014 Adsorption and heterogeneous oxidation of arsenite on modified granular natural siderite Characterization and behaviors Appl Geochem 48 184-192