ICWES15 -Comparative Absorption of Copper from Synthetic and Real Wastewater by Uncalcined Sodium Exchanged and Acid Modified Montmorillonite. Presented by Dr christianah Olakitan

Christy Ijagbemi Ph. D

Department of Mechanical Engineering Federal University of Technology, Akure, NIGERIA

Adsorption of Copper from Synthetic and Real Wastewater by Un-calcined Sodium Exchanged and Acid Modified

Montmorillonite

Escape into the environment pose a serious health hazard – escapes on the increase

Accumulate in living tissues throughout the food chain

At higher concentrations they can lead to poisoning

The Problem - threat to the Environment

Health and environmental concerns about heavy metal ions - Why ?

Introduction

Heavy Metals

Are natural components of the earth’s crust.

Relatively high density - > 5 g/cm3

May exist as oxides, hydroxide, sulfide and carbonate salts – soluble, sparing soluble or insoluble in water.

Possess a cationic nature (monovalent, divalent or trivalent) e.g Ag+ , Cd 2+, Hg2+, Ni2+, Cu2+, Pb2+ , Fe2+ or Fe3+, Zr4+ has multiple oxidation states.

Cannot be degraded or destroyed - can only be changed in valence or by chelation.

Toxic or poisonous at low concentrations, some are carcinogenic. Greater solubility = Greater toxicity

- Constitute the Group III transition metals, the actinides series, the lanthanide series, and three of the Group IV metalloids - Readily loses electrons to form positive ions (cations) - Have metallic bonds

Metals

Background

Hg Al

BaPb Cd Fe

Heavy Metals

Toxic Heavy Metals

Industries Cd Cr Cu Fe Hg Pb Ni Zn

Pulp, paper mills, board mills x x x x x x

Organic chemical, petrolchemicals x x x x x x

Alkalis, inorganic chemicals x x x x x x

Fertilizers x x x x x x x x

Petroleum refining x x x x x x x x

Basic steel work foundries x x x x x x x

Motor vehicles, aircraft plating and finishing

x x x x x x

Steam generation power plats x x

Heavy metals employed in some major industries (Palmer et al., 1988).

Introduction

Recent toxicology studies Stricter regulations with regard to toxic metal ions discharge,

particularly in industrialized countries. Conventional materials and techniques:

- secondary problems of metal-bearing sludge. - ineffective at low metal ion concentrations - expensive and non-regeneration of adsorbent (activated carbon)

Developing an alternative material to the conventional adsorbent – activated carbon, normally used in adsorption processes of removing heavy metal ions in water and wastewater treatment facilities would result in a more cost-effective way of treating heavy metal.

Current Situations and Arising NeedsIntroduction

Why MMT?

Montmorillonite is a clay silicate formed by crystallization from solution high in soluble silica and magnesium.

MMT is a member of the smectite family, a 2:1 clay, has 2 tetrahedral sheets sandwiching a central octahedral sheet.

The particles are plate-shaped with an average diameter of approximately 1 micrometer.

Increases greatly in volume when it absorbs water.

Chemically, it is hydrated sodium calcium aluminium magnesium silicate hydroxide (Na,Ca)0.33(Al,Mg)2(Si4O10)(OH)2·nH2O. Potassium, iron, and other cations are common substitutes.

Montmorillonite

Background

Mg2+ for Al3+ leads to permanent negative charge

Mg2+ move to interlayer space

At the interlayer Mg2+, Ca2+ or Na+ can react with water – Free expansion

Large internal surface

Poorly crystallize - difference in sizes - isomorphous substitution - large cation adsorption

MMT as metal ion adsorbent

Background

Adapted from Olphen and Fripiat, 1979

OT

Mg2+ for Al3+

Al3+ or Fe3+ for Si4+

T

T

TO

Inte

rlay

er

Research goal: To develop an effective and regenerative material from MMT and

evaluate its application potentials to replace activated carbon for the treatment of heavy metal- loaded industrial effluents

Research idea

To provide explicit information on how the physicochemical nature and behavior of a natural clay (montmorillonite - MMT) surface can be articulated for designing effective heavy metal ion treatment strategies in water and wastewater systems.

To provide explicit information on how the physicochemical nature and behavior of a natural clay (montmorillonite - MMT) surface can be articulated for designing effective heavy metal ion treatment strategies in water and wastewater systems.

Research idea and goal

To modify MMT surface properties and evaluate the effects of the modifications on adsorptive behavior of MMT for heavy metal ions removal in aqueous solutions.

Research Objective

• adsorption by (living or dead) microbial biomass, bioremediation systems • low operating cost, eco-friendly• most economical alternative compared with other processes• technical constraints – large land area, less flexibility in design and operation

• adsorption by (living or dead) microbial biomass, bioremediation systems • low operating cost, eco-friendly• most economical alternative compared with other processes• technical constraints – large land area, less flexibility in design and operation

Biological treatment process

• ultrafiltration, nanofiltration, reverse osmosis, electrodialysis, ion exchange, adsorption • membrane fouling occurs often not cost-effective

• ultrafiltration, nanofiltration, reverse osmosis, electrodialysis, ion exchange, adsorption • membrane fouling occurs often not cost-effective

Physical treatment process

• precipitation, coagulation-flocculation, flotation, electrochemical processes• although metal ions are removed, accumulation of concentrated sludge creates a disposal problem • a secondary pollution problem excessive chemical use

• precipitation, coagulation-flocculation, flotation, electrochemical processes• although metal ions are removed, accumulation of concentrated sludge creates a disposal problem • a secondary pollution problem excessive chemical use

Chemical treatment process

Treatment processes for industrial wastewater laden with toxic heavy metal ions

Background

Researchers have focused on use of other relatively cheaper adsorbents to replace activated carbon

AdsorptionBackground

Adsorption and Field application

MMT surface properties determination

CEC d-spacing Surface area

MMT surface properties modification

Salt treatment Acid treatment

Evaluation studies MMT for heavy metal pollution

remediation

Approach

Phase 1

Phase 2

Phase 3

Beaker

Charge determination

100 mL KCl electrolyte [conc (0.01- 0.001M)] 20g MMT added and titrated with

0.01M NaOH till pH 10.

Reversibility• Same suspension titrated with 0.01 M HCl till pH 2.5

pH measurement after stirring and equilibration for 1hr

Materials and methods

Sodium montmorilloniteSodium montmorillonite(Na-MMT)(Na-MMT)

MMT : 1 M NaCl solution = 1 g : 10 mL

Mechanical stirring (24 h), repeated 5 times

Centrifugation and AgNO3 test for Cl-

Drying at 105 oC for 6 h

Sieving to 150 μm

Synthesis( Na-MMT)Materials and methods

Acid treated montmorilloniteAcid treated montmorillonite(A-MMT)(A-MMT)

MMT : 4 N H2SO4 = 1 g : 40 mL

Drying at 105 oC for 6 h

Sieving to 150 μm

Synthesis (A-MMT) Materials and methods

Refluxing in a shaking water bath (3 h) at 90 oC

Centrifugation and BaCl2 test for SO42-

• Adsorbent (Na-MMT and A-MMT)

• Adsorbate (50 mL of Copper Solution)

• Adsorbent dosage (0.3 g)

Shaking(200 rpm) Filtration

Analysis

AAS

100mL Erlenmeryer flask

Parameters• Initial concentration of copper solution : 50 - 100 mg/L• Temperature : 15 - 45℃• pH: 2.3-10

Sorption Materials and methods

Parameters Quality/4 L of effluent

pH 6.1

COD 117.5 (mg)

Suspended solids 57.4 (mg)

Normal hexane 1.0

Total Nitrogen 57.78

Total Phosphorus 10.08

Cyanide 0.348 (mg)

Copper 124.37 (mg)

Nickel 60.19 (mg)

Chromium 0.317 (mg)

Materials and methods

Chemical assay of industrial wastewater.

Isotherm Empirical form Linear form Plot

Freundlich

Langmuir

Tempkin

Dubinin-Radushkevich

Redlich-Peterson

neFe CKq /1

e

eme BC

BCQq

1

eTT

e CAb

RTq ln

eF

Fe Cn

Kq ln1

lnln

m

e

me

e

Q

C

BQq

C

1

eTTTe CBABq lnln

Applied isotherm models

2lnln DRe Qq

eCRT

11ln

21E

e

eRe AC

CBq

1

)()ln()1ln( Ree

e BCq

CA

ee Cvsq ln.ln

ee

e Cvsq

C.

ee Cvsq ln.

2.ln vsqe

ee

e Cvsq

CA .1ln

Results and discussion

2exp DRe Qq

TT b

RTB

Vital information in optimizing the use of adsorbents: affinity between sorbates and sorbents bond energy and adsorption capacity

Isotherm Empirical form Linear form Plot

Pseudo first-order

Pseudo second-order

Elovich

Intra-particle

Applied kinetic models

tvsqq te .)ln(

tvsq

t

t

.

tvsqt ln.

Results and discussion

)exp1( 1tket qq tkqqq ete 1ln)ln(

ee

t

q

t

qk

tq

22

1 tqqkq

t

eet

112

2

tqt ln1

)ln(1

21tkq it

21tkCq it 2

1.tvsqt

Characterization of montmorillonites

Results and discussion

AdsorbentCEC

(meq/100g)d-spacing

(nm)Surface area

(m2/g)

MMT 89.24 0.126 267

Na-MMT 94.18 0.128 286

A-MMT 57.69 0.098 190

Effect of pH

Results and discussion

Effect of pH on the adsorption of Cu2+ onto Na-MMT and A-MMT (Cu2+ concentration, 100 mg/L; adsorbent dose, 6 g/L; equilibrium time, 250 min; temperature 25 ± 0.1 °C; 200 rpm)

2 3 4 5 6 7 8 9 10 1120

30

40

50

60

70

80

Ad

sorp

tion

(%

)

pH

Na-MMT A-MMT

Adsorption was highly pH dependent: imply that surface complexation contributes to Cu(II) adsorption.

Na-MMT displayed a higher adsorption capability.

Equilibrium sorbed amount of Cu2+ according to time by (a )Na-MMT and (b) A-MMT at different initial concentrations (adsorbent dose, 6 g/L; reaction time, 250 min; pH, 5.8 ± 0.1; temperature 25 ± 0.1 °C; 200 rpm).

(a) (b)

Effect of initial concentration and time

Results and discussion

Maximum adsorbed amount for Cu(II) with Na-MMT and A-MMT was achieved within 180 min.

Increase in initial concentration α increase adsorption.

0 50 100 150 200 250 300 350 400

4

6

8

10

12

q t mg

/g

t (min)

100 mg/L 75 mg/L 50 mg/L

0 50 100 150 200 250 300 350 4000

1

2

3

4

5

6

7

8

q t (m

g/g

)

t (min)

100 mg/L 75 mg/L 50 mg/L

Equilibrium models Parameters Na-MMT A-MMT

Freundlich

KF ((mg/g)(L/mg)1/n) 7.281 1.050

nF 9.373 1.986

qe Cal.(mg/g) 10.67 7.85

R2 0.998 0.971

Langmuir

Qm (mg/g) 10.89 12.14

B (L/mg) 0.867 0.032

qe Cal.(mg/g) 10.57 7.71

R2 0.999 0.986

Tempkin

AT 148.9 0.011

bT (kJ/mol) 2.495 0.798

qe Cal.(mg/g) 10.64 7.75

R2 0.999 0.982

Dubinin-Radushkevich

QDR (mg/g) 10.28 8.25

E (kJ/mol) 1.227 0.108

qe Cal.(mg/g) 10.23 7.59

R2 0.975 0.999

Redlich-Peterson

B 9.85 4.82

A 0.059 0.038

ζ 0.977 0.546

qe Cal. (mg/g) 10.61 7.79

R2 1.00 0.973

Experimental qe Exp.(mg/g) 10.61 7.59

Equilibrium isotherm model parameters for Cu(II) sorption onto modified montmorillonites.

Results and discussion Process of adsorption of metal ions occurred on

the homogeneous surface of MMT (a chemically equilibrated phenomenon).

Results and discussion

Kinetics

Kinetic models Parameters Na-MMT A-MMT

Concentration of Cu(II) solution (mg/L)

50 75 100 50 75 100

Pseudo

first-order

k10.013 0.027 0.024 0.016 0.022 0.024

qe Cal.(mg/g) 3.87 4.16 9.98 3.17 5.13 5.91

R2 0.968 0.976 0.944 0.989 0.964 0.995

Pseudo second-order

k2 (g/mg min) 0.011 0.032 0.004 0.007 0.007 0.001

qe Cal.(mg/g) 8.22 10.07 10.86 5.06 7.03 8.00

R2 0.999 0.999 0.998 0.999 0.999 0.999

Elovich

α(g/(mg min)) 1.90 1.67 2.50 1.09 4.35 3.26

τ (mg/g) 1.11 1.33 0.57 1.21 1.06 0.86

qe Cal.(mg/g) 8.69 7.78 11.26 3.64 7.02 6.14

R2 0.995 0.962 0.988 0.983 0.988 0.976

Intraparticle

kid (mg/g min1/2) 0.138 0.085 0.222 0.242 0.179 0.199

qe Cal.(mg/g) 8.41 8.23 10.74 5.11 7.29 8.09

R2 0.995 0.968 0.998 0.978 0.988 0.987

Experimental qe Exp.(mg/g) 7.94 9.89 10.61 4.76 6.71 7.59

Kinetic model parameters for the sorption of Cu(II) onto modified montmorillonites.

Chemisorption through sharing or exchange of electrons between sorbent and adsorbate .

Rate constant decreases with increasing initial metal ion concentrations i.e. time required for the adsorption may monotonically increase with increase in initial metal ions concentration in practical applications.

Thermodynamic parameters

Results and discussion

Adsorbent Temp (K) ∆Go (kJ/mol) ∆Ho (kJ/mol) ∆So (J/mol K)

Na-MMT

288 -13.00

11.56 85.30298 -13.86

303 -14.70

318 -15.56

A-MMT

288 -11.55

8.61 70.00298 -12.25

303 -12.95

318 -13.65

Thermodynamic parameters for the sorption of Cu(II) onto modified montmorillonites.

Adsorption increased with increase in temperature …Endothermic process

Adsorption is thermodynamically spontaneous and feasible

+ve entropy supports complexation and stability of sorption (irreversibility)

Results and discussion

Application to real industrial wastewater

Metals Effluent concentration/50 mL (mg/L)

Remaining concentration in mg/L (% removal)

Na-MMT A-MMT Zr-MMT AC

Cu(II) 69.67 10.01 (85.6) 28.43 (59.2) 19.47 (72.1) 3.68 (94.7)

Ni(II) 10.27 N.D N.D N.D N.DCr(VI) 0.049 N.D N.D N.D N.D

Removal of Cu(II) and Ni(II) from industrial wastewater by modified montmorillonites.

N.D : Not Dedectable

Conclusion and recommendation

The natural occurrence, availability, adsorption and regeneration capabilities, even cost, pose MMT as a substitute for activated carbon in toxic heavy metal ions treatment of industrial wastewater.

The application of these modified-MMTs by industrial units using a batch stirred-tank flow reactor is hereby recommended for direct solution to problems of heavy metal-loaded wastewater discharge.

The loaded MMT after several use, can be disposed off for brick making in the building industry.

Conclusions

Sources and Sinks of Heavy Metals

Modified – from http://pubs.usgs.gov/circ/circ1133/images/fig21.jpeg

Route of Exposure: Absorption, Ingestion, Inhalation

http:healtheffects.net/he/images/ToxTri.gif

Heavy metal

Rank Toxicities

Maximum effluent discharge standards

(mg/L)

EPA (CERCLA, 2005) USACr(VI) 18 Headache, nausea, diarrhea, vomiting

0.01

Pb(II)

02 Kidney damage, renal disorder, cancer 0.015

Zn(II)

74 Depression, lethargy, neurologic signs such as seizures and ataxia, and increased thirst

5.0

Cu(II) 133 Liver damage, Wilson disease, insomnia 1.3

Cd(II) 08 Kidney damage, renal disorder

0.005

Ni(II) - Dermatitis, nausea, chronic asthma, coughing

0.20

Maximum contaminant level (MCL) of heavy metals in surface water and their toxicities (prepared from http://www.epa.gov/safewater/mcl).

Numbers of tested adults reported to the NYS Department of health for (A) Arsenic and (B) Lead by level

(A)

(B)

USDA Report, 2005

Hg Al

Pb

Heavy Metals

Toxic Heavy Metals

Cu Cd Ni

Theory - ideal MMT

The amount of metal ion adsorbed per unit mass of adsorbent qt (mg/g) at each time t, by adsorbents was calculated from the mass balance expression:

and the percentage removal of metal ions was obtained using:

Removal (%)

V = volume of metal ion solution (mL) C0 = initial concentration of the metal ion solution (mg/L) Ct = liquid-phase concentrations of the metal ion solution at any time t (mg/L) m = amount of adsorbent used (g)

s

to

t m

VCCq 1000)(

o

to

C

CC100

Adsorption

Calculation

)( OHHo nFS

The net surface charge density, So, was calculated using the equation above.

So = surface charge (C cm−2) n = numbers of moles of ionsF = Faraday constant. ГH+ and ГOH- = adsorbed amounts of H+ and OH− ions (mol cm−2) during the titration process

In this manner, the dependence of the surface charge density on pH and the electrolyte concentration were obtained.

CalculationSurface charge density

- Large surface area

- Relative abundance of reactive surface groups on its surface

- Predominance in sub-surface

- Predominance as particles in suspensions in surface water

- Abundant natural mineral in many regions

Adsorbent Cd2+ Hg2+ Cu2+ Ni2+ Zn2+ Pb2+ Cr2+ Cost (kg/USD)

Chistosan 815 222 164 75 273 15.43

Zeolite 2.2 1.6 0.48 0.5 1.4 3.3 0.03-0.12

Clay (smectite) 0.04-0.12

Montmorillonite 4.72 4.98 0.68

Kaolinite 0.32 1.25 0.12

Illite 4.29

Peat 22.48 12.07 11.74 13.08 43.9 0.023

Fly ash 2.82 2.92

Activated carbon

(GAC)

44.44 0.87

Cellulose 73.46 1.07

Natural oxides

Aluminium oxides 31 33 11.7

Ferric oxide 72 230

Industrial waste

Lignin

(Black Liquor)

1865 1USD/ton

Sawdust 13.80

Adsorption capacities (mg/g) of adsorbent for different heavy metals

Babel, 2002

Montmorillonite Van Olphen, 1979

Schematic picture of the montmorillonite particle (A), the top plane (basal plane) possesses exchangeable sites, whereas the edge surface dissociable ones. Parts (B) and (C) show the electrical double layer model for both kinds of planes.

Duc et al., 2005

Mineral surface properties

Surface charge of an oxide mineral surface in aqueous systems will change with changing pH as a function of the PZC of that mineral.

Surface charge creates a surface condition in which there is an uneven charge distribution.

The consumption and release of protons during an acid/base titration can be due to:

– proton adsorption/desorption on the edge sites (i.e.aluminols and silanols)

– exchange reactions on basal planes to compensate the negative structural charge

– hydrolysis of aqueous cations released during mineral dissolution.

Surface Charge Theory

Surface Charge Development Theory

Three parameters contribute on surface charge of clay minerals: σO : the permanent structural charge density created by isomorphic substitutions

in a mineral structure,

σH : the net proton surface charge density created only by proton adsorption and desorption reactions at the interface clay-aqueous solution and,

Δq : the net adsorbed ion surface charge density from background electrolyte, exclusive of that contributed by adsorbed protons and hydroxide ions.

These components are related by the law of surface charge balance: σO + σH + Δq = 0

The sign of σH varies with aqueous solution pH, taking on zero at the point of zero net proton charge (PZNPC) and becoming negative at higher pH values.

Definitions of the surface charges of clays and relevant characteristic points determined from potentiometric titrations or electrokinectic measurements

Acronym Name Definition

Proton charge Surface charge developed by protonation- deprotonation of surface groups.

Lattice charge Charge originating from lattice substitutions by lower-charge metals and giving rise to the cation exchange capacity.

PZNPC Point of zero net Intersection between raw titration curve for the proton charge blank and for the suspension.

PZSE Point of zero salt Intersection between charge curves at different effect electrolyte concentrations

PZC Point of zero Common intersection point where both PZNPC charge and PZSE coincide.

IEP Isoelectric point pH of zero ζ potential on eletrokinectic curves

Surface Charge Development - Theory

In environmental chemistry and several industrial processes - PZC is a very important parameter playing a crucial role in many chemical phenomena , such as adsorption, interaction between particles in colloidal suspensions, coagulation, dissolution of mineral hydroxides and electrochemical phenomena.

The principal mechanism of the development of surface charge is the adsorption of protons, hydroxyls, metallic cations, anions and organics species.

a) Lattice imperfection b) Adsorption of ions

c) Chemical reactions on the surface (dissociation of functional surface groups)

d) Adsorption or dissociation of charge-bearing molecules

Metal Ionic radius Atomic radiusNa + 116 168H+ - 25Zr3+ 88.5 160Ni2+ 83 135Cu2+ 87 135Al3+ 53.5 125Mg2+ 86 150Si3+ - 110Fe3+ 63 140