Enhanced arsenic removal from groundwater by using an advance adsorbent – ferric oxide/activated rice husk ash material Dr. Trung Thanh, Nguyen
Enhanced arsenic removal from groundwater by using an advance adsorbent – ferric oxide/activated
rice husk ash material
Dr. Trung Thanh, Nguyen
Contents
• Effect of arsenic to human health • Mapping arsenic contamination in South East Asia • Arsenic removal technologies • Solid materials for aqueous arsenic removal• New approach for aqueous arsenic removal
Mapping arsenic contamination
Fig. 1. Distribution of arsenic contamination in South East Asia, showing the contamination in the Mekong Delta and Red river.
Arsenic effect to human health
The WHO guideline for safe levels of arsenic ingestion is a concentration of 10 µg/L in drinking water and a limit of 100 µg/L in untreated water prior to being processed for consumption
Arsenic is known as the “king of poisons”
Fig. 2. Blackfoot disease from approximately ten years of drinking 50 µg/L of arsenic contaminated groundwater
Arsenic removal technologies
Arsenic removal
engineering
Combining of oxidation and precipitation engineering
Nano filtration
Adsorption and ion exchange
Why is adsorption technology applied to remove the arsenic from groundwater?
(1) Low charge for operation of arsenic removal system(2) The adsorbent could be reused.(3) no toxic products are created by adsorption.(4) This tech. can be carried out with high arsenic concentration.
Solid materials for aqueous arsenic removal
New approaches for aqueous arsenic removal
Motivations
1. Ferric oxide /carbon material exhibited low arsenic capacity
2. Low durability due to weak interaction between ferric oxide and carbon support.
Oxide support Drawbacks
Low surface area
Complex synthesis procedure
Mechanism of arsenic adsorption on the ferric oxide surface
S.E. O'Reilly, D.G. Strawn and D.L. Sparks; Residence Time Effects on Arsenate Adsorption/Desorption Mechanisms on Goethite; Soil Science Society of America Journal, Vol. 65 No. 1, p. 67-77, 1999.
Fig. 3. Mechanism of arsenic adsorption on the ferric oxide surface
Approach 1
Ferric oxide/activated rice husk ash material for enhancing aqueous arsenic
removal from groundwater
New idea
Activated rice husk ash support
Ferric oxide nanoparticle
Strong interaction metal oxide support
Carbon and SiO2
High surface area
e-
Cheap
H2AsO4-
H2AsO3-
Adsorption
Results and discussions
Fig. 1. Images of rice husk ash (RHA), activated RHA and FexOy on RHA support materials
Sample color depends on the loading of ferric oxide
Characterizations SEM/TEM images and BET surface area
Material BET surface area (m2/g)
Activated RHA 433
FexOy/RHA 410
Nanomaterials with high surface area
Characterizations
Fig. 4. FTIR patterns of original and activated rice husk ashes.
Wave number (cm-1) Functional group
3404.31 -OH and Si-OH
2925.81 C-H streching of alkanes
1641.31-1737 C=O stretching of aromatic groups
1546.8-1652.88 C=C stretching of alkanes and aromatic
1461.94 CH2 and CH3
1379.01 Aromatic CH and carboxyl-carbonate
1238.21 CHOH stretching of alcohol group
1153.35-1300 CO group in lactones
1080-1090 Si-O-Si
935.41 C-C
469-800 Si-H
580-34 -OCH3
FTIR
Activated RHA contains Carbon and SiO2.
Characterizations
Fig. 5. XRD patterns of ferric oxide/RHA materials.
The ferric oxide nanomaterial is a muxture of Fe2O3 and FeO
FeCl3 chemical is ferric resource for ferric oxide synthesis.
Arsenic capacity
Experimental conditions:CAs: ~ 100 µg/LVolume: 50 mLAdsorbent dosage: 50 mgpH: ~ 7.0Room temp.Adsorption time : 20 mins
Fig. 6. Arsenic capacities of various adsorbents at room temperature
The 5 wt.% FeCl3-FexOy/RHA material shows highest arsenic capacity than that of others. The activated RHA is a good support of ferric oxide nanoparticles for
arsenic removal
~14 mgAs/gFe
~1.2
~5.8
Mechanism of Enhancing arsenic capacity of FexOy/RHA material
Fig. 7. Strong interaction metal oxide support
Positive charge on the iron oxide nanomaterial
Conclusions of approach 1
The activated RHA is good support for ferric oxide nanomaterial toward arsenic removal from groundwater.
The FexOy/RHA adsorbent shows high arsenic capacity due to high BET surface area of activate RHA support and a positive charge on the ferric oxide surface by a good interaction between ferric oxide and silica of activated RHA support.
Approach 2
Manganese –dopped Ferric oxide/activated rice husk ash material for enhancing
aqueous arsenic removal from groundwater
New idea
Activated rice husk ash support
Ferric oxide nanoparticle
Strong interaction metal oxide support
Carbon and SiO2
High surface area
e-
Cheap
H2AsO4-
H2AsO3-
Adsorption
Manganese oxide
e-Adsorption
Characterization
Fig. 8. XANES patterns of Fe7Mn3Oz/RHA; FexOy/RHA; and Fe (reference) materials
The Fe7Mn3Oz/RHA materials is observed
higher positive charge on ferric oxide surface than that of FexOy/RHA material
Results and discussions
Fig. 9. Arsenic capacities of various adsorbents at room temperature
Experimental conditions:CAs: ~ 100 µg/LVolume: 50 mLAdsorbent dosage: 50 mgpH: ~ 7.0Room temp.Adsorption time : 20 mins
The Fe7Mn3Oz/RHA material shows highest arsenic capacity than that of others. The present of manganese can enhance the arsenic capacity of ferric oxide nanomaterial.
~ 1,3~ 1.1
Conclusions of approach 2
The present of manganese can enhance the arsenic capacity of ferric oxide nanomaterial.
A project of arsenic removal for groundwater in Cambodia
Fig. 10. a photo of arsenic removal from groundwater in Anlong Veng Prov., Cambodia-2016
40 L/h
Ferric oxide on activated rice husk ash material
Water inlet
Water outlet
Sand
Sand
Adsorbent
Thank you very much for your attention!