This presentation is part of the ProSPER.Net Young Researchers' School 2017 ‘Water Security for Sustainable Development in a Changing Climate’.

1. Enhanced arsenic removal from
groundwater by using an advance
adsorbent – ferric oxide/activated
rice husk ash material
Dr. Trung Thanh, Nguyen

2. 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

3. Mapping arsenic contamination
Fig. 1. Distribution of arsenic contamination in South East Asia, showing the
contamination in the Mekong Delta and Red river.

4. 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

5. 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.

6. Solid materials for aqueous arsenic
removal

8. New approaches
for aqueous arsenic removal

9. 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

10. 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

11. Approach 1
Ferric oxide/activated rice husk ash
material for enhancing aqueous arsenic
removal from groundwater

12. 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

13. 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

14. 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

15. 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.

16. 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.

17. Arsenic capacity
Experimental conditions:
CAs: ~ 100 µg/L
Volume: 50 mL
Adsorbent dosage: 50 mg
pH: ~ 7.0
Room 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

18. Mechanism of Enhancing arsenic
capacity of FexOy/RHA material
Fig. 7. Strong interaction metal oxide support
Positive charge on the iron oxide nanomaterial

19. 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.

20. Approach 2
Manganese –dopped Ferric oxide/activated
rice husk ash material for enhancing
aqueous arsenic removal from groundwater

21. 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

22. 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

23. Results and discussions
Fig. 9. Arsenic capacities of various adsorbents at room temperature
Experimental conditions:
CAs: ~ 100 µg/L
Volume: 50 mL
Adsorbent dosage: 50 mg
pH: ~ 7.0
Room 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

24. Conclusions of approach 2
The present of manganese can enhance the
arsenic capacity of ferric oxide nanomaterial.

25. 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

26. Ferric oxide on activated
rice husk ash material
Water
inlet
Water
outlet
Sand
Sand
Adsorbent

27. Thank you very much for your attention!