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!