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Abstract

Arsenic, which is very toxic for human health, has many oxidation states and can exist in both inorganic and organic form. Mainly, inorganic Arsenic in (III) and (V) oxidation state are present groundwater. The maximum contamination level (MCL) of Arsenic present in drinkable water is set to 10 �¼g/L or 10 ppb by World Health Organization (WHO). As(III), called Arsenite is bound with three (OH)-atoms forming arsenous acid (H3AsO3 or As(OH)3) in circumneutral pH. As(V), called Arsenate is bound to four O-atom, is generally represented as AsO(OH)3 or H3AsO4 but in circumneutral pH it generally exist in -1 or -2 charged as H2AsO4 1- or HAsO4 2- forms. As per present techniques, removal efficiency of As(III) from natural contaminated groundwater without prior oxidation to As(V) is very low due to its neutrality at circumneutral pH. The problem is underground water of Bengal basin or most of the part of world has rather high amount of As(III) (as high as 67% to 99% of total As-content) than As(V). In case of Bengal basin As(III) content is as high as 80%. Tooeleite is a natural As(III)-bearing mineral discovered in the U.S. Mine Tooele Country, Utah in the year 1992. It is only arsenite-sulphur containing mineral in world. It has high Fe:As ratio (1.2) which was termed as a ready source for permanent remediation of As(III) in nature. Removal of arsenite from natural underground water in form of tooeleite is not feasible till date, as precipitation of tooeleite crystals demands quite low pH~3 (which is nowhere near pH~7 of groundwater) and may take ~30 days. In here it will be shown how As(III) present in natural contaminated water is arrested in tooeleite-like crystal at circumneutral pH, within 3 hrs of treatment using specialized nanostructures.

Biography

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