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ARSENATE AND ARSENITE SORPTION AND ARSENITE OXIDATION BY IRON (II, III) HYDROXYCARBONATE GREEN RUST
Citation:
Su, C. AND R T. Wilkin*. ARSENATE AND ARSENITE SORPTION AND ARSENITE OXIDATION BY IRON (II, III) HYDROXYCARBONATE GREEN RUST. Chapter 3, O'Day, Vlassopoulos, Meng, and Benning (ed.), Advances in Arsenic Research. American Chemical Society, Washington, DC, ACS Symp Series(915):25-40, (2005).
Impact/Purpose:
Purpose - to evaluate the influence of geochemical parameters such as pH, time, and arsenic concentration on the interactions of arsenic with iron corrosion products.
Description:
Iron (II, III) hydroxycarbonate green rust is a major corrosion product of zerovalent iron that is being used in permeable reactive barriers to remediate groundwater arsenic contamination. To optimize the design of iron barriers, it is important to evaluate the influence of geochemical parameters such as pH, time, and arsenic concentration on the interactions of arsenic with iron corrosion products. We synthesized iron (II, III) hydroxycarbonate green rust by neutralizing FeSO4 solution with NaOH and Na2CO3 or NaHCO3 followed by air sparging. The synthetic products were characterized with scanning electron microscopy, X-ray diffraction, and wet chemical analysis. We conducted batch sorption experiments with arsenate and arsenite in an anaerobic glovebox. The pH ranged from 7.5 to 10.7. Both arsenate and arsenite sorption increased with increasing time up to 60 days. More arsenite was sorbed at pH 10.5 than at pH 7.5. Arsenite showed much higher sorption than arsenate. Adsorbed arsenite (up to 90 g kg-1) was partially oxidized on solid surface. Oxidation of sorbed arsenite could be advantageous because arsenate is generally less toxic and less mobile than arsenite.
