The deleterious health effects associated with ingestion of arsenic and chromium that they be removed to levels below mug/L in potable water supplies. The proposed research investigates two removal methods which involve reduction of highly water soluble As(III), As(V) and Cre(VI) compounds to lower valence states which are less water soluble. Although laboratory investigations have demonstrated the short-term effectiveness of zerovalent iron for mediating the reductive precipitation of chromium and arsenic compounds, the long-term effectiveness of the process has not been established, and the conditions flavoring arsenic and chromium removal are not well understood. This research investigates the effects of water chemistry, surface precipitate buildup and iron surface aging on arsenic and chromium removal from contaminated waters by zerovalent iron. Additionally, this research also investigates arsenic and chromium removal via electrosorption and reduction by anodically polarized magnetite. The research objectives are: 1) to determine the long-term effectiveness of zero valent for arsenic and chromium removal in in-situ permeable barrier configurations; 3) to determine the effectiveness of anodically polarized magnetitite for removing arsenic and chromium oxyanions from contaminated waters; and 4) to develop a flow-through treatment process which removes dissolved arsenic compounds to levels below 1 mug/L for a variety of source waters. Both batch and column studies will be performed to measure arsenic and chromium removal kinetics by zerovalent iron and by anodically polarized magnetitite. The morphology and oxidation state of the arsenic and chromium precipitates, as well as the iron corrosion products, will be determined using electron microscopy and X-ray absorption spectroscopy. Thermodynamic solution modeling using the USEPA model NITEQA2 will be performed to determine the agreement between predictions based on equilibrium behavior and the observed results.
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