Project Summary (2000-2006)

This project is building on previous research showing that the particularly high affinity of Arsenic (As) for Fe-oxyhydroxides is a key factor regulating dissolved As concentrations in groundwater. Groundwater naturally or anthropogenically enriched in As poses serious health hazards in many parts of the world, including the U.S. The particular affinity of As for Fe-oxyhydroxides has been exploited for remediation by FeCl3 addition and co-precipitation. Project investigators are studying both As mobilization into, and As removal from reducing groundwater. The potential integrated release of As by reductive dissolution will be determined with hydroxylamine extraction from archived aquifer material covering a range of redox conditions. The spatial patterns of As and Fe released by reductive dissolution will be compared to the oxygen distribution in the aquifers. Fresh cores of aquifer material from selected sites are being incubated to quantify the rate of As and Fe exchange (adsorption or desorption). State-of-the-art surface analytical techniques are characterizing arsenic binding at model Fe oxide surfaces under a range of conditions representative of the natural environment. The mechanisms of As removal by Fe filings are being investigated using surface spectroscopy. Another objective is to develop practical ways of reducing the scale of As remediation. Research is focusing on Fe-oxyhydroxide-based treatment using the natural Fe content of groundwater. Additionally, the As-removal potential of existing Iron Removal Units in Bangladesh is being explored in collaboration with local government researchers.