Arsenite removal from waters by zero valent iron: batch and column tests.

This study investigates the efficiency of zero valent iron (ZVI) to remove arsenite from water. Batch experiments were carried out to study the removal rates of arsenite under different pH values and in the presence of low and high concentrations of various ions (chloride, carbonate, nitrate, phosphate, sulfate and borate), manganese and dissolved organic matter. Most of these parameters affect negatively the removal of arsenite. Particularly, borate and organic matter at high concentrations significantly inhibited the efficiency of ZVI. Column tests were carried out to investigate the removal of arsenic under dynamic conditions and breakthrough curves were found for arsenate, arsenite and a mixture of both. ZVI treatment was also applied to natural groundwaters with elevated arsenic concentrations under the geochemical conditions usually found in Greece. The method was efficient for groundwater containing As(V). However, in anoxic-reducing groundwaters with prevalence of As(III), treated water did not fulfill the guideline of 10 microg L(-1) for drinking water. Chlorination enhanced the ZVI efficiency producing concentrations below the proposed limit.