Removal of arsenic in aqueous solution by electrochemical peroxidation

Electrochemical Peroxidation (ECP), an emerging remediation technology, with direct electric current applied to steel electrode and small addition of H sub(2)O sub(2), has been used to remove As (III) from artificially contaminated aqueous solution ( similar to 0.250 mg L super(-1)). Bench scale experiments evaluated the sorption and distribution of arsenic between the soluble and solid-state hydrous ferric oxides (HFO) formed as a part of the ECP process. The effects of pH, hydrogen peroxide concentrations and electric current process time on the efficiency of the arsenic removal by ECP were examined. ECP was very effective in removing arsenic from arsenic aqueous solution, with 98% of the applied As (III) adsorbed on HFO. Removal was complete within 3 min of ECP treatment and apparently independent of the initial pH of the water, 3.5 to 9.5. Data obtained in the absence of H sub(2)O sub(2) showed that As is preferentially adsorbed by solid state iron at pH 9.2 than at 3.5, 260 vs. 175 mu g L super(-1). Thus H sub(2)O sub(2) revealed to be fundamental to oxidize As (III) to As (V), which is normally more strongly retained by HFO. The optimal operating conditions were pH < 6.5, H sub(2)O sub(2) concentration of 10 mg L super(-1) and current process time not exceeding 3 min.