Treatment of arsenite contaminated water by electrochemically activated persulfate oxidation process

Arsenic pollution in the groundwater is a serious worldwide problem, where arsenite and arsenate are the most prevalent forms in groundwater. Most of the conventional methods are able to remove arsenate effectively as compared with arsenite. Hence, for complete elimination of arsenic, prior oxidation of arsenite to arsenate is needed. The present work assessed the possibility of electrochemically activated persulfate (PS) based advanced oxidation process (EAOP) for arsenite removal from the aqueous medium. EAOP using Pt/Ti as both anode and cathode, can completely oxidize arsenite with an initial concentration of 1 mg L-1 within 60 min of electrolysis at pH 3; ferrous ion concentration 250 mg L-1, persulfate concentration 500. mg L-1, but failed to remove the arsenate (generated by the oxidation of asenite) from the aqueous medium. However, iron anode mediated persulfate advanced oxidation process was found to be more effective for both oxidation of arsenite and complete elimination of arsenic within 60 min of electrolysis at pH 3, applied voltage 2 V, and 500 mg L-1 PS. The average operating cost estimated is 0.33 $ m−3. At pH 3, the oxidation of arsenite is taking place by both hydroxyl and sulfate radicals; whereas, at neutral and alkaline conditions, hydroxyl radicals and ferryl ions play a major role in the oxidation of arsenite. Overall, persulfate mediated advanced oxidation is effective for arsenite removal from aqueous medium.