Comparison of inert and non-inert cathode in cathode/Fe3+/Peroxymonosulfate processes on iohexol degradation

Abstract

To investigate the effect of cathode materials on organics degradation in a cathode/Fe3+/PMS process, different cathode materials (platinum, copper and iron) were selected and their performances were compared with iohexol as target organics. The optimal conditions were found to be different for different cathode/Fe3+/PMS processes. With a relatively high cathodic current input (2.0 mA/cm2), similar results were found for all the three cathode/Fe3+/PMS processes. With a small cathodic current input (not higher than 1.0 mA/cm2), the iohexol removal followed the order of Fe-cathode/Fe3+/PMS > Cu-cathode/Fe3+/PMS > Pt-cathode/Fe3+/PMS, due to the corrosion of Cu-cathode and Fe-cathode and the more serious corrosion of Fe-cathode than Cu-cathode. The corrosion of non-inert cathode materials (Cu-cathode and Fe-cathode) meant that these cathodes not only transmitted electrons but also participated in aqueous reactions, which complicated the mechanisms of cathode/Fe3+/PMS processes. The radical identification experiments indicated that SO4- was more important than OH for iohexol degradation in Cu-cathode/Fe3+/PMS process, while OH played a major role in Pt-cathode/Fe3+/PMS and Fe-cathode/Fe3+/PMS processes. The different reaction mechanisms resulted in different iohexol transformation pathways in cathode/Fe3+/PMS processes with different cathode materials.