Performance of Cu-cathode/Fe3+/peroxymonosulfate process on iohexol degradation.

Abstract

Copper was used as a non-inert cathode material in a Cathode/Fe3+/peroxymonosulfate(PMS) system, and the performance of this novel Cu-cathode/Fe3+/PMS system was tested with a typical iodinated X-ray contrast media (iohexol) as target organics. The reaction mechanisms and the iohexol degradation pathways were investigated. The operational conditions of Cu-cathode/Fe3+/PMS process on iohexol degradation were optimized to be 1.0 mM Fe3+ dosage, 3.0 mM PMS dosage and 0.50 mA/cm2 of current input. The much lower current applied in the present study than previous reports would help to save energy and be more economical. Compared with typical inert cathode (Pt-cathode), the Cu-cathode/Fe3+/PMS process has better performance on both iohexol removal and deiodination, due to that Cu-cathode participated in Fe2+ regeneration and PMS activation via surface Cu°-Cu+(s)-Cu2+-Cu° redox cycle. Fe2+ could be produced via reactions between Fe3+ and Cu/Cu+(s) as well as cathodic reduction of Fe3+. SO4- was generated from PMS activation by Fe2+, Cu/Cu+(s) and cathodic reduction. OH was also generated in this process but SO4- played a dominant role in iohexol degradation. The intermediate products of iohexol and its transformation pathways were complex due to the varied reaction mechanisms involving both oxidation and reduction in Cu-cathode/Fe3+/PMS process.