Efficient degradation of contaminants of emerging concerns by a new electro-Fenton process with Ti/MMO cathode

The performance of a new electro-Fenton process with Ti-based mixed metal oxides (Ti/MMO) cathode, a dimensionally stable electrode, is evaluated for degrading contaminants of emerging concerns (CECs) in aqueous solutions. Bisphenol A (422μgL(-1)) is completely degraded in an undivided cell using Ti/MMO as the cathode in the presence of 6.9mgL(-1) Fe(2+) within 20min under conditions of pH 4 and 25mA. Both bisphenol A degradation and H2O2 production increase with decreasing solution pH and increasing current. Ti/MMO cathode is effective for reducing O2 to H2O2 and regenerating Fe(2+) from Fe(3+). OH radicals are validated to be the predominant reactive oxygen species (ROS) contributing to bisphenol A degradation. This new electro-Fenton process is also effective for degrading bisphenol A, triclosan and ibuprofen even at a relatively high concentration of 5mgL(-1). The partial removals of total organic carbon suggest a moderate extent of mineralization. The transformation pathways of the three CECs are proposed based on the intermediates identified by HPLC and GC-MS, showing that CECs are mainly transformed to nontoxic aliphatic acids. This study demonstrates that Ti/MMO can be used as the cathode in the electro-Fenton process for degrading CECs at trace levels in waters.