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

• A new electro-Fenton process with Ti/MMO cathode is developed.
• Contaminants of emerging concerns are effectively degraded.
• Influence of operating parameters is investigated.
• Degradation mechanisms and pathways are proposed.
• Contaminants are quickly transformed to nontoxic aliphatic acids.

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 (422 μg L−1) is completely degraded in an undivided cell using Ti/MMO as the cathode in the presence of 6.9 mg L−1 Fe2+ within 20 min under conditions of pH 4 and 25 mA. 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 Fe2+ from Fe3+. 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 5 mg L−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.

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