Heterogeneous electro-Fenton process with a MoS2-loaded bifunctional cathode for sulfamethazine degradation: Approach and mechanisms

Abstract

A bifunctional cathode with MoS2 powder and carbon black deposited on carbon felt (MCB@CF) was prepared and first applied as bifunctional cathode to heterogeneous electro-Fenton (EF). This cathode presented higher H2O2 production compared with other cathodes. Fe0 modified by sulfidation coupled with pre-magnetization (pre-S/Fe0) was used as a catalyst in the EF process. Compared to the conventional EF process, the established pre-S/Fe0-EF-MCB@CF process showed higher sulfamethazine (SMT) removal (removal rate constant improved by 3.01 times) and TOC removal (40% in 1 h) within wide pH range (pH 4–10). According to the radical quenching experiment, •OH was proved to be the main oxidation species for SMT degradation and O2•- played a marginal role. MoS2 surface presented Mo4+ active sites that could promote the conversion of Fe3+ to Fe2+, during which Mo4+ was oxidized to Mo6+. The promoted reduction of Fe3+ to Fe2+ enhanced the utilization of H2O2 and thus the generation of ∙OH. The six consecutive runs of pre-S/Fe0-EF-MCB@CF process proved the excellent stability and reusability of prepared MCB@CF cathode. Compared with that by Fe0-EF-CB@CF process, the removal rates of pesticides, phenols, dyes and drugs by pre-S/Fe0-EF-MCB@CF process was enhanced more than two times, demonstrating the potential of this process for wide application. This study provides a green and sustainable approach for the treatment of refractory pollutants by heterogeneous EF process in a wide pH range.