Enhanced degradation of Metronidazole by the coupling of photocatalytic and microbial fuel cell: Mechanism and electrochemistry characteristic

In this study, the attempt was made to enhance the degradation of the typical antibiotics, metronidazole (MNZ) by coupling three-electrode photocatalytic and microbial fuel cell systems (PMFC). The PMFC reactor was constructed, and the photocatalytic bioanode, attached with TiO₂, was synthesized and characterized using SEM, EDS, XPS methods. The stability of microbial on bioanode was tested during acclimatization process. Electrochemical characteristics, including power density, CV and EIS curve, were analyzed to explore the advantage of power generation and higher electron transfer interaction in the PMFC. Compared with the traditional MFC system, the improved degradation and enhanced mineralization of MNZ were achieved, and the 1.30 and 1.24-fold increase in MNZ and TOC removal were realized, respectively. The three degradation pathways of MNZ were identified by LC-MS in the coupling PMFC, and the intermediates were more easily to further degrade and mineralize. The structure of the microbial community was demonstrated, and the functional species consisted of MNZ degradation bacteria, exoelectrogens, hydrocarbon removal bacterial, and nitrogen removal bacterial, were largely enriched in the PMFC, contributing to the improved electricity production, MNZ degradation and photoelectric effect. Moreover, the photoelectric played the selective role in the enrichment of functional microbial. The study provides a promising and environmentally approach for the treatment of containing antibiotics wastewater in the practical application.