A microbial fuel cell with CuCo2S4 as cathode catalyst for peroxymonsulfate activation: Effect of electrons transfer on RhB removal and catalyst regeneration

Electrochemical method has been used to induce peroxymonosulfate (PMS) activation for removing contaminants, yet low PMS activation rate limited its reaction activity. In this study, a microbial fuel cell (MFC) system with CuCo2S4 as cathode catalyst for PMS activation (PMS/CuCo2S4-MFC) was established. The results showed that three-dimensional nanoflake structure of CuCo2S4 could provide more active sites for PMS activation and exhibited the excellent electrochemical performance. The apparent degradation rate (ka) of Rhodamine B (RhB) in this system was 6.5 times and 1.2 times higher than MFC and CuCo2S4 alone, suggesting that PMS activation was attributed to both CuCo2S4 and electrochemistry in the system. In addition, the decrease of ka over five cycles in the system was approximately 3 times slower than CuCo2S4 alone, indicating that the catalyst stability was improved significantly. This is mainly attributed to the in-situ regeneration of Cu2+ and Co3+ through receiving the electrons generated from MFC anode. The radical quenching results indicated that RhB was degraded mainly through the radical pathway, in which sulfate radical was the key reactive species. This study provides an energy-saving approach for PMS activation, which will be useful for further development of PMS-based advanced oxidation process.