Degradation of nitrobenzene in wastewater using a double-modified biofilm particle electrode with Fe and Mn oxides

Abstract

Particle electrodes in three-dimensional (3D) biofilm electrodes play a crucial role in microbial loading and electrochemical degradation. Traditional particle electrodes, such as those made from activated carbon, often experience issues like clogging and poor electrochemical catalytic performance. In this study, a novel particle electrode is developed using polyurethane foam as a biofilm carrier modified by Fe and Mn oxides. The electrode incorporates pre-loading and dynamic deposition of FeMn oxides to enhance performance and improve the removal efficiency of nitrobenzene (NB) compounds in wastewater. Under the experimental conditions of a hydraulic retention time (HRT) of 24 h, a power supply voltage of 6 V, and a Mn to Fe oxide loading ratio of 5:1, the removal rate of NB in the Fe-Mn-modified group tended towards 100 %, with a stable chemical oxygen demand (COD) removal rate of 92.0 ± 1 % and an NH₄⁺-N removal rate of 85.0 ± 1 %. Compared with the control group, the secondary loading of iron and manganese significantly enhanced the biological synergistic function and membrane stability, resulting in a marked improvement in pollutant-removal effectiveness. And Fe concentrations in the effluent below 0.29 mg/L and Mn concentrations below 0.1 mg/L, no secondary pollution is caused. The synergistic degradation of pollutants by FeMn and microorganisms in the particle electrode biofilm was the primary factor contributing to the increased degradation efficiency. These results indicate that Fe-Mn-modified polyurethane foam exhibits excellent catalytic activity and microbial-loading performance, making it a novel and efficient particle electrode for enhancing pollutant-removal efficiency in 3D biofilm electrode reactors (BERs).