Treating nitrobenzene (NB) wastewater via an enhanced iron‒manganese oxides electron transfer strategy: Methods and mechanisms.

Nitrobenzene (NB) is widely used in the fine chemical, pharmaceutical, and textile industries, but its toxicity and resistance to degradation present challenges, and traditional treatment methods are limited due to costs and a lack of efficiency. In this study, using a three-dimensional biofilm electrode reactor (3D-BER) enhanced with iron-manganese oxide catalysts was explored for the treatment of NB wastewater. Modifying polyurethane (PU) sponge fillers with Fe₃O₄ and Mn₃O₄ improved the conductivity and microbial electron transfer of the 3D-BER, significantly enhancing organic compound degradation, nitrogen and phosphorus removal. At the optimal voltage of 6 V and hydraulic retention time (HRT) of 24 h, the reactor achieved CODCr and ammonia nitrogen removal rates of 93.04 % and 86.25 %, respectively, which were more than 20 % higher than those in the control group. The iron and manganese present facilitated increased microbial activity and electron transfer efficiency, and metagenomic sequencing revealed shifts in the microbial communities and the enrichment of specific functional genes related to NB degradation. This integrated bioelectrochemical approach offers an effective and low-cost solution for treating NB wastewater, with broader implications for organic chemical wastewater management.