Riboflavin Enhances the Synergy of Electroactive Bacteria and Fenton Reaction, Improving Chlorophenol Degradation and Fe Circulation

Electroactive bacteria (EAB) could drive the Fenton reaction for purifying wastewater and recovering power simultaneously. However, the toxicity could damage EAB and reduce extracellular electron transfer (EET) efficiency, leading to declined current generation and more Fe sludge production. This study hypothesizes that electron shuttle riboflavin could enhance the synergy of EAB and the Fenton reaction, thereby improving refractory degradation and power generation under refractory stress. A microbial electro-Fenton (MEF) system employing 4-chlorophenol (4-CP) as the model toxic pollutant was set up, and 3 μM riboflavin was supplemented. The results showed that the total resistance reduced by 14%, and the current output and Fe(II) proportion improved by 25% and 38%, respectively. Due to the supplementation of riboflavin, the 4-CP degradation kinetic constant increased by 3.8 times, and the two-component system upregulation and extracellular polymer synthesis improvement contributed to the acceleration of biofilm formation. The EET processes via electron shuttle and nanowire pathways were improved with riboflavin addition, achieving the promotion of the electro-Fenton reaction and the production of less toxic intermediates. The downregulation of the microbial antioxidant enzyme system (with vs without riboflavin) also confirmed the elimination of toxic stress. This study provided a feasible strategy to improve the performance of MEF reactors.