Quinones contained in wastewater as redox mediators for the synergistic removal of azo dye in microbial fuel cells. (1st January 2022) - Li, Tao
Abstract: The present paper aimed to investigate the roles of quinones contained in wastewater and the enhanced effects on microbial fuel cells (MFCs) under different redox conditions. The feasibility of using wastewater rich in quinones to act as co-substrate and redox mediators (RMs) library to strengthen the synergistic removal of azo dye in MFCs was evaluated. The results demonstrated that quinones achieved enhanced effects on electricity generation and COD removal of MFC better at higher current intensity. The addition of pure quinone decreased electron transfer resistance (Rct) of MFCs from 4.76 Ω to 2.13 Ω under 1000 Ω resistance and 1.16 Ω–0.75 Ω under 50 Ω resistance. Meanwhile, higher coulombic efficiency was achieved. Compared with sodium acetate, using quinone-rich traditional Chinese medicine (TCM) wastewater as the co-substrate enhanced the synergistic removal of reactive red 2 (RR2) in MFCs from 79.58% to 92.45% during 24 h. RR2 was also degraded more thoroughly due to the accelerated electron transfer process mediated by RMs. Microbial community analysis demonstrated that the presence of quinone in TCM wastewater can enrich different exoelectrogens under varied redox conditions and thus influenced the enhanced effects on MFC. Metagenomic functional prediction results further indicated that the abundance of functional genes involved in carbohydrate metabolism, membrane transport metabolism, biofilm formation, and stress tolerance increased significantly in presence of RMs. Redundancy analyses revealed that RMs addition was the more important factor driving the variation of the microorganism community. This study revealed the potential effect of quinones as redox mediators on the bioelectrochemical system for pollutants removal. Graphical abstract: The quinones in wastewater played a key role in enhancing the synergistic removal of azo dye and enriching exoelectrogens. The function of stress tolerance and biofilm formation were strengthened due to presence of external redox mediators. Image 1 Highlights: Redox mediators (RMs) enhanced MFCs' performance better at higher current density. Quinones in wastewater increased external stress tolerance and biofilm formation. Quinones in wastewater accelerated electron transfer and enriched exoelectrogens. Wastewater rich in quinones provided co-substrate and RMs to decolorize RR2. Quinones in wastewater contributed to more adequate degradation of RR2 in MFC.