Performance and mechanism for efficient dechlorination in 3D-macroporous-bioanode-installed microbial fuel cells

Anode morphology is the main factor influencing the removal of chlorine-containing pollutants through promising microbial fuel cells (MFCs). Large-pore three-dimensional sponge-like anodes (nickel foam [NF], carbon felt [CF], and reticulated vitreous carbon [RVC]), are used as metal-, carbon-, and carbon–metal-based materials. Compared to MFC-NF and MFC-CF, the output voltage (55% and 61%, respectively) and average chlorobenzene (CB) degradation rate (285.4% and 52.8%, respectively) of MFC-RVC are higher. Meanwhile, the coulombic efficiency reaches a maximum (12.4%), while the dechlorination efficiency reaches 95.6%. The outperformance of MFC-RVC is related to its higher resistivity (5.8 × 10−6 Ω m; 1.6-fold that of CF, and close to that of NF) as well as its specific surface area and hydrophilic properties. The amounts of biomass and CB degraders (Actinobacteria) in the RVC biofilm greatly exceeded those of the other two anodes, with living microorganisms maintained at almost 88% after long-term operation, and the cellular activity reaching a maximum (10.80 U g−1 and 105.13 nmol L−1 for dehydrogenase and cytochrome C, respectively). Additionally, the mechanism underlying enhanced CB degradation by carbon–metal RVC anodes is elucidated by comparing Cl- and CO2 production, and suggestions for electrode selection, alongside guidance for CB removal in bioelectrochemical systems, are provided.