Enhancing bioelectrocatalytic oxidation of gaseous chlorobenzene by introducing transmembrane Ru4+/Ru3+-mediated reversible intracellular electron transfer

Microbial electrolysis cell (MEC) is a cost-effective process to eliminate chlorinated volatile organic compounds. Poor mass transfer and sluggish intracellular electron transfer remain obstacles. To overcome these, a Ru-mesoporous TiO2/macroporous carbon (Ru-MeT/MaC) bio-anode was tailored here. The hierarchically meso-macroporous structure separated biofilm formation and chlorobenzene adsorption, improving chlorobenzene mass transfer. Further, modifying Ru created a reversible intracellular electron transfer pathway by introducing transmembrane Ru4+/Ru3+ redox couple within bacteria. Such a unique transmembrane introduction induced a compelling bacteria-electricity synergism accompanied by the acclimation of dual-functional genera (degrader & exoelectrogen), promoting the decomposition of aromatic compounds toward organic acids. Those features enabled the resulting MEC to exhibit a super-prominent chlorobenzene elimination capacity (136.7 g m−3 h−1) with a short empty bed residence time (60 s), superior to those of state-of-the-art bioelectrocatalytic processes reported. Leveraging the reversible electron transfer, the Ru-MeT/MaC bio-anode was operated in the charging-discharging mode to further enhance chlorobenzene removal. The concept of introducing bioavailable conductive redox couple into bacteria via reasonably designing the functional structure of the bio-anode is expected to enhance the bioelectrocatalytic oxidation of hydrophobic Cl-VOCs and therefore alleviate air pollution.