Production Of Acetate From Inorganic Carbon Reduction And Its Influential Cr??? Stress In Photo-assisted WO₃/MoO₃/g-C₃N₄ Cathode Of MES

Microbial electrosynthesis system?MES?shows promising due to the simultaneous extraction of chemical energy from organic wastes in the bioanode with production of hydrogen or valuable chemical products at the biocathode.In this study,production of acetate from inorganic carbon reduction was achieved in the photo-assisted WO₃/MoO₃/g-C₃N₄cathode of MES incorporating with Serratia marcescens Q1.In addition and under the stressful Cr???conditions,simultaneous enhanced Cr???removal and acetate production was successfully achieved in this MES.Main results include:?1?The WO₃/MoO₃/g-C₃N₄ loaded graphite felt cathode exhibited a stable photocurrent of0.62 mA,4.8 times as that of the controls with g-C₃N₄ only.Production of acetate?3.12±0.20mM/d?with a coulometric efficiency?73±4%?and a circuit current?2.5±0.3 A/m²?was achieved in this MES.Photogenerated electrons in the conduction band of WO₃/MoO₃/g-C₃N₄were used for evolution of hydrogen,which were metabolized by S.marcescens for production of acetate from HCO₃^-reduction.Photogenerated holes in the valence band of WO₃/MoO₃/g-C₃N₄ captured more electrons from the anode and thus favored for higher circuit current.These processes not only improved the separation efficiency between photogenerated electrons and holes,but also created an additional driving force for the electrons to transfer from anode to cathode,both of which favored for subsequent production of acetate from inorganic carbon reduction.?2?Simultaneous efficient Cr???removal and acetate production is demonstrated in a photo-assisted WO₃/MoO₃/g-C₃N₄ graphite felt cathode of MES supporting S.marcescens Q1electrotroph,achieving 6.1±0.3 mg/L/h?acetate production?and 4.5±0.1 mg/L/h?Cr???removal?at a circuital current of 2.8±0.1 A/m².These values were 2.4-fold?acetate?,1.7-time?Cr???removal?and 1.6-fold?circuital current?of those in the controls in the absence of WO₃/MoO₃/g-C₃N₄,and 1.6-fold?acetate?and 1.8-time?circuital current?of those in the absence of both Cr???and WO₃/MoO₃/g-C₃N₄.Electrons on the conduction bands of WO₃/MoO₃/g-C₃N₄ favored direct or indirect?via S.marcescens?reductions of both Cr???and H⁺with the latter produced H₂ metabolized by S.marcescens with HCO₃^-to acetate,while the semiconductors holes were filled by the electrons travelling from the anodic chamber,achieving higher circuital currents favorable for not only direct or indirect?via S.marcescens?reductions of Cr???and H⁺but also S.marcescens direct or indirect?via H₂?utilization for acetate production.In summary,this study provided an alternative and feasible approach not only for efficient production of acetate from inorganic carbon reduction,but also for simultaneous efficient production of acetate and removal of heavy metals from heavy metal-contaminated and organic-barren waters and wastewaters.