Environmentally available biowastes as substrate in microbial fuel cell for efficient chromium reduction

Dual chambered microbial fuel cells with Potassium dichromate (22 g/L, MFC-1) and tannery effluent waste water containing 26 mg/L (MFC-2), 5 mg/L (MFC-3) of Cr(VI) as catholyte, sweet lime waste inoculated by cowdung as anolyte and graphite electrodes were used to reduce toxic Cr(VI) to Cr(III) with simultaneous power generation. Cr (VI) in the cathode chamber reduced to Cr₂O₃ within 24 h. Complete reduction of Cr(VI) from tannery effluents by microbial fuel cell is noticed within 10 days. The 16 s rRNA sequencing studies demonstrated presence of Geobacter Metallireducens in mixed culture bacteria in anaerobic anode. The power density of the device is 396.7 mW/m²on day1which is 7.2 times higher than literature data of 55.5 mW/m². The processes involved on the biofilm/electrolyte interface and graphite/electrolyte interface is studied by Electrochemical Impedance Spectroscopy. Electrochemical studies demonstrated the active growth of biofilm on anode which reduces charge transfer resistance from day 1 to day 25. The concentration of Cr(VI) reduced in the present studies are approximately 1000 times higher than those reported in the literature.