Reduction of chromium(VI) with energy recovery using microbial fuel cell technology

A simple microbial fuel cell (MFC) method for the reduction of hexavalent chromium (Cr6+) at an abiotic cathode by using an exoelectrogenic biofilm on the biotic anode, has been established. Two different Cr6+-containing effluents were synthetically prepared in the laboratory (4 and 8 mg l−1). The chromium effluents were used as catholyte and anaerobic microorganisms as anodic biocatalyst. 4 mg l−1 of Cr6+ was reduced 95% while, 8 mg l−1 reduced 86% during 456 h reaction in the MFC systems investigated. The MFC system with 4 mg l−1 of chromium exhibited a maximum power density of 89 ± 3 mW m−2 and a maximum voltage of 931 mV. A power density of 69.5 ± 2.1 mW m−2 and voltage of 700 mV was obtained by 8 mg l−1 chromium containing MFC cell. This work verifies the possibility of current production and simultaneous cathodic Cr6+ reduction. The novelty and significance of this system is that it uses an uncomplicated and economical salt bridge which replaces costly membranes like Nafion and an abiotic cathode.