Effect of Set Potential on Hexavalent Chromium Reduction and Electricity Generation from Biocathode Microbial Fuel Cells

Abstract

Setting a biocathode potential at −300 mV improved the subsequent performance of an MFC for Cr(VI) reduction compared to a control (no set potential). With this set potential, the startup time was reduced to 19 days, the reduction of Cr(VI) was improved to 19.7 mg/L d, and the maximum power density was increased to 6.4 W/m³ compared to the control (26 days, 14.0 mg/L d and 4.1 W/m³). Set potentials of −150 mV and −300 mV also improved system performance and led to similarly higher utilization of metabolic energy gained (PMEG) than set potentials of +200 mV and −450 mV. We observed putative pili at −150 and −300 mV potentials, and aggregated precipitates on bacterial surfaces in both poised and nonpoised controls. These tests show that there are optimal potentials that can be set for developing a Cr(VI) biocathode.