Metals as electron acceptors in single-chamber microbial fuel cells

Two typical oxidized-status metals (Fe(III) and Cr(VI)) were studied as electron acceptors on cathodes in single chamber microbial fuel cells (SCMFCs) to explore novel sustainable technology for metal treatment. The batch-mode tests indicated that the voltages of SCMFCs steadily increased with Fe(III) concentrations (10, 30, and 50 mg L−1) and Cr(VI) concentrations (1, 3, and 10 mg L−1). The maximum power density was 658 ± 6 mW m−2 at 50 mg L−1 of Fe(III), and 419 ± 4 mW m−2 at 10 mg L−1 Cr(VI). The conversion efficiency of Cr(VI) and Fe(III) were high (>89%), and coulombic efficiency ranged 23-100%. Cr(VI) concentration of 10 mg L−1 started to irreversibly inhibit SCMFCs. The open circuit potentials (OCPs) well reflected the organic substrate removal in anode and metal reduction on cathode. Cathode liner sweep voltammetry (LSV) showed the electrochemical activity increased with metal concentrations, and the cathode of Fe(III) had better LSV performance than Cr(VI). Microbial community analysis of biofilms showed that the DNA band patterns of anode biofilms were similar, while cathode biofilms varied with electron acceptors. This study demonstrated the high power generation of SCMFCs with metals as electron acceptors, and revealed the great potential of expanding MFCs for diverse waste treatment.