LAUSR

Abstract For the first time, an osmotic microbial fuel cell (OsMFC) was employed for simultaneous hexavalent chromium [Cr(VI)] removal, organic contaminant removal, energy production, and water reclamation. In this system, draw solutions were prepared from 0 to 1 M NaCl mixed with 12 mg/L Cr(VI). Cr(VI) reduction and power generation at different pH were studied. In terms of power generation, the results revealed that the highest power density of 6.6 mW/m2 (170 mW/m3) was obtained using the 1 M NaCl catholyte at pH 7. However, the greater Cr(VI) reduction of 44.5% and 97.6% was achieved using the 0.2 M NaCl/Cr(VI) based catholyte at pH 7 and 2, respectively. This can be attributed to the competition between Cr(VI) and H2O reduction at higher concentrations of NaCl, as supported by the observation of H2 on the cathode. Moreover, through cyclic voltammetry, the signals of oxidation-reduction peaks were observed in the case of 0.2 M NaCl/Cr(VI), while, reduction peaks mostly disappeared in other cases. Additionally, more precipitate [Cr(OH)3(s)] was observed to be deposited on the surface of the cathode electrode when 0.2 M NaCl was used as the draw solution. Hence, 0.2 M NaCl was the optimal catholyte concentration for Cr(VI) reduction. The Cr(VI) removal efficiency was 97.6% for an initial pH of 2 with the 0.2 M NaCl catholyte because low pH is thermodynamically favored for Cr(VI) reduction.