Desalination combined with hexavalent chromium reduction in a microbial desalination cell

• Cr6 + removal and desalination were realized in a microbial desalination cell (MDC).
• The effects of initial pH and Cr6 + concentration were investigated.
• The Cr6 + acted as electrons accepter in MDC system and the reduction was Cr2O3.

The microbial desalination cell (MDC) was a novel technology to desalinate saline water, simultaneously producing electricity and treating wastewater. In our research, an MDC using a synthetic Cr (VI)-containing wastewater as the catholyte was used to desalinate brine in the desalination chamber and simultaneously to reduce Cr (VI) in cathode chamber. Below a pH value of 2.0 with an initial Cr (VI) concentration of 100 mg/L, the hexavalent chromium removal rate was 75.1 ± 3.8% with a current density 760 mA/m2, and the desalination rate was 2.1 mg/h. As the initial concentration of chromium increased from 200 to 1000 mg/L, the current density also increased from 884.8 mA/m2 to 1339.8 mA/m2, with an increase in the salt removal rate from 2.2 mg/h to 3.0 mg/h. The  analyses of scanning electron microscope-energy dispersive spectrometer (SEM-EDS) and X-ray photoelectron spectroscopy (XPS) indicated that the Cr (VI) was reduced to Cr2O3 and deposited on the cathode surface. The deposition of Cr2O3 on the cathode surface would affect the performance of the MDCs. These results suggested that an MDC using Cr (VI) as an electron acceptor could further enlarge the application range of MDCs.

The construction of a microbial desalination cell (MDC).Figure optionsDownload as PowerPoint slide