From an air-cathode microbial fuel cell (MFC) to an air-cathode microbial desalination cell (MDC)

An air-cathode MDC was built by modifying a MFC to include three compartments, with the middle desalination compartment separated from the anode by an anion exchange membrane, and the air-cathode by a cation exchange membrane. Bacteria oxidize organic matter on the anode and release electrons to the anode and protons into the water producing electrical current. In order to balance charges, sodium chloride ions are removed from the middle compartment. Thus water is desalinated by the electricity generated by the bacteria. Parameters that were investigated include the concentrations of the initial substrate and the salt water. To improve the extent of desalination, we examined the performance of two custom-made membranes having higher ion exchange capacities than the commercially available membranes. Desalination was improved by 26%. Using this air-cathode MDC we achieved up to 63% desalination and produced power densities as high as 480 mW/m². Coulombic efficiencies reached 60%.