Electrochemistry and influence of flowrate to a reverse electro-dialysis stack in microbial reverse electrodialysis cell

Abstract

An MRC is a bio-electrochemical system combining a microbial fuel cell (MFC) with a RED stack to generate electricity from salinity gradient and organic wastewater with simultaneous treatment. Operating an MRC at an optimum flow rate to RED is important because it is closely related with energy production rate and economic feasibility. However, influence of RED flowrates on MRC electrochemistry and power production have not been investigated. For this purpose, four different flowrates of high concentration and low concentration solutions were tested. Maximum power density was highest in 10 mL/min (3.71 W/m2) and optimum current density was highest in 7.5 mL/min (5.36 A/m2). By mere increasing the flowrate to MRC, maximum power and optimum current densities increased by 17.7% and 16.2%. EIS showed that impedances of anode, cathode and full-cell were decreased by 51%, 31% and 19%, respectively. Anode CV showed that peak current density was increased by 25.7%. COD removal and CE were not affected by RED flowrate. Power generation at 7.5 mL/min and 10 mL/min were not so different, but current production was better at 7.5 mL/min. Therefore, considering energy production, the RED flowrate of 7.5 mL/min is a reasonable choice for MRC operation.