Power density of microbial electrochemical system responds to mass transfer characters of non–ion–selective microbial separator

The microbial separator (MS) was promising alternative of ion exchange membrane for biocathode microbial electrochemical system (MES). Four microbial separators developed from porous matrixes were equipped in biocathode MESs. The power generation of MESs responded to cross-separator transfer characters of ions, dissolved oxygen (DO) and chemical oxygen demand (COD). The MES with carbon felt (CF) obtained 31% higher maximum power density at 70 ± 3 mW m⁻² and 51% higher current density at 271 ± 21 mA m⁻² than those of cation exchange membrane (CEM) separator. All MSs showed higher ionic conductivity than CEM. However, the power variation was mainly due to cathodic equilibrium potential changes rather than internal resistance. The power density demonstrated negative correlation with mass transfer coefficients of DO and COD. The cross-separator transfer of COD caused cathode variation and was identified as the primary parameter for further optimization of MES with microbial separators.