Enhancing proton conduction by regulating proton carrier position in polyamide layer of forward osmosis membrane in osmotic microbial fuel cell

Abstract

Osmotic microbial fuel cell (OsMFC) encounters the problem of slow transport of proton, which results in a pH imbalance between the anode and cathode, and then a decreased cell performance. Forward osmosis (FO) membrane plays a critical role in proton transport in OsMFC, but the proton transmembrane migration is greatly hindered by the absence of particular proton transfer unit in FO membrane. In this study, high proton conductive carrier sulfo (−SO3H) was imported in the polyamide (PA) layer of FO membrane. The results demonstrated that the position of sulfo on benzene ring in PA polymer chain had a significant effect on proton migration and further the OsMFC property. As sulfo is in the ortho and para of the amino group on benzene ring, the optimal FO-1 membrane was acquired. It indicated that the OsMFC loaded with FO-1 membrane completed 88.31 % increase of water extraction, 50.72 % promotion of maximum power density and 6.02 % enhancement of chemical oxygen demand (COD) removal compared to those of the OsMFC with commercial FO membrane. The molecular dynamics simulation elucidated that the hydrogen bond and electrostatic interaction between atoms both played crucial roles in the proton-transfer process. This method of introducing proton carrier at molecular level aiming to alleviate the rising catholyte pH is economical and convenient for the potential scale-up applications of the OsMFC.