Facilitating proton transport by endowing forward osmosis membrane with proton conductive sites in osmotic microbial fuel cell

A major challenge of the osmotic microbial fuel cell (OsMFC) application is the sluggish proton transport from anode to cathode. As a result, an extra overpotential is caused by the remarkable catholyte alkalinization and anolyte acidification. Thus, the efficiency of water extraction and biodegradation of organic pollutants are adversely affected simultaneously. To address this issue, proton conductive sites were introduced into the for-ward osmosis (FO) membrane by importing sulfonic acid radical groups. The results demonstrated that the proton transport flux improved after FO membrane modification. The OsMFC system with an optimal FO membrane achieved a 58.86 % reduction in artificial seawater salinity, enhanced the volume of water extraction by 61.90 %, increased the chemical oxygen demand removal efficiency by 6.39 %, and improved the current density by 16.56 %. In particular, the maximum power density of the optimized OsMFC (7.08 +/- 0.42 W.m(- 3)) was enhanced by 108.85 % and 60.18 % compared with those with Nafion and pristine FO membrane, respectively. Meanwhile, the mechanism of proton transport in the OsMFC system has been elucidated. The proton migration was reinforced under the synergistic effect of improved water flux and electromigration derived from internal electric field. This method to mitigate the catholyte pH through self-buffering in situ is green and economical. This will further open a novel avenue for OsMFC application in large-scale actual wastewater treatment.

Automated summary

A major challenge of the osmotic microbial fuel cell (OsMFC) application is the slow transport of protons from anode to cathode. To solve this problem, proton conductive sites were introduced into the forward osmosis (FO) membrane, improving proton transport flux. The optimized OsMFC system showed significant improvements in reducing salinity, increasing water extraction volume, enhancing chemical oxygen demand removal efficiency, and improving current density.