Effects of current generation and electrolyte pH on reverse salt flux across thin film composite membrane in osmotic microbial fuel cells. (15th November 2016)

• Record Type: Journal Article
• Authors: Qin, Mohan; Abu-Reesh, Ibrahim M.; He, Zhen
• Is Part Of: Water research. Volume 105(2016)
• Page Start: 583
• Page End: 590
• Publication Date: 2016-11-15
• Subjects: Osmotic microbial fuel cells -- Reverse salt flux -- Electricity generation -- Catholyte pH -- Ion transport; Water -- Pollution -- Research -- Periodicals; 363.7394
• DOI: 10.1016/j.watres.2016.09.028
• Languages: English
• ISSNs: 0043-1354

Abstract

Abstract: Osmotic microbial fuel cells (OsMFCs) take advantages of synergy between forward osmosis (FO) and microbial fuel cells (MFCs) to accomplish wastewater treatment, current generation, and high-quality water extraction. As an FO based technology, OsMFCs also encounter reverse salt flux (RSF) that is the backward transport of salt ions across the FO membrane into the treated wastewater. This RSF can reduce water flux, contaminate the treated wastewater, and increase the operational expense, and thus must be properly addressed before any possible applications. In this study, we aimed to understand the effects of current generation and electrolyte pH on RSF in an OsMFC. It was found that electricity generation could greatly inhibit RSF, which decreased from 16.3 ± 2.8 to 3.9 ± 0.7 gMH when the total Coulomb production increased from 0 to 311 C. The OsMFC exhibited 45.9 ± 28.4% lower RSF at the catholyte pH of 3 than that at pH 11 when 40 Ω external resistance was connected. The amount of sodium ions transported across the FO membrane was 18.3–40.7% more than that of chloride ions. Ion transport was accomplished via diffusion and electrically-driven migration, and the theoretical analysis showed that the inhibited electrically-driven migration should be responsible for the reduced RSF. These findings are potentially important to control and reduce RSF in OsMFCs or other osmotic-driven processes. Graphical abstract: Highlights: Bioelectricity generation can greatly reduce reverse salt flux in an OsMFC. A lower catholyte pH results in lower reverse salt flux. Ion transport is accomplished via diffusion and electrically-driven migration. The reduced reverse salt flux is due to decreased electrically-driven migration.