Insights into enhanced current generation of an osmotic microbial fuel cell under membrane fouling condition

• Fouling blocked water permeation but increased current generation in an OsMFC.
• FO membrane had higher ion permeability and proton flux upon fouling.
• Membrane fouling raised the flux of net positive charges to cathode.
• OsMFC with fouled FO membrane had lower internal resistance than the control.

Osmotic microbial fuel cells (OsMFC), which incorporates forward osmosis (FO) in MFC design, favors an improved electricity generation and effluent quality over conventional MFCs that use proton exchange membranes. However, fouling of the FO membrane during long-term operation is unavoidable, and it is unclear how this would affect the MFC performance. Here, we found that the current generation of an OsMFC increased upon membrane fouling despite of the loss of water flux, and the internal resistance decreased relative to the pristine membrane conditions. A further examination of the pH changes and ion flux by electrochemical test revealed that the diffusion of protons and other ions through the membrane was significantly promoted upon fouling. The underlying mechanisms of the fouling-induced diffusion enhancement were also investigated. The finding of this work broadens our understanding about the fouling properties of FO membrane, and implies that FO membrane could serve as a potential fouling-tolerant separator for MFCs and other bioelectrochemical applications.

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