Understanding electricity generation in osmotic microbial fuel cells through integrated experimental investigation and mathematical modeling

• Osmotic microbial fuel cells produce more electricity than regular MFCs.
• The improvement is likely resulted from lower membrane resistance.
• The resistance of forward osmosis membrane is also affected by water flux.
• The first mathematical model for osmotic microbial fuel cells has been developed.
• The model confirms the experimental findings about membrane resistance.

Osmotic microbial fuel cells (OsMFCs) are a new type of MFCs with integrating forward osmosis (FO). However, it is not well understood why electricity generation is improved in OsMFCs compared to regular MFCs. Herein, an approach integrating experimental investigation and mathematical model was adopted to address the question. Both an OsMFC and an MFC achieved similar organic removal efficiency, but the OsMFC generated higher current than the MFC with or without water flux, resulting from the lower resistance of FO membrane. Combining NaCl and glucose as a catholyte demonstrated that the catholyte conductivity affected the electricity generation in the OsMFC. A mathematical model of OsMFCs was developed and validated with the experimental data. The model predicated the variation of internal resistance with increasing water flux, and confirmed the importance of membrane resistance. Increasing water flux with higher catholyte conductivity could decrease the membrane resistance.

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