Effects of draw solutions and membrane conditions on electricity generation and water flux in osmotic microbial fuel cells

This study provided an early effort to investigate the draw solutions as catholytes, FO membrane conditions, and backwash for membrane cleaning in an osmotic microbial fuel cell (OsMFC). The results demonstrated that sodium chloride was a suitable candidate as a catholyte solute with good performance in both electricity generation and water flux, although its pH required buffering via acid addition. Adding a small amount of hydrochloric acid decreased the catholyte pH from 9.0 to 2.5 and increased the current generation by 50%, but did not affect water flux. It was also found that the fouled FO membrane improved electricity generation but lost the function of water flux. The damaged FO membrane resulted in a water flux of 0.39 LMH, much lower than 2–3 LMH with a new FO membrane. Backwash with adding NaCl (0.2–0.5 M) into the anolyte was examined but did not obviously alleviate membrane fouling.

► Sodium chloride is a suitable solute as catholyte in OsMFCs.
► Calcium chloride and glucose impede electricity generation.
► Fouled FO membrane improves electricity but loses the function of water extraction.
► Effective membrane cleaning should minimize the influence on anode microbes.