Impact of cleaning procedures on restoring cathode performance for microbial fuel cells treating domestic wastewater.

Degradation of cathode performance over time is one of the major drawbacks in applications of microbial fuel cells (MFCs) for wastewater treatment. Over a two month period the resistance of air cathodes (RCt) with a polyvinylidene fluoride (PVDF) diffusion layer increased of 111% from 70 ± 10 mΩ m2 to 148 ± 32 mΩ m2. Soaking the cathodes in hydrochloric acid (100 mM HCl) restored cathode performance to RCt = 74 ± 17 mΩ m2. Steam, ethanol, or sodium hydroxide treatment produced only a small change in performance, and slightly increased RCt. With a polytetrafluoroethylene (PTFE) diffusion layer on the cathodes, RCt increased from 54 ± 14 mΩ m2 to 342 ± 142 mΩ m2 after two months of operation. The acid concentration was critical for effectiveness in cleaning, as HCl (100 mM) decreased RCt to 28 ± 8 mΩ m2. A lower concentration of HCl (<1 mM) showed no improvement, and vinegar (5% acetic acid) produced 48 ± 4 mΩ m2.