A microbial fuel cell capable of converting gaseous toluene to electricity

• A new anode allowing direct supply of toluene vapor to the biofilm was constructed.
• The anode serves as a support for the biofilm and a separator between the gas and water phase.
• This design offers the advantage of enhanced toluene supply.
• Enhanced toluene supply leads to higher active biomass production in the biofilm.
• A maximum power density of 6.2 mW m−2 and toluene removal efficiency of 91% were obtained.

Toluene is a typical volatile organic compound that is widely used for the production of other chemicals and as organic industrial solvents for paints, inks, adhesives and glues. In this work, a new anode design allowing direct delivery of the gaseous substrate to the biofilm was developed by spraying an additional hydrophobic gas layer and PTFE layers onto the gas side of the anode. The results show that the MFC with this design exhibited an approximately eight-fold increase in the maximum power density (from 0.72 ± 0.02 to 6.19 ± 0.45 mW m−2) and a two-fold increase in the toluene removal efficiency (from 43.1 ± 2.7 to 91.2 ± 2.4%) compared to the MFC equipped with a sparger for toluene delivery. These increases can be mainly attributed to the higher active biomass production resulting from the enhanced toluene supply from gas phase to the biofilm attached on the anode surface. The MFC also showed a maximum toluene elimination capacity of 274.5 ± 14.4 g m−3 h−1, which is higher than the values usually reported for biofiltration systems and comparable with those with biotrickling filters. These results demonstrated that the MFC offers a useful alternative for the environmentally friendly removal of gaseous toluene in combination with electricity generation.