Deterioration in the Cathode Performance during Operation of the Microbial Fuel Cells and the Restoration of the Performance by the Immersion Treatment

Abstract

Microbial fuel cells were operated with synthetic wastewater containing phosphate as a buffer and sodium acetate as a substrate. Linear sweep voltammetry showed the deterioration in the performance of the cathodes after operation (18-31% decrease of current density at 0.1V vs. Ag/AgCl). The immersion of the deteriorated cathodes in Milli-Q water and acidic and basic buffer solution improved the performance. The treatment with the acidic buffer solution restored the performance of the cathode to the extent almost equivalent to that of the cathode before operation (98-107% of current density at 0.1V vs. Ag/AgCl), whereas the treatment with Milli-Q water and the basic buffer solution did not restore the performance to that extent (92% of current density at 0.1V vs. Ag/AgCl). The improved performance by the immersion in Milli-Q water or the acidic buffer solution indicates that the water-soluble components are responsible for the deterioration in the cathode performance. Almost complete recovery of the performance in acidic condition suggests that salts that are highly soluble in acidic condition and poorly soluble in basic condition are responsible for the deterioration. The analysis of the eluted substances in the immersion solution suggests that these salts contained phosphorus, magnesium and calcium in a high concentration.