Simultaneous decolorization and bioelectricity generation in a dual chamber microbial fuel cell using electropolymerized-enzymatic cathode

Effect of cathodic enzymatic decolorization of reactive blue 221 (RB221) on the performance of a dual-chamber microbial fuel cell (MFC) was investigated. Immobilized laccase on the surface of a modified graphite electrode was used in the cathode compartment in order to decolorize the azo dye and enhance the oxygen reduction reaction. First, methylene blue which is an electroactive polymer was electropolymerized on the surface of a graphite bar to prepare the modified electrode. Utilization of the modified electrode with no enzyme in the MFC increased the power density up to 57% due to the reduction of internal resistance from 1000 to 750 Ω. Using the electropolymerized-enzymatic cathode resulted in 65% improvement of the power density and a decolorization efficiency of 74%. Laccase could act as a biocatalyst for oxygen reduction reaction along with catalyzing RB221 decolorization. Treatment of RB221 with immobilized laccase reduced its toxicity up to 5.2%. Degradation products of RB221 were identified using GC-MS, and the decomposition pathway was proposed. A discussion was also provided as to the mechanism of dye decolorization on the enhancement of the MFC performance.