The kinetics of the simultaneous decolorization and desulfurization of azo dye wastewater in a microbial fuel cell

This study investigated the effects of a microbial fuel cell (MFC) on the simultaneous decolorization and desulfurization of azo dye wastewater. It showed that the conversion of sulfur at the anode had a significant effect on electricity generation and decolorization. After adding 800 mg/L sulfate, the active brilliant red X-3B (ABRX3) concentration in the effluent decreased from 208 to 67 mg/L and the maximum power density output increased by 20%. To quantify the reaction processes, a kinetics model based on a one-dimensional biofilm was developed. It showed that sulfur ions had a direct decolorization effect on ABRX3. The reaction of sulfide and ABRX3 at the anode was a first-order reaction. The decolorization and desulfurization mechanisms were validated by analyzing the microbial community at the anode. Sulfate-reducing bacteria (SRB) on the anode fermented the lactate to acetate. Then, electrogenic Geobacter used the acetate produced as a carbon source for electricity generation. The sulfide produced by SRB acted as additional fuel and a reductant and promoted the current generation and the reduction of azo bonds in the azo dye. Hence, the MFC showed potential for treating industrial textile wastewater.