Enhanced simultaneous decolorization of azo dye and electricity generation in microbial fuel cell (MFC) with redox mediator modified anode

Although the electrogenesis and decolorization performance can be effectively improved by adding redox mediator (RM) in MFC azo dye decolorization process, RMs are lost in vain when replacing substrates for batch run. To address this issue, RM modified anodes are prepared by electrodepositing riboflavin (RF) and humic acid (HA) on the surface of graphite felt, and air-cathode single-chamber MFCs with different modified anodes are built to decolour Congo red and generate electricity. Compared to the bare anode MFC, MFC with 0.5C RF, 0.5C HA, 1.25C RF and 2.5C HA modified anode exhibited excellent electrocatalysis activity and show 31%, 34%, 44% and 49% decrease in internal resistance along with 20%, 21%, 40% and 66% increase in maximum power density. MFCs with 2.5C HA and 1.25C RF modified anode result in high decolorization efficiency of Congo red to 86% and 75% in 16 h, which are higher than that of the bare controlled group. There are significant RM crystals on the modified anodes, and bacterial colonies on the anode surface after MFC running. The RM crystals on the modified anodes can accelerate electron transfer, which benefit both bioelectricity generation and decolorization.