Effect of k3fe (cn)6 on long-term electrochemical power output of four series stack mfcs

Two single microbial fuel MFCs with different roughness (roughened and without roughened) were firstly constructed and the effect of the roughness on optimal power density was studied. It was found that the power density of MFC with roughened electrodes (50 mW•m–2) was two times as high as that of MFC with unroughened electrodes, showing that roughness plays an important role in improving power density. Four series stack MFCs with roughened electrodes were then constructed to further improve power density and long-term performances of the MFCs were studied over 160 days. The effect of K3Fe(CN)6, which added to catholyte, on power output of the MFCs was also investigated. A maximum power density output of 126.5 mW•m–2 was achieved at 62th day with the four series stack MFCs during the long term test. The optimal powers of the MFCs tend to become closer to each other after 160 days, which ranged from 52.0 mW•m–2 to 73.4 mW•m–2, showing a considerably stable power output was maintained during the period of 160 days. The output power densities of each MFC in the four series stack MFCs increased rapidly with increasing K3Fe(CN)6 concentration, and a maximum power density output of 560 mW•m−2 was observed by injecting 15 mL 200 mM K3Fe(CN)6 solution into cathode container. This value is 10.8 times of that without adding K3Fe(CN)6 solution at the same conditions, showing that K3Fe(CN)6 solution has a significant effect on improving the MFC powers. This study provides a foundation for further development of an industrially relevant MFC for water treatment.