Effect of Humic Acid on the Electrochemical Performance of Microbial Fuel Cells (MFCs)

Microbial fuel cell (MFC) are bioelectrochemical system using exoelectrogenic microorganisms to produce electricity, electrons are transferred through a biofilm growth on the anode surface (Sund et al., 2007), the humic acid  had optimal biofilm formation, reducing the lag-time and improve the performance of the MFCs. The aim of this work was to evaluate the effect of humic acid addition on the performance of MFC. The biofilm growth with and without humic acid was evaluated by cyclic voltammetry (CV), chronopotentiometry at open circuit potential and scanning electron microscopy (SEM), the performance of MFC was evaluated by polarization curves and values of voltage, current density and power density achieved with data acquisition system. Triplicate measurements made in a MFC with two chambers of 375 mL, carbon cloth electrodes and proton exchange membrane. From the 5th day, the MFC without humic acid showed a voltage  of 0.1 V in response to biofilm wrowth and a steady voltage of 0.34 V after 40 days, cyclic voltammetry showed reduction signs in -0.284 to 0.259 V Vs SHE and oxidation signs in  -0.643 to 0.060 V Vs SHE, showing electroactivity biofilms. Optimal biofilm formed reduce the internal resistance from 50 to 4.5 kµÙ, also the anode potential changed from -0.251 to -0.512 V Vs SHE for better performance of MFC. The MFC showed a maximum power density of 1.78E-03 W/m², current density of 3.6 mA/m² and power density of 1.4 W/m². The optimal biofilm formation is important for the performance of MFCs (Martin et al., 2013) and humic acid had effect on the electrode surface supported the growth of biofilm due to functional groups with redox properties (Wandruszka Palmer, 2010).

References

Sund et al., 2007. Appl Microbiol Biotechnol. 76, 561-568.

Palmer y Wandruszka, 2010. Environmental Science & Pollution Research. 17, 1362-1370.

Martin et al., 2013. J. Appl. Electrochem. DOI 10.1007/510800-013-0537-2.