RESUMO
The short-arm air-cathode microbial fuel cell (ACMFC) was constructed using a cramp to fix the proton exchange membrane (PEM) and carbon paper with 0.5 mg/cm2 onto the short-arm side of the anode chamber. Exoelectrogens on the surface of graphite rod were enriched by a sludge microbial fuel cell from the anaerobic digestion sludge. And the cyclic voltammetry result showed these microbes had electrochemical activities. Using the graphite rod covered by exoelectrogens as the anode and sodium acetate as the substrate, the short-arm ACMFC showed a maximal power density (Pm) of 738 mW/m2, internal resistance (Ri) of 280 omega and open circuit voltage (OCV) of 741 mV. Continuous sparging the anode chamber with nitrogen or removal of the proton exchange membrane enhance the Pm of the cell to 745 mW/m2 and 759 mW/m2 respectively. When both of the two measures were used together, the Pm reached up to 922 mW/m2. Under these three conditions the Ri of the cell was kept around 280 omega. When the substrate concentration was 12.62-100.96 mg/L and external resistance was 510 omega, the maximal voltage of the cell and the substrate concentration showed an obvious linear relation (R2 = 0.99). But when the concentration was above 100.96 mg/L, the maximal voltage stably kept around 302mV(the external resistance was 510 omega). However, the Coulombic efficiency of the short-arm ACMFC gradually increased with the increase of the substrate concentration, from 31.83% to 45.03%.
