Influence of external resistance and anodic pH on power density in microbial fuel cell operated with B. Subtilis BSC-2 strain

Abstract

Microbial fuel cells (MFCs) are bioelectrochemical devices able to convert chemical energy into electricity. The selection of anodic pH and external resistances play a significant role in the overall performance of the device. This research presents the effect of operational conditions of the MFC using B. Subtilis in anode. The effect of pH and external resistance were determined by 32 full factorial design. Data were analyzed statistically by ANOVA and p ≤ 0.05 was considered statistically significant. The surface response analysis evidenced interaction and quadratic effect of the pH and external resistance on the power density generation. With a second-order polynomial model the optimum conditions of the system were determined. It maximized the power at pH of 8.6 and an external resistance of 220 Ω, delivering power density of 405 mW/m2. The chemical oxygen demand (COD) removal efficiency and coulombic efficiency (CE) were 82% and 15%, respectively. The maximum specific growth (μ) and substrate uptake (k1) rate for electrochemically active bacteria (EAB) at optimum conditions were 0.19/h and 0.019/h respectively. These experimental results show the importance of the simultaneous effect of pH and external resistance, which is even more influential then if they were studied separately.