Performance evaluation of novel ml-scale microbial fuel cells using different polymeric hollow-fiber membranes

Abstract

A novel-designed milliliter-scale MFC was fabricated using three different polymeric hollow fiber membranes of Polyethersulfone (PES), Polyacrilonitryl (PAN), and Polyvinyldenfluoride (PVDF). PES, with a maximum power density of 629 mW/m2, a current density of 1333 mA/m2, and a coulombic efficiency (CE) of 4.22 %, achieved the best performance among the others. After that, the PAN membrane gained power and current densities of 450 mW/m2 and 847 mA/m2, and the PVDF membrane obtained the lowest power and current density of 63 mW/m2 and 187 mA/m2. For all the MFCs, the ohmic resistance incorporates only 2.5 to 5 % of internal resistance due to the small thickness of hollow fibers and the short distance between the electrodes. In the case of the PES membrane, the presence of the sulfonic group resulted in superior proton conductivity (128.10 ± 0.37 mS/cm) and reduced ohmic resistance (24.86 ± 0.07 Ω) compared to the others. Moreover, the charge transfer impedances of both electrodes for PES were nearly half of the values for PAN and about one-fifth of the values for PVDF. The increased electrical double layer capacitance nearby the electrodes of PES reveals more convenient growth of anodic exo-electrogenic bacteria and better accomplishment of cathodic reaction for this membrane. The COD removal efficiencies of 11.48 %, 10.55 %, and 6.48 % have been attained for PES, PAN, and PVDF, respectively.