Synthesis and characterization of organic agar-based membranes for microbial fuel cells

The goal of this work was the synthesis and characterization of agar membranes for microbial fuel cells applications. Three sets of membranes were synthesized. For a first set of membranes (2, 4, 6, and 8 wt% agar concentration), both proton conductivity (σ) and O2 permeability (OP) increased as a function of agar concentration, up to 4 wt% agar. Beyond this concentration, the σ levelled-off at 2.43 mS cm−1 and OP increased. A second one set was obtaining by mixing 2, 4, 6, and 8 wt% concentrations of agar with KCl 10 wt%. Both σ and OP increased as a function of increased agar concentration; nevertheless, the presence of KCl slightly affected in a negative way the OP. For the last set, agar concentration was fixed at 2 wt%, while KCl concentration was increased to 2, 4, 6, 8, and 10 wt%. The σ did not significantly increase with salt concentration and the worst values of OP were observed. It was thus confirmed that agar concentration plays a significant role in the increase of σ, but KCl does not improve membrane performance. Moreover, the agar membranes cost is two orders of magnitude lower than Nafion® 117. Therefore, the best membranes were those produced solely with agar. •Low-cost agar and agar-KCl membranes were synthetized for microbial fuel cells.•Performance of some agar membranes in microbial fuel cells has been studied.•The presence of KCl salt affect in a negative way the oxygen permeability.•Good membranes of agar-KCl were obtained from agar 4 wt% with 10 wt% of KCl.•Proton conductivity of agar membranes was in the range 1.81–2.43 mS cm−1