Electricity production from human urine in ceramic microbial fuel cells with alternative non-fluorinated polymer binders for cathode construction

Abstract

• Urine-fed ceramic MFCs for bioenergy production and urine treatment. • Alternative non-fluorinated polymers as binders in ceramic MFCs. • Chitosan-based cathodes allow MFCs to reach a maximum power of 510 μW. • 60.3% of the power output by PTFE obtained with 8 times less amount of chitosan. Polytetrafluoroethylene (PTFE) is one of the most common binders employed to prepare cathode electrodes in microbial fuel cells (MFCs) and yet this fluorinated polymer is neither sustainable nor environmentally friendly. In this work, four non-fluorinated polymers have been tested as alternative binders to PTFE in ceramic MFCs. The performance of ceramic MFCs using carbon-based cathodes containing silicone, polyvinyl chloride, Ludox® (colloidal silica) and chitosan, was compared with the performance of MFCs using cathodes prepared with PTFE. The results obtained confirm that polyvinylchloride, Ludox® and chitosan are suitable materials to be used as binders for MFC cathode construction. Amongst them, Ludox® and chitosan are the most sustainable options due to their chemical structure. Cathodes prepared with 2.5 wt% of chitosan – 8 times less than the amount needed for PTFE – in MFCs reached a maximum power of 510 μW, which represents 60.3% out of the power output from MFCs with PTFE-based cathodes. In terms of urine treatment capacity, the chemical oxygen demand (COD) removal was equivalent across the systems tested, due to the short retention time. However, chitosan-based MFCs reached COD removal rates of up to 26%, which was slightly higher than the COD removal rate measured for MFCs using PTFE-cathodes (23.5%).