Surface Modification of a Graphite Fiber Fabric Anode for Enhanced Bioelectrochemical Methane Production

The graphite fiber fabric (GFF), modified using different methods, was studied as an anode for enhanced bioelectrochemical methane production. The electrical conductivity of the GFF was significantly improved by loading the multiwall carbon nanotube (MWCNT) on the GFF surface via electrophoretic deposition (EPD) or the sonication method. The surface-modified GFF anodes were obtained by further processing to form a scaffold layer of exfoliated graphite (EG) and the MWCNT mixture using coal tar pitch or epoxy as the binder. In the batch bioelectrochemical reactor, the lag time for the GFF control anode was about 15.5 days in the methane production during the enrichment of electrochemically active bacteria (EAB). Interestingly, the lag time for the modified anode was increased more by the EPD treatment (20.8–23.3 days) than by the sonication (17.1–18.4 days) and was increased more by the epoxy binder (EB) (18.4–23.3 days) than by the coal tar pitch binder (CB) (17.1–20.8 days). However, the accumulated methane production of all modified GFF anodes increased by 12–70% more than the production of the GFF control anode after the enrichment of EAB. The highest values of the maximum methane production rate (47.4 mL CH4/g COD·d) and the methane yield (322.0 mL CH4/g CODr) were obtained from the anode modified using the CB after the EPD. On the basis of the electrochemical analysis, the nickel loaded by the EPD has a catalytic activity for the bioelectrochemical electron transfer, and the CB has a biocompatiblity higher than that of the EB on the GFF surface. The GFF anode modified with a scaffold layer of EG and MWCNT after the EPD treatment improves bioelectrochemical methane production.