Performance of graphite felt as anodes in the electro-Fenton oxidation systems: Changes in catalysis, conductivity and adsorption properties

Carbon-based three-dimensional fiber materials are often used as cathodes in electro-Fenton oxidation systems, and have rarely been used as anodes. In this work, graphite felt (GF) was used as anode, and its performance was investigated. The removal rate of methylene blue (MB) in the GF system was 27.17% higher than that of the conventional two-dimensional graphite system, which proved that GF can be used as a suitable anode material. After 175 reused, the methylene blue removal rate and current of the GF system decreased by 25.09% and 76.92%, while the adsorption performance increased by 298.65%. The maintenance of MB removal efficiency in the repeated use of GF anode was related to the improvement of adsorption performance rather than catalytic performance. Moreover, the characterization results showed that changes in surface structure, hydrophilicity, and functional groups affected the resistance, adsorption, and catalytic properties of GF. The change in adsorption properties of carbon fiber as anode was universal and mainly affected by pH and voltage. Finally, the quenching experiments and EPR tests revealed that MB was mainly removed by direct oxidation on the surface of the GF anode and hydroxyl radicals generated by Fenton reaction.