Cu-doped Fe2O3 nanoparticles/etched graphite felt as bifunctional cathode for efficient degradation of sulfamethoxazole in the heterogeneous electro-Fenton process

Bifunctional electrodes have attracted significant research interest in the field of heterogeneous electro-Fenton (hetero-EF) process for efficient treatment of antibiotic-containing wastewater. In this study, etched graphite felt (EGF) was used as the matrix material because of its excellent electrochemical properties, rich pore structure, and large specific surface area. The transition metals Cu and Fe were in situ grown on the EGF electrode surface without polymer binder by a one-step hydrothermal method. The obtained electrode consisting of Cu-doped Fe2O3 nanoparticles/EGF (Cu-Fe2O3/EGF) was used in the hetero-EF process for in situ electro-generation and activation of hydrogen peroxide (H2O2) for efficient degradation of sulfamethoxazole (SMX). The Cu-Fe2O3/EGF electrode demonstrated a wide pH application range of 3.0–9.0. According to electron spin resonance and free-radical quenching experiments, hydroxyl radical and superoxide anion were the dominant species in the hetero-EF process, while the hydroxyl radical played a major role in the degradation of SMX. In consecutive runs, the electrode exhibited low metal ion leaching and excellent stability. Furthermore, the possible mechanism for the production and activation of H2O2 as well as possible SMX degradation pathways were proposed. The toxicity of SMX samples during degradation exhibited a decreasing trend according to the results of toxicological simulation and Escherichia coli growth test. This study provides a new strategy for the construction of an efficient and stable bifunctional cathode for the advanced treatment of antibiotic-containing wastewater.