Enhancement of Activity of Activated Carbon Fiber for Electro-Fenton Process by Loading it with SiO₂ having Tunable Hydrophobic/Hydrophilic Moieties

Electro-Fenton (EF) process is promising for achieving satisfactory oxidation of organic contaminants. However, the sluggish kinetics of in situ production of H2O2 and slow rate of Fe2+ regeneration remain its limitations. In this work, SiO2 with tunable methyl and hydroxyl moieties on the surface (M x OHSiO2; x denotes the mass ratio of diethoxydimethylsilane to tetraethyl orthosilicate) was successfully loaded onto activated carbon fiber (ACF) to construct an ACF-supported cathode (M x OHSiO2/ACF) for the degradation of bisphenol A (BPA). The M x OHSiO2/ACF exhibited substantially higher activity than bare ACF in the EF process. The removal of BPA proceeded most rapidly with M0.75OHSiO(2)/ACF with an initial pH of 3.0, an electrolyzing voltage of 20 V, and an Fe2+ dosage of 0.5 mM. The mineralization efficiency was 79.3% after 360 min, with the complete disappearance of BPA recorded at 60 min during the EF process. In addition, the M0.75OHSiO(2)/ACF catalytic electrode remained stable for five successive cycling tests. Because of the synergistic effect of the hydrophobic methyl moiety and electron-rich hydroxyl moiety on SiO2, the H2O2 electro-generation and Fe2+ regeneration at M0.75OHSiO(2)/ACF were simultaneously improved. This work provides an effective strategy for the application of EF technology in future.