Activated carbon fiber as an efficient co-catalyst toward accelerating Fe2+/Fe3+ cycling for improved removal of antibiotic cefaclor via electro-Fenton process using a gas diffusion electrode

Abstract

The electro-Fenton (EF) based on gas-diffusion electrodes (GDEs) reveals promising application prospective towards recalcitrant organics degradation because such GDEs often yields superior H₂O₂ generation efficiency and selectivity. However, the low efficiency of Fe²⁺/Fe³⁺ cycle with GDEs is always considered to be the limiting step for the EF process. In this study, activated carbon fiber (ACF) was firstly employed as co-catalyst to facilitate the performance of antibiotic cefaclor (CEC) decomposition in EF process. It was found that the addition of ACF co-catalyst achieved a rapid Fe²⁺/Fe³⁺ cycling, which significantly enhanced Fenton's reaction and hydroxyl radicals (^•OH) generation. X-ray photoelectron spectroscopy (XPS) results indicated that the functional groups on ACF surface are related to the conversion of Fe³⁺ into Fe²⁺. Moreover, DMSO probing experiment confirmed the enhanced ^•OH production in EF + ACF system compared to conventional EF system. When inactive BDD and Ti₄O₇/Ti anodes were paired to EF system, the addition of ACF could significantly improve mineralization degree. However, a large amount of toxic byproducts, including chlorate (ClO₃^-) and perchlorate (ClO₄^-), were generated in these EF processes, especially for BDD anode, due to their robust oxidation capacity. Higher mineralization efficiency and less toxic ClO₄^- generation were obtained in the EF + ACF process with Ti₄O₇/Ti anode. This presents a novel alternative for efficient chloride-containing organic removal during wastewater remediation.

Keywords: Activated carbon fiber; Cefaclor degradation; Electro-Fenton; Fe(3+)/Fe(2+) cycling; Gas diffusion electrode.