Study on the performance of metal-loaded carbon black cathode for electro-Fenton degradation of SMX

Abstract

Sulfamethoxazole (SMX) is a kind of widely used antibacterial antibiotic, which can be detected in different water bodies, and poses great harm to aquatic organisms and human health. In this study, different transition metal-loaded carbon oxide blacks (M−OBC, M = Mn, Fe, Cu, or Co) were prepared as cathodic catalysts for the degradation of SMX in the electro-Fenton system. Under optimal conditions of 0.3 mM Fe²⁺ concentration, −0.5 V, and pH 3, the Mn-OBC catalyst exhibited the most remarkable degradation efficiency, achieving a complete removal of SMX from the water within a mere 10 min. The relationship between catalyst structure and performance was further investigated through morphological and structural characterization. It was revealed that the existence of Mn³⁺/ Mn⁴⁺ significantly accelerates the rapid conversion of Fe²⁺ and H₂O₂. Electrochemical performance tests were used to investigate the redox capacity of the catalysts, while radical quenching experiments and electron paramagnetic resonance (EPR) spectroscopy were employed to qualitatively detect ·OH radicals as active oxygen species. Three degradation pathways were ascertained by LC-MS. Simultaneously, toxicity analysis of degradation intermediates showed that most of the intermediates were less toxic than SMX. Therefore, this study provides a reference value for solving low-concentration persistent organic pollutants in water.