Reduced graphene oxide supported CoFe2O4 composites with enhanced peroxymonosulfate activation for the removal of sulfamethoxazole: Collaboration of radical and non-radical pathways

Abstract

In this work, an environmentally friendly reduced graphene oxidized supported cobalt ferrite (CFO/rGO) catalyst was constructed using a hydrothermal technique to heterogeneously activate peroxymonosulfate (PMS) and utilized for the degradation of sulfamethoxazole (SMX) antibiotic in aqueous solution. The results exhibited that the complete degradation of SMX was achieved in 25 min under optimal conditions ([SMX] = 8.0 mg/L, [CFO/rGO-30%] = 0.5 g/L, [PMS] = 5.0 mM, pH = 7.0) in the presence of CFO/rGO-30%/PMS with a rate constant of 0.3076 min˗1, which was roughly 6.08 times higher compared to the CoFe2O4/PMS system (0.0506 min˗1). The enhanced degradation of SMX in the CFO/rGO-30%/PMS system might be attributed to the large surface area of the CFO/rGO-30% (98.11 m2/g) catalyst compared to the pristine CoFe2O4 (24.31 m2/g), which increased the availability of active sites for PMS activation. Furthermore, the influence of pivotal reaction parameters and interfering anions on SMX mineralization was also scrutinized. The formation of free radicals (SO4•−, •OH, and 1O2) was established through quenching experiments and electron paramagnetic resonance analysis. The degradation mechanism of SMX was speculated based on the identification of degradation intermediates and X-ray photoelectron spectroscopy spectral analysis. Mechanistic investigations suggested that the transition of Co2+/Co3+ and Fe3+/Fe2+ pairs on the catalyst surface was responsible for the PMS activation, and the SMX degradation was accomplished through radical and non-radical pathways. Furthermore, CFO/rGO-30% exhibited high stability after four consecutive cycles and maintained catalytic activity. Finally, the developed CFO/rGO-30% catalyst exhibited promising potential for the purification of SMX polluted water.