Degradation of organic contaminants in the CoFe2O4/peroxymonosulfate process: The overlooked role of Co(II)-PMS complex

Abstract

Cobalt ferrite (CoFe2O4) has been widely employed as a catalyst for the activation of peroxymonosulfate (PMS), in which hydroxyl radicals (•OH) and sulfate radicals (SO4•−) are generally recognized as the main reactive species responsible for the degradation of pollutants. In this study, we find that both one-electron transfer and oxygen-atom transfer reactions are involved in the CoFe2O4/PMS process, by using methyl phenyl sulfoxide (MPSO) as a chemical probe. Results from radical quenching and electron paramagnetic resonance (EPR) experiments indicate that the free radicals (i.e., •OH and SO4•−) play only a minor role in the degradation of sulfamethoxazole (SMX). A mechanism involving Co(II)-PMS complex both on the surface of CoFe2O4 and in solution as the dominant reactive species is proposed. Furthermore, the degradation performance of SMX under different conditions were investigated to further cognize the Co(II)-PMS complex-mediated oxidation process. This study broadens our understanding of the role of transition metal-based catalysts in the activation of PMS for the degradation of organic pollutants.

Keywords

• Peroxymonosulfate
• Advanced oxidation processes
• Cobalt ferrite
• Water treatment
• Co(II)-PMS complex complex