Selective oxidation of diclofenac sodium with different electronegative moieties via coexisting SO4•- and •OH

The selective oxidation capacity of free radicals in advanced oxidation processes (AOPs) is important for the accurate determination of the degradation pathways of organic contaminants when various active species coexist in the catalytic system. In this study, diclofenac sodium (DCF) was selected as a model contaminant due to its toxicity and structural characteristics (containing organic moieties with varying electronegativity). A 3D hexagonal star shaped cobalt oxide electrode was synthesized and used as the electric anode to simultaneously combine with AOPs based on peroxymonosulfate (EAOPs/PMS) to generate two active species (SO4 center dot(-) and center dot OH) and achieve efficient mineralization of DCF. The selectivity property of the free radicals was investigated by comparing DCF transformation pathways in three systems: EAOPs/PMS (containing both SO4 center dot(-) and center dot OH), EAOPs/PMS + TBA (containing only SO4 center dot(-)), and Fe2+/H2O2 (containing only center dot OH). When present simultaneously, SO4 center dot(-) favored attacking the electron-donating moieties (amino groups and aromatic rings), while center dot OH was more disposed to attack the electron-withdrawing moieties (carboxyl groups and chlorine atoms). This study, for the first time, sheds light on the selective oxidation capacity of coexisting SO4 center dot(-) and center dot OH towards organic moieties with differing electronegativity and provides an in-depth analysis of the degradation pathways of an organic contaminant. (C) 2021 Elsevier B.V. All rights reserved.

Automated summary

This study investigates the selective oxidation capacity of coexisting SO4 center dot(-) and center dot OH towards organic moieties with differing electronegativity, shedding light on the degradation pathways of an organic contaminant.