Degradation of 2, 4‐dichlorophenol by peroxymonosulfate catalyzed by ZnO/ZnMn2O4

Abstract In this study, a highly efficient peroxymonosulfate (PMS) activator, ZnO/ZnMn 2 O 4 , was synthesized using a simple one‐step hydrothermal method. The resulting bimetallic oxide catalyst demonstrated a homogenous and high‐purity composition, showcasing synergistic catalytic activity in activating PMS for degrading 2, 4‐dichlorophenol (2, 4‐DCP) in aqueous solution. This catalytic performance surpassed that of individual ZnO, Mn 2 O 3 , and ZnMn 2 O 4 metal materials. Under the optimized conditions, the removal efficiency of 2, 4‐DCP reached approximately 86% within 60 min, and the catalytic ability remained almost constant even after four cycles of recycling. The developed degradation system proved effective in degrading other azo‐dye pollutants. Certain inorganic anions such as HPO 4 − , HCO 3 − , and NO 3 − significantly inhibited the degradation of 2, 4‐DCP, while Cl − and SO 4 2− did not exhibit such interference. Results from electrochemical experiments indicated that the electron transfer ability of ZnO/ZnMn 2 O 4 surpassed that of individual metals, and electron transfer occurred between ZnO/ZnMn 2 O 4 and the oxidant. The primary active radicals responsible for degrading 2, 4‐DCP were identified as SO 4 •− , OH • and O 2 •− , generated through the oxidation and reduction of PMS catalyzed by Zn (II) and Mn (III). Furthermore, X‐ray photoelectron spectroscopy (XPS) analysis of the fresh and used catalysts revealed that the exceptional electron transfer ability of ZnO facilitated the valence transfer of Mn (III) and the transfer of electrons to the catalyst's oxygen surface, thus enhancing the catalytic efficiency. The analysis of radicals and intermediates indicates that the two main pathways for degrading 2, 4‐DCP involve hydroxylation and radical attack on its aromatic ring. Practitioner Points A bimetallic ZnO/ZnMn 2 O 4 catalyst was synthesized and characterized. ZnO/ZnMn 2 O 4 can synergistically activate PMS to degrade 2, 4‐DCP compared with single metal oxide. Three primary active radicals, O 2 •− , • OH, and SO 4 •− , were generated to promote the degradation. ZnO promoted electron transfer among the three species of Mn to facilitate oxidizing pollutants. Hydroxylation and radical attack on the aromatic ring of 2, 4‐DCP are the two degradation pathways.