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In this study, a highly efficient peroxymonosulfate (PMS) activator, ZnO/ZnMn2O4, 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, Mn2O3, and ZnMn2O4 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 HPO4−, HCO3−, and NO3− significantly inhibited the degradation of 2, 4‐DCP, while Cl− and SO42− did not exhibit such interference. Results from electrochemical experiments indicated that the electron transfer ability of ZnO/ZnMn2O4 surpassed that of individual metals, and electron transfer occurred between ZnO/ZnMn2O4 and the oxidant. The primary active radicals responsible for degrading 2, 4‐DCP were identified as SO4•−, OH• and O2•−, 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/ZnMn2O4 catalyst was synthesized and characterized.ZnO/ZnMn2O4 can synergistically activate PMS to degrade 2, 4‐DCP compared with single metal oxide.Three primary active radicals, O2•−, •OH, and SO4•−, 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. [ABSTRACT FROM AUTHOR]

Silver-based materials have emerged as excellent catalysts for peroxymonosulfate (PMS) activation in wastewater pollutants degradation. However, the mechanism of pure silver oxides towards PMS activation remains insufficient. In this work, Ag 2 O and AgO were selected as typical silver oxides to detect the catalytic performance. AgO/PMS possessed higher activity for p-nitrophenol and other pollutants degradation than Ag 2 O/PMS. The stability experiment and structure changes characterized from XRD, FTIR, and XPS, as well as quenching research, demonstrated that SO 4 •− was the main free radical produced from the oxidation of Ag(I) to Ag(II) and reduction of Ag(II) to Ag(I) by PMS; meanwhile, the high valence Ag(II) could directly oxidize the pollutants, which was also contributable to the degradation. Compared with Ag 2 O, AgO exhibited better efficiency and recyclability. These results provide key mechanistic insights into silver oxides towards PMS activation. [Display omitted] • Silver based oxides Ag 2 O and AgO was used for PMS activation. • The two catalysts showed similar performance for PNP degradation. • The reusability and stability of AgO was much better than that of Ag 2 O. • SO 4 •− radicals were produced from the oxidation of Ag(I) by PMS. • The high active Ag(II) species contributed to the degradation process. [ABSTRACT FROM AUTHOR]

Graphitic carbon nitride materials (g-C 3 N 4 ) were prepared from melamine hydrochloride under different calcination temperatures, and were investigated as metal-free catalysts for Acid Orange 7 degradation in the presence of peroxymonosulfate (PMS) under visible light. It was found that with the increase of calcination temperature, the morphological features of g-C 3 N 4 change from a typical flat layer structure with numerous mesopores to a thinner platelet-like structure, accompanied by the increase of BET surface area. The increase of heating temperature can also enlarge the band gap of g-C 3 N 4 . But under a higher temperature of 600 °C, the band gap is significantly reduced, probably due to the decrease of the structure defects. The obtained samples can effectively activate PMS under visible light irradiation to generate reactive species such as sulfate radicals, superoxides and photogenerated hole for dye degradation. Compared with the samples obtained from melamine, the activity is much higher, attributed to the dramatic enhancement of BET surface area. The catalysts also present a long-term stability during multiple runs. The effect of several reaction parameters and the formation of intermediates were also discussed. This study can improve our understanding of PMS activation on g-C 3 N 4 catalysts under visible light for pollutants removal. [ABSTRACT FROM AUTHOR]

• MnHA hybrid was prepared by deposition of HA on OMS-2. • Synergistic activation of PMS by MnHA hybrid was observed. • Interaction between OMS-2 and HA was characterized and discussed. • Detailed mechanism of MnHA+PMS system was proposed. The development of environmental friendly and efficient catalysts in advanced oxidation processes to degrade organic pollutants is highly desired. The complex metal oxides usually exhibit superior performance due to the potential synergistic effects between different metal oxides. In this study, hydroxyapatite (HA) coupled with manganese oxide OMS-2 hybrid (MnHA) was prepared and investigated as a catalyst for synergistic activation of peroxymonosulfate (PMS). The degradation of Acid Orange 7 with the hybrid was 2.94 and 10.8 times higher than those with pure OMS-2 and HA respectively. More importantly, it was found that Ca was not only coordinated with P O/P O groups in HA but also with Mn O groups on the surface of OMS-2; and then electrons were suggested to be transferred from HA to OMS-2 to decrease the Mn O Mn bond energy, leading to easier oxidation of Mn species by PMS. HO, SO 4 − , O 2 − and 1O 2 were found to be involved as reactive species in MnHA+PMS system, but 1O 2 played a more important role. The performance of the system under different conditions such as solution pH and concentrations of catalyst, pollutant and PMS was also studied. This work is expected to be helpful to design new and highly active catalysts for PMS activation. [ABSTRACT FROM AUTHOR]