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[Display omitted] • The silver-copper mixed-oxide Ag 2 Cu 2 O 3 was successfully prepared. • The catalyst showed high performance for PNP degradation via PMS activation. • The synergistic effect between Cu and Ag in the catalyst was clarified. • A possible mechanism for PNP degradation was proposed. Recently, the development of efficient mixed metal oxide catalysts for organic pollutants degradation via peroxymonosulfate (PMS) activation is a hot topic in the area of wastewater treatment. In this work, the silver-copper mixed-oxide, Ag 2 Cu 2 O 3 (ACO) was reported for the first time as a highly active catalyst for removing organic pollutants in the presence of PMS. ACO was successfully synthesized from Ag+ and Cu2+ ions at 60 °C, and its structure was strongly influenced by the temperature. The catalyst could almost completely remove p -nitrophenol and other pollutants with 0.65 mM PMS after 20 min, and also exhibited satisfactory stability and recyclability. The system efficiency was shown to vary with the concentration of PMS and catalyst, as well as solution pH. Scavenger experiment and EPR analysis indicated that radicals produced by the oxidation of Ag(I) and Cu(I) with PMS could promote degradation reaction. The synergistic effect between Cu and Ag in the bimetallic catalyst was demonstrated to contribute to the high performance: Cu(II)-O-Ag(I) bonds promote the conversion of Cu(II) species to Cu(I) through reaction with PMS, and facilitate the oxidation of Cu(I) and Ag(I) by PMS to generate active radicals. The study provides a feasible strategy to design efficient and stable bimetal oxide catalysts for PMS activation. [ABSTRACT FROM AUTHOR]

[Display omitted] • Mullite YMn 2 O 5 with abundance surface labile oxygen species was prepared. • The catalyst shows high activity for BPA degradation via PMS activation. • The degradation rate is linearly dependent on the ratio of labile oxygen species. • Direct electron transfer process plays a significant role in BPA degradation. • Possible degradation pathway of BPA was proposed. The development of efficient and eco-friendly Mn-based catalysts for peroxymonosulfate (PMS) activation and revealing the mechanism are highly desired for pollutants removal in wastewater. In this study, a ternary mullite oxide YMn 2 O 5 (YMO) was synthesized for bisphenol A (BPA) degradation in the presence of PMS for the first time. Combined with XPS, EPR and TG, abundant surface labile oxygen species (O lab) with a ratio of 39.7% were identified in the mullite materials, which was higher than that for α-, β-, γ- and δ-MnO 2. YMO also exhibited higher interfacial conductivity and stronger interactions among the catalyst, PMS and BPA than other MnO 2. Superior performance in BPA degradation was observed with YMO, and O lab was suggested as the main active sites, for the normalized first-order rate constant was linearly dependent on the ratio of the oxygen species. Chemical quenching experiments, EPR and open circuit potential suggested that the degradation of BPA was mainly caused by the direct electron transfer process through the reactive O lab -PMS complexes. The influence of YMO concentration, PMS concentration, solution pH, different anions and reaction temperature was thoroughly studied. Moreover, the intermediates were identified and the possible degradation pathways were proposed. This work demonstrated that mullite oxide YMO with enriched O lab species can be used as eco-friendly catalysts for efficient PMS activation to remove recalcitrant organic compounds in wastewater. [ABSTRACT FROM AUTHOR]

A possible overall sulfite activation mechanism on Mn 2 O 3 @Mn 5 O 8 catalyst for organic contaminant degradation. [Display omitted] • Mn 2 O 3 @Mn 5 O 8 shows better catalytic performance than other S(IV) activators. • S(IV) is activated by Mn 2 O 3 @Mn 5 O 8 , generating SO 3 •−, SO 5 •−, SO 4 •−, and •OH radicals. • Experiments show phenol is mainly removed by •OH, and partially by SO 4 •− and SO 5 •−. • At an initial solution pH of 3.0–7.0, stable degradation of phenol is achieved. • Low toxicity and high S(IV) activation ability of Mn 2 O 3 @Mn 5 O 8 affords a green method. Less-toxic, cost-effective, stable, and highly efficient catalysts for sodium sulfite (S(IV)) activation are required to degrade organic pollutants from wastewater. Herein, we report the facile thermal synthesis of Mn 2 O 3 @Mn 5 O 8 that activates S(IV) more efficiently than other Mn and transition-metal oxides. Mn 2 O 3 @Mn 5 O 8 exhibits good performance and long-term stability for eliminating various contaminants from aqueous media, including phenol, bisphenol A, nitrobenzene, 2,4-dichlorophenol, and acetaminophen. Its high performance is attributed to its multivalency, unique architecture, surface hydroxyl groups (–OH), and high surface area. X-ray diffractometry and high-resolution transmission electron microscopy revealed that Mn 2 O 3 @Mn 5 O 8 comprises well-combined cubic Mn 2 O 3 and monoclinic Mn 5 O 8 crystalline structures, whereas electron paramagnetic resonance spectroscopy and scavenging tests showed that SO 5 •−, SO 4 •−, and •OH radicals are generated during S(IV) activation, with SO 3 •− as a precursor. The mixed-valence state provides effective and favorable electron transfer via Mn redox cycling (Mn(II) ↔ Mn(III) ↔ Mn(IV)), improving the S(IV) activation performance and catalytic activity. Mn 2 O 3 @Mn 5 O 8 /S(IV) system shows stable performance in the 3.0–7.0 pH range. Density functional theory calculations confirmed the higher catalytic activity as indicated by high –OH adsorption energy and significant inter-charge transformation. This study provides new insights and strategies for the activation of S(IV) using less-toxic metal oxides as catalysts and broadens the scope of heterogeneous Mn-based catalysts and S(IV) chemistry in real-world applications, particularly for the treatment of wastewater. [ABSTRACT FROM AUTHOR]