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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]

The development of efficient and eco-friendly catalysts for peroxymonosulfate (PMS) activation is highly desired for pollutants removal in wastewater. Recently calcium ion (Ca2+) has been recognized to promote the catalytic performance of Mn oxides by enhancing the oxidizing power of PMS. However, the impact of pollutants types and influence of solution pH on the catalyst-oxidant interaction towards Ca2+ promotion have not been considered until now. This study investigated the effect of Ca2+ for pollutant degradation by Mn 2 O 3 activated PMS system, with various factors considered in detail such as the dose of Ca2+, pK a of organic pollutants, and solution pH. To deepen the understanding of the formation of Mn 2 O 3 /PMS complex in the presence of Ca2+, XPS, ATR-FTIR, radical scavenging, EPR, as well as PMS decomposition experiments, were analyzed. The binding of Ca2+ on the surface of Mn 2 O 3 efficiently promoted PMS decomposition and accelerated the redox cycles of Mn(III)/Mn(IV) with a faster rate for the production of HO• and 1O 2. Ca2+ also enriched the pollutants with negative charges around the catalyst to speed up the degradation process. This work points out a novel thought on the improvement of the PMS activation system with nonreducible metal ions. [Display omitted] • Ca2+ is used as a promoter in Mn 2 O 3 /PMS system for pollutants degradation. • Accelerated degradation of different pollutants with Ca2+ depends on their structures. • Binding of Ca2+ with the surface hydroxyls of Mn 2 O 3 promoted its contact with PMS. • Addition of Ca2+ speeds up the production of active species. [ABSTRACT FROM AUTHOR]

p-Nitrophenol (PNP) is one of the highly toxic and mutagenic pollutants existed in aquatic environment. In this work, the crednerite CuMnO 2 nanoflake was prepared and used to degrade PNP with peroxymonosulfate (PMS) as the oxidant. It was found that CuMnO 2 exhibited much higher activity than other Cu-based catalysts such as CuO, Cu 2 O, CuFe 2 O 4 and CuFeO 2 , with 90% of PNP degraded after 10 min under mild reaction conditions. The catalyst was also stable during five successive runs. Sulfate and hydroxyl radicals produced from PMS reduction by Cu(I) species, as well as superoxide ions and single oxygen, contribute to the degradation of PNP. More importantly, the interactions between Mn and Cu species in CuMnO 2 were identified by X-ray photoelectron spectroscopy (XPS), fourier transform infrared spectroscopy (FT-IR) and linear sweep voltammetry (LSV), and were further confirmed by the control experiment with the mixture of Cu 2 O + Mn 2 O 3. The results implied that the high valent Mn(III) species acted as Lewis acids to withdraw electron from PMS, resulting that the Cu(I) species can be easier oxidized to Cu(II) by PMS with the formation of radicals. These findings provide an ideal bimetallic heterogeneous catalyst and a new mechanism for PMS-mediated reaction. [Display omitted] • Crednerite CuMnO 2 was prepared by a simple hydrothermal method. • The catalyst showed high activity for PNP degradation via PMS activation. • CuMnO 2 was excellently reusability during consecutive cycles. • A synergistic effect between Cu(I) and Mn(III) was confirmed. • Possible degradation mechanism of PNP was proposed. [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]