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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]

Developing new strategies to design more practicable and efficient g-C 3 N 4 based photocatalysts is important to solve the environmental issues. Thiosulfate (STS) is a common residual product found in wastewater and removal of STS remains a matter of great environmental concern. In this work, however, STS is activated by g-C 3 N 4 under visible light irradiation, resulting in a fast degradation of Rhodamine B (RhB) and other pollutants. The performance of g-C 3 N 4 prepared from urea was much higher than that from melamine, due to the higher surface area and more negative conduction band potential of the former catalyst. In addition, comparison with other oxidants and reductants such as peroxymonosulfate, peroxydisulfate, hydrogen peroxide and sulfite, the use of STS in g-C 3 N 4 /Vis system showed the highest efficiency for RhB degradation. During ten successive cycles, the excellent reusability of the catalyst was also obtained. The effect of different concentrations of STS and g-C 3 N 4 , and initial solution pH on the performance of the system were also studied. The mechanism study suggests that STS is first oxidized to S 2 O 3 − radicals by photohole, which will be transformed to other oxysulfur radicals such as SO 3 − and finally to SO 4 2− ions. At the same time, the rate of O 2 reduction by photoelectrons to O 2 − radicals as well as RhB degradation increases. The finding of this study provides a promising advanced oxidation process for organic pollutants degradation via STS activation. [Display omitted] • The g-C 3 N 4 +STS/Vis system showed high activity for RhB degradation. • The catalyst was excellently reusability during consecutive cycles. • Superoxide radicals dominated the degradation of RhB in the system. • The transformation of STS in the g-C 3 N 4 +STS/Vis system was investigated. [ABSTRACT FROM AUTHOR]

• Co-MOFs were synthesized by a simple hydrothermal process. • Co-MOFs showed high activity for MO degradation via SO 3 2− activation. • The mechanism of pollutants degradation with SO 3 2− was illustrated. • The influence of several reaction parameters was studied. Activation of sulfite (SO 3 2−) by heterogeneous catalysts draws increasing attention due to their promising performance and environmental benignity. In this work, Co-based metal organic framework (Co-MOF) was synthesized and directly used as a catalyst to activate SO 3 2− for contaminants degradation. The Co-MOF catalyst exhibited high catalytic activity for Methyl Orange (MO) degradation in alkaline aqueous solution. Impressively, the catalytic performance of Co-MOF was more efficient than Co2+ and cobalt oxides of Co 3 O 4 , CoFe 2 O 4 and Co nanoparticles embedded in carbon tubes. Radical quenching experiments and electron paramagnetic resonance suggested that special coordination and redox of Co(II) and Co(III) in the pristine of Co-MOF initiated a series of chain reaction of SO 3 2− oxidation, with the formation of several oxysulfur radicals such as SO 3 −• and SO 4 −•. This work provides new insights into the stereoscopic cobalt based catalysts of sulfite catalysis and can guide new insights in future catalyst development in advanced oxidation process. [ABSTRACT FROM AUTHOR]