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The development of transition metal based heterogeneous catalysts with efficient reactivity and intensive stability is of great demand in peroxymonosulfate based AOPs in water treatment. Herein, we present a novel approach of creating stable and effective nano-rod catalyst of CuCo@MnO 2 with tetragonal structure. A remarkable synergetic effect was found between bi-metallic oxides of Cu and Co: 0.5%Cu-2%Co-MnO 2 can efficiently degrade 100% of 30 ppm phenol, while 0.5%Cu@MnO 2 or 2%Co@MnO 2 alone is apparently sluggish for the degradation of organic contaminants. The nanocatalyst retained good stability in recycling tests, during which little leaching of Co and Cu ions can be detected and crystallinity of support α˗MnO 2 remained unchanged. Mechanism study indicated that SO 4 − and OH are accounted to participate the degradation, and the generation of radicals is originated from the interaction of CuCo@MnO 2 and PMS through metal site with peroxo species bond. The redox cycle among the active metals (M 2+ ↔ M 3+ ↔ M 2+ ) and Cu enhanced generation of Co(II)–OH complex are critical for the remarkable performance in CuCo@MnO 2 /PMS system. Both the synergetic acceleration of catalyst activity and instinct mechanism are highly suggestive to the design of heterogeneous catalysts for the degradation of organic contaminants in PMS based advanced oxidation processes. [ABSTRACT FROM AUTHOR]

The development of new strategies to improve the removal of organic pollutants with permanganate (KMnO 4) is a hot topic in water treatment. While Mn oxides have been extensively used in Advanced Oxidation Processes through an electron transfer mechanism, the field of KMnO 4 activation remains relatively unexplored. Interestingly, this study has discovered that Mn oxides with high oxidation states including γ-MnOOH, α-Mn 2 O 3 and α-MnO 2 , exhibited excellent performance to degrade phenols and antibiotics in the presence of KMnO 4. The MnO 4 - species initially formed stable complexes with the surface Mn(III/IV) species and showed an increased oxidation potential and electron transfer reactivity, caused by the electron-withdrawing capacity of the Mn species acting as Lewis acids. Conversely, for MnO and γ-Mn 3 O 4 with Mn(II) species, they reacted with KMnO 4 to produce cMnO 2 with very low activity for phenol degradation. The direct electron transfer mechanism in α-MnO 2 /KMnO 4 system was further confirmed through the inhibiting effect of acetonitrile and the galvanic oxidation process. Moreover, the adaptability and reusability of α-MnO 2 in complicated waters indicated its potential for application in water treatment. Overall, the findings shed light on the development of Mn-based catalysts for organic pollutants degradation via KMnO 4 activation and understanding of the surface-promoted mechanism. [Display omitted] • Mn oxides with high oxidation states exhibited higher activity for KMnO 4 activation. • Mn(II) species in MnO reacted with KMnO 4 to produce cMnO 2. • KMnO 4 can form stable complexes with the surface Mn(III/IV) species. • The oxidation potential and ET reactivity of adsorbed KMnO 4 increased. • Direct ET mechanism played a significant role in phenol degradation. [ABSTRACT FROM AUTHOR]

The development of efficient and eco-friendly Mn-based hybrids for the degradation of biorefractory organic pollutants via peroxymonosulfate (PMS) activation is highly desired. In this study, a novel graphite nanosheet (GNs)-based Fe-Mn bimetallic oxide (Fe doped birnessite MnO 2 , FeMn/GNs) was synthesized under mild conditions. Compared with monometallic Fe or Mn oxide on GNs, FeMn/GNs exhibited a higher surface area, decreased Mn oxidation states, stronger interaction with GNs, and more active sites for PMS adsorption. Among different Fe/Mn ratios, Fe 2 Mn 1 /GNs showed the optimum performance for bisphenol A (BPA) degradation with the first-order rate constant of 0.22 min−1, which was about 8.5 and 12.9 times higher than that of Mn/GNs and Fe/GNs, respectively. Different from the pollutant-catalyst-PMS electron transfer mechanism for Mn/GNs, the direct two-electron transfer in FeMn/GNs+PMS system, was mainly processed between the simultaneously activated BPA and PMS. This was probably based on the double adsorption sites of Fe and Mn species on the same catalyst: PMS was adsorbed by Fe species through hydroxyl groups, while BPA was mainly coordinated with Mn species due to the layered structure and hydrophobicity of the Mn oxide. This study is expected to provide the rational design of efficient Mn-based hybrids for PMS activation. [Display omitted] • A novel FeMn/GNs composite was synthesized under mild conditions. • The influence of Fe and GNs on the structure of δ-MnO 2 was discussed. • The strong interactions improved the performance of PMS activation. • Direct electron transfer mechanim plays a significant role in BPA degradation. • The process was mainly through the simultaneous activated PMS and BPA. [ABSTRACT FROM AUTHOR]