Synergistic degradation of phenols using peroxymonosulfate activated by CuO-Co₃O₄@MnO₂ nanocatalyst

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@MnO₂ with tetragonal structure. A remarkable synergetic effect was found between bi-metallic oxides of Cu and Co: 0.5%Cu-2%Co-MnO₂ can efficiently degrade 100% of 30ppm phenol, while 0.5%Cu@MnO₂ or 2%Co@MnO₂ 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-MnO₂ remained unchanged. Mechanism study indicated that SO₄^- and OH are accounted to participate the degradation, and the generation of radicals is originated from the interaction of CuCo@MnO₂ and PMS through metal site with peroxo species bond. The redox cycle among the active metals (M²⁺↔M³⁺↔M²⁺) and Cu enhanced generation of Co(II)-OH complex are critical for the remarkable performance in CuCo@MnO₂/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.