Preparation of Cu2(OH)3NO3/ZnO, a novel catalyst for methyl orange oxidation under ambient conditions

This work reports a novel process to synthesize copper hydroxyl nitrate/zinc oxide composites (Cu2(OH)3NO3/ZnO), and their application as a highly effective and reusable catalyst for wet oxidation of methyl orange (MO) under ambient conditions. No additional air or oxygen flow is required. Using a metal oxide assisted method, the Cu2(OH)3NO3/ZnO composites were hydrothermally obtained by varying the Cu:Zn mole ratio (2:1, 4:1, and 6:1) and the structural, chemical and surface properties of the composites were investigated. Decolorization of 500 ppm MO can be effectively catalyzed by the Cu2(OH)3NO3/ZnO composite (Cu:Zn = 4:1) with the color, chemical oxygen demand (COD) and total organic carbon (TOC) removal efficiencies being greater than 99%, 98% and 94%, respectively, after 20 min treatments using the catalyst loading of 3 g L−1. Results from systematic catalytic activity tests strongly suggested that MO was oxidized by oxygen dissolved in the dye solution, and that the degradation pathway of MO possibly occurred through radical and H2O2 generation. The application of highly efficient Cu2(OH)3NO3/ZnO catalysts in wastewater remediation may be attractive alternative to existing oxidation catalyst systems as they are low-cost, simple to prepare, feasible to operate under ambient conditions.

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► New synthetic route for copper hydroxide nitrate by a metal oxide assisted method.
► Catalytic wet oxidation of organic dye was promoted without addition of oxidizer.
► This cheap-to-produce catalyst has high performance under ambient conditions.
► The catalyst can be reused effectively, without regeneration requirement.
► Efficiency testing results suggested radical assisted oxidation of the organic dye.