Formation of CuO Solid Solution via High-Frequency Electromagnetic Field-Assisted Ball Milling: The Reaction Mechanism.

The contamination of environmental water with organic pollutants poses significant challenges for society, and much effort has been directed toward the development of catalysts and methods that can decompose these pollutants. While effort has been directed toward the fabrication of CuO catalysts by ball milling, this technique can involve long preparation times and provide low yields. In this study, we synthesized a solid solution of CuO in 22 h by high-frequency electric-field-assisted ball milling below 40 °C in only one step under aqueous conditions. We investigated the catalytic activities of the produced CuO solid solution in the microwave-assisted degradation of dyes, namely rhodamine B, phenol red and methyl orange. The prepared CuO solid solution was very catalytically active and completely degraded the above-mentioned dyes within 2 min. The one-dimensional diffusion model and the phase boundary (planar) model were found to describe the kinetics well. Synergism between ball milling and the high-frequency electromagnetic field plays a key role in the preparation of CuO solid solution nanoparticles. Ball milling facilitates the relaxation of the CuO lattice and high-frequency electromagnetic radiation accelerates the diffusion of Fe atoms into the CuO crystal along the (111) crystal plane, quickly leading to the formation of a CuO solid solution.