Thiamethoxam Insecticide Degradation with a Leaf-Like Cupric Oxide Monoclinic Structure Synthesized via the Microwave Method

Leaf-like cupric oxide (CuO) with a high purity phase monoclinic structure was synthesized via a microwave method for use as a photocatalyst in the degradation of thiamethoxam insecticide. The synthesis process used copper nitrate and ammonia solution as precursors. The suspensions were treated via microwave irradiation at 600–800 W for 30 min, followed by a constant-temperature calcination process. The phase transitions, thermal stabilities, morphologies, chemical compositions, functional groups, and optical properties of the resulting leaf-like CuO powders were characterized via X-ray powder diffraction, TGA/DSC, SEM, particle size distribution analysis, EDS, FT-IR, UV-DRS, and PL. The experimental findings showed that increasing the microwave power resulted in favorable chemical and physical properties for the powders’ photocatalytic reactions, such as high purity phases, high crystallinity, high uniformity of the leaf-like shapes, smaller particle sizes, narrower size distributions, lower energy bandgaps, and lower rates of electron-hole pair recombination. The photocatalytic degradation of thiamethoxam insecticide using these leaf-like CuO powders under visible light illumination was studied. The concentration of thiamethoxam was analyzed using UV-Vis spectrophotometry. The highest thiamethoxam degradation efficiency was achieved by the CuO powder synthesized via microwave irradiation at 800 watts. Its efficiency was 48.65% in 60 min at a kinetic rate constant of 10.9 × 10 −3 min −1 .