Green Synthesis of Flower-Shaped Copper Oxide and Nickel Oxide Nanoparticles via <i>Capparis decidua</i> Leaf Extract for Synergic Adsorption-Photocatalytic Degradation of Pesticides

Green manufacturing of catalysts enables sustainable advanced oxidation processes and water treatment processes for removing trace contaminants such as pesticides. An environmentally friendly biosynthesis process produced high-surface-area CuO and NiO nanocatalysts using phytochemicals in the Capparis decidua leaf extract, which served as a reductant and influenced catalyst shape. Capparis decidua is a bushy shrub, widely distributed in dry and arid regions of Africa, Pakistan, India, Egypt, Jordan, Sudan, Saudi Arabia. The synthesized CuO and NiO nanoparticles were characterized by UV-vis spectroscopy (UV-vis), field emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectroscopy (EDS), Fourier transform infrared spectroscopy (FT-IR), and X-ray diffraction (XRD) and thermo-gravimetric analysis/differential thermal analysis (TGA/DTA). The produced nanoparticles were spherical and flower-like in shape and have a characteristic face-centered cubic structure of CuO and NiO. Biosynthesized catalysts were photoactive and degraded recalcitrant pesticide Lambda-cyhalothrin (L-CHT). Photocatalytic degradation of L-CHT was affected by the initial L-CHT concentration, solution pH levels between 5 and 9, and photocatalyst concentration. The L-CHT removal percentage attained by CuO photocatalyst (~99%) was higher than for NiO photocatalyst (~89%). The degradation of L-CHT follows a pseudo-first-order kinetic model, and the apparent rate constant (kapp) decreased from 0.033 min−1 for CuO to 0.0084 min−1 for NiO photocatalyst. The novel flower-shaped nanoparticles demonstrated high stability in water and recyclability for removing L-CHT pesticide contamination in water