Green biosynthesis of multifunctional copper oxide nanoparticles using a leaf extract for potential applications: process optimization, wastewater treatment, phytotoxicity assessment, and antioxidant activity

This study presents the green synthesis of copper oxide nanoparticles (CuO NP) utilizing an extract from Carpobrotus edulis leaves, and evaluates their effectiveness in the removal of phosphate ions (PO 4 3- ) and Malachite Green (MG) dye from aqueous solutions. The CuO NP were subjected to physicochemical characterization, which indicated that the redox processes were carried out effectively. Furthermore, the material exhibited promising properties for the removal of both types of pollutants such as numerous adsorption groups (carbonyl groups, phenolics, and other reducing agents), high specific surface area (301.2 m 2 /g), and SEM presented the pore of various sizes. The percentage of elimination from the best combination of variables of the adsorption process is obtained using a two- step optimization, namely, the Taguchi experimental design (TED) followed by response surface methodology (RSM). The findings results indicate that the two-step optimization approach, incorporating both TED and RSM, achieves superior removal performance compared to the single-step process. The kinetic values were consistent with the pseudo-second order model with higher R 2 and lower χ 2 and APE values. The maximum adsorption capacity of PO 4 3- and MG was determined by the equilibrium study, with 807.76 and 668.07 mg/g, respectively, and the experimental values were most consistent with the Freundlich model. After five regeneration cycles, the regeneration efficiency remained at 75.44% for PO 4 3- and 63.98% for MG, indicating sustained performance. These results underscore the viability of synthesizing CuO NP using C.edulis extract and demonstrate their potential for applications in phytotoxicity assessment, antioxidant activity, and environmentally sustainable treatment of municipal wastewater.