Green synthesis of cubic CuO nanoparticles for biomedical applications and the photodegradation of methylene blue: RSM-BBD optimization of the reaction parameters and stability studies

Abstract

Aquatic pollution poses an immense risk to human health and environmental preservation, with azo dyes from textile wastewater being a major source. Nanotechnology offers excellent methods for wastewater treatment, particularly through sunlight-driven photocatalysis. In this study, copper oxide nanoparticles (CMFE@CuO NPs) were produced via an eco-friendly green approach using the C. macrocarpa fruit extract. The produced NPs were thoroughly examined using advanced analytical techniques, revealing a crystallite size of 16.9 nm and high stability. The CMFE@CuO NPs displayed outstanding photocatalytic performance for methylene blue degradation under sunshine. The reaction conditions were tuned via the response surface approach based on a Box–Behnken design. Under optimal parameters (50 mg catalyst, 10 ppm dye, pH 8, and temperature 358 K), 99.9% dye degradation was achieved within 120 minutes, at a rate constant of 4.44 × 10⁻² min⁻¹. Total organic carbon analysis demonstrated 81% mineralization within 4 hours, while regeneration experiments confirmed significant reusability with only a 7% activity decrease after five cycles. Radical scavenging investigations supported the postulated degradation mechanism. In addition to photocatalytic activity, the CMFE@CuO NPs demonstrated considerable biological performance, demonstrating strong antibacterial efficacy and high antioxidant activity, comparable to gallic acid. Overall, the findings indicate CMFE@CuO NPs as very effective, reusable, and versatile nanocatalysts for wastewater treatment and environmental remediation.