Plant mediated green synthesis of zinc oxide nanoparticles for photocatalytic degradation of trypan blue: Optimisation via box-Behnken design

This study highlights an environmentally and efficient route for the green synthesis of zinc oxide nanoparticles (ZnO NPs) through plant extracts. ZnO NPs were successfully prepared using Goji berry (GB) leaf extract as a sustainable capping agent showing the efficient photocatalytic degradation of Trypan Blue (TB) dye. X-ray diffraction (XRD) confirmed the synthesis of pure hexagonal ZnO phase with an average crystallite size of 15 nm, while scanning electron microscopy (SEM) analysis revealed well-dispersed quasi-spherical morphology. The nanoparticles exhibited a remarkable degradation rate, achieving approximately 98.78% degradation of TB (10 mg L −1 ) within 50 min under UV light irradiation. Critical operational parameters including pH (2−10), catalyst dose (0.3–1.5 g L −1 ), initial TB concentration (10–30 mg L −1 ), and reaction time (20–60 min) were optimized using a Box-Behnken experimental design. Analysis of Variance (ANOVA) demonstrated statistically significant effects ( p < 0.05) for all investigated factors (pH, catalyst dose, TB concentration, contact time) and their interaction terms on the degradation efficiency. The catalyst demonstrated excellent reusability, maintaining high degradation efficiency (>95%) over four consecutive cycles. These outcomes highlight the potential of green-synthesized ZnO NPs as a sustainable and efficient photocatalyst for textile wastewater treatment.