Abstract
Zinc oxide nanoparticles (ZnO NPs) were biosynthesized. According to GC/MS analysis, chalcone; the main phytochemical; is probably complexed with Zn ions that are then oxidized to ZnO NPs by atmospheric O2 during heating. The ZnO NPs were characterized by TG, FTIR, XRD, FESEM, TEM, eEDAX, and BET surface area analysis. Sphere-like ZnO NPs were formed with 11 nm mean crystallite size, 5.2 m2 g−1 surface area, and 0.02 cm3 g−1 total pore volume. The synthesized ZnO showed excellent photocatalytic degradation (96.5±0.24% in 1 hour at 25 °C) of malachite green (MG) in aqueous solutions under UV light at optimum conditions; pH 10, MG initial concentration of 20 mg L−1, and ZnO dose of 1.5 g L−1. Also, ZnO showed very good reusability (92.9± 0.2% after 5 runs). The experimental data obeyed pseudo-first-order kinetics (R2=0.92). The photocatalysis process is dependent on the following species in the order: OH. > electron/positive hole pairs > O2.−. Moreover, photodegradation efficiency decreased in the presence of CO32−, HCO3−, and Cl−, but increased in the presence of NO3−, and SO42− ions. Thus, the green synthesized ZnO NPs can be applied as an efficient photocatalyst for the removal of MG from aqueous media.