Green synthesis of ZnO nanoparticles using Hibiscus rosa-sinensis leaves extracts and evaluation of their photocatalytic activities

A green reflux method was adopted to synthesize ZnO nanoparticles using Hibiscus rosa-sinensis leaves extracts as a reducing and capping agent. The ZnO samples were characterized in details using fourier-transform infrared spectroscopy, X-ray diffraction, energy dispersive X-ray, UV-vis diffuse reflectance spectroscopy and field-emission scanning electron microscopy analyses. The microscopic analysis revealed that the synthesized ZnO nanoparticles were observed as spherical-like in particles with measured sizes ranging from 15-50 nm. The synthesized ZnO exhibited superior UV photodegradation on palm oil mill effluent as compared to that of commercial ZnO. The photoactivity improvement was ascribed to the presence of high amount of OH⁻ groups, good crystallinity, good optical properties and small particle sizes, which could yield large amount •OH radicals in the photocatalytic reaction. Phytotoxicity of POME over synthesized ZnO was also performed using Vigna radiata seeds.