Green Synthesis of Zinc Oxide Nanoparticles Using Aqueous Extracts of Hibiscus cannabinus L.: Wastewater Purification and Antibacterial Activity

Abstract

The green preparation of metal oxide nanoparticles is an environmentally friendly method, which could reduce the use of toxic solvents and their impact on the environment. The purpose of this study is to investigate the green synthesis of zinc oxide (ZnO) nanoparticles using extracts of Hibiscus cannabinus leaves and to evaluate their potential applications in environmental remediation. In this work, ZnO nanoparticles were successfully prepared and thoroughly characterized using UV–vis, Fourier transform infrared analysis (FTIR), X-ray diffraction (XRD), transmission electron microscope (TEM) analysis, and scanning electron microscope (SEM) with energy dispersive x-ray analysis (EDAX). As a result, the synthesized ZnO nanoparticles showed a good adsorption capacity for Congo red (CR), and satisfactory antioxidant and antibacterial activities. They exhibited good adsorption and removal abilities for CR in aqueous solutions. With the conditions optimized, the adsorption kinetics and isotherms were fitted to the pseudo-second-order model and the Langmuir model. The ZnO nanoparticles could also effectively scavenge 2-2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2′-azino-di(3-ethylbenzthiazoline sulphonate) (ABTS) radicals, and appeared to inhibit the growth of Escherichia coli and Staphylococcus aureus bacteria. Based on the identified adsorption capacity, the green synthesized ZnO nanoparticles demonstrated their potential to be used in the removal of dyeing wastewater and in the further purification of water due to their antioxidant activity and antibacterial activity.