Remarkable performance of GO/ZnO nanocomposites under optimized parameters for remediation of Cd (II) from water

Abstract

The rapid increase in toxic Cd (II) levels in water demand urgent steps toward its remediation. Here, we synthesized graphene oxide/zinc oxide (GO/ZnO) nanocomposites for Cd(II) ion removal from water, using modified Hummers and chemical precipitation methods to synthesize GO and ZnO nanoparticles, respectively. Nanocomposites were synthesized with 0.1, 0.5, and 1 wt% GO and 2.5 wt% ZnO by solution mixing in ethanol followed by characterization of its morphology, surface chemistry, crystal structure, and specific surface area. Adsorption studies were carried out at room temperature and parameters such as pH, initial metal ion concentration, and contact time were optimized for maximizing Cd(II) removal. Adsorption process followed Langmuir isotherm and pseudo-second-order kinetics. Nanocomposites with GO: ZnO in the weight ratio of 2:98 had the highest adsorption capacity for Cd(II) ions of 4125 ± 796 mg/g. Post-adsorption studies confirmed Cd(II) in the X-ray photoelectron spectra of the composite due to chemisorption of Cd(II) on the GO/ZnO surface. The synergistic effect of enhancement functional groups and the increase in the specific surface area made the GO/ZnO nanocomposite a promising material for effective removal of excess Cd(II) from water and maintaining it within WHO limit.