Effective Removal of Selective Heavy Metal Ions from Aqueous Solution through Green Synthesized Zinc Oxide Nanoparticles

Abstract

In this work, zinc oxide nanoparticles (ZnO NPs) derived from the flower of Nyctanthus arbor-tristis have been synthesized in an environmentally benign, safe and non-toxic way. The adsorption of U(VI), Pb(II), Cr(VI) and Cd(II) ions from aqueous solutions by Nyctanthus arbor-tristis flower extract was investigated under laboratory conditions to assess its potential in removing these metal ions. The impacts of the experimental factors, such as ZnO NPs dosage, solution pH and contact time, were optimized. The study shows that the majority of the toxic metal ions can be adsorbed from the solution in a relatively short duration of time under ambient conditions. The adsorption behaviour of toxic metal ions onto the ZnO NPs was analyzed with Freundlich as well as Langmuir rate equations and the results were supported by the pseudo-second-order kinetic models. The study provides a safe, non-toxic and eco-friendly green synthesis method and also demonstrated excellent performance of the synthesized ZnO NPs.