The ability of zinc oxide nanostructures for removal of Pb²⁺, Cu²⁺, Ag²⁺ and Cd²⁺ ions from wastewater: computational perspective

In the heavy metal removal industry, adsorption is a famous and commonplace procedure well-recognized for its flexibility and utility. It is also a cost-effective procedure. Moreover, there are several adsorption procedures that are reversible on the one hand, and adsorbents may be reused after passing different desorption techniques on the other. The foundation of this research is to apply the calculations of the density functional theory (DFT) based on ab initio with an aim to explore the heavy metal atoms’ adsorption properties on ZnO–graphene resembling structure sheets and zinc oxide (ZnO) nanotubes. The heavy metals considered in this study include (Cu2+), (Pb2+), (Cd2+), and (Ag2+). In the initial stage, this study optimises both nanostructures. In the next phase, this study computes the steadiest configuration, the energy of adsorption, and the distance of equilibrium for each heavy metal with nanostructures utilising the mentioned DFT method. The findings were analyzed and compared. According to our case-by-case findings, ZnO-nanotubes exhibited better adsorption behaviour than ZnO–graphene sheets due to a smaller distance for equilibrium and higher adsorption energy. we’ve created the diagrams of the electronic density of states (DOS) in order to analyze the molecule adsorption electrical properties.