Theoretical investigation on the performance of simple and doped graphenes for the surface adsorption of various ions and water desalination

Abstract

In this work, the abilities of simple and heteroatom-doped graphenes for the adsorption of several ions (sodium, calcium, magnesium, chloride, carbonate, sulfate, and nitrate) were studied using theoretical methods. The results of this work could be helpful for future studies in the water desalination projects because the considered ions are the major existing ions in water. The structures of all graphenes and their complexes with these ions were optimized in the gas phase and water (using PCM model). Moreover, the interaction energies in the gas phase and water, atomic charges, second-order perturbation energies (from NBO calculations), and QTAIM results were obtained to provide more evidences related to these interactions. The obtained energies showed more favorable interactions in water versus than those in the gas phase. Among all graphenes, aluminum-doped graphene showed the highest and nitrogen-doped graphene showed the least adsorption energies. QTAIM calculations indicated the noticeable electron densities in bond critical points for all interactions, and the Laplacians of electron densities confirmed nonbonding nature for the most of interactions. Population analyses revealed that the HOMO-LUMO gap in doped graphene was increased in comparing with simple graphene that make them as potential candidates for detection of these ions.