Theoretical calculation of simple and doped CNTs with the potential adsorption of various ions for water desalination technologies

Abstract

In this work, the interactions between simple carbon nanotubes (CNTs) and doped carbon nanotubes (DCNTs; with sulfur, boron, aluminum, silicon, phosphorus, or nitrogen) as good adsorbents with various ions such as Fe2 +, Na +, Ca2 +, Mg2 +, Cl−, CO32−, SO42−, and NO3− were fully considered through density functional theory (DFT), natural bond orbital (NBO), quantum theory of atoms in molecules (QTAIM) calculations. The adsorption energies (Ead) demonstrated that these ions could be adsorbed on the surface of the CNTs and DCNTs via the exothermic process, especially in the gas phase. QTAIM analysis confirmed that there are non-covalent interactions between these ions and CNT or DCNTs. The calculated energies illustrated that Si-CNTs and B-CNTs have the highest Ead values in the gas and solvent phase, respectively. Moreover, CNTs had the least Ead values in both phases and the best ion with the minimum Ead value in both phases is iron. Finally, population analyses were performed to obtain the reactivity parameters, molecular properties, bonding structural, and density of states (DOS) plots of all structures.