Water desalination through armchair carbon nanotubes: a molecular dynamics study

Abstract

In this paper, molecular dynamics simulations were performed to study the desalination performance of armchair carbon nanotubes (CNTs). The studied systems included (7, 7) and (8, 8) CNTs embedded in a silicon nitride membrane immersed in an aqueous ionic solution. For desalinating water, an external electrical field was applied to the systems along the axis of the nanotubes. The results indicated that the (7, 7) and (8, 8) CNTs were exclusively selective to ions. The (7, 7) CNTs selectively separated sodium ions from aqueous solution. In contrast, the (8, 8) CNTs selectively separated chlorine ions. The ion selectivity of the CNTs is justified by calculating the potential of mean force for each ion in the related system. Also, the results were confirmed using the following simulated properties: ion current, retention time of the ions, transport rate for water molecules, average density of water inside the CNTs, and radial distribution functions of ion–water. Based on the findings of this study, the studied systems can be recommended as models for the desalination of water.