A theoretical study of nanostructure membranes for separating Li+ and Mg2+ from Cl−

Abstract

In this paper, molecular dynamics simulation was used to investigate the separation of Li+, Mg2+ and Cl− ions from aqueous solution through armchair carbon and boron nitride nanotubes under the application of electric fields. The investigated systems included (7,7) and (8,8) carbon and boron nitride nanotubes embedded in a silicon nitride membrane in the aqueous ionic solution of LiCl+MgCl2. For separating ions, a specific range of electric fields was applied to the simulated systems. The following properties were meticulously examined: potential mean force, ionic current, water density, number of hydrogen bonds, normalized transport rate of water with respect to the number of separated ions, the residence time of ions in the nanotubes and the radial distribution functions of ions–water molecules. The results of the study indicate that the permeation of ions across nanotubes depends upon the diameter of the considered nanotubes. Under the applied electric fields, (7,7) carbon and boron nitride nanotubes were able to extract Li+ and Mg2+ ions from the aqueous solution; however, Cl− ions permeated through (8,8) nanotubes. The current generated in the system by the passage of ions through nanotubes in different electric fields was measured by Ohm’s law. The findings of the present study indicate that the examined systems can be utilized as a model in ion separation devices.