The effect of an electric field on ion separation and water desalination using molecular dynamics simulations

Using molecular dynamics simulations, we analyze ion separation and water purification through a piston-driven graphene/carbon-nanotube filter in the presence of an external electric field. Three different magnitudes of electric field are applied along the nanotube's axial direction with the goal of separating sodium and chloride ions in a NaCl aqueous solution. For comparison purposes, we also study the same system in zero fields. Our results show that sufficiently large values of the electric field strength greatly improve the ion separation process. At the highest field strength, the theoretical efficiency of the filter in removing salt from water exceeds 95% indicating its applicability in commercial filtration processes to produce fresh water. These results suggest that the proposed set-up can be used to design highly efficient nanostructured membranes for water desalination.