Molecular Dynamics Simulation of Salt Rejection in Model Surface-Modified Nanopores

Abstract

This Letter describes molecular dynamics simulations of pressure-induced flow of water and aqueous salt solutions through model nanopores. The systems studied are comprised of (n,n) carbon nanotubes (CNT) that span a membrane constructed of parallel graphene walls separating two solution reservoirs. We employ this system as an idealized model of surface-modified nanoporous membranes, and thus, both native hydrophobic CNT and nanotubes with artificial surface partial charge patterns are considered. The dependence of the fluxes of water and ions on the nanopore size, nanopore charge patterns, and pressure difference are explored using nonequilibrium molecular dynamics simulation. We demonstrate size- and structure-dependent salt rejection and show evidence of salt flux rectification for our asymmetric nanopore model.