Molecular dynamics study on water desalination through functionalized nanoporous graphene

Abstract

Molecular dynamics simulations were employed to investigate water desalination through functionalized nanoporous graphene membranes. Six graphene membranes were considered in which the carbon atoms of the pores were terminated by hydrogen or hydroxyl functional groups. The results demonstrate that water desalination occurs under external pressure and water flux permeating the membranes scales linearly with external pressure and pore diameter. The hierarchy of water flux through the functionalized graphene membranes was explained by potential of mean force. The salt rejection from smallest pore was 100% and decreases as pore diameter increases. Both Na+ and Cl− ions permeate through membrane with the largest pore, and the selectivity of the ions permeating exhibits a significant correlation with functional group. The designed graphene membrane shows excellent performance in terms of both salt rejection and water transport. Ultrahigh water permeance of 785.6 L per m2·h·bar obtained is two or three orders of magnitude higher than current commercially available reverse osmosis (RO) and nanofiltration membranes. This simulation study provides a microscopic insight into water desalination in various functionalized graphene membranes and reveals governing factor for water flux and also suggests a potential candidate as a RO membrane.