Molecular Dynamics Evaluation of Differing Pore Geometry in Nanoporous Membranes for Reverse Osmosis Desalination

Nanoporous membranes based on nanoporous graphene or other emerging classes of materials have shown huge potential in reverse osmosis (RO) water desalination for their high throughput and excellent salt rejection. Recently, a number of promising RO membrane candidates have been proposed, but a closer understanding of the mechanisms behind variations in performance of these materials is needed for their further selection and development. The geometry of the pores in these nanoporous materials has proven critical to their ultimate performance, so it is desirable to understand the effect of various pore geometries and the nature of their interactions with saline water. This project aims to develop a widely applicable interpretation to this problem by testing a generalized toy model with varying representative pore shapes using molecular dynamics. Simplified pores exhibiting roughly circular, square, and triangular geometries with a range of pore sizes have been tested to identify differences in key performance markers of flux and salt rejection. Additionally, the use of molecular dynamics enables an atomistic understanding of the separation process through each pore shape, and has provided insights into the distribution and movement of water molecules and salt ions within and around the pores. This information about relative efficacy of differing pore geometries as well as insight into the dynamics of individual particles within the pores will be useful in streamlining and informing future study of nanoporous materials for improved RO membranes.