Molecular dynamics simulations of the effect of starch on transport of water and ions through graphene nanopores

We use molecular dynamics simulations to unravel the molecular level mechanisms underlying the structure and dynamics of water and ions flowing through nanoporous starch-graphene membranes. Our findings indicate that there is a significant tendency for the formation of short-range order in close proximity to the graphene membrane surface. This leads to a greater concentration of water and ions, suggesting strong interactions between the membrane and the saltwater solution. Furthermore, we found that the starch-graphene membrane was most efficient in sieving out ions when the starch loading is 15 wt.%, and the pore diameter is 14 Å. At these conditions, the starch-graphene membrane showed a high water transport rate and maintained a high level of ion rejection.

We investigated the effect of loading of starch and the pore diameter on the pressure-induced transport, structure, and dynamics of Na⁺, Cl⁻, and water using the GROMACS 2021.4 package. We further analyze the density profiles of water and ions in the context of ion-polymer and water-polymer interactions and provide mechanistic insights into the piston-induced flow of saltwater through the starch-graphene membranes using Visual Molecular Dynamics (VMD) software.