Molecular dynamics simulation of carbon peapod-like nanomaterials in desalination process

Abstract

In this research, the performance of carbon peapod-like nanomaterials consisting 1 and 3 fullerenes into (13,13) armchair carbon nanotube (CNT) has been investigated in desalination process using molecular dynamics (MD) simulations with the applied pressure of 350 MPa. We have also examined different charge effects on the fullerene, nanotube, and graphene surfaces in this work. We have calculated different properties including water and ion flux, self-diffusion coefficient, radial distribution function (RDF), hydrogen bonding (HB) analysis, potential of mean force (PMF), and barrier energy of penetration. Our results showed that the highest and lowest water fluxes are for the pure CNT (2565 ns−1) and reverse charged fullerene peapod (270 ns−1) systems, respectively. The pure CNT also showed the highest ion flux (26 ns−1) than the other systems. Presence of fullerene into nanotube decreased the ion flux (6.5 ns−1) which represents acceptable performance of the peapods in salt rejection during desalination process. Using of N-doped fullerenes has small effect and increased the ion rejection more than the pure fullerenes. Our results also indicated that using of charged plates, CNTs, and peapods leads to complete salt rejection (zero ion flux). The pure CNT has the smallest barrier energy whereas the reverse charged CNT and the reverse charged plates have the biggest barrier energy required to water molecules to penetrate into the nanotube. Presence of fullerenes into the CNT also changes the orientations of the confined water molecules.