Molecular Dynamics Simulation of Desalination Process Using Li@C₆₀ Fullerenes Confined between Graphene Plates

Abstract

The Li@C 60 endohedral fullerene is particularly interesting because of its near-spherical shape, which has been the subject of some new experiments in recent years. In this study, we have examined the effect of positioning of Li + @C 60 endohedral and pure C 60 fullerenes between parallel graphene surfaces with flat and cross-sectional configurations at different external pressures in the desalination process using molecular dynamics (MD) simulations. Another membrane was also modeled by positioning of five graphene layers in the flat configuration as a layer-by-layer membrane. Our results showed that the salt rejection rate increases as the number of the confined fullerene increases. The presence of one Li + @C 60 fullerene increases the rejection rate two times more than the empty system. The presence of nine Li + @C 60 fullerenes leads to the complete rejection rate. The Li + @C 60 endohedral fullerenes also show more rejection rate than the pure C 60 fullerenes, which is due to the stronger fullerene−ion interactions. Although the presence of confined fullerenes between graphene plates decreases the water flux, the layer-by-layer configuration increases the water flux four times more than the one-layer system. Our results also indicated that the water flux is much smaller in the cross-sectional configuration than the flat one, which is due to the confined mobile fullerenes between the graphene plates. The ion rejection is also much greater in the cross-sectional configuration so that we have complete ion rejection in the five confined endohedral fullerene system. Our results have been also approved by the potential of mean force and self-diffusion coefficients.