Seawater desalination using pillared graphene as a novel nano-membrane in reverse osmosis process: nonequilibrium MD simulation study

Abstract

Herein, the applicability and efficiency of two types of pillared graphene nanostructures, namely, (6,6)@G and (7,7)@G, were investigated as membranes in reverse osmosis seawater desalination using extensive nonequilibrium molecular dynamics simulations. The water permeability for (6,6)@G and (7,7)@G membranes was estimated at 4.2 and 6.6 L h⁻¹ cm⁻² MPa⁻¹, respectively. According to the results, a complete (100%) and pressure-independent salt rejection was estimated for both membranes. In addition, the mechanism of seawater desalination through the pillared graphene membranes was investigated via the density distribution profile of water molecules inside the pillar channels. Furthermore, a series of steered MD simulations were performed to construct the potential of mean force (PMF) profile of water molecules and salt ions passing through the membranes channels. The passing free energy barriers of Na⁺ and Cl⁻ ions and water molecules are 0.86, 0.62, and 0.22 eV, respectively, for the (6,6)@G membrane. The corresponding quantities for the (7,7)@G membrane are 0.71, 0.44, and 0.11 eV, respectively.