Comparative analysis of graphene and h-BN nanochannel membranes for confined water purification: Insights into desalination performance through molecular dynamics simulation

Abstract

Layer-by-layer assembled graphene and boron nitride membranes are suggested as novel materials for reverse osmosis (RO) desalination applications. However, there is no detailed comparison of their desalination performance. In this study, molecular dynamics (MDs) simulations are used to compare and characterize the separation performance of boron nitride nanochannel (BNNC) and graphene nanochannel (GNC) membranes. For this purpose, the effects of various parameters, such as channel height, applied pressure, ion concentration, and membrane flexibility are considered. Moreover, the dynamic parameters of confined water, including friction coefficient, viscosity and diffusion coefficient are computed to clarify the effects of confined on the water transport properties. Results demonstrate that hydrophilicity and hydrophobicity of nanomaterials directly affect the water permeation through the membrane. In this regard, water permeation through GNC is generally higher than BNNC due to less friction against the water molecules. Furthermore, distance between layers of 7.675 Å can be considered as an optimum channel height. Additionally, in the GNC membrane, size exclusion is the main mechanism of ion rejection; On the contrary, in the BNNC membrane, both size exclusion and electrostatic interactions are involved in ion rejection. Overall, this study highlights how different 2D materials have different characteristics and how these characteristics affect desalination performance.