Molecular dynamics simulation of separation of water/methanol and water/ethanol mixture using boron nitride nanotubes

Abstract The efficient separation of methanol and ethanol from water is an important issue due to the applications of these alcohols in many fields. This is a molecular dynamics simulation study of water/methanol and water/ethanol mixtures separations using four different types of armchair boron nitride nanotube (BNNT) including (7,7), (10,10), (12,12), and (13,13) BNNTs. The radial distribution function of solvents, density profile of solvent molecules, and number of hydrogen bonds between molecules were investigated to study the structural and dynamical properties of molecules inside the BNNTs and also, in the feed and permeate sides of the simulation box. Under a concentration gradient, (10,10) BNNT and (13,13) BNNT could selectively separate methanol and ethanol molecules from water molecules, respectively. BNNTs diameter sizes, hydrogen bonding between solvent molecules, and Van der Waals interactions between solvent molecules and BNNT were influential factors on the selective separation of methanol and ethanol molecules from water. Furthermore, the influence of applied hydrostatic pressure and electric field on the permeation of solvent molecules through BNNTs was investigated. It was revealed that these external applied forces were effective in the passage of molecules through BNNT in comparison to when applied hydrostatic pressure and electric field were absent.