Molecular dynamics study on water desalination performance and related mechanism of hydrophobic α-Al2O3 ceramic membrane

Abstract

With LAMMPS software, the non-equilibrium molecular dynamics (NEMD) simulations study was conducted for the membrane distillation process with the hydrophobic α-Al2O3 ceramic membrane (HCM). It could further help to explain the macroscopic laws and phenomena that appeared in the membrane distillation tests with HCM. In this study, the average temperature (Tr) of raw water and the negative pressure (Pcon) on the cold side of HCM were taken as the investigation variables to research the microscopic water desalination performance of HCM, transport/diffusion properties of water molecules, and related mechanisms. The results showed that the root means square displacement (MSD) of water molecules on the cold side of HCM positively changed with time by the linear trend. The height of the transmembrane energy barrier mainly depends on the atomic structure of the HCM. The diffusion type of free-state water molecules in the membrane micropores of HCM was the main ballistic-transport-like accompanied by rebound-jump. The influence level of Tr on the number of water molecules in the cold side of HCM was much greater than that of Pcon under the dynamic equilibrium state. The essential reason Tr determined the HCM molecular flux was that it changed the hydrogen bond lifetime in the microporous membrane of HCM.