Molecular dynamics insights into interfacial water accumulation for optimizing ceramic membrane-based air dehumidification

Abstract

Ceramic membranes, due to their excellent structural stability and permeability, have emerged as a highly promising alternative for membrane-based dehumidification. However, systematic and in-depth studies on the molecular-level diffusion and adsorption behaviors of water molecules in ceramic membrane dehumidification remain limited. Previous studies have mainly focused on simpler binary systems, while the competitive adsorption in ternary composite systems has rarely been addressed. To address these issues, this study employs all-atom molecular dynamics simulations to systematically investigate the nanoscale transport and adsorption behavior of water vapor in a composite system comprising 50%wt LiBr aqueous solution, Al2O3 ceramic membrane, and water vapor molecules. The calculated diffusion coefficient of water vapor molecules through the membrane is 3.58 × 10−7 m2·s−1, which is of the same order as the experimental value. Molecular dynamics results show that water vapor molecules can successfully diffuse through the ceramic membrane and be effectively absorbed by the LiBr aqueous solution. However, persistent water molecule accumulation at the ceramic membrane interface is observed, which will increase resistance to air dehumidification. Interaction energy analysis reveals that the contribution of the membrane to water vapor adsorption increases from 6.3% at the initial adsorption stage to 30.8% at equilibrium, indicating a significant competitive adsorption effect in this ternary system. These findings indicate that hydrophobic modification of A12O3 ceramic membranes is essential to minimize interfacial water retention and enhance dehumidification performance. This work provides molecular-level quantitative insights into competitive adsorption in ternary composite systems, advancing the development of high-efficiency ceramic membranes for liquid desiccant air dehumidification.