Electrodialysis based direct air dehumidification: A molecular dynamics study on moisture diffusion and separation through graphene oxide membrane

Abstract

To compromise shortages of traditional dehumidification methods, an electrodialysis based direct air dehumidification with higher efficiency and respondency was proposed. This technique could be accomplished via directional migration of charged water molecules and subsequent separation from air composition by the membrane. Notably, the water molecules diffusion and separation through the membrane are challenging and fundamental tasks to support the proposed novel dehumidification strategy. The purpose of this paper is to evaluate the dynamic diffusion behavior of water molecules across the double-layered nanoporous graphene oxide (2NPGO) membrane under the external electric field. Thence, molecular dynamics (MD) simulations of atmospheric gas, including water and nitrogen, were conducted. Once the electric field was applied, the self-diffusion coefficient of water increased from 2.421 × 10-9 m2·s−1 to 7.566 × 10-8 m2·s−1. In the presence of nitrogen, an electric field strength of 10-6 V/ Å would contribute to the increased permeation rate of 2.83 × 103 mol·m-2s−1 for water and a selectivity of 4.918 over nitrogen. Further study in hydrogen bond evolution and interaction energy variation versus electric field strength illustrated the mechanism of enhanced diffusion of water molecules.