(398ac) A Molecular Simulation Protocol for Membrane Pervaporation

Pervaporation (PV) has emerged as a breakthrough technology for the separation of liquid mixtures. As a unique integration of membrane permeation and evaporation, PV offers several advantages such as low energy consumption, high separation capability and easy scaling-up. Consequently, PV has been regarded as a potential technology in chemical separation of azeotropic mixtures, thermally sensitive compounds, organic-organic mixtures and also for the removal of dilute organics from aqueous solutions.

Practically, PV is conducted with a vapor-liquid equilibria in the feed side and simultaneously a vanishingly low pressure in the permeate side. To the best of our knowledge, there is no reported molecular simulation study to mimic PV. In this study, a simulation protocol is proposed. To demonstrate, two different types of feed solutions (seawater and water-ethanol mixture) are examined through zeolitic imidazolate framework (ZIF) membranes. For each case, first, a molecular model is constructed including vapor-liquid equilibria in the feed side and an adsorbing plate on the permeate side. Then, the adsorption interaction strength in terms of É›/k_b systematically varies, and the optimal value of É›/k_b is identified to be 10000 K. With this optimal value, water flux remains constant despite changing the size of permeate side. Good agreement with experiment is found for the PV of seawater through ZIF-8, and high water permeability through ZIF-93 is observed for the PV of water-ethanol mixture. The proposed simulation protocol can be generally applied to other PV systems.