Experimental and Theoretical Study of Enhanced Vapor Transport through Nanochannels of Anodic Alumina Membranes in a Capillary Condensation Regime

The pressure-driven flow of condensable and permanent gases was studied experimentally for anodic alumina membranes with channel diameters ranging from 20 to 90 nm depending on feed and permeate pressures. A substantial permeability rise for condensable gases was detected under capillary condensation conditions. A self-consistent theoretical model for mixed liquid–gas transport through the nanopore was suggested based on the obtained experimental results. The model was used for the evaluation of the pressure drop in a liquid defined by menisci curvatures and determination of the optimal conditions to enhance the membrane performance. The highest pressure difference in a liquid can be obtained by decreasing the entrance meniscus curvature with a simultaneous increase in the curvature of the evaporating meniscus. This case was realized in asymmetric membranes with multiple branching of channels into 5 nm nanocapillaries, resulting in up to 10× enhancement of isobutane permeability (up to 450 m3/(m2·bar·h)) ...