Ultrathin High Flux Membranes: Importance of Microporous Support

Membrane separation has enjoyed significant growth in the last three decades achieved by continual improvement in membrane separation performance and cost reduction.  Industrial membranes are often thin film composites comprised of a thin, dense skin layer (0.1 µm) performing molecular separation and a porous bulk of the membrane (150-200 µm) providing mechanical strength and no resistance to mass transport.  As the selective layer is produced thinner to enhance the permeance and thus reduce the capital cost, the geometric structure of the microporous support becomes more important, because the porosity and pore size may restrict the concentration profile of the permeant in the selective layer.  There is a crucial need to understand the effect of the support layer on the thin film composite membranes to further increase the competitiveness of the membrane technology over conventional separation technologies such as distillation and absorption.

This presentation will discuss the effect of the support geometry on the membrane permeance using an integral approach combining computational fluid dynamics simulations and experiments.  The performance of the membrane structure is simulated using a three-dimensional (3D) computational model.  The steady-state flux distribution through the separating membrane is studied as a function of various membrane parameters including the thickness of the thin, selective layer and the pore size and porosity of the microporous support.  Thin film composite membranes comprised of support membranes with well controlled pore size and porosity are prepared and characterized.  Approaches to mitigate the adverse effect of support membranes will be discussed.