Analysis of permeance vs. Support porosity for thin film composite membranes

Membranes are an important technology for industrial gas separation, seawater desalination and emerging applications such as CO₂ capture. The key in steady growth of membrane applications is high performance thin film composite (TFC) membranes comprised of a thin selective layer (∼100 run or less) on a porous support that provides mechanical strength. As the selective layer becomes thinner to increase gas permeance and thus reduce the capital cost, the support surface morphology restricts the concentration profile of the penetrant in the selective layer. This geometric restriction of membrane permeance has been demonstrated using computational simulations. However, there are no rigorous experimental results to verify the modeling results. In this presentation we compare the measured and predicted permeance for two-layer model TFC membranes that are respectively comprised of track-etched polycarbonate (PC), nanofiltration membranes and industrial polyethersulfone (PES) ultrafiltration membranes, as porous supports, and perfluorinated glassy polymers, Teflon AF1600 and Hyflon AD 80, with excellent film formation and good stability as the selective layer materials. We discuss the fabrication and characterization of the membranes and show that the measured membrane permeance is consistent with predictions obtained using a three-dimensional (3D) computational mass transport model that predicts the steady-state penetrant concentration in the selective layer.