GAS-TRANSPORT THROUGH HOMOGENEOUS AND ASYMMETRIC POLYETHERSULFONE MEMBRANES

Both homogeneous and asymmetric polyethersulfone (PES) membranes were prepared by solvent casting. The sorption and permeation behavior of C O2, O2, and N2 Using these two kinds of cast PES membranes and commerc ially available homogeneous PES film was investigated to extract the p ressure dependence of gas permeability and the permselectivity for CO2 relative to N2, and to confirm the validity of the working assumption that a skin layer in an asymmetric membrane can be essentially replac ed by a thick homogeneous dense membrane. The pressure dependence of t he mean permeability coefficient to CO2 in homogeneous membranes obeys the dual-mode mobility model. The ideal separation factor for CO2 rel ative to N2 at an upstream pressure of 0.5 MPa attains ca. 40, while t he permeability to CO2 is about 2.7 Barrer at the same upstream pressu re. The same separation factor in asymmetric membranes amounts to 35. The diffusion behavior for the skin layer in an asymmetric membrane wi th a thin skin layer can be simulated approximately by that in a homog eneous dense membrane.