Sulfonated polyphenylene oxide-polyethersulfone thin-film composite membranes - Effect of counterions on the gas transport properties

Thin film composite membranes based on sulfonated poly(phenylene oxide) (SP PO) as the top selective layer and PES ultrafiltration membrane as the supp ort layer, were prepared. The effect of the support membrane pore size dist ribution, and the effect of exchanging the proton of the sulfonic acid grou ps with mono-, di- and trivalent cations on the gas transport properties of the TFC membranes were studied. It was found that the resistance to gas pe rmeation imposed by the PES support layer increased significantly upon expo sure to the solvent in the coating solution. The differences in the perform ance of the TFC membranes having different metal cation replacing the proto n of the sulfonic acid groups were explained in terms of the metal cations' electronegativities and sizes. Very high selectivity associated with reaso nable permeance was obtained when the SPPO was in the Al3+-form. (C) 2001 E lsevier Science B.V. All rights reserved.