THIN AND COMPOSITE HIGH-FLUX MEMBRANES OF PERFLUOROSULFONATED ION-EXCHANGE POLYMER

We report the techniques of casting thin and composite membranes of perfluorosulfonic acid polymer (PFSA). The thin PFSA membrane was prepared by a hot-casting method using an aqueous methanol solution with nonsolvents cyclohexanol and dimethylformamide. The composite PFSA membrane was cold-cast and subsequently cured at a higher temperature. Scanning electron micrographs showed the thin membrane to be asymmetric, whereas the composite membrane had a thin homogeneous polymer layer on the porous support. Permeation through the membranes was tested using several amino acids and their mixtures as model permeants. We found that membranes of both types provided higher fluxes than the commercial membrane of the same polymeric material. Permeation studies on amino acid mixtures using the composite membrane revealed that glycine permeated faster than either L-alanine or L-phenylalanine, and that glycine separation factors were higher for the composite PFSA membrane than for other polymeric membranes. © 1990.