Facilitated transport of ethyl docosahexaenoate through solution-cast perfluorosulfonated ionomer membranes

The facilitated transport of ethyl docosahexaenoate (DHA-Et) through the th in solution-cast perfluorosulfonated ionomer membranes has been studied. Th e carrier of DHA-Et was silver ion and was immobilized in the support ionom er membrane by electrostatic forces. In this system, the feed phase, membra ne phase, and receiving phase had the same solvent. This system was already proved to be highly stable in our previous work. When ethanol/water (85/15 ) was used as the solvent, the DHA-Et permeance in the cast membrane was ab out four times higher than that in the commercial Nafion(R) 117 membrane, d ue to the smaller membrane thickness. In the case of acetone solvent, a hig h selectivity of DHA-Et to ethyl oleate of 42 and a high facilitation facto r of 153 were obtained. These membrane performances were superior to those of the Nafion(R) 117 membrane. The effects of membrane preparation conditio ns, such as annealing temperature and kinds of polar solvents added to the ionomer solution before annealing, on the membrane performance was investig ated in detail. Furthermore, small-angle X-ray scattering (SAXS) measuremen t was carried out to study the membrane structure. The experimental result suggests higher crystallinity in the cast membrane annealed at higher tempe rature. (C) 1999 John Wiley & Sons, Inc.