SELF-DIFFUSION OF WATER-ETHANOL MIXTURES IN POLYACRYLIC-ACID POLYSULFONE COMPOSITE MEMBRANES OBTAINED BY PULSED-FIELD GRADIENT NUCLEAR-MAGNETIC-RESONANCE SPECTROSCOPY

The self-diffusion of water, ethanol and water-ethanol mixtures in pol yacrylic acid (PAA) and PAA-polysulfone (PSF) composite membranes was measured with pulsed-field gradient (PFG)-nuclear magnetic resonance ( NMR) spectroscopy. The partial solubilities and self-diffusion coeffic ients were obtained. An attempt was made to explain the transport prop erties of water and ethanol through the PAA layer and PAA-PSF composit e membranes. It was concluded that there are two types of channels for diffusate transfer in PAA: an ionogenic hydrophilic channel which is selective for water and a hydrophobic channel which contains a predomi nance of ethanol molecules. The existence of aluminum nitrate in PAA i nfluences the morphology of the latter channel, There is a good agreem ent between of the separation factors estimated from PFG-NMR data and those obtained by pervaporation testing.