Multilayer poly(vinyl alcohol)-zeolite 4A composite membranes for ethanol dehydration by means of pervaporation

Zeolites are known to have pronounced molecular sieving effect and selective adsorption capacity, the incorporation of zeolite particles into a selected polymer thus can be used to tailor the material intrinsic properties. In this work, zeolite 4A has been employed to prepare polyvinyl alcohol (PVA)-based composite membranes for ethanol-water pervaporation separation. These zeolite-embedded hybrid membranes are manufactured by using a casting machine with polyester nonwoven fabric as the supporting layer, polyacrylonitrile (PAN) as the porous backing layer and PVA as the active separating layer. The effect of feed composition, feed temperature and zeolite loading on the membrane separation performance are discussed in detail. Experimental results show the water-ethanol separation selectivity has been greatly improved after adding zeolite 4A and that reasonably high separation factor can be achieved for feed ethanol concentration above 80 wt.%, probably due to the superior molecular sieving effect of added zeolite 4A on the water-ethanol system. In the meantime, the Arrhenius activation energy approximated is found to significantly decrease for water but obviously increase for ethanol after the zeolite incorporation, indicating that water molecules require much less energy whereas ethanol molecules need much more energy to transport through the membrane because of the hydrophilic characteristics of zeolite 4A. (C) 2006 Elsevier B.V. All rights reserved.