Dehydration of acetic acid by pervaporation with charged membranes

Modified Nafion membranes were prepared by charging Nafion 117 membrane wit h different long-chained counter ions and used for pervaporation of acetic acid-water mixture. It was observed, that the selectivity of Nafion membran e was enhanced by charging with long-chained counter ions. However, it led to a decrease in permeate flux because of decreasing solubility and diffusi vity of the membranes. The results of small angle X-Ray diffraction (XRD) m easurement of wet Nafion and modified Nafion samples showed that the cluste r dimension of the membranes decreased after charging the membrane with lon g-chained counter ions. The estimation of the pore diameter of the membrane s by Kozeny-Carman equation resulted in a similar tendency. Among the modif ied Nafion membranes, Nafion (C8H17)(4)N+ is concluded to be the most suita ble membrane with a flux of 0.18 kg/m(2) h and a selectivity of 243 for the feed concentration of 90 wt.% acetic acid. (C) 1999 Elsevier Science B.V. All rights reserved.