Water permselectivity in the pervaporation of acetic acid-water mixture using crosslinked poly(vinyl alcohol) membranes

The states of water absorbed in the crosslinked poly(vinyl alcohol) (PVA) m embranes was studied thermally using differential scanning calorimetry (DSC ). It was observed that water absorbed in the membranes was distinguished i nto free water, freezing bound water and non-freezing bound water. As the c rosslinking time increased, the nonfreezing bound water, the freezing bound water and the free water contents decreased. The bound water acted as an e ffective plasticizer for the polymer due to its interaction with the polyme r. In the pervaporation of acetic acid-water mixture using the crosslinked PVA membranes, the decrease in the acetic acid and water permeation with in creasing crosslinking time was correlated with the crosslinked structure of the membranes and the decrease in the bound water content in the polymer w hich led to a decrease in the plasticization effect. As a result, the separ ation factor increased with increasing crosslinking time. (C) 2000 Elsevier Science B.V. All rights reserved.