The pervaporation separation of acetic acid-water mixtures was performed over a range of 10-90 wt.% acetic acid in the feed at temperatures ranging 25-50 °C using acrylonitrile (AN) grafted poly(vinyl alcohol) (PVA) membranes. The permeation and separation characteristics of PVA-g-AN membranes were studied as a function of membrane thickness, feed composition, operating temperature and pressure. When the downstream pressure increased permeation rate increased with decreasing separation factor and at high acetic acid concentrations PVA-g-AN membranes shows grater tendency for the separation of acetic acid-water mixtures. Depending on the membrane thickness, feed composition and temperature PVA-g-AN membranes gave separation factors 2.3-14 and permeation rates 0.18-1.17 kg/m2 h. It was also determined that PVA-g-AN membranes were found to have lower permeation rate and grater separation factors than PVA membranes. © 2004 Elsevier B.V. All rights reserved.