The separation of acetic acid-water mixtures was carried out using pervaporation (PV) and temperature difference evapomeation (TDEV) methods. For the separation process, 4-vinyl pyridine was grafted on poly(vinyl alcohol). Membranes were prepared from the graft-copolymer by casting method and crosslinked by heat treatment. The effects of feed composition on the separation characteristics were studied and the performances of the separation methods were compared. Permeation rates were found to be high in PV whereas separation factors were high in TDEV method. Membranes gave permeation rates of 0.1-3.0 kg/m(2)h and separation factors of 2.0-61.0 depending on the composition of the feed mixture and the method.