The pervaporation separation of acetic acid-water mixture was carried out using poly(vinyl alcohol) (PVA) membranes modified using malic acid (MA). The effects of PVA/MA ratio, membrane thickness, operating temperature, feed concentration on the transmembrane permeation rate and separation factor were investigated. Optimum PVA/MA ratio was determined as 85/15 (v/v) for 20 wt.% acetic acid mixtures at 40 degrees C. The influence of membrane thickness on the separation factor and the permeation rate was studied in the range of 50-100 mu m at constant acetic acid concentration. It was observed that separation factor was independent of membrane thickness below a limit value of 70 mu m and permeation rate was found to be inversely proportional to the membrane thickness. The prepared membranes were also tested to separate various compositions of acetic acid-water mixtures with 20-90 wt.% acetic acid content at 40 degrees C. Typically, separation factor of 670 and total permeation rate of 4.8 x 10(-2) kg/m(2) h was obtained for 90 wt.% acetic acid concentration in the feed. Arrhenius-type relation and activation energy of 41 kJ/mol was also found for acetic acid-water mixtures. (c) 2005 Elsevier B.V. All rights reserved.