Separation characteristics of acetic acid-water mixtures by pervaporation using poly(vinyl alcohol) membranes modified with malic acid

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 °C. The influence of membrane thickness on the separation factor and the permeation rate was studied in the range of 50-100 μm at constant acetic acid concentration. It was observed that separation factor was independent of membrane thickness below a limit value of 70 μm 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 °C. Typically, separation factor of 670 and total permeation rate of 4.8 × 10−2 kg/m2 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.