Permeation and separation characteristics of acetic acid-water mixtures through poly(vinyl alcohol)/malic acid membranes by evapomeation and temperature difference controlled evapomeation

Abstract

The characteristics of permeation and separation of acetic add-water mixtures through 85/15 (v/v) poly(vinyl alcohol)/malic acid (PVA/MA) membranes were investigated by evapomeation (EV) and temperature difference controlled evapomeation (TDEV) methods. The effects of permeation temperature, membrane surrounding temperature, and feed composition on the permeation rate and the separation factor were studied. The permeation rates increased but separation factors decreased with an increase in permeation temperature in EV method. Permeation activation energy of acetic acid and water in the evapomeation were calculated as 107.4 kJ/mol and 36.5 kJ/mol, respectively, using an Arrhenius type relationship. When the temperature of feed solution was kept constant and the temperature in the membrane surrounding was dropped, it was observed that the permeation rate and separation factor were significantly influenced by the temperature of membrane suroundings. The increase in the acetic acid concentration in the feed vapor mixture decreased the permeation rate and increased the separation factor except 40 wt% acetic acid content. The best separation factor was found at a composition of 90 wt.% acetic acid as 800 in the EV and 860 in the TDEV. Separation index in both methods were also calculated, the separation index of TDEV method was found to be higher than that of EV method for azeotropic composition of acetic acid-water. TDEV method for separation of acetic acid-water mixtures through the PVA/MA membranes was found to he more effective than evapomeation method. Copyright © Taylor & Francis, inc.