Correlation of physicochemical characteristics with pervaporation performance of poly(vinyl alcohol) membranes

In this research, hydrophilic poly(vinyl alcohol) PVA membranes were prepared and its surface and bulk properties, e.g. surface roughness and crosslinking, were characterized using Fourier transform infrared (FTIR) spectroscopy, atomic force microscopy (AFM) and differential scanning calorimetry (DSC) and contact angle measurements. The PVA membranes were crosslinked in two ways: by heating at 125 °C or by chemical reaction with glutaraldehyde at room temperature. They were used for pervaporation applications, and dehydration of ethanol–water mixture was demonstrated in this paper. Compared to non-crosslinked membranes, the crosslinked membranes were shown to change in chemical structure by FTIR and become less hydrophilic by water contact angle measurement. The contact angle of the membranes increases with increasing the glutaraldehyde concentration used in crosslinking solution. AFM surface scans showed that the membrane surfaces are rough in nanometer scale and affected by the crosslinking treatment on the membranes. DSC measurements showed an increase in melting temperature of the polymer membranes after crosslinking. Dehydration of ethanol–water mixture was conducted over a range of ethanol concentrations (10–70 wt.%) in feed solution and at varied temperatures (from 25 to 50 °C). The dehydration results are presented and correlated with the results of the physicochemical measurements of the membranes.