Separating a water-propanol mixture using PDMS pervaporation membranes

Abstract

Recovering and purifying organic solvents during chemical and pharmaceutical synthesis has great economic and environmental importance. Water-alcohol mixture pervaporation was investigated using a pervaporation cell and hydrophobic membranes. This work studied polydimethylsiloxane (PDMS) membrane performance and hydrophobic membranes for removing propanol from aqueous mixtures. PDMS is recognised as being alcohol permselective during pervaporation. It was also observed that water was transferred through a hydrophobic membrane as water’s molecular size is smaller than that of propanol. A laboratory-scale pervaporation unit was used for studying this membrane’s separation characteristic in terms of pervaporation flux and selectivity for feeds containing up to water mass and 30°C-50°C. Total propanol/water flux was observed to vary as operating temperature increased. Although PDMS membranes presented good characteristics for separating water/propanol mixtures, the separation factor and pervaporation flow decreased as water content in the feed increased. The tested membrane was found to be very efficient for water concentrations of less than 0.3, corresponding to total flux transfer maximum.