PHOSPHOTUNGSTIC ACID LOADED MIXED MATRIX BLEND MEMBRANES OF POLY(VINYL ALCOHOL)/GELLAN GUM FOR PERVAPORATION DEHYDRATION OF ISOPROPANOL

Abstract

Mixed matrix blend membranes of Poly (vinyl alcohol) (PVA)/Gellan gum (GG) were prepared using solution casting method by incorporating 5, 10 and 15 Wt.% of phosphotungstic acid (PWA). These membranes were crosslinked with glutaraldehyde and tested for the pervaporation (PV) dehydration of isopropyl alcohol (IPA) at 30˚C. These membranes were characterized by Fourier transform infrared spectroscopy (FTIR) to confirm crosslinking and assess the intermolecular interactions present between polymers and PWA. Thermal stability and crystallinity of these membranes were determined from thermo gravimetric analysis (TGA), Differential scanning calorimetry (DSC) and X-ray diffraction (X-RD) studies. The morphology of membranes was characterized by SEM studies, which indicated good compatibility of these membranes. Swelling studies were carried out to evaluate the extent of hydrophilicity with and without PWA particles and also based on their nature. The pervaporation performance was evaluated by varying experimental parameters such as feed composition, different polymer compositions, PWA content and found to be promising membrane for separation of water- isopropanol mixtures. From the results it was concluded that the phosphotungstic acid, with its hydrophilic nature as well as its molecular sieving effect and its favourable interaction with hydrophilic PVA and GG, was responsible to enhance the PV dehydration of isopropanol in terms of selectivity (α), flux (J), and pervaporation separation index (PSI).The results pertaining to the 15 wt% PWA loaded blend membrane had the highest selectivity 4,491 which was attributed to the combined effect of molecular adhesion between PWA and PVA-GG blend matrix as well as hydrophilicity.