Synthesis and characterization of polyelectrolyte complex membranes for the pervaporation separation of water-isopropanol mixtures using sodium alginate and gelatin

Using a solution technique, polyelectrolyte complex (PEC) membranes were prepared by the complexation of sodium alginate (SA) with gelatin (Ge). The physico-chemical properties of these PEC membranes were studied by Fourier transform infrared spectroscopy (FTIR), wide-angle X-ray diffraction (WAXD), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and scanning electron microscopy (SEM). The pervaporation characteristics of membranes were investigated with water-isopropanol mixtures. The effects of Ge content and feed compositions on the pervaporation performance of the membranes were analyzed. The data thus obtained were employed to explain permeation behavior of water and isopropanol through PEC membranes. The experimental results showed that the membrane containing 10 mass% of Ge exhibits the highest separation selectivity of 4277 with a flux of 8.47 9 10(-2) kg/m(2) h at 30 degrees C for 10 mass% of water in the feed. The total flux and flux of water are found to be overlapping each other, particularly, for PEC membranes, manifesting that the developed membranes could be used effectively to break the azeotropic point of water-isopropanol mixtures. From the temperature dependent diffusion and permeation values, the Arrhenius activation parameters were estimated. The activation energy values obtained for water permeation (E-pw) are significantly lower than those of isopropanol permeation (E-pIPA), suggesting that the Ge-incorporated membranes have higher separation ability for water-isopropanol system. The negative heat of sorption (Delta H-s) values was obtained for all the membranes, suggesting that Langmuir's mode of sorption is predominant.