Preparation and characterization of novel pervaporation membranes for the separation of water–isopropanol mixtures using chitosan and NaY zeolite

Abstract

Novel polymeric membranes were prepared by incorporating the NaY zeolite into chitosan. The resulting composite membranes were characterized by Fourier transform infrared spectroscopy and wide-angle X-ray diffraction. The effect of membrane swelling on the separation performance was studied by varying the water concentration in the feed. The membranes were tested for the pervaporation separation of water–isopropanol mixtures in a temperature range of 30–50 °C. The experimental results showed that both flux and selectivity increased simultaneously with increasing zeolite content in the membrane. This was explained on the basis of enhancement of hydrophilicity, selective adsorption and molecular sieving action by the creation of pores in the membrane matrix. The membrane containing 30 mass% of zeolite shows the highest separation selectivity of 2620 with a substantial flux of 11.50 × 10 −2 kg/m 2h at 30 °C for 5 mass% of water in the feed. The total flux and flux of water are found to be almost close to each other for all the membranes studied, suggesting that the membranes could be used effectively to break the azeotropic point of water–isopropanol mixture, so as to remove a small amount of water from isopropanol. 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) values, suggesting that the developed membranes have higher separation efficiency in water–isopropanol system. The activation energy values for total permeation and water permeation are found to be almost same for all the membranes, signifying that coupled-transport is minimal due to a higher selective nature of membranes. The negative heat of sorption (Δ H s) observed for water sorption in all the membranes suggests the Langmuir's mode of sorption.