Development of novel composite membranes using quaternized chitosan and Na+-MMT clay for the pervaporation dehydration of isopropanol

Novel polymer-clay-based composite membranes were prepared by incorporating sodium montmorillonite (Na+-MMT) clay into quaternized chitosan. The resulting membranes were characterized by Fourier transform infrared spectroscopy (FTIR), wide-angle X-ray diffraction (WXAD), and thermogravimetric analysis (TGA). The effect of membrane swelling was studied by varying the water concentration in the feed. The membranes were employed for the pervaporation dehydration of isopropanol in terms of feed composition and Na+-MMT clay loading. The experimental results demonstrated that membrane containing 10 mass% of Na+-MMT clay showed the highest separation selectivity of 14,992 with a flux of 14.23 x 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 clay-incorporated membranes, signifying that the composite membranes developed in the present study involving quaternized chitosan and Na+-MMT clay are highly selective toward water. From the temperature-dependent diffusion and permeation values, the Arrhenius activation parameters were estimated. The resulting activation energy Values obtained for water permeation (E-pw) are much lower than those of isopropanol permeation (E-pIPA), suggesting that the developed composite membranes have higher separation efficiency for the water-isopropanol system. The estimated E-p and E-D values ranged between 8.97 and 11.89, and 7.56 and 9.88 kJ/mol, respectively. The positive heat of sorption (Delta H-s) values were obtained for all the membranes, suggesting that Henry's mode of sorption is predominant in the process. (C) 2009 Elsevier Inc. All rights reserved.