Synthesis and characterization of hybrid membranes using chitosan and 2-(3,4-epoxycyclohexyl) ethyltrimethoxysilane for pervaporation dehydration of isopropanol

Abstract

Chitosan based hybrid membranes were prepared by incorporating 2-(3,4-epoxycyclohexyl) ethyltrimethoxysilane (ETMS) into chitosan matrix using a sol–gel technique. The resulting membranes were studied using Fourier transform infrared spectroscopy (FTIR), wide-angle X-ray diffraction (WAXD), differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). After measuring the swelling data at different mass% of water, membranes were employed for pervaporation separation of water–isopropanol mixtures in a temperature range of 30–50°C. The experimental results demonstrated that membrane containing 40 mass% of ETMS showed the highest separation selectivity of 17,990 with a flux of 2.92×10−2kg/m2h at 30°C for 10 mass% of water. The values of total flux and flux of water are found to be overlapping particularly for hybrid membranes, suggesting that the developed hybrid membranes could be effectively used 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 (EPw) are two times lower than those of isopropanol permeation (EPIPA), suggesting that the developed membranes have higher separation efficiency for water–isopropanol system. The estimated Ep and ED values were ranged between 21.64 to 33.26, and 22.62 to 33.49kJ/mol, respectively. The negative heat of sorption (ΔHS) values was observed in all the hybrid membranes, indicating that Langmuir's mode of sorption is predominant.