To solve the trade-off phenomenon existing between permeation flux and selectivity of membranes in pervaporation, organic−inorganic hybrid membranes composed of chitosan and TiO2 were prepared using a solution technique. The resulting hybrid membranes were characterized by Fourier transform infrared spectroscopy (FTIR), wide-angle X-ray diffraction (WAXD), scanning electron microscopy (SEM), and thermogravimetric analysis (TGA). Compared to pure chitosan membrane, the hybrid membranes exhibited high thermal stability and low crystallinity. These membranes were tested for their ability to separate water−isopropanol mixtures by pervaporation in the temperature range of 30−50 °C. The experimental results demonstrated that both flux and selectivity increased simultaneously with increasing TiO2 content in the membrane. The permeation flux of pure chitosan membrane increased dramatically from 3.06 to 12.17 × 10−2 kg/(m2 h) when 40 mass % of TiO2 was incorporated, and correspondingly its separation factor increased from 509 to 94 984 at 30 °C for 5 mass % of water in the feed. The total flux and flux of water were found to be almost overlapping particularly for hybrid membranes, suggesting that these 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) were significantly lower than those of isopropanol permeation (E pIPA), suggesting that the developed membranes have higher separation efficiency for water−isopropanol systems. The negative heat of sorption (ΔH S) values were observed in all the membranes, indicating that Langmuir’s mode of sorption is predominant.

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Using a sol-gel technique, organic-inorganic hybrid membranes were prepared using chitosan and mixed silica precursors such as tetraethoxysilane and γ-glycidoxypropyltrimethoxysilane. The γ-glycidoxypropyltrimethoxysilane acted as a coupling agent to enhance the compatibility between the organic (chitosan) and the inorganic (tetraethoxysilane) phase. Different techniques such as Fourier transform infrared spectroscopy (FTIR), wide-angle X-ray diffraction (WAXD), scanning electron microscopy (SEM), and thermogravimetric analysis (TGA) were employed to study the physicochemical changes in the resulting membranes. These membranes were tested for their ability to separate water + isopropanol mixtures by pervaporation in the temperature range of (303 to 323) K. The experimental data demonstrated that both flux and selectivity were increased simultaneously with increasing the amount of γ-glycidoxypropyltrimethoxysilane. However, this trend no longer remained when the content of γ-glycidoxypropyltrimethoxysilane was increased beyond 0.25 mass fraction. The membrane containing 0.25 mass fraction of γ-glycidoxypropyltrimethoxysilane (M-2) exhibited the highest separation selectivity of 18 981 with a thickness-normalized flux of 7.45 · 10 -7 kg · m -1 · h -1 at 303 K. The total flux and flux of water were found to be overlapping with up to 0.25 mass fraction of γ-glycidoxypropyltrimethoxysilane, suggesting that these membranes could be used effectively to break the azeotropic point of water-isopropanol mixtures. From the temperature-dependent 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 developed membranes have demonstrated an excellent separation performance for water-isopropanol systems.