Organic−Inorganic Hybrid Membranes: Solving the Trade-off Phenomenon Between Permeation Flux and Selectivity in Pervaporation

• Published in: Industrial & engineering chemistry research Vol. 48; no. 8; pp. 4002 - 4013
• Main Authors: Kariduraganavar, Mahadevappa Y, Varghese, Jolly G, Choudhari, Santosh K, Olley, Robert H
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 15.04.2009
• Subjects: Applied sciences; Chemical engineering; Exact sciences and technology; Membrane separation (reverse osmosis, dialysis...); Separations; Membrane separation; Permeation; Pervaporation
• ISSN: 0888-5885; 1520-5045
• DOI: 10.1021/ie8016626

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.