Novel approach for the development of pervaporation membranes using sodium alginate and chitosan-wrapped multiwalled carbon nanotubes for the dehydration of isopropanol

Using a solution technique, chitosan-wrapped multiwalled carbon nanotubes (CS-wrapped MWCNTs) incorporated sodium alginate (SA) membranes were prepared. After studying the physico-chemical properties of these membranes using Fourier transform infrared spectroscopy (FTIR), wide-angle X-ray diffraction (WAXD), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and scanning electron microscopy (SEM), the membranes were subjected to pervaporation dehydration of isopropanol. The effects of CS-wrapped MWCNTs and feed composition on the pervaporation performance of the membranes were systematically studied. The membrane containing 2 mass% of CS-wrapped MWCNTs exhibited the highest separation selectivity of 6419 with a flux of 21.76×10−2 kg/m2 h at 30 °C for 10 mass% of water in the feed. The total flux and flux of water are found to be almost overlapping each other, manifesting that the developed 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 (Epw) are significantly lower than those of isopropanol permeation (EpIPA), suggesting that the developed membranes have higher separation ability for water–isopropanol system. The estimated Ep and ED values were ranged between 14.42 and 10.79, and 14.97 and 11.73 kJ/mol, respectively. The negative heat of sorption (ΔHs) values was obtained for all the membranes, suggesting that Langmuir's mode of sorption is predominant.

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► Membrane with 2 mass% of CS-wrapped MWCNTs showed excellent performance.
► CS-wrapped MWCNTs incorporated SA membranes overcome the trade-off phenomenon.
► Membranes have lower Epw compared to EpIPA, showing higher separation efficiency.
► Membranes exhibit negative ΔHs values, suggesting the Langmuir's mode of sorption.