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ABSTRACT:Tetraethylorthosilicate crosslinked poly(vinyl alcohol) membrane was modified by varying the amounts of chitosan. The resulting membranes were characterized by Fourier transform infrared spectroscopy and differential scanning calorimetry. The effects of chitosan content and feed composition on the pervaporation performance of the membranes were analyzed. The modified membranes exhibit simultaneous increase of both flux and selectivity. The membrane containing 15 mass % of chitosan shows the highest separation selectivity of 2991, with a flux of 2.39 ϫ 10 Ϫ2 kg/(m 2 h) at 30°C for 10 mass % of water in the feed. The total flux and flux of water are almost overlapping each other, manifesting that the membranes could be used effectively to break the azeotropic point of waterisopropanol mixture, so as to remove water from the isopropanol. From the temperature dependent diffusion and 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 membranes developed here have higher separation ability for water-isopropanol system. In addition, difference was negligibly small between the activation energy values of total permeation (E p ) and water permeation (E pw ), indicating that coupled transport is minimal because of a higher selective nature of membranes. The E p and E D values ranged between 40.92 and 52.60, and 39.58 and 52.47 kJ/mol, respectively. The positive heat of sorption (⌬H s ) values observed in all the membranes suggests that Henry's mode of sorption is predominant.

ABSTRACT:The pervaporation (PV) separation and swelling behavior of water-acetic acid mixtures were investigated at 30, 40, and 50°C using pure sodium alginate and its zeolite-incorporated membranes. The effects of zeolite loading and feed composition on the pervaporation performance of the membranes were analyzed. Both the permeation flux and selectivity increased simultaneously with increasing zeolite content in the polymer matrix. This was discussed on the basis of a significant enhancement of hydrophilicity, selective adsorption, and molecular sieving action, including a reduction of pore size of the membrane matrix. The membrane containing 30 mass % of zeolite showed the highest separation selectivity of 42.29 with a flux of 3.80 ϫ 10 Ϫ2 kg m Ϫ2 h Ϫ1 at 30°C for 5 mass % of water in the feed. From the temperature dependency of diffusion and permeation data, the Arrhenius activation parameters were estimated.

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