PVA membrane filled beta-cyclodextrin for separation of isomeric xylenes by pervaporation

Polyvinyl alcohol (PVA) membrane filled beta-cyclodextrin (beta-CD) was pre pared by casting an aqueous solution of PVA and beta-CD oligomer. The membr ane was crosslinked with glutaraldehyde for one hour. The weight content of beta-CD in the membrane was 33%. The membrane was used for separation of p -xylene/m-xylene mixture by pervaporation. Based on the experiments of sorp tion equilibrium, the solubility and the diffusion coefficient of the perme ates in the membrane was obtained. Compared with PVA membrane, the solubili ties of pure p-xylene and m-xylene in PVA membrane filled P-CD increased fr om 0.92, 0.78 to 10.4, 2.6 g (xylene)/100 g (dried membrane), respectively, and the solubility selectivity S-p/S-m increased from 1.18 to 4.0. Also, t he diffusion coefficients of p-xylene and m-xylene decreased from 8.45 x 10 (-12), 8.23 x 10(-12) to 6.83 x 10(-12), 7.23 x 10(-12) m(2)/s, respectivel y, and diffusion selectivity decreased from 1.03 to 0.94. These effects of beta-CD can be interpreted in terms of the inclusion strength in the cavity . The pervaporation performance of the PVA membrane filled beta-CD was inve stigated. A separation factor of 2.96 and a permeation rate of 95 g/m(2) h through the beta-CD filled PVA membrane for a 10 wt.% feed p-xylene concent ration were obtained at 25 degrees C. The results indicated that PVA membra ne filled beta-CD effectively improved the pervaporation performance, espec ially on the separation factor. (C) 2000 Elsevier Science S.A. All rights r eserved.