Preparation Of β-CD Polymer/PVA Blend Membrane And Separation Of Xylene Isomers

It is difficult to separate xylene isomers with traditional methods, and it has some defect, for example high energy consumption, high pollution and complex process. Pervaporation has been the effective and energy saving technique for separation of xylene isomers. If the CDs that have the selective discernment for xylene isomers are used to separate xylene isomers, which is of great significance. The topic of this paper is the preparation of β-CD crosslinked polymer/PVA blend membrane and separation of xylene isomers. By studying on this membrane, it was excepected to find out the rules of membrane formation and to make excellent membranes.First, in the work, the water soluble crosslinked polymers of β-cyclodextrin with epoxy chloroproane (EP) are prepared in the alkali solution. The structures and molecular weight of different β-CD crosslinked polymers were characterized by IR and GPC. The results indicated that the solubility of β-CD crosslinked polymers linearly increased with the quantity of EP and the maximal solubility was 61.5g, which was larger 30 times than solubility of β-CD. The molecular weight also logarithmicly increased with the quantity of EP, obtaining 10⁶. From the IR we found that the β-CD crosslinked polymers preserved the original cavity structure on β-CD.In the work, two kinds of membranes were prepared, non-bottom film and β-CD crosslinked polymer/PVA/PAN (polyacrylonitrile) composite membrane. The swelling behaviors of β-CD-EP/PVA blend membranes in xylene isomers have been investigated, and then it was found the swelling degrees of blend membranes are higher than that of PVA membrane,Finally, this paper investigated the influence factors of blend membrane pervaporation separation properties, including feed concentration, cross-linking ratio of β-CD-EP, concent of β-CD-EP in blend membrane and concentration of PVA in membrane solution. Compared with PVA film, at 30℃, 6:1 cross-linking ratio of β-CD-EP, 10w.t% β-CD-EP content of blendmembrane, 8w.t% PVA contentration of membrane solution, when the contentration of PX was 20w.t%, separation factor increased from 1.17 to 2.86, and flux inceased from 22.6 to 245.0 g.m^-2.h^-1. For the β-CD crosslinked polymer/PVA/PAN composite membrane, separation factor α =1.0-2.0, flux J =30.0-100.0 g.m^-2.h^-1.