Abstract
A method is presented for grafting mesoporous γ-alumina (pore size 5 nm), supported on an α-alumina ceramic membrane, with polyethylene glycols (PEG). The grafting performance of γ-Al2O3 powders with various PEG grafting agents, having different molecular weights, alkoxy groups, and ureido functionality, was analyzed by TGA, 29Si-NMR, FTIR, and the BET method. FTIR analysis indicated that grafting has occurred. It was found that the molecular weight, the presence of an ureido functionality and the number of hydrolyzable groups of the grafting agents influenced the grafting density. The highest grafting density in this work was obtained by using a silylated ureido PEG with the shortest chain length (n = 10), while the number of alkoxy groups of the grafting agents influenced the structural configuration of the grafted moiety. The grafted membrane surface showed a hydrophilic character. A decrease in solvent permeation of both ethanol and hexane after grafting was observed, due to the presence of the grafted moiety inside the membranes reducing the membrane pore diameter. The permeability with respect to different types of solvents (polar and nonpolar) was investigated. Lower permeability of ethanol than hexane was observed accompanied by a higher retention of Sudan Black in ethanol than in hexane. This effect is explained by the difference in solvent sorption in the grafted moiety for different types of permeating solvents.
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