Vapor permeations of a series of VOCs/N2 mixtures through PDMS membrane

The permeation performances of volatile organic compounds (VOCs)/nitrogen mixtures through poly(dimethylsiloxane) have been measured at various operating conditions by a newly developed permeation apparatus which could measure its permeation transient rapidly, precisely and directly. In this study, a series of chlorinated hydrocarbons, that is, methylene chloride, chloroform, 1,2-dichloroethane and 1,1,2-trichloroethane were adopted as organic vapor. The permeability, diffusion, and solubility coefficients of the VOC mixtures were evaluated from the determined permeation transients. The permeation performance of the mixture as well as the selectivity towards VOC component showed a strong dependence of both VOC content in feed and the condensability of VOC. In the permeation of the VOC mixture, the nitrogen permeability was depressed below pure nitrogen permeability by the preferential sorption of VOC into PDMS membrane. This effect was more noticeable for the more condensable VOCs. Also, it is observed that the permeation and separation of the mixtures were more controlled by sorption process rather than by diffusion process. Through a quantitative analysis of the permeation parameter and apparent activation energies, the transport of VOC component in the permeation of the mixtures was discussed, in compared with pure nitrogen permeation. (C) 2002 Published by Elsevier Science B.V.