A characterization of concentration polarization in a boundary layer in the permeation of VOCs/N2 mixtures through PDMS membrane

Influence of concentration polarization in the boundary layer in feed adjacent to the membrane surface has been investigated on the vapor permeation and separation of volatile organic compounds (VOCs)/N2 mixtures through poly(dimethylsiloxane) (PDMS) membrane. The chlorinated hydrocarbons that were part of the homologous series of chloromethanes and chloroethanes were used as organic vapor. The vapor permeation experiments were carried out at various VOCs concentrations in feed, operating temperatures and feed flow rates. With decreasing feed flow rate, the membrane performances, that is, permeation rate and selectivity were reduced in the permeation of the VOCs/N2 mixture by reducing VOC solubility in the membrane. Especially the reducing of the membrane performance was found to be more significant when the condensability of VOC was greater, VOC content in the feed mixture was higher or operating temperature was lower. These observations were discussed in terms of the effect of concentration polarization on the permeation of VOCs/N2 mixture through the PDMS membrane.