Modelling of water/organic vapor dehydration by glassy polymer membranes

Hydrophilic glassy polymers are suitable membranes for the dehydration of water/organic vapor mixtures. Vapor permeation is the predominant process for the dehydration of organic vapors employing glassy polymers. The permeation of vapor mixtures through this type of membrane is usually analyzed in terms of a dual-mode transport model which fails to predict well the separation behavior of a vapor mixture. The dehydration of organic vapor mixtures by glassy polymers was modeled using the Maxwell-Stefan formulation approach considering multicomponent thermodynamic and kinetic coupling effects. The model developed is a general one, applicable to all permeation processes for the separation of gaseous and vapor mixtures using a glassy polymer. The equilibrium sorption behavior of the vapor mixture was described by the dual-mode sorption model and the concentrationdependent diffusivities were recovered from sorption and permeation data. The experimental data available in the literature for sorption and permeation of pure ethanol and water vapor and their mixture through glassy polyvinylcholoride were used to examine the validity of the developed model. The results indicated that the model developed showed good predictability for mixed vapor permeation using the data from only pure component and also gave good information about the transport mechanism within the membrane.