A GENERALIZED SOLUTION DIFFUSION-MODEL OF THE PERVAPORATION PROCESS THROUGH COMPOSITE MEMBRANES .1. PREDICTION OF MIXTURE SOLUBILITIES IN THE DENSE ACTIVE LAYER USING THE UNIQUAC MODEL

The non-ideal solubilities of both liquid and vapor mixtures in the non-porous active layer of composite membranes are calculated with the UNIQUAC model. The prediction of multicomponent mixture solubilities requires only binary interaction parameters between all pairs of the components present in the swollen membrane material of the dense layer. These parameters are obtained from the binary vapor-binary equilibria data of the low molecular weight components and from the vapor sorption isotherms of the pure components in the polymer material of the dense layer. The UNIQUAC model gives excellent results in the case of polar liquid mixtures and hydrophilic membranes. This is demonstrated by comparing the predicted solubilities of aqueous/organic mixtures in poly (vinyl alcohol) membrane material with the experimental data of six mixture systems.