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 no n-porous active layer of composite membranes are calculated with the U NIQUAC model. The prediction of multicomponent mixture solubilities re quires only binary interaction parameters between all pairs of the com ponents present in the swollen membrane material of the dense layer. T hese parameters are obtained from the binary vapor-binary equilibria d ata 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 co mparing the predicted solubilities of aqueous/organic mixtures in poly (vinyl alcohol) membrane material with the experimental data of six m ixture systems.