Transport of small polar molecules across nonporous polymeric membranes: I. Experimental procedures and data analysis

The transient measurement of concentration profile within the liquid boundary layer close to the membrane interface and the flux of permeating species across the membrane coupled with transient model of membrane allows a more critical evaluation of membrane transport performance. The experimental procedure for transient measurement of pervaporation fluxes and data obtained for the {ethanol–water}/silicone rubber system and experimental set up for transient dialysis measurement by interferometry technique for the same system was described. A detailed analysis of optical effect accounting for the light deflection in a medium of varying refractive index profile was presented. A numerical procedure was described which is capable to handle the transient models consist of highly nonlinear partial differential equations. The potential of recovering the transport model parameters from the interference fringes was tested by using a hypothetical model system. The results obtained confirm that both the diffusive and equilibrium parameters can be recovered from the interference fringes. The possibility of recovering the transport model parameters for the {ethanol–water}/silicon rubber system from dialysis data and using those parameters for predicting pervaporation performance for the purpose of model validation will be described in forthcoming articles.