Application of the mass-based UNIQUAC model to membrane systems: A critical revision

The UNIQUAC model is very suitable in describing (liquid + liquid) as well as (vapor + liquid) equilibrium for a wide range of systems. It can be extended to (solvent + polymer) systems for describing sorption equilibria. The original model is expressed in molar-based terms, but requires knowledge of structural parameters and molar masses of all components. Since these cannot always be easily determined for membranes, a conversion to mass-based terms is often performed, which eliminates this issue. Many studies use this model to calculate sorption equilibria in (solvent + polymer) systems. Nevertheless, in this work the conversion from molar to mass-based parameters is postulated to be erroneous. This even leads to an incorrect description of simple (vapor + liquid) equilibrium of pure liquid mixtures and hence it is advised not to use this model for further modeling of sorption equilibrium in (solvent + polymer) systems. In this paper, the errors in the conversion are pinpointed, and the effects it can have on the description of (vapor + liquid) equilibrium, if used improvident, are demonstrated. Furthermore, it is shown that in fact a simple and straightforward conversion can be performed. Finally, in the case when polymers are involved, an adaption and simplification to the model was successfully applied

Performance of PDMS membranes in pervaporation: Effect of silicalite fillers and comparison with SBS membranes

Laboratory-made silicalite filled PDMS membranes were tested by means of concentration and temperature influence on the membrane performance in removal of ethanol from ethanol/water mixtures This allowed studying the applicability of solution-diffusion model in the transport mechanism description Experiments were performed by varying the ethanol concentration in the feed and temperature Two types of fillers were incorporated into the PDMS network commercial zeolite silicalite (CBV 3002) and laboratory-made colloidal silicalite-1 Obtained results were then compared with data gathered for unfilled PDMS membranes to examine the effect of fillers incorporation Moreover, the comparison with novel block co-polymer based porous and dense SBS membranes was done. It was found that the solution-diffusion model was a good representation of ethanol transport through both filled and unfilled PDMS membranes, whereas the water flux did not obey this model due to the swelling effects Incorporation of the fillers increased membrane stability and improved the selectivity Performance of the SBS membranes characterized by a dense structure was found to be similar to the performance of filled PDMS membranes. (C) 2010 Elsevier Inc. All rights reserved.status: publishe