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

• Published in: The Journal of chemical thermodynamics 2012-05, Vol.48, p.260-266
• Main Authors: Chovau, S., Van der Bruggen, B., Luis, P.
• Format: Article
• Language: English
• Subjects: (Vapor + liquid) equilibrium; Chemical thermodynamics; Chemistry; Conversion; Exact sciences and technology; General and physical chemistry; General. Theory; Liquids; Mass-based UNIQUAC; Mathematical models; Membrane; Membranes; Simplification; Solvents; Sorption; Sorption equilibrium; Thermodynamics
• ISSN: 0021-9614; 1096-3626
• DOI: 10.1016/j.jct.2011.12.034

► UNIQUAC model in mass-based terms is considered for the description of sorption equilibria in membrane systems. ► Model validation of molar and mass-based model is performed on simple (vapor+liquid) equilibrium. ► Discrepancy is found between molar and mass-based model, which is attributed to an incorrect conversion. ► Novel model based on correct thermodynamics is provided for future research. 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.