Application of the Pitzer model for the estimation of activity coefficients of electrolytes in ion selective membranes

J.H.G. van der Stegen, H. Weerdenburg, A.J. van der Veen, J.A. Hogendoorn, G.F. Versteeg*

*Corresponding author for this work

    Research output: Contribution to journalArticleAcademicpeer-review

    21 Citations (Scopus)

    Abstract

    The Pitzer model can be applied to predict the mean activity coefficients of salts in aqueous electrolyte solutions as a function of the molality. In this work it is shown that the mean activity coefficients for NaOH and NaCl solutions as predicted by the Pitzer model are in good agreement with experimental data from literature. Hereafter, the Pitzer model was extended to the description of the activity coefficients in ion selective membranes. Experimental sorption data of NaOH and NaCl obtained for sulfonic DuPont membranes with EWdry=1.10 and 1.50, respectively, were used to determine the Pitzer parameters describing the interaction between the fixed charged groups of the membrane and the other ions dissolved in the membrane. In the application of the Pitzer model to the membrane, it was assumed that the fixed charged groups of the membrane can be considered as ‘ordinary' ions evenly distributed in the aqueous solution inside the membrane. The results indicate that the Pitzer model can be used to describe the experimental mean activity coefficients in sulfonic DuPont membranes, provided the molality of the membrane, as used in the Pitzer relations, is multiplied by a constant representing a shielding term. This shielding term, fshielding, is a scaling factor depending on the equivalent weight.
    Original languageEnglish
    Pages (from-to)181-196
    Number of pages15
    JournalFluid phase equilibria
    Volume157
    Issue number2
    DOIs
    Publication statusPublished - 1999

    Keywords

    • Activity coefficient
    • Chemical potential
    • Pitzer model
    • Ion selective membranes

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