Browsing by Author "Klinowski, Jacek"

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    Ion Exchange in Mordenite
    (Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1974, 70 (12), 1974) Barrer, Richard M.; Klinowski, Jacek
    Ion-exchange isotherms have been measured for synthetic mordenite involving the cation pairs Na+⇌Cs+, NH+4⇌K+, NH+4⇌Na+, NH+4⇌Li+, 2NH+4⇌Ca2+, 2NH+4⇌Sr2+ and 2NH+4⇌Ba2+. In all cases except those involving Ca2+ and Sr2+ reversible exchange was effected. The values of the thermodynamic equilibrium constant, Ka, and the standard free energy of exchange, ΔG⊖, were calculated for the reversible pairs. For additional combinations of the reversible ionic pairs, Ka and ΔG⊖ were obtained using the triangle rule. The thermodynamic affinity sequence is Cs+ > K+ > NH+4 > Na+ > Ba2+ > Li+. The thermodynamic affinity sequence among monovalent alkali metal ions established in this work for mordenite was found to be repeated for other zeolites, provided exchanges which do not go to completion are normalised by considering the equilibrium only in terms of the exchangeable fraction of the ions.
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    Ion-exchange Selectivity and Electrolyte Concentration
    (Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1974, 70 (11), 1974) Barrer, Richard M.; Klinowski, Jacek
    It is shown how, from a given exchange isotherm at a given total solution normality, one may calculate isotherms and exchange selectivity coefficients at other total normalities. When the exchange ions have different valences the isotherms depend strongly upon the total normality, and the selectivity of the exchanger, for the ion of higher valence increases without limit with increasing dilution. Also when the ions have different valences isotherms without inflexion points can become sigmoid with increasing dilution and sigmoid isotherms can loose their inflexions. In these circumstances sigmoid isotherms, for example in zeolites, cannot provide evidence that there is more than one kind of exchange site in the exchanger. However, the changes in isotherm shape or position with dilution are very small when the ions have the same valence. A way of diagrammatic representation of isotherms has been described which is independent of electrolyte concentration.