Equilibria and heats of exchange of alkaline-earth metal ions on the Na form of mordenite |
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Authors: | Yu I Tarasevich V E Polyakov and D A Krysenko |
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Institution: | (1) Laboratory on Biocoordination and Bioanalytical Chemistry, Department of Analytical Chemistry, Faculty of Chemistry, Sofia University, 1, J. Bourchier Blvd., 1164 Sofia, Bulgaria;(2) Institute of Organic Chemistry with Center of Phytochemistry, Bulgarian Academy of Sciences, Acad. G. Bontchev Str., Bl. 9, 1113 Sofia, Bulgaria;(3) Lehrstuhl f?r Analytische Chemie, Ruhr-Universit?t Bochum, 44780 Bochum, Germany |
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Abstract: | Sorption-analytic studies of ion exchange equilibria combined with direct calorimetric measurements of the heats of ion exchange
sorption of the Ca2+, Sr2+, and Ba2+ cations were performed over the whole range of solid phase fillings with sorbed cations on the Na forms of two mordenites
prepared from natural specimens rich in Na+ and Ca2+ cations. Ion exchange constants were determined and the Gibbs energies and entropies of ion exchange were calculated. The
thermodynamic characteristics obtained were analyzed taking into account the preferable localization of alkaline-earth metal
ions on certain exchange centers in the structure of mordenite. The presence of natural mordenite memory effects with respect
to extra-framework Ca2+ cations in the presence of which these zeolites were crystallized in nature was established. |
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