The mechanism of ion exchange in zirconium phosphates. 16. Calorimetric determination of heats of lithium(1+)-hydrogen(1+) exchange
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The heats of Li+-H+ exchange have been measured calorimetrically on zirconium phosphates of different crystallinities. For the most crystalline exchanger the reaction is exothermic up to about 50% Li+ uptake. This is followed by a mildly endothermic reaction to about 77% lithium loading and a more highly endothermic reaction at still higher loading. These heat effects correspond to the formation of three separate exchange phases identified earlier by x-ray methods. In the case of the nearly amorphous exchanger the reaction is initially very slightly exothermic but soon becomes endothermic. The overall enthalpy is H = 2.57 kcal/mol and the entropy, S = -10.6 eu. Qualitative explanations for the enthalpy and entropy effects are presented and the results compared to those obtained with other alkali metal cations.
The Journal of Physical Chemistry
author list (cited authors)
Clearfield, A., & Tuhtar, D. A.
complete list of authors
Clearfield, Abraham||Tuhtar, Dinko A