On the mechanism of ion exchange in zirconium phosphates—XXIX Calorimetric determination of heats of K+-H+ exchange with α-zirconium phosphate
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The heats of K+-H+ exchange have been measured calorimetrically on three samples of zirconium phosphate of widely differing crystallinities. The more crystalline exchangers both exhibit exothermic reaction over the full range of composition. There is, however, a distinct break in the curves at a composition of approx. 50% corresponding to two exchanged phases previously identified. The nearly amorphous exchanger shows an initially exothermic reaction followed by an endothermic process. The thermodynamic equilibrium constant for the exchange process has been evaluated as 3.1 × 10-5 resulting in a ΔG° of +6.15 kcal/mole. The overall enthalpy change, ΔH°, is found to be 1.58 kcal/mole and the resultant ΔS° = -15.3 eu. Qualitative explanations for these effects are presented and results compared briefly with previous work. © 1981.
author list (cited authors)
Clearfield, A., Day, G. A., Ruvarac, A., & Milonjic, S.