Transition metal ion exchange in zeolites. Part 4.—Exchange of hydrated and amminated silver in sodium X and Y zeolites and mordenite

Abstract

The ion-exchange properties of hydrated and amminated silver(I) ions in synthetic sodium X and Y zeolites and mordenite (MOR) were examined at 25 °C and at a total solution normality of 0.1 g equiv dm^–3. Ion exchange isotherms were constructed for each system and a thermodynamic affinity sequence of X ≫ Y > MOR was found for the Ag_(aq)⇌ Na exchange equilibria. In contrast, a selectivity sequence at MOR ≫ Y > X was observed for the Ag(NH₃)₂⇌ Na equilibria. These sequences are rationalised using simple dielectric theory or, in the cases involving the hydrated silver ion, using a modification of the theory.