Ion exchange in synthetic zeolites. Part 2.—Thermodynamic formalism for incomplete exchange
In zeolites, ion-exchange phenomena can be limited by steric or ion-sieve effects. A thermodynamic study of the ion-exchange in these systems, using the Gaines and Thomas equation, requires the application of adequate normalization and correction procedures to the experimental exchange isotherms. Such a procedure is developed, and a practical demonstration is given for the exchange of sodium ions by n-alkylammonium ions in synthetic faujasite. The correctness of the method is substantiated by a thermodynamic development, in which the formulae are derived starting from the Gibbs-Duhem equation.