A recently developed temperature-dependent semiempirical thermodynamic ion-exchange model is used to predict ion-exchange equilibrium behavior of a binary and ternary system onto a natural zeolite material. The ion-exchange system involves the cations ammonium, potassium, and calcium, at chloride concentrations ranging from 0.005 to 0.25 M and temperatures ranging from 4.0 to 40.0 degrees C +/- 0.2 degrees C. The model describes the ion-exchange behavior well, considering the natural variability of the zeolite material.