A sodium-form chelating ion-exchange resin, Amberlite IRC-748, and a natural zeolite were investigated for the exchange of copper and ammonium ions from aqueous solutions at three temperatures ((4.0, 20.0, and 40.0) +/- 0.2) degrees C. Maximum exchange capacities were determined, and a temperature-dependent, semi-empirical thermodynamic ion exchange model used to describe the ion exchange behavior of the binary systems. It was found that the model selected fitted the data well for both systems. The resin was significantly more selective toward copper compared to zeolite, and the zeolite preferred ammonium to copper cations. Both systems exhibited an increase in selectivity toward copper or ammonium with an increase in temperature.