Figure 2 shows the cation-exchange isotherms at 18, 35, and 50 7C. The isotherms indicate that Jordanien phillipsite tuff prefers ammonium ions over sodium regardless of the temperature. However, the selectivity decreases at higher temperature. Similar behavior was observed by
Shibu (1981) for the Nac–K exchange in phillipsite and by Garcia Hernadez and others (1994), for the Nac–NH4