Multicomponent ion exchange isotherms in NaX zeolite

In this work the ion exchange isotherms of Cr3+, Mg2+, Ca2+ and K+ in single solutions and in binary mixtures (Cr/K, Cr/Ca, Cr/Mg) using NaX zeolite at 30degreesC, 45degreesC and 60degreesC were reported. NaX isotherms were very favorable for all metal cations studied. The respective isotherms had some differences in shape, a consequence of competition for the exchange sites. The Kielland plots of all systems were non linear, which is a characteristic of sites of different energies involved in the exchange process. Temperature influenced the ion exchange as it could alter the hydration sphere of the in-going ions. Consequently, differences in thermodynamic properties and also in the selectivity were seen. It was concluded that NaX did not have a pronounced selectivity towards chromium.