Troca iônica em zeólitas NaY e CrY. Termodinâmica

Isotherm ion exchange of Y zeolite has been studied at different temperatures. The direct exchanges of chromium in NaY show a very high selectivity to the in-going Cr 3+ ion. It was also shown that exchange increases with increasing temperature. On the other hand, the reverse isotherms in Cr-NaY are non-preferential process. In both cases Kielland plots and thermodynamic properties such as standard enthalpy of ion exchange (ΔH o ), standard free energy of ion exchange (ΔG o ), and standard entropy of ion exchange (ΔS o ) were calculated. Thermodynamic properties show a favorable process for direct exchange. The reverse exchange process is less sensitive to the changes in temperature due to the high energy needed to replace 3Na + by Cr 3+ in the zeolitic phase