NaY and CrY zeolites ion exchange. Thermodynamics

Abstract

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 Cr³⁺ 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 Cr³⁺ in the zeolitic phase