N. Birkner, V. Proust, J. Schaeperkoetter, A. T. Ta, A. Gossard, M. Badawi, A. Daouli, N. Cassell, S. Misture, S. R.  Phillpot, A. Grandjean, H.-C. zur Loye and K. S. Brinkman, Microporous and Mesoporous Materials, 373, 11310 (2024). https://www.sciencedirect.com/science/article/pii/S138718112400132X?via%3Dihub

Cs-137 is a radionuclide fission product that poses a significant risk to life, making it crucial to develop effective
methods for its separation and sequestration from nuclear waste streams. Zeolitic structures have emerged as
promising materials. This work examines the influence of structure, exchange site energetics, and formation
enthalpies of nascent and cation-exchanged Faujasite-X, -Y, and -HY zeolites in terms of their Cs-exchange
selectivity. Their interplay was quantified with the application of high-temperature calorimetry, adsorption
isotherms, X-ray diffraction and density functional theory (DFT) calculations. Greater efficacy of Cs+ exchange
was demonstrated for the Na+-substituted Fau-Y (NaY) zeolite than that of the Fau-X (NaX) and Fau-HY (Na-HY) zeolites. This is explained by a higher amount of Na+ in un-exchangeable sites in the case of NaX and a lower stability in NaY that favors the ionic exchange with Cs+. Moreover, Cs+ incorporation in the structure increases the stability of each kind of zeolite. Correspondingly, structure and DFT analyses demonstrated site-exchange thermodynamic favorability as well as the contribution from cage cell, which resulted in an energy landscape far more conducive to Cs+ incorporation for NaY than either NaX or Na-HY.