Szilard-Chalmers recoil of rare-earth cations in zeolite Y

Abstract

Szilard—Chalmers recoils of the cations La 3+, Ce 3+, Tb 3+, Yb 3+ and Lu 3+ located in the supercage sites of zeolite Y have been determined. On irradiation with thermal neutrons ∼90% of the recoiling cations are still to be found in the supercage sites. This figure of 90% has been shown to be independent of the character and concentration of the cation in the zeolite. The free volume theory has been shown, once again, to hold. The Szilard—Chalmers recoil of the above ions from the sodalite cage and hexagonal prism sites into the supercage sites of zeolite Y has also been studied. The target cation was exchanged into the zeolite at room temperature, fixed into the small cavities by calcination and then the zeolite eluted with NH 4Cl solution at 25°C to remove rare-earth cations from the supercage sites before irradiation in a nuclear reactor. When the target cations are La 3+, Tb 3+, Yb 3+, and Lu 3+ recoil from the sodalite cages and hexagonal prism sites into the supercage sites occurs with a probability which decreases from ∼70% to ∼60% on increasing the calcination temperature from 100° to 720°C. Cerium, however, recoiled from these sites with an 80% probability at all calcination temperatures between 100° and 500°C. An attempt has been made to place the cations among sites I and I′ as a function of calcination temperature.