Fixation of Caesium, Strontium and Thorium Ions in Commercial Synthetic Zeolite Matrices by Thermal Treatment.

Abstract

Synthetic zeolites AR-1 (a mordenite), 4A and 13X, all in their Na-forms, have been found to be suitable for the uptake of Cs, Sr and Th ions, respectively. Samples of Cs-loaded AR-1, Sr-loaded 4A and Th-loaded 13X were prepared and heated in a furnace to various temperatures (up to 1,200°C), for fixing the exchanged ions in the host zeolite matrix. X-ray diffraction patterns of the products indicated that the crystallinity of Cs-AR-1 and Sr-4A was intact till 500°C, partially lost between 500°C and 1,000°C, and improved again at 1,200°C. For Th-13X, the crystallinity was gradually lost after 500°C. Thermogravimetric-differential scanning calorimetrie (TG-DSC) studies indicated the occurrence of phase transformations at around 890–1,020°C, for Na-4A, Sr-4A, Na-13X and Th-13X. For Na-AR-1 and Cs-AR-1, no clear inference of change of phase could be drawn. Above 1,300°C, all the zeolites converted to a glassy mass. Desorption studies in vigorously stirred liquid media, viz. demineralized (DM) water, 10mMNaNO...