Processing of radioactive waste solution with zeolites, (1). Thermal transformation of Na, Cs and Sr type zeolites

Thermal transformation of Na, Cs and Sr type zeolites were studied by means of differential thermal analysis (DTA), thermogravimetric analysis (TGA) and X-ray powder diffraction. Synthetic zeolites A, X and Y, synthetic mordenite (Zeolon) and natural mordenite were used in this study. Na type zeolites of A and X recrystallized to Nepheline (NaAlSiO₄) above 1,000℃, but the structures of zeolite Y and mordenite collapsed above about 900℃ and did not recrystallize until 1,200℃. Cs type zeolites of A and X recrystallized to pollucite (CsAlSi₂O₆) above 1,000℃ and Cs type of zeolite Y recrystallized to it above 1,100℃, but the structure of mordenite collapsed above 1,000℃ and did not recrystallize until 1,200℃. On Sr type zeolites, zeolite A and X recrystallized to strontium aluminosilicate (SrAl₂Si₂O₈) above 1,100℃ and zeolite Y recrystallized to it above 1,200℃, but the structure of mordenite collapsed above 1,000℃. The results described above were supported by microscopic observation and the measurement of density. If this solidifications by calcination of zeolites are further studied, new informations concerning the fixation of Cs and Sr will be obtained. (auth.)