Hydrothermal reactions of zeolites loaded with cesium or s trontium

Cesium-loaded zeolites of low Si/Al atomic ratios such as CsA, CsX and CsY were converted to pollucite ((Cs, Na) A1Si₂O₆) by hydrothermal treatment above 243°C, but Cs-mordenite of a high Si/Al ratio yielded no structural change owing to its high thermal stability. The structural degradation of zeolite and recrystallization to other minerals much depended on the treating temperature and time; CsA was completely converted into pollucite at 300°C for 2 h and at 243°C for 24 h. The hydrothermal treatment of zeolites A and X partially replaced Na with Cs resulted in the formation of solid solutions occluding pollucite in analcime (NaAlSi₂O₆·H₂O). As for Sr-loaded zeolites, Sr-feldspar (SrA1₂Si₂O₈) crystallized from SrA or SrX under mild conditions (150°C, 1 d) compared with those for Cs-loaded zeolites.