Distribution and fixation of cesium and strontium in zeolite a and chabazite

The selective removal and fixation of Cs and Sr have been studied in zeolite A and chabazite. Cesium ion was preferentially distributed into chabazite with a high distribution coefficient (K_CS>10³ cm³ g^–1) in the presence of NaCl (10^–1 mol dm^–3). The K_Sr values for zeolite A attained about 10³ cm³ g^–1 in the pH range of 8˜10, and they gradually decreased with an decrease in pH. The initial rate of Cs adsorption was fairly fast in chabazite, and the adsorption ratio reached almost 100% within a few hours. The adsorption ratio of Sr in binderless A zeolite reached almost 100% after 15 h. The adsorption of Cs and Sr on these zeolites was followed by Langmuir-type isotherm. Cesium forms of these zeolites recrystallized to pollucite (CsAISi₂O₆) above 900°C for zeolite A and above 1,200°C for chabazite. As for Sr forms, these zeolites changed to SrAl₂Si₂O₈ above 900°C. These recrystallized phases were suitable hosts for the immobilization of Cs and Sr in the nuclear waste solutions.