Safe trapping of cesium into pollucite structure by hot-pressing method

• Published in: Journal of nuclear materials 2016-06, Vol.474, p.35-44
• Main Authors: Omerašević, Mia, Matović, Ljiljana, Ružić, Jovana, Golubović, Željko, Jovanović, Uroš, Mentus, Slavko, Dondur, Vera
• Format: Article
• Language: English
• Subjects: Cs disposal; Heat treatment; Hot pressing; Ion exchange; Leaching; Leaching tests; LTA zeolite; Micrographs; Nuclear engineering; Photomicrographs; Pollucite; Sintering; Zeolites
• ISSN: 0022-3115; 1873-4820
• DOI: 10.1016/j.jnucmat.2016.03.006

A simple one-step method with direct thermal conversion at lower temperatures for preparing a stabile Cs-aluminsilicate phase, known as pollucite, is presented. Cs-exchanged form of Na, Ca-LTA type of zeolite (Cs-LTA) was pressureless sintered and hot pressed at certain temperatures in order to obtain pollucite. XRD and FTIR analysis were used to study structural changes of Cs-LTA before and after thermal treatments. Pressureless sintered sample recrystallized into pollucite phase after heat treatment at 1000 °C (3 h) (PLS1000) and hot pressed sample at 750 °C (3 h) using pressure of 35 MPa (HP750), indicating reduced temperature of 250°. SEM micrographs confirmed that HP750 has higher density than PLS1000 which leads to higher value of compressive strength. The HP750 showed better resistance to Cs leaching than the PLS1000. Base on these results one can conclude that hot pressing is the promising method for the permanent disposal of Cs radionuclides. [Display omitted] •Na, Ca-LTA zeolite showed high affinity for Cs ions.•Pollucite phase was obtained using hot pressing at temperature as low as ​750 °C.•HP750 shows better mechanical and morphological properties than PLS1000.•HP750 has lower leaching rate of Cs ions than PLS1000.