One-step immobilization of cesium and strontium from alkaline solutions via a facile hydrothermal route

• Published in: Journal of nuclear materials Vol. 510; pp. 243 - 255
• Main Authors: Vereshchagina, Tatiana A., Kutikhina, Ekaterina A., Chernykh, Yana Yu, Solovyov, Leonid A., Zhizhaev, Anatoly M., Vereshchagin, Sergei N., Anshits, Alexander G.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01-11-2018; Elsevier BV
• Subjects: Alkalinity; Aluminum oxide; Aluminum strontium alloys; Analcime; Cenospheres; Cesium; Cesium oxides; Crystallization; Fly ash; Glass; Hydrothermal synthesis; Hydrothermal treatment; Immobilization; Mathematical morphology; Microspheres; Pollucite; Radioactive waste; Radioactive wastes; Silicates; Silicon dioxide; Sodium hydroxide; Solid solutions; Strontium; Topology; Cenospheres; Radioactive waste; Hydrothermal synthesis; Pollucite; Analcime
• ISSN: 0022-3115; 1873-4820
• DOI: 10.1016/j.jnucmat.2018.08.015

Hydrothermal treatment of coal fly ash cenospheres (Si/Al = 2.7) as a glassy source of Si and Al was carried out in 1.5 M NaOH at 150 °C in the presence of Cs+ and Sr2+ to study the possibility of Cs+ and Sr2+ immobilization in mineral-like compounds. Systems Na2O-H2O-(SiO2-Al2O3)glass, Na2O-Cs2O-H2O-(SiO2-Al2O3)glass with Cs+/Na+ ratios of 0.05 and 0.5, and Na2O-SrO-H2O-(SiO2-Al2O3)glass with Sr2+/Na+ ratios of 0.25 and 0.025 were under study. Structure, composition and morphology of solid products were characterized by PXRD, SEM-EDS and STA methods. In the Cs+/Sr2+ free systems the deep crystallization of cenosphere glass takes place resulting in hollow polycrystalline analcime microspheres. Microsphere solids including phases of ANA topology (analcime, pollucite or analcime-pollucite solid solutions) and Cs+/Sr2+ silicates are produced as Cs+ and Sr2+ immobilized forms in the Cs+/Sr2+ bearing systems. The degree of Cs+ and Sr2+ recovery from alkaline solutions was 90–99%.
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•Analcime-pollucite solid solutions crystallize as host phases immobilizing Cs+.•Cs+ and Sr2+ were immobilized by hydrothermal treatment of coal fly ash cenospheres.•Sequestration of Cs and Sr from alkaline solutions was 90–99%.