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Retention mechanism of cesium in chabazite embedded into metakaolin-based alkali activated materials
Title: | Retention mechanism of cesium in chabazite embedded into metakaolin-based alkali activated materials |
Authors: | Chaerun, Raudhatul Islam Browse this author | Soonthornwiphat, Natatsawas Browse this author | Toda, Kanako Browse this author | Kuroda, Kazuma Browse this author | Niu, Xiaobo Browse this author | Kikuchi, Ryosuke Browse this author →KAKEN DB | Otake, Tsubasa Browse this author →KAKEN DB | Elakneswaran, Yogarajah Browse this author | Provis, John L. Browse this author | Sato, Tsutomu Browse this author →KAKEN DB |
Keywords: | K-based AAM | Pollucite | Chabazite | TEM | FE-EPMA Raman | spectroscopy |
Issue Date: | 15-Oct-2022 |
Publisher: | Elsevier |
Journal Title: | Journal of hazardous materials |
Volume: | 440 |
Start Page: | 129732 |
Publisher DOI: | 10.1016/j.jhazmat.2022.129732 |
Abstract: | Disposal of cesium-137 (Cs-137)-loaded chabazite generated from decontaminating cooling water of the damaged reactor at the Fukushima Daiichi Nuclear Power Station (FDNPS) has become a crucial concern. The potassium aluminosilicate-based alkali activated material (K-AAM) matrix is one of the candidate encapsulation matrices proposed for encapsulating cesium-137. In this study, chabazite loaded with a low Cs concentration (1 mg/g of Cs), embedded into a K-AAM matrix (K-AAM-C), was analysed to determine its capability to immobilise Cs, which was investigated by batch leaching experiments, field emission-electron probe microscopy analysis (FE-EPMA), X-ray diffraction (XRD), transmission electron microscopy (TEM), and Raman spectroscopy. The leaching experiments revealed that K-AAM-C efficiently immobilised Cs, with only 3 % of the Cs leached out after 360 days of leaching in deionised water. Characterisation using XRD, TEM, and Raman analysis confirmed that the alkali-activator was responsible for the phase transformation of chabazite. FE-EPMA demonstrated that K entered the chabazite structure. This phenomenon resulted in the breakdown and subsequent reconstruction of the chabazite structure. TEM observation showed that the Cs was concentrated into the aggregates of pre-cipitates, heterogeneously forming a pollucite-like structure in the chabazite after the fabrication process. Thermodynamic calculations indicated that pollucite was preferably stable in an AAM environment. When immersed in water, the amount of nano-pollucite increased over time, leading to the structural re-arrangement of aluminosilicate rings of chabazite according to TEM and Raman analysis. Pollucite is well known as a Cs-bearing natural zeolite, which can encapsulate Cs in its structure. Therefore, Cs retention was achieved in the spent chabazite adsorbent embedded into the K-AAM due to the resultant pollucite structure formed during AAM fabrication. |
Type: | article |
URI: | http://hdl.handle.net/2115/87024 |
Appears in Collections: | 工学院・工学研究院 (Graduate School of Engineering / Faculty of Engineering) > 雑誌発表論文等 (Peer-reviewed Journal Articles, etc)
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