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Retention mechanism of cesium in chabazite embedded into metakaolin-based alkali activated materials

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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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