Retention Mechanism of Cesium in Chabazite Embedded into Metakaolin-Based Alkali Activated Materials
Retention Mechanism of Cesium in Chabazite Embedded into Metakaolin-Based Alkali Activated Materials
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DOI：
10.1016/j.jhazmat.2022.129732
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发表时间：
2022-08
影响因子：
13.6
通讯作者：
Raudhatul Islam Chaerun;N. Soonthornwiphat;K. Toda;K. Kuroda;Xiaobo Niu;Ryosuke Kikuchi;T. Otake
中科院分区：
文献类型：
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作者：
Raudhatul Islam Chaerun;N. Soonthornwiphat;K. Toda;K. Kuroda;Xiaobo Niu;Ryosuke Kikuchi;T. Otake
福岛第一核电站（FDNPS）受损反应堆的净化冷却水产生的含铯-137 （Cs-137）的chahabazite的处理已经成为一个关键问题。钾铝硅酸盐基碱活化材料（K-AAM）基体是铯-137包封的候选包封基质之一。在本研究中，通过批浸实验、场发射电子探针显微镜分析（FE-EPMA）、x射线衍射（XRD）、透射电子显微镜（TEM）和拉曼光谱研究了装载低Cs浓度（1 mg/g Cs）的chaabuite嵌入K-AAM基质（K-AAM- c），以确定其固定Cs的能力。浸出实验表明，K-AAM-C有效地固定了碳，在去离子水中浸出360天后，只有3%的碳被浸出。通过XRD、TEM和拉曼分析，证实了碱活化剂是导致霞辉石相变的原因。FE-EPMA分析表明，钾元素进入了茶巴石结构。这一现象导致了茶巴石构造的破裂和随后的重建。TEM观察表明，Cs在制备过程中被集中到沉淀的聚集体中，在恰巴石中不均匀地形成了一种类似污染石的结构。热力学计算表明，污染石在AAM环境中具有较好的稳定性。当纳米污染石浸泡在水中时，随着时间的推移，纳米污染石的含量增加，TEM和拉曼分析显示，这导致了茶巴石铝硅酸盐环的结构重排。Pollucite是一种天然的含碳沸石，它可以在其结构中包裹碳。因此，由于在AAM制造过程中形成的污染石结构，在嵌入K-AAM中的废钙辉石吸附剂中实现了Cs的保留。
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 precipitates, 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.