Development of metakaolin-based geopolymer for selenium oxyanions uptake through in-situ ettringite formation
Development of metakaolin-based geopolymer for selenium oxyanions uptake through in-situ ettringite formation
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DOI：
10.1016/j.seppur.2023.124530
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发表时间：
2023-07
影响因子：
8.6
通讯作者：
Xiaobo Niu;Y. Elakneswaran;Raudhatul Islam Chaerun;Chuwei Fang;N. Hiroyoshi;John L. Provis;Tsutomu Sato
中科院分区：
文献类型：
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作者：
Xiaobo Niu;Y. Elakneswaran;Raudhatul Islam Chaerun;Chuwei Fang;N. Hiroyoshi;John L. Provis;Tsutomu Sato
研究表明，偏高岭土基地质聚合物具有吸收阳离子放射性核素（如Cs+和Sr 2+）的显著能力。然而，缺乏对阴离子放射性核素的吸收能力代表了改进利用这种材料用于核废物处置应用的潜在途径。此外，钙矾石作为在碱性环境（例如水泥水合）中形成的阴离子交换剂的普遍性在本领域中被广泛认可。然而，没有先前的研究已经进行，以探索在开发用于阳离子和阴离子放射性核素的综合掺入方法中利用基于偏高岭土的地质聚合物和钙矾石两者的有利品质。在这项研究中，提出了组合物和一套制备条件，以修改偏高岭土为基础的地质聚合物，导致在原位形成钙矾石，其目的是提高其吸收能力的硒含氧阴离子。通过共沉淀实验、结合分析和结构分析，提出了钙矾石和原位生成钙矾石的地聚合物的吸附行为和机理。结果表明，钙矾石可以通过共沉淀的方式吸附SeO 32-和SeO 42-，但其吸附作用仅限于SeO 32-，其吸附机理取决于Se含氧阴离子的浓度。另一方面，改性的地质聚合物与原位钙矾石保留其能力，吸收阳离子放射性核素，如Cs+和Sr 2+，同时发展到表现出吸收SeO 32-的能力。根据离子交换机理进行了热力学模拟，有效地预测了低浓度下SeO 32-的吸收。所提出的组合物和制备条件具有开发阳离子和阴离子放射性核素的有效掺入过程的潜力。本研究的结果增强了对硒含氧阴离子的吸收行为的理解，并提供了对偏高岭土基地质聚合物固定阴离子的潜力的深入了解。
Studies have demonstrated the remarkable capacity of metakaolin-based geopolymers for the uptake of cationic radionuclides, such as Cs+and Sr2+. However, the lack of uptake ability towards anionic radionuclides represents a potential avenue for improvement in utilising this material for nuclear waste disposal applications. Additionally, the prevalence of ettringite as an anion exchange agent formed in alkaline environments, such as cement hydration, is widely acknowledged in the field. However, no previous studies have been conducted to explore the utilisation of the advantageous qualities of both metakaolin-based geopolymer and ettringite in developing a comprehensive incorporation process for both cationic and anionic radionuclides. In this study, compositions and sets of preparation conditions were proposed to modify metakaolin-based geopolymer, resulting in the in-situ formation of ettringite, with the aim of enhancing its uptake capabilities for selenium oxyanions. The uptake behaviour and mechanism of ettringite, and geopolymer with in-situ ettringite, were proposed through co-precipitation experiments, binding and structural analysis. The results reveal that the ettringite can uptake SeO32-and SeO42-through co-precipitation; however, its effectiveness is limited to SeO32-in the uptake process, where the mechanism is contingent on the concentration of Se oxyanions present. On the other hand, modified geopolymer with in-situ ettringite retained its capacity to uptake cationic radionuclides such as Cs+and Sr2+while evolving to exhibit an ability to uptake SeO32-. Thermodynamic modelling was carried out according to the ion exchange mechanism, which effectively predicts the uptake of SeO32-at low concentrations. The proposed composition and preparation conditions hold the potential for developing an effective incorporation process for cationic and anionic radionuclides. The outcomes of this research enhance the understanding of the uptake behaviour of Se oxyanions by ettringite and provide insight into the potential of metakaolin-based geopolymers to immobilise anions.