Geochemical analyses on long-term performance of engineered barrier

工程屏障长期性能的地球化学分析

• 批准号: 09308013
• 负责人: SUZUKI Atsuyuki
• 金额: $ 12.54万
• 依托单位: THE UNIVERSITY OF TOKYO
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (A).
• 财政年份: 1997
• 资助国家: 日本
• 起止时间: 1997 至 2000
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-09308013/
• 关键词: engineered barrier; Bentonite; sorption; Smectite; Neptunium; hydrotalcite; 収着; ヨウ青酸イオン; ヨウ素酸イオン; 吸着; 遂次脱離; 人口バリア; 核種移行

For the improvement of safety assessment of radioactive waste disposal, it is important to install the material that has high capacity to sorb IO_3^-. Hydrotalcite-like compound, of which CO_3^<2->, NO_3^- or Cl^- etc. is contained in its interlayer, is considered to be a potential clay mineral for sorbing IO_3^-. In the present study, we studied the sorption behavior of IO_3^- to CO_3^<2->-hydrotalcite (HTCO_3) that contains CO_3^- as interlayer anion and NO_3^--hydrotalcite (HTNO_3) that contains NO_3^- as interlayer anion in order to understand the difference of the sorption mechanism of IO_3^- to the different type of hydrotalcite. It was found that the time to reach sorption equilibrium was shorter for HTCO_3 than that for HTNO_3, that the sorption isotherm for HTCO_3 consisted of two Langmiur type sorption processes but that for HTNO_3 consisted of one, and that the desorption behavior was quite different each other. These results suggest that the sorption of IO_3^- is occurred weakly on the external surface of HTCO_3 and includes two mechanisms of sorption. On the other hand, the sorption of IO_3^- to HTNO_3 is occurred in its interlayer by the anion exchange reaction. Furthermore, the sorption mechanisms of IO_3^- to HTCO_3 and HTNO_3 were also discussed from DTA/TG and Powder-XRD measurement.

为了提高放射性废物处置的安全性评价，安装高吸收率的材料是很重要的。类水滑石化合物，其夹层中含有CO_3^<2->、NO_3^-或Cl^-等，被认为是一种潜在的吸附IO_3^-的粘土矿物。本文研究了以CO_3^-为层间阴离子的CO_3^<2->-水滑石（HTCO_3）和以NO_3^-为层间阴离子的NO_3^-水滑石（HTNO_3）对IO_3^-的吸附行为，以了解IO_3^-对不同类型水滑石吸附机理的差异。HTCO_3比HTNO_3达到吸附平衡的时间短，HTCO_3的吸附等温线由两个Langmiur型吸附过程组成，HTNO_3的吸附等温线由一个Langmiur型吸附过程组成，两者的解吸行为差异较大。这些结果表明，HTCO_3的外表面对IO_3^-的吸附是微弱的，并包含两种吸附机制。另一方面，通过阴离子交换反应，IO_3^-吸附在HTNO_3的中间层中。此外，还从DTA/TG和粉末xrd测试等方面探讨了IO_3^-对HTCO_3和HTNO_3的吸附机理。

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