11:00 AM - 1:00 PM
[HCG24-P07] Sorption/desorption behavior of Eu(Ⅲ) onto clay minerals
Keywords:Clay minerals, Eu(Ⅲ), ICP-MS, FIB-TEM, EPMA, Geological disposal of high-level radioactive waste
In the geological disposal of high-level radioactive waste, various radionuclides are possibly eluted into groundwater and further move to the environment near the surface of the earth on a long-term scale of more than thousands of years. However, researches on actinide-series radionuclides with a long half-life such as Am-241 (433 years), Am-243 (7370 years) and Np-237 (2.14 million years) have been relatively limited. In the environment, clay minerals have an excellent adsorption capacity and largely influence on the behavior of cations. For instance, bentonite, which is mainly composed of montmorillonite, will be used for the geological disposal and expected to play a role in delaying the leakage of radionuclides. Thus, in order to understand the behavior of the actinide series radionuclides in the environment, this study has been conducted to clarify the adsorption/desorption behavior onto various clay minerals.
Various clay minerals such as biotite, kaolinite, montmorillonite, and hydrobiotite were prepared for the adsorption/desorption experiments using Eu, which is considered to be an analog of Am. In the adsorption experiments, the concentrations of Eu and the pH were changed from 10-3 to 10-7 M and from 3 to 9, respectively. The adsorption experiments indicated that the Eu adsorption ratios tended to increase with increasing pH in the clays. On the other hand, the desorption experiments (pH 5.2) suggested that Eu was particularly strongly fixed in biotite and hydrobiotite. Furthermore, for the particles of biotite and hydrobiotite absorbing Eu (10-3 M, pH 5.2), the elemental mappings were measured by EPMA. The elemental mappings showed that Eu was well concentrated around the edges of the particles, and Eu also penetrated between the layers of the hydrobiotite particle.
This work was supported by the Ministry of Economy, Trade and Industry (METI) of Japan.
Various clay minerals such as biotite, kaolinite, montmorillonite, and hydrobiotite were prepared for the adsorption/desorption experiments using Eu, which is considered to be an analog of Am. In the adsorption experiments, the concentrations of Eu and the pH were changed from 10-3 to 10-7 M and from 3 to 9, respectively. The adsorption experiments indicated that the Eu adsorption ratios tended to increase with increasing pH in the clays. On the other hand, the desorption experiments (pH 5.2) suggested that Eu was particularly strongly fixed in biotite and hydrobiotite. Furthermore, for the particles of biotite and hydrobiotite absorbing Eu (10-3 M, pH 5.2), the elemental mappings were measured by EPMA. The elemental mappings showed that Eu was well concentrated around the edges of the particles, and Eu also penetrated between the layers of the hydrobiotite particle.
This work was supported by the Ministry of Economy, Trade and Industry (METI) of Japan.