Adsorption structures and bonding states of cesium and barium adsorbed on various sites of vermiculite

Yamaguchi, Akiko; Okumura, Masahiko; Kawamura, Naomi*; Takahashi, Yoshio*

Science of the Total Environment, 964, p.178585_1 - 178585_13, 2025/02

https://doi.org/10.1016/j.scitotenv.2025.178585

There are many unresolved issues in the adsorption reactions of clay minerals. One of the reasons is the existence of multiple adsorption sites. It is known that the contribution of each adsorption site depends on the concentration of adsorbed ions, and there is a challenge in comprehensively correlate the results of atomic-level simulations that employ limited number of atoms and inevitably deal high-concentration samples with actual environmental samples where concentrations are orders of magnitude lower. In this study, we combined experiments using synchrotron radiation and first-principles calculations to comprehensively elucidate the systematic changes in the local structure of adsorption sites and adsorbed ions based on the adsorption concentration at the atomic level, and demonstrated that the interaction between adsorbed ions and clay minerals involves ionic bonding.

Interpretation of vertical migration and enrichment processes of rare earth elements (REEs) in ion-adsorption-type mineralization in Japan based on REE speciation analyses

Nagasawa, Makoto*; Shimizu, Yusuke*; Yamaguchi, Akiko; Tokunaga, Kohei; Mukai, Hiroki*; Aoyagi, Noboru; Mei, H.; Takahashi, Yoshio*

Chemical Geology, 670, p.122431_1 - 122431_25, 2024/12

https://doi.org/10.1016/j.chemgeo.2024.122431

Characterization of mineral composition using PIXE and EXAFS analyses to elucidate the Barium adsorption mechanism

Oguri, Kaori; Hagura, Naoto*; Yamaguchi, Akiko; Okumura, Masahiko; Matsuura, Haruaki*; Tsunashima, Yasumichi; Aoki, Katsumi; Arai, Yoichi; Watanabe, So

Nuclear Instruments and Methods in Physics Research B, 556, p.165516_1 - 165516_8, 2024/11

https://doi.org/10.1016/j.nimb.2024.165516

Ningyo-toge is the uranium mine that has been operated in Japan. Various radioactive elements such as Uranium (U), and Radium (Ra) are still present in the mine ground water with very small amount, and behavior of those elements is not fully understood. In this study, we investigated the composition of metal oxides and clay minerals in a soil of slag deposit at the mine, and systematics of adsorption structure of various ions were examined. Identifying the composition and chemical forms of minerals present in the soil of slag can provide useful information for the safety assessment and evaluation of influence on the surrounding environment.

Microbially formed Mn(IV) oxide as a novel adsorbent for removal of Radium

Tanaka, Kazuya; Yamaji, Keiko*; Masuya, Hayato*; Tomita, Jumpei; Ozawa, Mayumi*; Yamasaki, Shinya*; Tokunaga, Kohei; Fukuyama, Kenjin*; Ohara, Yoshiyuki*; Maamoun, I.*; et al.

Chemosphere, 355, p.141837_1 - 141837_11, 2024/05

https://doi.org/10.1016/j.chemosphere.2024.141837

In this study, biogenic Mn(IV) oxide was applied to remove Ra from mine water collected from a U mill tailings pond in the Ningyo-toge center. Just 7.6 mg of biogenic Mn(IV) oxide removed more than 98% of the Ra from 3 L of mine water, corresponding to a distribution coefficient of 10 mL/g for Ra at pH 7. The obtained value was convincingly high for practical application of biogenic Mn(IV) oxide in water treatment.

The First observation of hydrated radium at the molecular level

Yamaguchi, Akiko; Okumura, Masahiko; Takahashi, Yoshio*

Isotope News, (789), p.20 - 23, 2023/10

https://www.jrias.or.jp/pdf/2310_TRACER_YAMAGUCHI_HOKA.pdf

Radium is a radioactive element produced from uranium and thorium and is important for environmental contamination issues around uranium mines and for geological disposal. In addition, radium is used in radiometric dating and cancer therapy, making it important not only in environmental chemistry but also in many other fields, including geochemistry and nuclear medicine. However, because radium is a radioactive element with no stable isotopes, spectroscopic measurement of radium is difficult, and little information at the molecular level has been obtained so far. In this study, we have clarified the molecular-level information of hydrated radium for the first time in the world by combining extended X-ray absorption fine structure (EXAFS) measurements and first-principles molecular dynamics simulations.

Investigation of environmental behavior of multiple ions based on systematic understanding of adsorption reaction on clay minerals

Yamaguchi, Akiko

Hosha Kagaku, (48), p.56 - 59, 2023/09

http://www.radiochem.org/pdf/rad_nw48.pdf

The adsorption reaction on clay minerals is an important chemical reaction that controls the environmental behaviors of various ions at the Earth's surface, but the details are unknown due to the complexity of the reaction, such as the diversity of clay mineral compositions and the existence of multiple adsorption sites. In this study, we focused on the adsorption structure on clay minerals at the atomic level, and clarified it in detail by combining X-ray absorption fine structure (XAFS) methods and first-principles calculations. In particular, XAFS measurements of radium, which has the largest ionic radius among alkaline earth metals and has been difficult to measure at the atomic level, were successfully performed, and new knowledge was obtained by comparing the results with those of other elements.

High-sensitive XANES analysis at Ce L-edge for Ce in bauxites using transition-edge sensors; Implications for Ti-rich geological samples

Li, W.*; Yamada, Shinya*; Hashimoto, Tadashi; Okumura, Takuma*; Hayakawa, Ryota*; Nitta, Kiyofumi*; Sekizawa, Oki*; Suga, Hiroki*; Uruga, Tomoya*; Ichinohe, Yuto*; et al.

Analytica Chimica Acta, 1240, p.340755_1 - 340755_9, 2023/02

https://doi.org/10.1016/j.aca.2022.340755

no abstracts in English

Extended X-ray absorption fine structure spectroscopy measurements and molecular dynamics simulations reveal the hydration structure of the radium(II) ion

Yamaguchi, Akiko; Nagata, Kojiro*; Kobayashi, Keita; Tanaka, Kazuya; Kobayashi, Toru; Tanida, Hajime; Shimojo, Kojiro; Sekiguchi, Tetsuhiro; Kaneta, Yui; Matsuda, Shohei; et al.

iScience (Internet), 25(8), p.104763_1 - 104763_12, 2022/08

https://doi.org/10.1016/j.isci.2022.104763

no abstracts in English

Hydration structures of barium ions; molecular dynamics simulations using the SCAN meta-GGA density functional and EXAFS spectroscopy studies

Yamaguchi, Akiko; Kobayashi, Keita; Takahashi, Yoshio*; Machida, Masahiko; Okumura, Masahiko

Chemical Physics Letters, 780, p.138945_1 - 138945_5, 2021/10

https://doi.org/10.1016/j.cplett.2021.138945

no abstracts in English

Thermally altered subsurface material of asteroid (162173) Ryugu

Kitazato, Kohei*; Milliken, R. E.*; Iwata, Takahiro*; Abe, Masanao*; Otake, Makiko*; Matsuura, Shuji*; Takagi, Yasuhiko*; Nakamura, Tomoki*; Hiroi, Takahiro*; Matsuoka, Moe*; et al.

Nature Astronomy (Internet), 5(3), p.246 - 250, 2021/03

https://doi.org/10.1038/s41550-020-01271-2

Here we report observations of Ryugu's subsurface material by the Near-Infrared Spectrometer (NIRS3) on the Hayabusa2 spacecraft. Reflectance spectra of excavated material exhibit a hydroxyl (OH) absorption feature that is slightly stronger and peak-shifted compared with that observed for the surface, indicating that space weathering and/or radiative heating have caused subtle spectral changes in the uppermost surface. However, the strength and shape of the OH feature still suggests that the subsurface material experienced heating above 300 C, similar to the surface. In contrast, thermophysical modeling indicates that radiative heating does not increase the temperature above 200 C at the estimated excavation depth of 1 m, even if the semimajor axis is reduced to 0.344 au. This supports the hypothesis that primary thermal alteration occurred due to radiogenic and/or impact heating on Ryugu's parent body.