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Journal Articles

Desorption of cesium from Fukushima soils using a mechanochemical method

Kaneta, Yui; Kobayashi, Toru; Tsuji, Takuya; Honda, Mitsunori; Yokoyama, Keiichi; Mampuku, Yuzo*; Yaita, Tsuyoshi*

Clays and Clay Minerals, 73, p.e26_1 - e26_8, 2025/04

https://doi.org/10.1017/cmn.2025.9

The desorption behavior of stable Cs adsorbed onto weathered biotite (WB), a clay mineral abundant in Fukushima soils, was investigated using a mechanochemical (MC) method that combines physical grinding by ball impact with a wet process promoting chemical reactions. The results, oxalic acid desorbed Cs to some extent without significantly affecting the layered structure of the clay minerals; ammonium chloride, showed an exfoliation of the layer structure, resulting in a stable desorption of Cs independent of samples. Regarding the real soil samples collected in Fukushima, the MC method using ammonium chloride solution desorbed 80% of $^{137}$ Cs. In contrast, oxalic acid did not always result in radioactive Cs made sufficiently desorbed for all the samples. Based on these findings, the MC method with ammonium chloride effectively promotes radioactive Cs desorption from interlayers due to synergistic effects from the layered structure's exfoliation and chemical interaction.

Journal Articles

Effect of interlayer cations on montmorillonite swelling; Comparison between molecular dynamic simulations and experiments

Yotsuji, Kenji*; Tachi, Yukio; Sakuma, Hiroshi*; Kawamura, Katsuyuki*

Applied Clay Science, 204, p.106034_1 - 106034_13, 2021/04

https://doi.org/10.1016/j.clay.2021.106034

Times Cited Count：107 Percentile：99.77(Chemistry, Physical)

Journal Articles

Stability of montmorillonite edge faces studied using first-principles calculations

Sakuma, Hiroshi*; Tachi, Yukio; Yotsuji, Kenji; Suehara, Shigeru*; Arima, Tatsumi*; Fujii, Naoki*; Kawamura, Katsuyuki*; Honda, Akira

Clays and Clay Minerals, 65(4), p.252 - 272, 2017/08

https://doi.org/10.1346/CCMN.2017.064062

Times Cited Count：3 Percentile：17.97(Chemistry, Physical)

Structure and stability of montmorillonite edge faces (110), (010), (100), and (130) of the layer charges y = 0.5 and 0.33 are investigated by the first-principles electronic calculations based on the density functional theory. Stacking and single layer models are tested for understanding the effect of stacking on the stability of montmorillonite edge faces. Most stacking layers stabilize the edge faces by making hydrogen bonds between the layers; therefore, the surface energy of stacking layers is reduced rather than the single layer model. This indicates that the surface energy of edge faces should be estimated depending on the swelling conditions. Lowest surface energies of (010) and (130) edge faces were realized by the presence of Mg ions on the edge faces. These edge faces have a strong adsorption site for cations due to local negative charge of the edges.

Journal Articles

First principles molecular dynamics study of interlayer water and cations in vermiculite

Ikeda, Takashi

Clay Science, 18(2), p.23 - 31, 2014/06

https://doi.org/10.11362/jcssjclayscience.18.2_23

To clarify possible origins of irreversible adsorption exhibited by cesium on clay minerals, we performed FPMD simulations for vermiculite including water molecules along with Mg $^{2+}$ , K $^{+}$ , and Cs $^{+}$ in its interlayers. Our close examination on the structural and dynamical properties of interlayer water included together with the cations shows that Mg $^{2+}$ and Cs $^{+}$ form respectively outer- and inner-sphere surface complexes in the interlayers, while K $^{+}$ forms both types. The structure of electric double layers formed in the interlayers is found to depend significantly on the type of surface complexes of interlayer cations. The reorientational motions of H $_{2}$ O are suggested to be enhanced by Cs $^{+}$ in contrast to a minor influence of Mg $^{2+}$ and K $^{+}$ . Our observed enhanced diffusion of interlayer H $_{2}$ O along with their rapid reorientation indicates that Cs $^{+}$ ions work as structure-breaking ions even in confined 2-dimensional interlayers.