Evaluation of thermodynamic model of Pd(II) complex formation with isosaccharinic acid

Kimuro, Shingo; Taneichi, Yayoi; Iwata, Hajime; Ishidera, Takamitsu; Kitamura, Akira; Tachi, Yukio; Tanaka, Takeru*; Hirano, Kana*; Hieda, Manami*; Miyabe, Shunsuke*; et al.

Journal of Solution Chemistry, 53(6), p.854 - 868, 2024/06

https://doi.org/10.1007/s10953-023-01352-6

Iron-induced association between selenium and humic substances in groundwater from deep sedimentary formations

Terashima, Motoki; Endo, Takashi*; Kimuro, Shingo; Beppu, Hikari*; Nemoto, Kazuaki*; Amano, Yuki

Journal of Nuclear Science and Technology, 60(4), p.374 - 384, 2023/04

https://doi.org/10.1080/00223131.2022.2111376

Thermodynamic study of the complexation of humic acid by calorimetry

Kimuro, Shingo; Kirishima, Akira*; Kitatsuji, Yoshihiro; Miyakawa, Kazuya; Akiyama, Daisuke*; Sato, Nobuaki*

Journal of Chemical Thermodynamics, 132, p.352 - 362, 2019/05

https://doi.org/10.1016/j.jct.2019.01.011

A combination of potentiometry and calorimetry was used for the determination of the thermodynamic quantities of complexation of generic and groundwater humic acid (HA), which was isolated from deep groundwater at Horonobe, Hokkaido, Japan, with copper (II) ions and uranyl (VI) ions. The apparent complexation constant of Horonobe HA was independent of the pH, whereas that of generic HA was dependent on the pH. This observation indicates that the polyelectrolyte effect of Horonobe HA is negligible because of its small molecular size. In addition, the effect of the heterogeneity of Horonobe HA was not significant. Moreover, the complexation enthalpy of Horonobe HA was consistent with that of homogeneous poly(acrylic acid), which means the complexation of Horonobe HA was not affected by the functional group heterogeneity. Consequently, the characteristic complexation mechanism of Horonobe HA was revealed based on the determined thermodynamic quantities.

Interaction of rare earth elements and components of the Horonobe deep groundwater

Kirishima, Akira*; Kuno, Atsushi*; Amamiya, Hiroki; Kubota, Takumi*; Kimuro, Shingo*; Amano, Yuki; Miyakawa, Kazuya; Iwatsuki, Teruki; Mizuno, Takashi; Sasaki, Takayuki*; et al.

Chemosphere, 168, p.798 - 806, 2017/02

https://doi.org/10.1016/j.chemosphere.2016.10.133

For better understanding of the migration behavior of minor actinides (MA) in deep groundwater, the interaction of doped rare earth elements (REEs) and components in Horonobe deep groundwater was studied. Appx. 10 ppb of rare earth elements, i.e., Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Er, Tm and Yb were doped to the sample groundwater collected from a packed sections in borehole drilled from 140 m depth experiment drift of Horonobe underground research laboratory (URL), Hokkaido, Japan. Then, that groundwater was sequentially filtrated by 0.2 micron pore filter, 10 kDa, 3 kDa and 1 kDa of nominal molecular weight limit (NMWL) ultrafilters by keeping inert condition. After that, the filtrate solutions were analyzed by ICP-MS to determine the concentrations of retained REEs at each filtration steps, while the used filters were analyzed by the neutron activation analysis (NAA) and TOF-SIMS element mapping to know the amount and chemical speciation of trapped fraction of the REEs on each filter. A remarkable relation between the retention ratios of REEs in the filtrate solutions and the ionic radius was observed, i.e., smaller rare earth element solves more in liquid phase under the Horonobe groundwater condition. NAA and TOF-SIMS analyses revealed that certain portions of REEs were trapped by 0.2 micron pore filters as rare earth phosphates which corresponded with the predicted predominant species by a chemical equilibrium calculation for the Horonobe groundwater condition, while small portions of colloidal REEs were trapped by 10 kDa and 3 kDa NMWL ultrafilters. The result suggested that phosphate anion plays an important role in the chemical behavior of REEs in saline (seawater based) groundwater, which could be referred for the prediction of migration behavior of trivalent actinide released from the repository of radioactive waste in far future.

Assessment of the effect of organic materials for the solubility of technetium(IV)

Kimuro, Shingo; Iwata, Hajime; Eguchi, Ayano; Nishikawa, Yoshiaki*; Tachi, Yukio

no journal, , 

no abstracts in English

Characterization and thermodynamic study of the protonation of humic acid dissolved in deep groundwater at Horonobe, Hokkaido, Japan

Kimuro, Shingo*; Kirishima, Akira*; Akiyama, Daisuke*; Sato, Nobuaki*; Nagao, Seiya*; Saito, Takumi*; Amano, Yuki; Miyakawa, Kazuya

no journal, , 

In this study, size exclusion chromatography (SEC), flow-field flow fractionation (Fl-FFF) and calorimetry were applied to the humic acid isolated from the groundwater collected at 350m below the ground level at the Horonobe Underground Research Laboratory, JAEA. First, the characteristic molecular weight distribution of Horonobe humic acids were observed from the SEC analysis. Second, the small hydrodynamic diameter of Horonobe humic acids were observed by the Fl-FFF. Finally, the protonation enthalpies of Horonobe humic acids were determined by the combination of potentiometry and calorimetry. The values of protonation enthalpy of Horonobe humic acids were close to simple organic acids (i.e., benzoic acid and phenol). It was suggested that Horonobe humic acids have lower molecular weight than IHSS surface soil humic acids (Elliot Soil and Waskish Peat) and the simple protonation mechanism, which is not affected by the heterogeneity.

Characterization and determination of thermodynamic quantities of humic acid dissolved in deep groundwater at Horonobe, Hokkaido, Japan, 2

Kimuro, Shingo*; Kirishima, Akira*; Akiyama, Daisuke*; Sato, Nobuaki*; Nagao, Seiya*; Amano, Yuki; Miyakawa, Kazuya; Terashima, Motoki

no journal, , 

no abstracts in English

The Effect of carbonate ion on the dissolution of UO pellet

Moroi, Yuriko*; Kirishima, Akira*; Akiyama, Daisuke*; Sato, Nobuaki*; Kitamura, Akira; Kimuro, Shingo

no journal, , 

Direct disposal of spent nuclear fuel is considered as an alternative option of geological disposal of high level radioactive wastes. In this case, the dissolution speed of uranium should be one of the most important parameter. In this study, the dissolution behavior of UO in the simulated groundwater contains high concentration of carbonate ion was investigated, then, it was revealed that uranium dissolution was promoted by the carbonate ion.

The Effect of carbonate ion for the leaching of uranium dioxide

Moroi, Yuriko*; Kirishima, Akira*; Akiyama, Daisuke*; Sato, Nobuaki*; Kitamura, Akira; Kimuro, Shingo

no journal, , 

The technical investigations of direct disposal of spent nuclear fuel are necessary for the progress of back-end strategy, which was affected by the severe accident of Fukushima No.1 Nuclear Power Plant. In this study, the effect of carbonate ion for the leaching of uranium dioxide, which is the main component of spent nuclear fuel, was tested by the batch experiment. The leaching tests carried out in Ar gas atmosphere in glove box and sodium dithionite was used as reductant to simulate the deep underground environment. As a result, the leaching of uranium dioxide was clearly promoted by the carbonate ion. In addition, the dissolution rate of uranium also increased with the concentration of carbonate ion.

Thermodynamic study of complexation of deep groundwater humic acid by calorimetry

Kimuro, Shingo; Terashima, Motoki; Tachi, Yukio; Kitatsuji, Yoshihiro; Miyakawa, Kazuya; Akiyama, Daisuke*; Sato, Nobuaki*; Kirishima, Akira*

no journal, , 

Humic acid is confirmed to be present even in deep underground where radioactive wastes are planned to be disposed. Although the characteristic properties and reaction mechanism of humic acid are strongly affected by its origin, the reaction enthalpy and entropy for groundwater humic acid complexation are only estimated values obtained from the equilibrium constants at different temperature despite these thermodynamic quantities is necessary for the discussion of reaction thermodynamics. In this study, the thermodynamic quantities of the complexation of deep groundwater humic acid at Horonobe, Hokkaido, Japan with copper (II) and uranyl (VI) ion were determined by the combination of the potentiometry and calorimetry to cultivate a better understanding of the reaction mechanism. By the comparison of thermodynamic quantities with typical humic acid and simple organic acid, the characteristic reaction mechanism of Horonobe humic acid was revealed. In addition, thermodynamic equilibrium calculations based on the determined thermodynamic quantities were performed for the discussion of the impact of humic acid complexation and the origin of humic acid in the migration of radionuclide.