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and Eu
ions onto sedimentary rock in the presence of gamma-irradiated humic acidZhao, Q.*; Saito, Takeshi*; Miyakawa, Kazuya; Sasamoto, Hiroshi; Kobayashi, Taishi*; Sasaki, Takayuki*
Journal of Hazardous Materials, 428, p.128211_1 - 128211_10, 2022/04
Times Cited Count：5 Percentile：62.11(Engineering, Environmental)The influence of humic acid and its radiological degradation on the sorption of Cs and Eu by sedimentary rock was investigated to understand the sorption process of metal ions and humic substances. Aldrich humic acid (HA) solution was irradiated with different doses of gamma irradiation using a Co-60 gamma-ray source prior to the contact between the metal ions and the solid sorbent. The HA molecule decomposed to smaller molecules with a lower complexation affinity. Batch sorption experiments were performed to evaluate the effect of gamma-irradiated HA on the sorption of Cs and Eu ions. The addition of non-irradiated HA weakened the sorption of Eu because of the lower sorption of the neutral or negatively charged Eu-HA complexes compared with free Eu ions. The sorption of monovalent Cs ions was barely affected by the presence of HA and its gamma irradiation. The concentration ratio of HA complexed species and non-complexed species in the solid and liquid phases was evaluated by sequential filtration and chemical equilibrium calculations. The ratios supported the minimal contribution of HA to Cs sorption. However, the concentration ratio for Eu in the liquid phase was high, indicating that the complexing ability of HA to Eu was higher than that of HA to Cs ions. Therefore, the sorption of free Eu would predominate with the gamma irradiation dose applied to the HA solution under a radiation field near the HLW package.
and Tb measured by gel electrophoresis techniquesNakano, Sumika*; Marumo, Kazuki*; Kazami, Rintaro*; Saito, Takumi*; Haraga, Tomoko; Tasaki-Handa, Yuiko*; Saito, Shingo*
Environmental Science & Technology, 55(22), p.15172 - 15180, 2021/11
Times Cited Count：5 Percentile：35.21(Engineering, Environmental)Humic acid (HA) can strongly complex with metal ions to form a supramolecular assembly via coordination binding. However, determining the supramolecular size distribution and stoichiometry between small HA unit molecules constituting HA supramolecule and metal ions has proven to be challenging. Here, we investigated the changes in the size distributions of HAs induced by Cu and Tb ions using a unique polyacrylamide gel electrophoresis (PAGE) for the separation and quantification of HA complexes and metal ions bound, followed by UV-Vis spectroscopy and EEM-PARAFAC. It was found that the supramolecular behaviors of Cu and Tb complexes with HA collected from peat and deep groundwater (HHA) differed. Our results suggest that this supramolecular stoichiometry is related to the abundance of sulfur atoms in the elemental composition of HHA. Our results provide new insights into HA supramolecules formed via metal complexation.
Nagao, Seiya*; Fujitake, Nobuhide*; Kodama, Hideki*; Matsunaga, Takeshi; Yamazawa, Hiromi
Journal of Radioanalytical and Nuclear Chemistry, 255(3), p.459 - 464, 2003/03
Times Cited Count：8 Percentile：49.89(Chemistry, Analytical)no abstracts in English
Tanaka, Tadao; Nagao, Seiya; Sakamoto, Yoshiaki; Ogawa, Hiromichi
Journal of Nuclear Science and Technology, 39(Suppl.3), p.524 - 527, 2002/11
Influence of humic acid on the sorption of Pu onto a coastal sand, which does not sorb humic acid, and an ando soil, which sorbs humic acid very well, was examined with respect to molecular sizes of humic acid. Sorption affinity of Pu for the coastal sand decreased with increasing humic acid concentration. As to the ando soil, the sorption affinity of Pu in the presence of humic acid was larger than that in the absence of humic acid, in low humic acid concentration range. These results suggest that apparent sorption affinity of Pu on the soils is dependent on the complexation ability with humic acid and the sorption affinity of the resulting humic complexes. Concentration profiles of Pu in each size fraction of solution before and after the sorption experiment were obtained by ultrafiltration technique. It was found that the complexation and sorption properties of humic acid are dependent on its molecular size and the important molecular size relating to the complexation and sorption properties tends to shift into smaller size ranges with increasing humic acid concentration.
Tanaka, Tadao; Nagao, Seiya; Ogawa, Hiromichi
Analytical Sciences (CD-ROM), 17(Suppl.), p.1081 - 1084, 2002/03
Structural information of humic acid dissolving in aqueous solution has been studied by ATR-FTIR spectroscopy. Two types of humic acid fractions were prepared: one is dominated by aliphatic structure and another is dominated with aromatic structure. The functional groups of both fractions have been characterized with respect to their ATR-FTIR spectral structures (ATR spectra) measured in pH range of 2 - 10. The ATR spectra were compared with the infrared spectra of the freeze-dried humic acid fractions, which were obtained using transmission Fourier transform infrared spectroscopy with KBr pellet (KBr spectra) and using diffuse reflectance infrared Fourier transform spectroscopy (DRS spectra). In a comparison between spectra obtained from the three infrared spectroscopic methods, the major absorptions of the ATR spectra for both fractions are in well agreement with those of the KBr spectra and the DRS spectra, each other. These show that the functional groups of the humic acid dissolving in aqueous solution could characterize by using the ATR-FTIR spectroscopy.
Nagao, Seiya; Tanaka, Tadao; Nakaguchi, Yuzuru*; Suzuki, Yasuhiro*; Muraoka, Susumu; Hiraki, Keizo*
Understanding and Maraging Organic Matter in Soils, Sediments and Waters, p.525 - 532, 2001/00
no abstracts in English
Nagao, Seiya; Nakaguchi, Yuzuru*; Fujitake, Nobuhide*; Ogawa, Hiromichi
Proceedings of 10th International Meeting of the International Humic Substances Society (IHSS10), p.1143 - 1146, 2000/07
no abstracts in English
Nagao, Seiya;
Humic Substances and Organic Matter in soil and Water Environments: Characterization,Transformations, 0, p.71 - 79, 1996/00
no abstracts in English
Nagao, Seiya; Tanaka, Tadao; Sakamoto, Yoshiaki;
Radiochimica Acta, 74, p.245 - 249, 1996/00
no abstracts in English
Nagao, Seiya
Hoshasei Haikibutsu Kenkyu, 1(2), p.231 - 242, 1995/05
no abstracts in English
Nagao, Seiya*;
Science of the Total Environment, 117-118, p.439 - 447, 1992/00
no abstracts in English
; ;
Water Res., 20(7), p.885 - 891, 1986/00
Times Cited Count：31 Percentile：82.08(Engineering, Environmental)no abstracts in English
; ; ;
JAERI-M 83-149, 50 Pages, 1983/09
no abstracts in English
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.
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.
