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Sasaki, Yuji; Kaneko, Masashi; Ban, Yasutoshi; Suzuki, Hideya*
Journal of Nuclear Science and Technology, 11 Pages, 2023/11
Times Cited Count：0 Percentile：0.01(Nuclear Science & Technology)The mutual separation of Am and Cm is conducted using an alkyl-diamide amine (ADAAM) extractant. ADAAM exhibits extremely high separation factor with respect to Am and Cm separation (5.9) in a nitric acid-
-dodecane system. The batch-wise multistage extractions are performed using a system containing 0.2 M ADAAM and 1.5 M nitric acid. In this multistage extraction, an organic solvent give 96.5% and 1.06% yields of Am and Cm. After the mutual separation of Am and Cm, an additional extraction step is included to reduce the volumes of these aqueous and organic phases. Taking these steps, Am and Cm can be recovered in just two or three stages in the aqueous phases.
Sasaki, Yuji; Kaneko, Masashi; Ban, Yasutoshi; Kinoshita, Ryoma; Matsumiya, Masahiko*; Shinoku, Kota*; Shiroishi, Hidenobu*
Analytical Sciences, 39(9), p.1575 - 1583, 2023/09
Times Cited Count：0 Percentile：0(Chemistry, Analytical)Extraction of Rh from HCl can be performed by NTAamide(C6) (hexahexyl-nitrilotriacetamide) and other related compounds into n-dodecane. We use ion-pair extraction of anionic species of Rh-chloride and protonated extractant. Rh behave as anion in hydrochloric acid and the tertiary nitrogen atom in extractant may be protonated to produce the quaternary amine in acidic condition. From the present work, the maximum distribution ratio of Rh(III) is 16. The D(Rh) values are changeable during preparation of the aqueous solutions because different Rh-Cl-H
O complexes are formed in HCl media and show the slow exchange rate between Cl and HO. Using the UV spectrum, Rh-chloride solution having the peak of spectrum at 504 nm can be extracted effectively, where RhCl
(HO)
and RhCl
(H
O)
exist mainly from DFT calculation. Stoichiometry of one-one complex of Rh and NTAamide is obtained from slope analysis, and 85 mM of concentrated Rh ion can be extracted.
Sasaki, Yuji; Nakase, Masahiko*; Kaneko, Masashi; Kobayashi, Toru; Takeshita, Kenji*; Matsumiya, Masahiko*
Analytical Sciences, 5 Pages, 2023/00
Times Cited Count：0 Percentile：0(Chemistry, Analytical)We conducted three field researches on Ru-extraction, XANES, and DFT-calculation. The order of the distribution ratio, D(Ru), from acid, HCl 
HSO
HNO
HClO, by MIDOA is studied by XANES spectra, which indicates the valency change of Ru in HCl media and supports the ion pairing extraction of anionic Ru ion and cationic MIDOA. The same extractant trend, NTAamide MIDOA IDOA, due to D values as the energy gap of HOMO and LUMO could be found by DFT calculation, which suggests that the reaction heat has a positive correlation with extractability for extractant.
Sasaki, Yuji
Bunri Gijutsu, 52(2), p.103 - 107, 2022/03
We develop all-inclusive partitioning method for actinides and fission products in high-level radioactive waste. This process is based on the sequential solvent extraction. In order to recover Cs and Sr for the management by interim storage, crown ether compounds are employed. For the removal of Pd and Mo due to production of a stable vitrified object, methylimino-dioctylacetamide (MIDOA) is taken as an extractant. DGA can extract both actinides and trivalent lanthanides. In order to separate each other, dietylenetriamine-triacetic-diamide (DTBA) for the stripping reagent of MA. For the mutual separation of Am/Cm, DGA and DOODA extraction system is taken into consideration.
Nomizu, Daiki; Sasaki, Yuji; Kaneko, Masashi; Matsumiya, Masahiko*; Katsuta, Shoichi*
Journal of Radioanalytical and Nuclear Chemistry, 331(3), p.1483 - 1493, 2022/03
Times Cited Count：4 Percentile：68.71(Chemistry, Analytical)We studied the successive formation of water soluble DGA (diglycolamide) and DOODA (dioxaoctanediamide) for the mutual separation of Ln in this extraction system. TODGA (tetraoctyl-diglycolamide) and DOODA(C8) (tetraoctyl-dioxaoctanediamide) have the opposite trend to extract light and heavy Ln through Ln-patterns. Metal-complexes of two folding Ln ions with water-soluble DOODA and three folding with DGA are found and their observed formation constants are calculated. The suitable separation condition (aqueous phase: 30 mM DOODA(C2) in 1 M nitric acid, organic phase: 0.1 M TODGA in n-dodecane) of multi-stage extraction (10 
10) is conducted. From the present work, it is clear that La, Pr and Nd are mainly present in aqueous phase, instead Sm-Dy exist in the organic phase.
Sasaki, Yuji; Kaneko, Masashi; Ban, Yasutoshi; Matsumiya, Masahiko*; Nakase, Masahiko*; Takeshita, Kenji*
Separation Science and Technology, 57(16), p.2543 - 2553, 2022/00
Times Cited Count：3 Percentile：29.84(Chemistry, Multidisciplinary)The mutual separation of actinides (An) from lanthanides (Ln) using the masking agent of DTPA (diethylenetriamine-pentaacetic acid) or DTBA (diethylenetriamine-triacetic acid-bis(diethylacetamide)) in the aqueous phase through DGA extraction, referring TALSPEAK method, is focused. We investigate to obtain the same separation performance using commercially available DTPA on that using DTBA. In this work, we select lactic acid (LA) of pH buffer from 10 organic acids and ethylenediamine (ED) for the pH adjustment. Almost the same D and SF values are obtained among the conditions: TODGA-DTPA-LA-NaOH, TODGA-DTPA-LA-ED, and TODGA-DTBA-LA. The experimental results using batchwise multi-stage extractions show the average yields of Ln (La to Gd) and Am to be 3.73 and 98.1% in the aqueous phase using DGA-DTPA-LA-ED, to be 3.1 and 97.0% using DGA-DTPA-LA-NaOH, and to be 1.61 and 98.7% using DGA-DTBA-LA.
Sasaki, Yuji; Kaneko, Masashi; Matsumiya, Masahiko*; Nakase, Masahiko*; Takeshita, Kenji*
Solvent Extraction and Ion Exchange, 40(6), p.620 - 640, 2022/00
Times Cited Count：1 Percentile：14.86(Chemistry, Multidisciplinary)Owing to the chemical behavior of trivalent lanthanide and actinide ions with similar ionic radii, realizing this separation is still challenging. All lanthanides, Am, and Cm can be extracted using diglycolamide (DGA), and relatively high An/Ln separation efficiencies have been obtained using diethylenetriamine-triacetic-bisamide (DTBA). To improve the previous results as well as the separation conditions, we used organic acids for pH adjustment. The advantages of this modification included low HNO
, DTBA concentrations and pH stability owing to the addition of lactic acid. Under these modified conditions, the recovery rates observed were as follows: 97.1% for Nd with the co-existence of 1.59% Am in organic phase, and 98.4% for Am with the co-existence of 2.95% Nd in aqueous phase.
Matsutani, Takafumi; Sasaki, Yuji; Katsuta, Shoichi*
Analytical Sciences, 37(11), p.1603 - 1609, 2021/11
Times Cited Count：7 Percentile：48.15(Chemistry, Analytical)We investigated the chemical behavior of lanthanides (Ln) using diglycolamide extractant with multistage extraction. We obtained the breakthrough curves for light and middle Ln. Our study reveals that the metal extraction limit depends on their 
values and metal concentrations used in the experiments. From the multistage extractions of 15 aqueous phases and 15 organic phases, three curves (extraction curves, back-extraction curves, and separation curves) were obtained by changing the nitric acid concentration. As an example, under a condition of the separation curve experiment (aqueous phase: 0.5 M HNO, organic phase: 0.1 M TDDGA (
-tetradecyl-diglycolamide) in -dodecane), a recovery of more than 99% of Sm in the organic phase with less than 1% Nd can be obtained.
Kaneko, Masashi; Sasaki, Yuji; Wada, Eriko*; Nakase, Masahiko*; Takeshita, Kenji*
Chemistry Letters, 50(10), p.1765 - 1769, 2021/10
Times Cited Count：0 Percentile：0(Chemistry, Multidisciplinary)Density functional theory calculation is applied to predict the stability constants for Eu
and Am complexes in aqueous solution for molecular modelling of novel separation agents for minor actinides over lanthanides. Logarithm of experimental stability constants correlates with calculated complex formation enthalpies with high reproducibility (R
0.98). Prediction of stability constants of novel chelates is demonstrated and indicates a potential availability of the derivatives of diethylenetriaminepentaacetic acid type chelate in acidic condition and enhancement of Am selectivity over Eu.
/Eu selectivity with diethylenetriaminepentaacetic acid and its bisamide chelates.Kaneko, Masashi; Sasaki, Yuji; Matsumiya, Masahiko*; Nakase, Masahiko*; Takeshita, Kenji*
Journal of Nuclear Science and Technology, 58(5), p.515 - 526, 2021/05
Times Cited Count：3 Percentile：35.51(Nuclear Science & Technology)Density-functional theory calculations were applied to molecular structure and complex formation reaction modelings of metal ion complexes with diethylenetriaminepentaacetic acid (DTPA) and its bisamide (DTPABA) chelates to understand the metal ions selectivity between Am and Eu. The calculated complexes with DTPA and DTPABA chelates reproduced the coordination geometries of experimental crystal structures. Calculated Gibbs free energies of the complex formation reactions indicated that Am ion forms higher stable complexes with both chelates than Eu ion, being consistent with the experimental results. The higher Am selectivity over Eu was suggested to originate in the larger bond overlap between Am 5f-orbital and N 2s, 2p-orbital. This mean that the covalent contribution between metal ion and donor atoms differentiates the complex formation stabilities, leading to the Am/Eu selectivity. We expect that this study contributes to systematize the origin of metal ions selectivity and to accelerate novel ligands exploration.
Sasaki, Yuji; Morita, Keisuke; Matsumiya, Masahiko*; Ono, Ryoma*; Shiroishi, Hidenobu*
JOM, 73(4), p.1037 - 1043, 2021/04
Times Cited Count：4 Percentile：34.69(Materials Science, Multidisciplinary)The separation of Dy from Nd is studied from the viewpoint of recycling Dy from Nd magnets. Both metals are lanthanide elements, which means their mutual separation is difficult because of their similar chemical behaviors. All lanthanide elements can be extracted easily by using tetradodecyl-diglycolamide (TDdDGA) extractants, and it has a relatively high separation factor (SF) between Dy and Nd (SF over 10). In the present study, by performing eight extraction steps with the organic phase (0.1M TDdDGA in dodecane), ten steps with an aqueous phase (0.7 M HNO with metals), and six steps with another aqueous phase (0.7 M HNO without metals), approximately 99% Dy was recovered into the organic phase with 1% co-extraction of Nd.
Matsumiya, Masahiko*; Nomizu, Daiki*; Tsuchida, Yusuke*; Sasaki, Yuji
Hydrometallurgy, 199, p.105539_1 - 105539_8, 2021/02
Times Cited Count：4 Percentile：33.99(Metallurgy & Metallurgical Engineering)The synergistic solvent extraction of lanthanide(III) with mixtures of di-(2-ethylhexyl)phosphoric acid (D2EHPA, A) and monoisodecyl phosphoric acid (MIDPA, B) in phosphonium-based ionic liquid was investigated. In the case of D2EHPA or MIDPA single extractant system, Ln(III) (Ln = Pr and Nd) was extracted as [LnAHA] or [LnBHB], respectively, the extracted species of Tb(III) or Dy(III) were determined by slope analysis. According to the equilibrium constants (
, 
and 
) and the formation constants (
, and 
), it was found that the extracted complex [TbHAB or [DyHAB] was more stable than [LnAHA] or [LnBHB]. The synergistic extraction effects were investigated to study the possibility of separating Dy(III) from Pr(III) and Nd(III) according to their separation factors.
Matsumiya, Masahiko*; Tsuchida, Yusuke*; Sasaki, Yuji; Ono, Ryoma*; Nakase, Masahiko*; Takeshita, Kenji*
Journal of Radioanalytical and Nuclear Chemistry, 327(1), p.597 - 607, 2021/01
Times Cited Count：2 Percentile：24.28(Chemistry, Analytical)To achieve trichotomic separation of light lanthanides (Ln), heavy Ln, and Am, batchwise multi-stage extractions using tetraoctyl-diglycolamide (TODGA) extractant from organic acids are studied. Malonic acid (MA) has high solubility in water and is used as the main component of the aqueous phase. It is clear that the separation factor (SF) for Nd/Am from MA and that for La/Am from MA + HNO are both around 30. The light Ln (e.g., La and Ce) flowed-out in 1 M MA+0.05 M HNO (1st soln.), Am is recovered into 3 M MA (2nd soln.), and middle and heavy Ln (Nd and other heavy Ln) are back-extracted into 0.1 M TEDGA/water (3rd soln.). This extraction method can give 95% recovery of Am with total Ln of less than 16% present in high-level radioactive waste.
Sasaki, Yuji; Morita, Keisuke; Kitatsuji, Yoshihiro; Ito, Keisuke*; Yoshizuka, Kazuharu*
Solvent Extraction Research and Development, Japan, 28(2), p.121 - 131, 2021/00
Times Cited Count：2 Percentile：14.88(Chemistry, Multidisciplinary)High concentration of Cs is present in high-level radioactive waste. It is well-known that Cs is an alkali element and difficult to extract completely into an organic phase. Crown ether compounds are widely available for Cs extractants; DtBuDB18C6 (di-
-butyl-dibenzo-18crown6), was used in this study. Organic solvents used for the industrial applications, such as -dodecane and 1-octanol, have low solubility concerning the compound; other solvents were employed and tested. In this study, ketone-, ether-, and ester-type solvents showed high solubility for DtBuDB18C6 and DtBuDB18C6, when dissolved in ketones and alcohols, exhibited relatively high Cs distribution ratios ((Cs)), closely to 10.
-diketone extractant and a neutral ligandMatsumiya, Masahiko*; Nomizu, Daiki*; Tsuchida, Yusuke*; Sasaki, Yuji
Solvent Extraction and Ion Exchange, 39(7), p.764 - 784, 2021/00
Times Cited Count：3 Percentile：22.95(Chemistry, Multidisciplinary)We investigated the solvent extraction of four rare earth (RE) elements (Pr, Nd, Tb, and Dy) from Nd-Fe-B magnets using mixtures of 1-(2-thienyl)-4,4,4,-trifluoro-1,3-butanedione (Htta) or 4,4,4-trifluoro-1-phenyl-1,3-butanedione (Hbfa) chelating extractants and tri-n-octylphosphine oxide (TOPO) neutral ligand in phosphonium based ionic liquids. A synergistic effect was observed for the extraction of the RE elements with the combination of extractant and neutral ligand. The separation of Tb(III) and Dy(III) from other RE(III) components was performed with seven extraction cycles.
Sasaki, Yuji; Matsumiya, Masahiko*; Tsuchida, Yusuke*
Analytical Sciences, 36(11), p.1303 - 1309, 2020/11
Times Cited Count：4 Percentile：16.26(Chemistry, Analytical)The mutual separation of lanthanides is studied by multi-stage extraction using extractant, DGA (diglycolamide) compounds. Tetraoctyl-DGA (TODGA) has a high extractability to lanthanides and relatively high separation factor (SF) between Dy and Nd (SF: over 20). The complete separation with such SF value can be achieved by multi-stage extraction. Less information on multi-stage extraction compared to batch extraction is presented up to now, thus we conduct the basic study about that. Confirming the experimental data to be identical to the calculation, the sample solution including both metals is employed for the batchwise multi-stage extraction. Ninety-seven % of Dy with under detection limit of Nd can be recovered into the organic phase from Nd with ten times higher concentration than Dy using the condition, 0.1 M TODGA/n-dodecane and 0.3 M HNO by multi-stage extraction of 99 for organic and aqueous phases.
Sasaki, Yuji; Nakase, Masahiko*
Petorotekku, 43(11), p.782 - 787, 2020/11
As analog compounds of DGA (diglycolamide), MIDOA(methylimino-diacetamide) and TDGA(thia-diglycolammide) are used for the extractants of platinum group metals. These extractants can be extracted noble metals and oxyanions, which followed by HSAB theory. The high concentration of these metals can be also extracted by these compounds. The research of metal-complex structures gives the information on the ability and role for complex-formation, which will be useful for the development of novel extractants.
-tetraoctyl-diglycolamide from organic acidSasaki, Yuji; Matsumiya, Masahiko*; Nakase, Masahiko*; Takeshita, Kenji*
Chemistry Letters, 49(10), p.1216 - 1219, 2020/10
Times Cited Count：9 Percentile：45.29(Chemistry, Multidisciplinary)Lanthanide (Ln) extractions from organic acids to -dodecane by -tetraoctyl-diglycolamide (TODGA) were conducted. Four organic acids (lactic acid, malonic acid, tartaric acid, and citric acid) were employed. Although these acids stabilize lanthanides in the aqueous phase, a distribution ratio () greater 1 was obtained for heavy Ln. Ln patterns ((Ln) against atomic number of Ln) show maximum values of Ho and Er. In order to obtain high values, the addition of HNO in aqueous phase is found to be effective.
Sasaki, Yuji
Kagaku Kogaku, 84(9), p.425 - 427, 2020/09
The reduction of waste volume and hazardous substance though separation methods concerning atomic energy must be requested. As disposal methods or temporary measures, geological disposal, transmutation and interim storage are proposed. In order to perform effectively the disposal methods, the development of separation method of aimed elements is indispensable. Here, the new separation method of U and Pu from spent nuclear fuel and minor actinide separation and fission products from high level radioactive waste are explained.
systemSasaki, Yuji; Morita, Keisuke; Matsumiya, Masahiko*; Nakase, Masahiko*
Radiochimica Acta, 108(9), p.689 - 699, 2020/09
Times Cited Count：9 Percentile：75.92(Chemistry, Inorganic & Nuclear)The simultaneous separation of Am and Cm from lanthanides is important for atomic energy fields. All lanthanides, Am, and Cm can be extracted by diglycolamide (DGA). In addition, relatively high separation factors between An and Ln were obtained by the extraction system of TODGA, DTPA (diethylenetriamine-pentaacetic acid) and HNO. In this work, DTPA-BA (diethylenetriamine-triacetic-bisamide), which is an improved version of DTPA, was employed for the separation of Ln and An. A relatively high separation factor (approximately 8) for actinides/lanthanides was obtained. Then, the multi-step extraction was performed. Thus, the recoveries of 94.7% for Nd and 4.7% for Am and Cm in organic phase, and 5.3% Nd and 95.3% for Am and Cm in aqueous phase were obtained.
