Kazushige Nishizawa

Synergistic ion-pair extraction of lanthanide(III) with thenoyltrifluoroacetone and crown ether into 1,2-dichloroethane

ABSTRACT Synergistic extraction of trivalent lanthanides(Ln) was investigated using thenoyltrifluoroacetone(HTTA) and crown ether(CE). Characteristic ion-pair extraction of the lighter Ln(III) was observed with 1,2-dichloroethane containing HTTA and 18-crown-6 or dicychlohexano-18-crown-6, in which the cationic complex, Ln(TTA)2CE+, was formed and extracted. Remarkable increases of an extractability and a selectivity were attained in the synergistic ion-pair extraction of the lighter Ln ions, which could be elucidated on the basis of size-fitting effect in the complex formation of the lighter Ln ions with CE.

Strontium Isotope Effect in Liquid-Liquid Extraction of Strontium Chloride Using a Crown Ether

Isotope effects in a liquid-liquid extraction of strontium with dicyclohexano-18-crown-6 (DC18C6) were investigated. Unit mass enrichment factors were observed to increase with concentrations of strontium salt in an aqueous phase. Isotope distinguishing ability of DC18C6 to strontium isotopes was calculated as an intrinsic separation factor to be K c =1.00051±0.00004. An odd mass number isotope, 87Sr, was recognized to behave differently from even mass number isotopes, 84Sr, 86Sr and 88Sr. The enrichment factor induced by a nuclear property (odd or even mass number) other than the mass difference was eO/E = −8.0 × 10−4 which was observed with 3.2M Sr aqueous solution. Isotope shift of energy state for 5S-orbital of strontium produces the isotope shift in vibrational energy between the strontium ion and the DC18C6.

Extractive Behavior of Magnesium Chloride and Isotopic Enrichment of Magnesium by a Crown Ether

Abstract Magnesium chloride was extracted into an organic phase including dicyclohex-ano-18-crown-6 (DC18C6). The partition coefficient showed its highest value for a liquid-liquid extraction system of 3.5 M MgCl2 aqueous phase. Magnesium isotopes 24Mg, 25Mg, and 26Mg were enriched in the system with their respective enrichment factors. The enrichment factor for 24Mg/26Mg was e = 0.0112 as a maximum value. The enrichment factors for a unit difference of mass numbers varied depending on the MgCl2 concentrations in the aqueous phase. The isotope-recognizing ability of DC18C6 was K c - 1.0016, which is smaller than the separation factor due to an exchange of the aqua/dichloro complex of Mg2+, K p - 1.0040. An odd/even isotope effect was observed, and it was assigned to nuclear properties other than mass difference. Odd/even staggering associated with the optical transition of electrons offers a consistent explanation to the different behaviors of isotopes with odd or even mass numbers.

Extractive Separation of Lithium Isotopes by Crown Ethers

Abstract Separative abilities of crown ethers to lithium isotopes were investigated for the number of oxygen atoms composing crown rings and for the substituted groups to 15-crown-5. The separation factors at 0°C were 1.057 for 12-crown-4, 1.042 for benzo-15-crown-5, 1.041 for lauryloxymethyl-15-crown-5, 1.043 for tolyloxymethyl-15-crown-5, and 1.024 for dicyclohexano-18-crown-6. The enthalpy change of the isotopic equilibrium in the absolute value was the greatest for 12-crown-4; ΔH° = −0.78 kJ/mol. In the substituted 15-crown-5s the separation factor was greatest for tolyloxymethyl-15-crown-5, and ΔH° values decreased in the order: benzo- > tolyloxymethyl- > lauryloxymethyl-15-crown-5. For enthalpy changes, benzo-15-crown-5 has the possibility of giving a larger separation factor than the present one, α = 1.042, by choosing more suitable conditions. In spite of its large distribution coefficient, dicyclohexano-18-crown-6 is not superior for isotopic separation of lithium in regard to the small enthalpy ...

Zinc isotope effects in complex formation with a crown ether

Abstract Isotope effects for zinc upon complex formation with dicyclohexano-18-crown-6 were investigated. The single stage separation factor for unit mass difference (α = 1.013) was great compared with that of calcium isotopes. One of the isotopes, 67Zn, showed a larger isotope effect than the other isotopes of even mass number.

Separation of Zinc Isotopes by Liquid-Liquid Extraction Using a Crown Ether

Abstract The zinc isotope effect in a liquid-liquid extraction system using dicyclohexano-18-crown-6 was investigated. The enrichment factor for a unit difference of mass number was ∊u = 0.018 as a maximum, which is greater than that for magnesium isotopes. The enrichment factor to eliminate 64Zn from 66Zn, 67Zn, 68Zn, or 70Zn is over 0.036. The isotope with an odd mass number, 67Zn, behaved differently from those with even mass numbers. This odd/even isotope effect was ∊O/E = 0.056. From the values of ∊u and ∊O/E, it was found that the crown ether separated the zinc isotopes more effectively on the basis of an odd or an even mass number than of mass difference. The separation factors vary with the concentrations of salt and/or conjugated acid in the initial aqueous phases of extraction. The optimal concentration necessary to obtain the largest separation factor had components of 2.0 M ZnCl2 and 1.0 M HCl. The large value of ∊u for the high atomic number zinc and the notable ∊O/E make it clear that the vi...

Contributions of Nuclear Size and Shape, Nuclear Mass, and Nuclear Spin to Enrichment Factors of Zinc Isotopes in a Chemical Exchange Reaction by a Cryptand

ABSTRACT The isotope effect of zinc in the chemical exchange reaction using a macrocyclic ligand was not found to be ruled by the Bigeleisen-Mayer approximation, which suggested that the enrichment factor is proportional to the mass difference and is inversely proportional to the product of the masses of the isotopes. The separation factors of zinc isotopes in the chemical exchange reaction using cryptand(2B,2,l) polymer were precisely measured by means of an ICP mass spectrometer equipped with nine collectors as ion detectors. The liquid chromatography of a column packed with the cryptand polymer was used for the separation of the zinc isotopes. The enrichment factor e67,66 for 67Zn to 66Zn was −3.3329(3) × l0−4.That for 68Zn to 66Zn was 1.846(1) × 10 −4 and that for 70Zn to 68Zn was 7.19(2) × 10−4.They were not scaled with δm/mm′, where δm is the mass difference between the isotope pairs, and m and m′ represent the masses of the isotopes. The isotope effect of zinc is implicated with the isotope shift, ...

Extractive Separation of Lithium Isotopes Using Benzo-15-Crown-5. Effect of Salt Concentration

Abstract In an extractive separation of lithium isotopes with benzo-15-crown-5, the greater separation factor is obtained from more concentrated LiCl solution. The intrinsic separation factor of benzo-15-crown-5 is determined to be α = 1.045 at 20°C.

SEPARATION OF SAMARIUM ISOTOPES BY A CROWN ETHER

ABSTRACT Samarium isotopes were fractionated in a liquid-liquid extraction system using dicychlohexano-18-crown-6. High precision isotope ratio measurements with a multicollector mass spectrometer made it possible to evaluate the contributions of the nuclear size and shape and the nuclear spin to the chemical isotope separation effect. The maximum value of the unit mass enrichment factor (ϵu was observed to be 0.00161 ± 0.00002. The odd/even enrichment factor of 147Sm was ϵO/E = −0.00101 ± 0.00062 and that of 149Sm was ϵO/E = −0.00049 ± 0.00050. Enrichment factors were affected by nuclear mass, nuclear volume and nuclear spin in addition to vibrational motion of molecule. The nuclear volume effect was 1.94 times as large as the nuclear mass effect. The odd/even atomic mass effect was explained with 6s2-6s6p transition in optical isotope shift of Sm I. The correction due to the nuclear spin of 147Sm was ϵspin; = −0.0016 and that of 149Sm was ϵspin; = −0.0014.

NUCLEAR SIZE AND SHAPE EFFECT IN CHEMICAL ISOTOPE EFFECT OF GADOLINIUM USING DICYCLOHEXANO-18-CROWN-6

ABSTRACT Gadolinium isotopes were fractionated in a liquid-liquid extraction system using dicyclohexano-18-crown-6. The isotope enrichment factors showed breakdowns of the conventional Bigeleisen-Mayer approximation for every condition of the initial phases; the concentrations of gadolinium and hydrochloric acid and the type of organic solvents. The nuclear mass effect and the field shift effect were estimated by use of the isotope pairs 152Gd-160Gd and 154Gd-160Gd. Since both isotopes, 152Gd and 154Gd, have the unique characteristics of the nuclear charge radii, s, the unusual isotope effects due to the field shifts took place, while the mass effects of the other isotopes canceled the field shift effects. The maximum isotope effect was observed to be e160,152 =0·0252 ± 0·0024 whose initial aqueous phase was 0·023 M GdCl3 in 12 M HC1, and its organic phase was 0·2 M DC18C6 in chloroform: this was 0·00315 ± 0·00030 in terms of the enrichment factor for unit mass.