Morikazu Hosoe

Fractionation of Strontium Isotopes in Cation-Exchange Chromatography

Abstract Ion-exchange displacement chromatography of calcium has been carried out successfully for the purpose of observing calcium isotope fractionation effects. Small but definite accumulation of the heavier isotopes has been observed at the front parts of the calcium adsorption bands, which means they are preferentially fractionated into the solution phase. The average values of the single-stage separation factor minus one per unit mass difference between isotopes (∊/Δ M) have been 2.0 × 10−5 for the calcium chloride system, 5.2 × 10−5 for the calcium lactate system, and 2.3 × 10−5 for the calcium acetate system at 25°C. The reduced partition function ratios of the calcium species involved in the present study have been estimated by using separation factor data and available data on calcium hydration under appropriate assumptions. The reduced partition function ratios of the complex species have been found to be larger than that of the simple hydrated calcium ion, which is a cause of the experimental r...

Characterization of semicrystalline titanium(IV) phosphates and their selectivity of cations and lithium isotopes

A semicrystalline layered titanium phosphate (scTiOP), which showed the chemical properties of a cation exchanger, was synthesized from a mixed solution of titanyl sulfate and ammonium dihydrogenphosphate solutions under mild conditions. Based on the results of 31P MAS NMR measurements, infrared measurements, thermogravimetry–differential thermal analysis, ICP atomic emission spectroscopic analysis and powder X-ray diffraction analysis, the ion exchanger was identified as Ti2O3(H2PO4)2·2H2O. Ion exchangers with varying degrees of condensation of the dihydrogenphosphate groups, and consequently having three-dimensional cross-linked structures with minutely controlled ion exchange sites, were obtained by the thermal treatment of scTiOP at different temperatures. The ion exchangers obtained by thermal treatment at temperatures from 200 to 600 °C showed a high affinity toward sodium ion among the alkali metal ions, whereas scTiOP and the ion exchanger treated at 100 °C showed no specific selectivity of any alkali metal ion. The single-stage separation factor, S, for the lithium isotopes was a slow increasing function of the temperature of the thermal treatment up to 600 °C, and the maximum S value at 25 °C was 1.028. The occurrence of a high affinity to sodium ion, the increase in S value and the development of a three dimensional –O–P–O– network seemed mutually correlated.

Boron Isotope Fractionation in Liquid Chromatography with Boron-Specific Resins as Column Packing Material

Boron-specific resins with n-methyl glucamine as the functional group were used as column packing material of liquid chromatography for boron isotope separation. The shapes of chromatograms in reverse breakthrough experiments were heavily dependent on the pH of the eluents, and there existed a pH value at which a chromatogram of the displacement type was realized nearly ideally. The value of the single-stage separation factor for the boron isotopes varied between 1.010 and 1.022, depending on the temperature and the form of the resins. The existence of the three-coordinate boron species in addition to the four-coordinate species in the resin phase is suggested.

Alkali Metal Ion and Lithium Isotope Selectivity of HZr2(PO4)3

HZr2(PO4)3 has been synthesized by the heat treatment of NH4Zr2(PO4)3 and its properties as an ion exchanger have been examined with the main focus on its alkali metal ion and lithium isotope selectivity. The distribution coefficients for alkali metal ions revealed that HZr2(PO4)3 was lithium ion-specific and showed little affinity toward potassium, rubidium or cesium ion. The lithium and sodium ion uptakes from aqueous solutions were monotonously increasing functions of pH. Isotopically, HZr2(PO4)3 was 6Li-specific. Contrary to ion uptake, the lithium isotope effect was a monotonously decreasing function of pH; a larger separation factor was observed at a lower pH. This result was consistent with the existence of two different ion exchange sites formed in lithium ion-inserted HZr2(PO4)3.

Cubic Antimonic Acid as Column-Packing Material for Chromatographic Lithium Isotope Separation

The applicability of granular cubic antimonic acid (C-SbA) as column packing material in chromatographic lithium isotope separation was investigated. The feed solution should have the buffer capacity to promote lithium uptake, and its pH has to be kept as low as 2.25 to prevent the decomposition of the granular C-SbA in order to obtain a sharp front boundary of the lithium sorption zone. The pH and the chemical composition of the eluent should be finely controlled to obtain a displacement-type chromatogram. The lithium isotope separation effect was about ten times larger than that achieved on an organic ion exchanger.

Lithium Isotope Selectivity of Sorbents Prepared from Lithium Manganese Oxides

Sorbents are prepared by extracting lithium ions from lithium manganese oxides with the lithium/manganese mole ratio (Li/Mn ratio) varying between 0.42 and 0.84, and their lithium isotope selectivities are investigated. All the sorbents are 6Li-specific and the values of the 7Li-to-6Li isotopic separation factor (S) are between 1.0040 and 1.0092 at 25°C. The S value is slightly dependent on the Li/Mn ratio; it takes on the maximum at a Li/Mn ratio of 0.5 and decreases as the ratio deviates from this value. This indicates that the lithium isotope effect between the tetrahedral sorption sites of the sorbents and the external solution phase is larger than that between the octahedral sorption sites and the solution phase.

Selectivity of Lithium Isotopes on Semicrystalline Titanium(IV) Phosphate

Lithium isotope separation is a subject of great concern in nuclear science and technology due mainly to the large demand for enriched and/ or isolated 6Li expected in future. Materials that show large lithium isotope effects have been sought for the development of efficient lithium isotope separation processes. It has been reported some inorganic ion exchangers show high selectivity of 6Li compared to organic ion exchangers, and metal(IV) phosphate-based ion exchangers are among them (1)-(3). In previous papersC2H 3), we reported selectivity of alkali metal ion and lithium isotopes on crystalline zirconium(IV) and zirconium(IV)-titanium(IV) phosphates. In this note, we report lithium isotope selectivity of semicrystalline titanium(IV) phosphate. Its property as cation exchanger heavily depends on the conditions in the preparation process, which indicates the possibility of easily controlling the size of its ion exchange sites and thus its lithium isotope selectivity. Ammonium dihydrogen phosphate solution was slowly added to titanyl sulfate solution at 70°C until the molar ratio of Ti(IV) to Polbecame 1:0.98. To the mixture solution added was ammonia to adjust the pH to 1. The solution with pH 1 was stirred twice a day for a couple of minutes while its temperature was kept at 100°C for 10 days. Aprecipitate, which was the precursor of the present amorphous titanium(IV) phosphate ion exchangers, was formed. The XRD (X-ray diffraction) pattern of the precursor is shown in Fig. 1 a). The intensity of the spectrum is weak as a whole, indicating the main phase of the precipitate is the amorphous phase, semicrystalline phase(4),

Isotope effects of rubidium in amalgam/aqueous solution systems

The isotope separation factor, α, for rubidium isotopes in the rubidium amalgam/aqueous rubidium hydroxide system has been investigated as a function of temperature by both single-stage and multi-stage methods. At 293 K the single-stage separation factor for 87Rb–85Rb was found to be 1.000 70 ± 0.000 06 by multi-stage experiments. The exothermic enthalpy of the isotope-exchange reaction was also estimated thermodynamically.

Boron isotope separation by ion-exchange chromatography using an anion-exchange resin in halide forms : Separation factors at 25°C

Abstract A series of chromatographic experiments were carried out to determine the values of the separation factors for the 10 B/ 11 B isotopic pair in the boron isotope separation systems of an anion-exchange resin in halide forms at 25°C. In every experiment, the lighter isotope, 10 B, was enriched in the rear part of the boron zone formed in the chromatographic column. The separation factors obtained were 1.0099 for the fluoride-form resin, 1. 0018 for the chloride-form resin and 1.0014 for the bromide-form resin, independent of the boron concentration. A theoretical consideration of them is given.

Boron Isotope Separation by Ion-Exchange Chromatography Using an Anion Exchange Resin in Halide Forms. Temperature Dependence of Separation Factor

Ion exchange chromatography of boric acid was carried out using an anion exchange resin in fluoride and chloride forms in order to investigate the temperature dependence of separation factor (S) for boron isotopes. The results are summarized as follows: For the fluoride form resin system, S− 1 = 1348/T2 − 0.0051 (between 5 °C and 35 °C) and for the chloride form resin system, S− 1 = 645/T2 − 0.0053 (between 5 °C and 50 °C) where T is the temperature in units of K.