Hideyo Takeishi

Comparative study on the hydration states of Cm(III) and Eu(III) in solution and in cation exchange resin

Abstract The sorption behavior and hydration structure of Cm(III) and Eu(III) in the cation exchange resin–acid solution systems were studied by measurements of the distribution coefficient K D and the inner-sphere hydration number N H 2 O of the ions in acid solution and in resin phase. The differences in the K D and N H 2 O values for Cm(III) and Eu(III) above 5 M HCl are K D (Eu)> K D (Cm) and N H 2 O (Eu)> N H 2 O (Cm), while the N H 2 O of Cm(III) in the resin phase in 0.1–11 M HCl solution are approximately equal to those of Eu(III). The N H 2 O of Cm(III) in HNO 3 or HClO 4 solution and in the resin phase are similar to those of Eu(III), in agreement with the similarity in the K D of the ions. The separation and sorption mechanisms of Cm(III) and Eu(III) are discussed from the K D and N H 2 O values.

Solvent extraction of uranium, neptunium, plutonium, americium, curium and californium ions by bis(1-phenyl-3-methyl-4-acylpyrazol-5-one) derivatives

Abstract Comprehensive study has been performed on the extraction of actinide ions of various oxidation states, An n + (An=U, Np, Pu, Am, Cm and Cf), with bis(1-phenyl-3-methyl-4-acylpyrazol-5-one) derivatives, H 2 BP n ( n ; number of polymethylene chain=3, 4, 5, 6, 7, 8, 10 and 22). All H 2 BP n derivatives showed higher extraction efficiencies for An n + than 1-phenyl-3-methyl-4-benzoylpyrazol-5-one (HPMBP) did, which is attributable to the strong multidentate interaction with An n + or high hydrophobicity of H 2 BP n in comparison with HPMBP. The highest efficiency for all An n + examined was obtained with H 2 BP8 or H 2 BP7. The extracted species were confirmed as An(BP n )(HBP n ) for Am 3+ , Cm 3+ and Cf 3+ , and An(BP n ) 2 for U 4+ , Np 4+ and Pu 4+ . The extracted species of UO 2 2+ depended on the length of the polymethylene chain. The species UO 2 (HBP n ) 2 was extracted with H 2 BP3 or H 2 BP4 and UO 2 (BP n ) with H 2 BP n of n ≥5. NpO 2 + was hardly extracted from the solution of pH less than 9. On the basis of the correlation between the distribution ratio and pH the procedure for the successive separation of the actinides in nitric acid medium was developed. The recommended procedure using H 2 BP8 was applied to the mutual separation of UO 2 2+ , NpO 2 + , Pu 4+ and trivalent transplutonium ions.

Determination of traces of ruthenium by addition of cerium(IV) and atomic absorption spectrometry

Abstract The sensitivity of the determination of ruthenium by flame atomic absorption spectrometry is increased 60 times by adding 1 × 10 −2 M cerium(IV). Calibration is linear over the range of 0.05–5 μg ml −1 ruthenium. A method applicable to nitrosylruthenium complexes is described. The increased sensitivity results from formation of ruthenium tetroxide.

Solid-liquid equilibria of Nd3+ in carbonate solutions

Abstract A redetermination of the solubility products of NdOHCO 3 (s) and Nd 2 (CO 3 ) 3 ·(4.5–6)H 2 O(s) in 0.1 M NaClO 4 is presented, extending existing data to a wider variety of CO 2 partial pressures and a wider concentration range. NdOHCO 3 (s) is found in equilibrium with 0.03% and 0.3% CO 2 partial pressures; Nd 2 (CO 3 ) 3 ·(4.5–6)H 2 O(s) is found in equilibrium with 1.0%, 8.0% and 100% CO 2 partial pressures. The solubility products log K sp (NdOHCO 3 ) = −20.12 ± 0.09 and log K sp (Nd 2 (CO 3 3 ·(4.5–6)H 2 O) = −31.54 ± 0.11 have been determined. Evidence is presented that Nd 2 (CO 3 ) 3 ·(4.5–6)H 2 O(s) is probably only metastable in equilibrium with 1.0% CO 2 partial pressure. Gibbs free energies of formation have been calculated as ΔG f o ((Nd2(CO 3 ) 3 (s)) = − 3115.9 ± 4.0 kJ mol −1 and ΔG f o (NdOHCO 3 (s)) = −14.76.0±2.9 kJ mol −1 .

Enhancement of ruthenium determination by inductively coupled plasma/atomic emission spectrometry by addition of periodic acid

Abstract A sensitive method for the determination of ruthenium involving the formation of volatile species in solution and subsequent nebulization for inductively coupled plasma/atomic emission spectrometry is proposed. The sensitivity of the determination of ruthenium was increased by a factor of 70 with the addition of 1×10 −2 M periodic acid as an oxidizing agent. The detection limit was 5 ng ml −1 of ruthenium and the calibration was linear over the range 0.01–0.5 μg ml −1 of ruthenium. Serious interferences were not found except from reducing agents.

Separation of Light Lanthanoids by Centrifugal Partition Chromatography in 30% TBP Extraction System

Abstract Separation of light lanthanoids (III) with centrifugal partition chromatography (CPC) in 30% tri-n-butyl phosphate (TBP) extraction system with the aid of salting-out agent lithium nitrate (LiNO3) was investigated. Carbon tetrachloride (CC14) and ndodecane were used as diluents to control the density difference between mobile and stationary phases. By a batch method, it was proved that distribution ratios (D) and separation factors (α) of several light lanthanoids increased with the LiNO3 concentration in 1 M (mol dm−3) nitric acid in the aqueous phase. Addition of CC14 to 30% TBP-n dodecane organic phase resulted in a decrease of the D values, holding the α values constant. On the basis of these data, separations of Ce, Pr and Eu with a CPC apparatus were successfully performed by decreasing the density difference. Although the chromatogram data differed considerably from the batch data owing to the concentration effect of the lanthanoids, satisfactory separation was obtained in 30% TBP-35% n do...

Recognition of metal complex guests: supramolecular extraction of water-soluble lanthanide complexes by biological lasalocid ionophore

Abstract Naturally occurring lasalocid ionophore was first demonstrated to extract water-soluble lanthanide tris(acetylacetonates) via inner-sphere complexation into CCl4. This offered higher extraction abilities for small Er3+ and Dy3+ complexes than for large Pr3+ and La3+ complexes. Since the lasalocid extracted lanthanide cations themselves non-selectively, this ‘metal complex recognition’ has new and interesting possibilities in separation and sensing of valuable lanthanides.

Spent fuel reprocessing based on electrochemical extraction process (SREEP)

Abstract A new concept of the electrochemical process for the reprocessing of nuclear spent fuel, SREEP, has been developed on the basis of fundamental studies of the electrochemical reactions of actinide elements and fission products. SREEP consists of unit processes for (1) spent fuel dissolution by electrolytic oxidation, (2) recovery of platinum group metals by electrodeposition, (3) TBP extraction of U, Pu and Np after the successive electrolytic preparation of U(VI), Pu(IV) and Np(VI), (4) recovery of Cs and Sr by electrolytic ion transfer extraction and (5) separation of transplutonium and lanthanide elements by electrodeposition in the molten salt.

Determination of concentration and distribution of (CuO)+ in high-Tc superconducting La2−xSrxCuOy pellet by flow-coulometry

Abstract The novel wet-chemical method for the analysis of the concentration and the distribution of constituent(s) at a higher oxidation state, [CuO] + , in superconducting La 2− x Sr x CuO y was developed. The sample pellet was dissolved in a flow of acid solution containing Fe 2+ , and the solution was introduced continuously into a flow-coulometric system composed of two-step column electrodes of glassy carbon fibers as working electrodes. Fe 3+ generated in the solution through the stoichiometric redox between [CuO] + and Fe 2+ was detected at the first column electrode, and Cu 2+ in the dissolving solution was detected at the second column. It was obvious that the [CuO] + concentration in the surface region of ca. 200 μm in depth from the surface was lower than that of the bulk pellet and the distribution of [CuO] + near the surface was dependent on such sample-preparation parameters as sintering time, annealing atmosphere and storage time of the pellets, etc.

ION EXCHANGE SEPARATION OF TRACE AMOUNTS OF URANIUM AND THORIUM IN TANTALUM FOR NEUTRON ACTIVATION ANALYSIS

Separation method of a few ppb of uranium and thorium in tantalum metal by ion exchange for neutron activation analysis was established. After dissolving tantalum metal by hydrofluoric acid, uranium and thorium were separated from tantalum using cation exchange resin column in 0.5M hydrofluoric −0.65M boric acid media. Both of the yields for uranium and thorium during separation were above 95% and the remaining amount of tantalum be lowered below 400 ng.