Zenzi Hagiwara

Enrichment of Stable Isotopes, (III) Enrichment of 6Li and 7Li by Ion Exchange Column

In search of a suitable ion exchange method for the enrichment of Li-isotopes, column elutions of Li-band have been examined under various conditions. For long distance displacement of the Li-band, BaAc2 and CaAc2 were found excellent for eluant, and the Li proved to be very well retained by hydrogen bed with Dowex 50 W-X 12, 50~100 mesh. From the standpoint of resin utilization and regenerant efficiency in cyclic column operation, CaAc2 is preferable to BaAc2. Enrichment experiments were carried out with Li-isotopes, using the above exchange systems, which proved that 7Li and 6Li were well concentrated in the respective ends of the Li-adsorption band. In one run, the 7Li and 6Li were enriched to 97.09 and 14.64% respectively in the front and rear edges of the band.

Elution of heavier rare earths with H.E.D.T.A. eluant at a high temperature

Abstract In order to study the detail behaviors on the separation of heavier rare earths by ion exchange with fairly high concentrations of H.E.D.T.A., the elutions have been performed at 60°C under steady state conditions. The theoretical plate height concerning the column efficiency was also investigated from the viewpoints of countercurrent extraction and rate theory, and the various experimental results relating to the mixed region of the adjacent rare earths were explained from the relation induced. Further, under different experimental conditions, the contamination of thorium present in a trace quantity in the heavier rare earth samples, was investigated at a temperature of 60°C. The small peak of thorium moved to the lutetium side with increase in the concentration of H.E.D.T.A. eluant.

Enrichment of Stable Isotopes, (IV) Theoretical Treatment of Ion-Exchange Systems Used for Lithium Isotope Separation

In order to gain an insight into exchange systems used for Li-isotope separation, experiments have been made from the point of rate theory. From the resulting data were derived equations related to the plate height due either to particle or to film diffusion. Using these equations, the plate height values based on particle and on film diffusion were determined by curve fitting. Further, ion-exchange reactions at the front and tail boundaries of the Li adsorption band were investigated in detail. Finally, the validity of the equations derived was proved by good agreement found with the experimental data obtained on an Li-elution system under steady state.

Theoretical treatment of the elution system of rare-earth with dilute H.E.D.T.A. eluant

Abstract The elution of a single rare-earth from cation exchange resins has been investigated by means of 0.015 M H.E.D.T.A. buffered solutions at pH-values ranging from 4·9 to 9·8. After the attainment of dynamic equilibrium in the exchange system by moving the rare-earth band through the hydrogen-retaining bed, the constituents in the aqueous and resin phases of the formed bands were determined, and fundamental correlations of the experimental data were found. Also, theoretical treatments of all the species involved in the exchange system have been made, applying material balance, electrical neutrality and other theories. Thus, several theoretical curves were finally obtained in order to check the experimental data. The agreement was excellent. Also, major selectivity coefficients related to the present exchange system were evaluated in detail.

The nature of the thermal decomposition products of zirconium salts

Abstract Zirconium oxynitrate and the oxychloride have been decomposed at a temperature range 350°–1000°C in an air atmosphere in order to investigate the effect of thermal decomposition temperature and the types of zirconium salts on internal factors. Under the same experimental conditions, the calcined powder of zirconium oxynitrate (ZON) showed much larger pore volume, surface area, and volume shinkage as compared with that of zirconium oxychloride (ZOC). In calcination at a low temperature, the crystallite of a metalstable tetragonal ZrO2 in the ZON was smaller than that in the ZOC. However, with increasing temperature, the former growth was performed more rapidly than the latter. Bulk densities of green compacts and sintered compacts were also measured.

The ErTm separation factor in the presence of chelating agent and elution behavior of binary mixtures of Er and Tm

Abstract In the presence of E.D.T.A. and sulfonated polystryrene type of resin, the ErTm separation factor suitable for the real elution system was measured at 60°C, and a value of 2·02 was obtained for the above pair. Further, under a temperature of 60°C, the rare earth bands involving binary mixture of Er and Tm were eluted down the copper retaining bed, using approximately 0·015 M E.D.T.A. solution buffered with ammonium hydroxide. From several series of the experimental data obtained by the elutions of above heavier rare earth under steady state, the values of a plane height were calculated on the basis of rate theory and countercurrent extraction. The plate height values due to film diffusion were in agreement with the H.E.T.P. values from countercurrent extraction. Also, it was found that a linear relation was held between the plate height based on film diffusion and the flow rate.

Studies on Ion-Exichange Equilibria for Cesium-Hydrogen System

Ion-exchange equilibrium between Cs and H on a sulfonated polystyrene resin of Dowex 50W with 8% crosslinking has been studied over a temperature range of 25°to 60°C, using 137Cs as radioactive tracer; the various experimental data related to the equilibrium experiments were examined in detail by several different methods; a new treatment to take into account the water uptake in the exchange system Cs-H was also applied with the aid of a radioactive tracer technique. The thermodynamic equilibrium constant Kcs H determined by the present study compares well with the values calculated indirectly from experimental data found by other investigators. Data are also given for the heats, free energies and entropies of the exchange reaction involving Dowex 50W. Fairly good results have been obtained on the exchange of Cs and H.

Behavior of small amounts of thorium in the separation of heavy rare earth elements by ion exchange

Abstract Under various experimental conditions, elutions of the heavy rare earth mixtures involving small amounts of thorium have been carried out in order to investigate the contamination of the rare earth fractions by thorium. With the HEDTA-eluant, the degree of contamination was reduced with an increase in the elution temperature, but the ytterbium and lutetium fractions obtained in elution at 60°C were still contaminated with thorium. On the other hand, in the elution system with EDTA, the bulk of the rare earth fractions of lutetium and ytterbium obtained in elution at ordinary temperature was slightly contaminated with thorium, while the rare earth fractions obtained at 70°C, for the most part, were free of thorium, due to complete elution of thorium ahead of lutetium. For the removal of 1 or 2 per cent thorium in the heavy rare earth mixture, the EDTA-eluant gave excellent effects, relative to the HEDTA-eluant.

STUDIES ON CATION EXCHANGE EQUILIBRIA FOR THE URANYL--HYDROGEN SYSTEM.

Selectivity coefficients of the uranyl-hydrogen ion exchange system have been determined in a series of sulfonated polystyrene type cation exchange resins in three different degrees of crosslinkage at four different temperatures. The standard free energies of exchange ΔG° and the heats of exchange ΔH were also estimated from the data of selectivity coefficients determined on the same resins. In general, the selectivity coefficient increased with both crosslinkage and temperature, and decreased with increasing proportion of uranyl in the resin phase. The study was further extended to the exchange system of uranyl-ammonium in order to ascertain the validity of the magnitudes of selectivity coefficients obtained for the uranyl-hydrogen system. Good results were obtained on the exchange equilibria.