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- Author or Editor: I. Alimarin x
- Chemistry and Chemical Engineering x
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Abstract
A method based on exchange reactions of metals with coordination compounds and termed displacement extraction chromatography is proposed. The method consists essentially in the successive displacement of elements with lower extraction constants, present in the form of coordination compounds in the organic phase on the column, by substoichiometric amounts of elements with higher extraction constants, admitted to the column in aqueous solution. The method was used to determine various contaminations in yttrium, molybdenum, zirconium, niobium and beryllium by activation analysis.
Abstract
A method has been developed for the activation analysis of boron and cadmium, taking into account neutron absorption of the sample. The concept of the screening coefficient, expressing the self-screening of the matrix on the contamination is introduced. A formula is proposed for calculation of the screening coefficient, based on the boron or cadmium ratios for the contaminating elements being determined. Good agreement between experimental and calculated values was obtained.
Abstract
A method of element separation has been worked out with the use of substoichiometric exchange reactions in combination with extraction chromatography. The principle of the method consists in the successive displacement of elements with lower extraction constants from their complexes by a substoichiometric amount of an aqueous solution of a competitive metal with a higher extraction constant. As stationary phase a chloroform solution of zinc diethyldithiocarbamate was used in the column, and a porous polytetrafluoroethylene (Ftoroplast PF-4) was employed as an inert supporting material. The method was used for the radioactivation determination of zinc, copper, cadmium, silver, mercury, managanese, cobalt and iron traces in yttrium, molybdenum, zirconium, niobium and beryllium. When samples weighing 0.1–1 g are irradiated for 20 hrs with a neutron flux of 1.2·1013 n·cm−2·sec−1, the determination sensitivity is 10−4−10−8%.
Abstract
A method with a sensitivity of 2·10−7 to 1·10−10% has been developed for determining Yb, Ho, Dy, Gd, Eu, Sm and La impurities in metallic uranium by means of neutron activation. The method is based on a preliminary chromatographic separation of the total amount of rare earth elements from uranium by passing the solution in sulphuric acid through KU-2 cation exchange resin and eluting the traces of uranium retained by the resin with a solution of ascorbic acid. The rare earth impurities are then eluted from the resin with 4–5N HCl, evaporated, and irradiated for 20 hours with a neutron flux of 1.2·1013 n·cm−2·sec−1. Subsequently the traces of the rare earth elements are co-precipitated with Fe(OH)3, dissolved in concentrated HCl and separated from the iron and other impurities by passing the solution through Dowex 1X8 anion exchange resin in the chloride form. The individual rare earth elements are then separated from each other using KU-2 cation exchange resin and a solution of ammonium α-hydroxyisobutyrate as the eluant.
Abstract
A neutron activation analysis method for determining Yb, Dy, Ho, Sm and La impurities in europium oxide with sensitivities of 10−5 to 10−7% is described. The method is based on a preliminary concentration of the rare earth elements by reducing europium(III) with zinc to europium(II), and separating the trivalent rare earth elements by extraction chromatography. After neutron irradiation, the individual radioisotopes of the rare earth elements are separated by using KU-2 cation exchange resin and ammonium α-hydroxyisobutyrate solution as the eluant.
Abstract
Interrelationship between the error of the radioanalytical methods and the concentration of the element to be determined has been found for extraction systems with different parameters Kex, pH, a concentration of the extractant. Based on a mathematical discussion of this interrelationship, the criterion of the estimation of sensitivity has been proposed for the different radioanalytical methods based on the substoichiometric principle as well as some deviations from it.
Abstract
Radioactivation analysis is the only method which allows the determination of individual rare earth element impurities in rare earth elements of high purity. The determination of dysprosium, europium, samarium and gadolinium in yttrium oxide is complicated by the short half-life of165Dy (138 min.) and by the difficulty of separating traces of these elements from the matrix. A chromatographic method has been developed, for the separation of traces of Dy, Eu, Sm and Gd from ytrium, on a column packed with anion exchangerAV-17, by means of elution with 0.1N and 0.3M solutions of EDTA-sodium salt, followed by the separation of the mixture of the rare earth impurities on a microcolumn of cation exchangerKU-2, using a 0.17M solution of ammonium α-hydroxyisobutyrate as the eluent. The sensitivity of the determination of Dy, in the case of irradiating 10 mg of Y2O3 with a flux of 1.2·1013 n·cm−2·sec−1 for 5 min. was 1·10−7%; the corresponding values for Sm, Eu and Gd, when irradiating a 100 mg sample of Y2O3 for 20 hours with the same flux, were 2·10−7%, 1·10−8% and 5·10−6%, respectively.
Abstract
The possibility of using coprecipitation on Cu(OH)2·nH2O and Fe2O3·nH2O precipitates to separate a part of zirconium unreacted with complexone in the presence of a 100-fold amount of impurities has been examined. The reaction between ethylenedia-minetetraacetic acid (EDTA) and zirconium 10−3−10−5 M has been used as substoichiometric reaction. A zirconium determination in the concentration range of 10−4−10−6 g/ml in artificial mixtures and steel samples has been developed using the systems of EDTA-Zr−Cu(OH)2·nH2O and EDTA−Zr−Fe2O3·nH2O.
