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  • Author or Editor: M. Kyrš x
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Abstract  

The history of the development of solvent extraction investigations with dicarbollides for the separation of metals is briefly treated and some inaccuracies in previous reviews are commented on.

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Abstract  

The distribution of a radioactively labelled substance was measured in two different solvent extraction systems in the presence of substoichiometric amounts of different masking reagents. The theory of the errors involved in the method is elaborated, recommendations are given for the choice of the conditions of the determination, e.g. which combination of extractant and masking reagent is preferable, which of the two elements should be labelled, what is the optimum concentration of the masking reagent and what values of distribution ratios are desirable.

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Abstract  

The theory is given of errors of the title method based on the solvent extraction reaction Aaq+Baq⇌ABorg, the minimum amounts which can be determined are assessed, the desirable values of ξ are recommended and the precision of the title method is compared with that of the concentration dependent distribution method. Tables are given allowing a rapid calculation of the error of determination for any reasonable concentration of the substance to be determined, any extractant concentration and a chosen value of ξ if the equilibrium constant of the above reaction is known.

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Abstract  

Liquid—liquid extraction of divalent palladium by solutions of the hexachloroderivate of cobalt dicarbolide (HBCl6) in the mixture of solvents (30 v/v % nitrobenzene+20 v/v % n-dodecane +50 v/v/ % toluene) from nitric acid medium has been studied. Besides HBCl6 the organic phase contained also 2,2′-dipyridyl (dipy). The yield of palladium extraction from 0.5M HNO3 is greater than 99.0%. The species extracted into the organic phase corresponds to the formula [Pd(dipy)2] (BCl6)2.

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Abstract  

The theory of errors of three variants of sub- and super equivalence method is given and errors for typical cases are tabulated. The principles of the variants are described. Recommendations are offered for a rational choice of a variant to be used and for that of the parameter . For the calculations the assumption is used that the analysis is based on the solvent-extraction equilibrium+ A+BABorg.

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Abstract  

A new radiochemical method for the determination of two chemically similar elements by the method of concentration dependent distribution is proposed. The method involves the measurement of the distribution ratio of the labelled substance added to the unknown sample in two different “substoichiometric” systems. The theory of the method is elaborated for the case of ion-exchange type solvent extraction systems. The shape of the calibration curve is theoretically derived, the influence of experimental conditions on the error of the determination is assessed and optimum labelling choice recommended.

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Abstract  

The precision of the title method is analyzed theoretically for a hypothetical case of solvent extraction involving the reaction. It was found that there exists a certain reagent concentration giving the lowest errors. If the error in the determination of distribution ratios is 2%, a broad range of conditions exists where the error of the result is near to or less than 1%. The ranges of the values H 1/N are found for N=1,2 3 for cases where the error of the results is 1%.

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Abstract  

The kinetics (1–1000 minutes shaking) of 5·10–4M Eu sorption from 0.1M HNO3 onto the support XAD-7 impregnated with approximately equimolecular mixture of DBDECMP and dicarbollide depends appreciably on the technique of the preparation of the impregnated support. The highest distribution factors are obtained if DBDECMP is only used to impregnate the support and dicarbollide is added directly to the aqueous phase. The rate of sorption increases slightly with adding 1·10–5M surfactants but the effect is too weak for practical use. The best stripping agent found is an equimolecular mixture of DCTA and citric acid at pH 7. This work is a continuation of the investigation1–3 of the synergic effect occurring in the sorption of low concentrations of europium due to the simultaneous presence of H+[(C2B9H8Cl3)2Co] (abbreviated as dicarbollic acid, HB) and di-butyl-N-di-ethyl-carbamoylmethyl phosphonate (DBDECMP) on a suitable support. The system is promising for the separation of small amounts of tervalent transuranium and lanthanoid elements from radioactive waste. In the previous paper we have investigated quasi-equilibrium sorption of various Eu concentrations (24 hour shaking). In the present paper kinetic data of sorption and quasi-equilibrium data on desorption are studied. Preliminary kinetic studies of similar systems2,3 have shown that the rate of both the sorption and desorption processes in this type of system is one of the decisive factors in the practical application of this separation method. Whereas in the previous paper1 both DBDECMP and CMPO (octyl-phenyl-N,N-diisobutyl carbamoylmethyl phosphineoxide) combined with dicarbollide were studied, for reasons given previously1 (mainly a higher synergic effect) herein DBDECMP was only investigated.

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Abstract  

The kinetics of Sr and Ba distribution both for extraction and back-extraction processes has been investigated. The influence of the equilibrium pH, the CDTA concentration and the Na/Li ratio on the distribution of the metals to be separated was established. Separation factors (Ba/Sr) achieved were not altered by replacing PEG 400 as the synergic agent by the cheaper technical product Slovafol 909. Practical hints for carrying out the separation for analytical purposes. are given.

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Abstract  

The optimum concentration of the extractants for rapid radiostrontium concentration is 0.1M HB (chlorinated cobalt dicarbollide acid) and 1.5% vol. of Slovafol 909 in a mixture of CCl4(40%) and nitrobenzene. The recommended initial carrier concentration is 2·10–4 M Sr, initial aq. pH4.3, time of shaking 3 min. Yield in the range 80–97% can be achieved in rapidly concentrating Sr from 1 dm3 aqueous phase into 10–20 ml of the extract. The yield decreases with increasing Ca concentration in the model water. The time needed for the concentrating does not exceed 30 min.

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