Berkelium , solvent

Peppard, D. F. Isolation of Berkelium by Solvent Extraction of the Tetra-... 

The berkelium(IV) complexes BkL4 [HL = CF3COCH2COBut395 and CF3COCH2CO(2-C4H3S)395,413] are formed by solvent extraction of aqueous Bk1 solutions with the j6-ketoenol. 

Attempts to obtain thermodynamic data for solvent extraction of Bk(III) by thenoyltrifluoroacetone in benzene and for complexation of Bk(III) by hydroxide and citrate ions were unsuccessful (202). The high extractability and complexability of the easily accessible tetrava-lent state of berkelium probably accounts for the difficulty encountered in this work. 

Indirect determinations of the formal oxidation potential of Bk(IV)-Bk(III) couple in sulfuric and nitric acids have been made by tracer measurement. From the Bk(IV)/Bk(III) ratios and the corresponding Ce(IV)/Ce(III) ratios at equilibrium conditions one can calculate the oxidation potential of the Bk(IV)-Bk(III) couple. The Bk(IV)/Bk(III) ratio can be determined by extracting Bk(IV) by an appropriate organic solvent. The formal oxidation potentials of the Bk(IV)-Bk(III) couple in IN and 0.5N sulfuric acid were found to be 1.42 and 1.44 volts using trilaurylmethylammonium sulfate in carbon tetrachloride as a solvent. In 6N nitric acid the oxidation potential of the couple was found to be 1.56 volts by using 0.18M tributylphosphate. Whereas, in IN to 2N nitric acid berkelium was not oxidized by cerium(IV). 

The berkelium (IV) extraction coefficients have been determined by stripping solvents previously loaded with tetravalent cerium and berkelium in the presence of sodium bismuthate. Sodium bismuthate has been found to be an efficient oxidizing agent for trivalent cerium. Because of its small solubility it does not affect the distribution coefficients of tetravalent cerium. These two properties have been demonstrated by comparing the distribution coefficients of cerium (IV) measured by spectrophotometry with those of cerium oxidized by sodium bismuthate and measured by beta counting of the cerium isotope tracer. The data are summarized in Table I and indicate no real difference in the distribution coefficients of cerium obtained by these two methods when using trilaurylmethylammonium salts-carbon tetrachloride as solvent. 

Procedure. Aqueous phases were prepared from samples of cerium (IV), cerium (III), berkelium, and acid and diluted by distilled water to the proper concentrations. Samples of cerium were chosen in order to obtain dijSerent cerium (IV)/cerium (III) ratios. The solutions were allowed to stand for six hours to reach the oxidation equilibrium. A 2 cc. sample of the solvent was added to the same volume of aqueous solution and mixed for 15 minutes. After separation by a centrifuge, samples of both phases were taken for the beta counting of berkelium and the spectrophotometric determination of cerium (IV). In addition, one aliquot of the loaded solvent was taken for determining the distribution coefficient of berkelium (IV). 

Many of the actinoids are also separated by exploiting their redox behavior. Thorium is exclusively tetravalent and berkelium is chemically similar to cerium, so iodate precipitation of Th and extraction of Bk(IV) with bis(2-ethylhexyl)orthophos-phoric acid (HDEHP) are used to isolated these elements. The differing stabilities of the (III), (IV), (V), and (VI) states of U, Np, and Pu have be exploited in precipitation and solvent extraction separations of these elements from each other and from fission product and other impurities with which they are found. Because of its technical importance, the process chemistry to separate U and Pu in nuclear materials has been highly developed. Extraction of Bk(IV) with HDEHP is used to separate Bk from neighbouring elements. 

A procedure for the rapid separation of berkelium from other actinides, lanthanides, and fission products was developed in order to measure the decay properties of short-lived isotopes [54]. Bk and Ce were separated from other elements using solvent extraction with HDEHP followed by cation-exchange high-pressure liquid chromatography (HPLC) using a-hydroxyisobutyrate as the eluant. The elution curve, showing a clean separation of Bk from Ce, is shown in... 

Desire, Hussonnois and GuUlaumont (1969) determined stability constants for the species AnOH + for the actinides, plutonium(III), americium(III), curium (III), berkelium(III) and californium (III) using a solvent extraction technique. The stability constants obtained for americium(III) and curium(III) are two orders of magnitude larger than other similar data available in the literature. The stability constants of the lanthanide(III) and actinide(III) ions are very difficult to obtain using solvent extraction due to problems associated with attainment of maximum extraction into the solvent phase before the narrow band of pH between the onset of hydrolysis reactions and the precipitation of solid hydroxide phases. Consequently, the data of Desire, Hussonnois and GuUlaumont (1969) are not retained in this review. 

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