Separation of americium from europium by solvent extraction from aqueous phosphonate media

Complexes between Am{sup 3+} or Eu{sup 3+} and phosphonoacetic acid differ in relative stability in accord with the electrostatic model of cation binding. The smaller Eu{sup 3+} cation forms stronger complexes with PAA than the larger Am{sup 3+} cation. The observed metal complexes in the acid range from 0.005 M to 0.02 M (at I= 0.5 M) are Eu(HL){sup +}, Eu(H{sub 3}L){sub 2}{sup +}, Eu(HL){sub 2}{sup {minus}} and Am(H{sub 2}L){sup 2+}, Am(HL){sup +}, Am(H{sub 2}L){sub 2}{sup +}. When used as a holdback reagent, PAA slightly enhances the separation of Am/Eu when used with sulfonic acids or CMPO/nitrate, but reduces separation efficiency with HDEHP. In a CMPO/SCN{sup {minus}} extraction system which favors extraction of Am over Eu, addition of PAA increases the separation efficiency by a factor of 2-3 at 0.3 M PAA/0.5 M SCN{sup {minus}}. The calculated stability constants can be used to explain the separation factors, but do not always accurately predict metal distribution ratios in the CMPO systems, implying that there are details of this system which have not been fully elucidated

Separation and Analytical Chemistry of the Actinides

The determination of low levels of actinides from water samples and aqueous waste streams involves a lengthy and complicated process which is characterized by low recoveries and poor precision. The objective of this work was to evaluate the use of a Photon Electron Rejecting Alpha Liquid Scintillation Spectrometer (PERALS{reg_sign}), in combination with extractive scintillators, for the detection of actinides. The results of the application of this method to aqueous samples containing uranium, thorium, plutonium, and americium, both individually and in mixtures showed promising results. Using a commercially available extractant, ALPHAEX{reg_sign}, recoveries of plutonium and americium were > 98.4% in individual samples and in mixtures with activities ranging from 6 pci to 500 pci. The separation of these two elements was accomplished by selective extraction after adjusting the acidity of the aqueous sample. The application of this technique to a raw waste sample showed reasonable recoveries when combined with classical anion exchange separation techniques. Efforts to develop an extractive scintillator using a recently synthesized tetradentate extractant were only moderately successful since solubility problems limit the extractant's efficiency in the scintillator. The application of a curve fitting program, PEAKFIT{reg_sign}, to spectra obtained using the PERALS{reg_sign} spectrometer provided useful isotropic information

Solvent extraction of thorium(IV), uranium(VI), and europium(III) with lipophilic alkyl-substituted pyridinium salts. Final report for subcontract 9-XZ2-1123E-1, June 1, 1992--December 1, 1995

In the treatment of high level nuclear wastes, aromatic pyridinium salts which are radiation-resistant are desired for the extraction of actinides and lanthanides. The solvent extraction of Th{sup +4}, UO{sub 2}{sup +2}, and Eu{sup +3} by three aromatic extractants, 3,5-didodecylpyridinium nitrate (35PY), 2,6-didodecylpyridinium nitrate (26PY), and 1-methyl-3,5-didodecyl-pyridinium iodide (1M35PY) has been studied in nitric acid media. The general order of extractability of the three extractants in toluene was 1M35PY>> 26PY > 35PY. The overall extraction efficiency of the metal ions was Th{sup +4} >UO{sub 2}{sup +2} > Eu{sup +3}. The extraction of HNO{sub 3}, which was competitive with the extraction of metal ions, was quantitatively investigated by NaOH titration and UV spectrometry. The loading capacity suggested that the extracted species in the organic phase for thorium was (R{sub 4}N{sup +}){sub 2}Th(NO{sub 3}{sup -}){sub 6}, where R{sub 4}N{sup +} denotes 1M35PY. A comparison of 1M35PY to the well-characterized extractant, Aliquat-336, an aliphatic ammonium salt was made. At the same extractant concentration, 1M35PY extracted thorium more efficiently than Aliquat-336 at high acidity. Thorium could be readily stripped with dilute nitric acid from 1M35PY. After irradiation of 0.1M 1M35PY with {sup 60}Co at 40R/min for 48 hours, no change in the extraction efficiency of thorium was observed

Preparation, characterization, and decay of einsteinium(II) in the solid state

Pour la première fois, des échantillons de EsCl2, EsBr2 et EsI2 ont été préparés par réduction des trihalogénures d'einsteinium correspondants par de l'hydrogène à des températures élevées. Les trois dihalogénures ont été caractérisés principalement par leurs spectres d'absorption. Les produits de décroissance d'échantillons de EsX2 maintenus à la température ambiante et à la température de l'hélium liquide ont été suivis par spectrophotométrie. Dans tous les cas, l'identification positive des espèces petit-fils, CfX2, a été faite. Aucune preuve spectrale définitive de la présence possible du produit fils BkX2 n'a été obtenue.Samples of EsCl2, EsBr2, and EsI2 have been prepared for the first time by reduction of the corresponding einsteinium trihalides with hydrogen gas at elevated temperatures. The three dihalides were characterized primarily by their absorption spectra. The products of the decay of EsX2 samples held at ambient and liquid helium temperatures have been monitored by spectrophotometry. In all cases positive identification of the granddaughter, CfX2, species has been made. No definite spectral evidence for the presence of the possible daughter products, BkX2, has been obtained