Chapter 5 Actinide elements and compounds
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Transuranium element
Bond-length distributions have been examined for eighty-four configurations of the lanthanide ions and twenty-two configurations of the actinide ions bonded to oxygen. The lanthanide contraction for the trivalent lanthanide ions bonded to O 2- is shown to vary as a function of coordination number and to diminish in scale with increasing coordination number.
Lanthanide contraction
Coordination number
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The Actinide-Lanthanide SEParation (ALSEP) concept is described. This concept is based on using an extractant phase consisting of either N,N,N’,N’-tetraoctyldiglycolamide (TODGA) or N,N,N’,N’-tetra(2-ethylhexyl)diglycolamide (T2EHDGA) combined with 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester (HEH[EHP]) to separate Am and Cm from lanthanide and other fission and activation products in a single solvent extraction cycle. The neutral TODGA or T2EHDGA serves to co-extract the trivalent actinide and lanthanide ions from nitric acid media. The distribution ratios for Am and the lanthanides increase with increasing nitric acid concentration. TODGA extracts these elements more strongly than T2EHDGA from nitric acid, but the weaker extracting ability of T2EHDGA could allow separation of Am from the light lanthanides during the extraction step. Switching the aqueous phase chemistry to a citrate-buffered diethylenetriaminepentaacetic acid (DTPA) solution at pH 2.5 to 4 results in selective transfer of the actinides to the aqueous phase, thus resulting in separation of these two groups of elements. Separation factors on the order of 20 to 40 can easily be achieved in the ALSEP systems.
Nitric acid
Aqueous two-phase system
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Bond-length distributions have been examined for eighty-four configurations of the lanthanide ions and twenty-two configurations of the actinide ions bonded to oxygen. The lanthanide contraction for the trivalent lanthanide ions bonded to O 2- is shown to vary as a function of coordination number and to diminish in scale with increasing coordination number.
Lanthanide contraction
Coordination number
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Abstract Solvent extraction is a powerful method for lanthanide and actinide intra- and inter-group separations. Apart of the general parameters governing the extraction.f-electron elements exhibit several peculiarities of the process. Two of them are described in the paper: double-double (tetrad) effect in the lanthanide and actinide series and itinerant properties of the actinides (III) in respect to the lanthanide series, as well as the effects of inner- and outer-sphere hydration of the extracted species. Extraction chromatography is presented as the most powerful technique of the extractive separation.
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This chapter contains sections titled: Important Lanthanide Radionuclides Chemical Properties of the Lanthanides Separation of Lanthanides from Actinides Lanthanides as Actinide Analogs 147Pm and 151Sm Essentials of Lanthanide Radiochemistry
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The trivalent actinide thiocyanate complexes of Am and Cm are synthesized for the first time along with their lanthanide homologues allowing comparison of the lanthanide and actinide bonding.
Thiocyanate
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A selection of supramolecular ligands designed to extract f-elements.
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