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The structures of CyMe4-BTBP complexes of americium(III) and europium(III) in solvents used in solvent extraction, explaining their separation properties

Ekberg, Christian and Löfström-Engdahl, Elin and Aneheim, Emma and Foreman, Mark R. StJ. and Geist, Andreas and Lundberg, Daniel and Denecke, Melissa and Persson, Ingmar (2015). The structures of CyMe4-BTBP complexes of americium(III) and europium(III) in solvents used in solvent extraction, explaining their separation properties. Dalton Transactions: an international journal of inorganic chemistry [incorporating Acta Chemica Scandinavica]. 44:42, 18395-18402
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Official URL: http://dx.doi.org/10.1039/c5dt02859k

Abstract

Separation of trivalent actinoid (An(III)) and lanthanoid (Ln(III)) ions is extremely challenging due to their similar ionic radii and chemical properties. Poly-aromatic nitrogen compounds acting as tetradentate chelating ligands to the metal ions in the extraction, have the ability to sufficiently separate An(III) from Ln(III). One of these compounds, 6,6'-bis(5,5,8,8-tetramethyl-5,6,7,8-tetrahydro-benzol[1,2,4]triazin-3-yl)-[2,2]bipyridine, CyMe4-BTBP, has proven to be resistant towards acidic environments and strong radiation from radioactive decomposition. EXAFS studies of the dicomplexes of CyMe4-BTBP with americium(III) and europium(III) in nitrobenzene, cyclohexanone, 1-hexanol, 1-octanol and malonamide (DMDOHEMA) in 1-octanol have been carried out to get a deeper understanding of the parameters responsible for the separation. The predominating complexes independent of solvent used are [Am(CyMe4-BTBP)(2)(NO3)](2+) and [Eu(CyMe4-BTBP)(2)](3+), respectively, which are present as outer-sphere ion-pairs with nitrate ions in the studied solvents with low relative permittivity. The presence of a nitrate ion in the first coordination sphere of the americium(III) complex compensates the charge density of the complex considerably in comparison when only outer-sphere ion-pairs are formed as for the [Eu(CyMe4-BTBP)(2)](3+) complex. The stability and solubility of a complex in a solvent with low relative permittivity increase with decreasing charge density. The [Am(CyMe4-BTBP)(2)(NO3)](2+) complex will therefore be increasingly soluble and stabilized over the [Eu(CyMe4-BTBP)(2)](3+) complex in solvents with decreasing relative permittivity of the solvent. The separation of americium(III) from europium(III) with CyMe4-BTBP as extraction agent will increase with decreasing relative permittivity of the solvent, and thereby also with decreasing solubility of CyMe4-BTBP. The choice of solvent is therefore a balance of a high separation factor and sufficient solubility of the CyMe4-BTBP ligand.

Authors/Creators:Ekberg, Christian and Löfström-Engdahl, Elin and Aneheim, Emma and Foreman, Mark R. StJ. and Geist, Andreas and Lundberg, Daniel and Denecke, Melissa and Persson, Ingmar
Title:The structures of CyMe4-BTBP complexes of americium(III) and europium(III) in solvents used in solvent extraction, explaining their separation properties
Series/Journal:Dalton Transactions: an international journal of inorganic chemistry [incorporating Acta Chemica Scandinavica] (1477-9226)
Year of publishing :2015
Volume:44
Number:42
Page range:18395-18402
Number of Pages:8
Publisher:Royal Society of Chemistry
ISSN:1477-9226
Language:English
Publication Type:Journal article
Refereed:Yes
Article category:Scientific peer reviewed
Version:Accepted version
Full Text Status:Public
Subjects:(A) Swedish standard research categories 2011 > 1 Natural sciences > 104 Chemical Sciences > Inorganic Chemistry
Agrovoc terms:chemistry
Keywords:solvent extraction, americium, europium, structure determination, organic solvents
URN:NBN:urn:nbn:se:slu:epsilon-e-3476
Permanent URL:
http://urn.kb.se/resolve?urn=urn:nbn:se:slu:epsilon-e-3476
Additional ID:
Type of IDID
Web of Science (WoS)000363580800014
DOI10.1039/c5dt02859k
ID Code:13338
Faculty:NJ - Fakulteten för naturresurser och jordbruksvetenskap
Department:(NL, NJ) > Department of Chemistry and Biotechnology (140101-161231)
External funders:Knut and Alice Wallenberg Foundation
Deposited By: SLUpub Connector
Deposited On:09 Jun 2016 11:47
Metadata Last Modified:16 Sep 2016 23:15

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