Solvent Extraction Studies for the Separation of Trivalent Actinides from Lanthanides with a Triazole-functionalized 1,10-phenanthroline Extractant

ABSTRACT

A new N-atom donor extractant 2,9-bis(1-(2-ethylhexyl)-1H-1,2,3-triazol-4-yl)-1,10-phenanthroline (EH-BTzPhen) was synthesized and used in solvent extraction studies to separate the trivalent minor actinide americium(III) and curium(III) from europium(III), representing fission product lanthanides. The extractant was found to be soluble in 1-octanol and in the Aliquat-336 nitrate ([A336][NO₃]) ionic liquid diluent, but insoluble in n-dodecane. The [A336][NO₃] is a fully incinerable room temperature ionic liquid, and has a higher flash point than aliphatic diluents such as 1-octanol. The EH-BTzPhen proved to be effective for selective minor actinide extraction only in combination with 2-bromohexanoic acid synergist when 1-octanol was used as a diluent (SF_Am/Eu > 200). The change of the diluent from 1-octanol to Aliquat-336 nitrate allowed selective An(III) extraction from low acidity feed solutions without the need of a synergist (SF_Am/Eu ~ 70 and SF_Am/Cm ~ 1.9–2.2). The phase transfer kinetics of the ligand-metal complexes is however very slow at 22 °C in the case of both solvents. With this newly synthesized extractant, the achieved SF_Am/Cm was comparable to the values achieved with the established CyMe₄BTBP and CyMe₄BTPhen extractants.

KEYWORDS:

• Minor actinides
• lanthanides
• solvent extraction
• Aliquat-336
• ionic liquids
• 1,2,3-triazole

Acknowledgments

The authors would like to thank Magda Ooms for the help with the alpha spectrometry measurements.

Supplementary material

Supplemental data for this article can be accessed on the publisher’s website.

Correction Statement

This article has been republished with minor changes. These changes do not impact the academic content of the article.

Additional information

Funding

P.Zs. acknowledges the SCK CEN for providing funding for a Ph.D. fellowship and the FOD Economie for providing additional support (Energietransitiefonds). T.O. is a doctoral fellow of FWO Vlaanderen (1154419N). Mass spectrometry was made possible by the support of the Hercules Foundation of the Flemish Government (grant 20100225-7).