After recovery of reusable plutonium and uranium from the used nuclear fuel, fission product lanthanides and highly radio-toxic, long-lived minor actinides are left in solution. The minor actinides (Am and Cm) can be transmutated to shorter-lived isotopes in future fast-neutron reactors, but lanthanides act as neutron poisons to this process. Due to this complication, the minor actinides must efficiently be separated from the lanthanides. Minor Actinides(III)/lanthanides(III) separation is a difficult task due to the prevalence of the trivalent oxidation state and their similar ionic radii. One approach for their separation is through the development of highly selective soft donor organic extractants. Many N-donor ligands, such as BTBPs (bis-triazinyl bipyridines), have been studied during the past decades for the purpose of conducting An(III)/Ln(III) separations. Despite their good selectivity, many of these reagents have been found to degrade under highly acidic and radiolytic conditions and also to suffer from slow extraction kinetics. In an attempt to overcome these drawbacks, new N-donor tetradentate ligands containing a bipyridine core substituted with 1,2,3-triazole rings have been synthesized and tested. The 6,6'-bis(1-(2-ethylhexyl)-1H-1,2,3-triazol-4-yl)-2,2'-bipyridine (EH-BTzBP) extracts Am(III) with a separation factor of 70 over Eu(III) in the presence of the lipophilic coextractant 2-bromohexanoic acid. The synergistic system was found to efficiently extract Am(III) at < 0.1 M HNO3; back-extraction can then be completed at higher nitric acid concentration. The ligand/extractant combination shows good solubility in toluene, fast phase transfer kinetics, resistance to acid hydrolysis and possibly to oxidizing agents created by radiolysis. Characterization of EH-BTzBP coordination chemistry will be investigated and compared to similar BTBPs.Work performed with support from the U.S. Department of Energy, Office of Nuclear Energy, Nuclear Energy University Programs (NEUP) project number 10-881.

Novel addition of 1,2,3-triazole rings on a bipyridine-based ligand for actinide(III)/lanthanide(III) separations

248th National Meeting (2014)

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