Development of extraction processes to separate the trivalent lanthanides from minor actinides is motivated by the goal of optimizing geological repository space and decreasing the long-term radiotoxicity of used nuclear fuel. The Actinide-Lanthanide Separation process – ALSEP – combines the neutral diglycolamide N,N,N’,N’-tetra-2-ethylhexyl diglycolamide (T2EHDGA) with the acidic extractant 2-ethylhexylphosphonic acid mono-(2-ethylhexyl) ester (HEH[EHP]) in an alkane diluent. The ALSEP solvent co-extracts trivalent actinides and lanthanides from a post-PUREX raffinate, which are subsequently separated by a stripping step using a buffered polyaminocarboxylic acid solution. The extraction mechanism(s) of the combined neutral/acidic extractant system is not fully understood, and requires probing several phenomena, including extractant aggregation, speciation and structure of the metal complexes in the organic solvent for each extractant, among others.<br/> <br/>Current research focuses on evaluation of the transport behavior of T2EHDGA and HEH[EHP] toward trivalent lanthanides and actinides from nitric acid solutions. Partitioning of nitric acid into the organic solvent is found to play an important role on the extractants’ aggregation behavior and impacts the extraction mechanism. The effect of aqueous phase conditions, as well as metal extraction, on organic phase aggregation provides insight toward process chemistry. We present our to-date results on the structural characterization of the supramolecular assemblies and aggregation phenomena in the ALSEP alkane and aromatic solvents investigated using X-ray absorption spectroscopy, Small Angle X-ray and Neutron Scattering and other techniques.

Supramolecular aggregation in the ALSEP system: Effect of diluent

254th National Meeting (2017)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.