Efficient separation of f-block metals, the lanthanides and actinides, is an ongoing technical challenge due to the chemical similarities of the elements, but needed for many metallurgy applications. One example is the reprocessing of spent nuclear fuel, where fissile material is recycled and long-lived isotopes, like Am and Cm, are separated and transmuted in order to minimise the radiotoxicity of the final waste, reducing the years needed in repository by multiple magnitudes of power. A common separation technique is solvent extraction with organic extractants, and the alkyl substituted diamide amine extractant (ADAAM) has been proposed for separation of Am and Cm. Mainly one derivative, 2-ethylhexyl diamide amine, has been studied previously and in this study more variants were tested for solvent extraction of f-block metals (rare earth elements, Am and Cm) in order to deepen the understanding of ADAAM properties and their potential as extractants in the recycling of spent nuclear fuel.

A method to synthesise ADAAM extractants with varying length alkyl substituents, butyl to dodecyl, was established and solvent extraction conducted in a dodecane, nitric acid system where the extraction performance of f-block elements was measured using ICP-MS. Results show that a high concentration of ADAAM (> 100 mM) is needed for sufficient extraction and that straight alkyl chain derivatives show varying selectivity for different metals depending on acidity, unlike the branched 2-ethylhexyl derivative that selectively extracted only the light metals. More experiments at higher ADAAM concentrations need to be conducted in order to analyse the impact of alkyl chain length and branching on the selectivity between Am and Cm, but even at low concentrations of extractant the clear affinity for Am and Cm over lanthanides was observed.