Selective Extraction of U(VI) by Counter-Current Liquid-Liquid Extraction with N,N-di(2-Ethylhexyl)-2,2-Dimethylpropanamide

A continuous counter-current extraction experiment for the selective extraction of U(VI) using N,N-di(2-ethylhexyl)-2,2-dimethylpropanamide (DEHDMPA) as an extractant was carried out with mixer-settler type extractors consisting of a U extraction step, a scrub step, and a U back-extraction step. DEHDMPA selectively extracted U(VI) over Pu(IV), and the decontamination factor against Pu(IV) in the U fraction was 990. Fractional distributions of U(VI) in the U fraction and Pu(IV) in the raffinate were 94.5% and 99.9%, respectively. Numerical simulation for calculating U(VI) and Pu(IV) concentrations in each stage of the mixer-settlers was performed. The calculated values agreed with experimentally- measured U(VI) and Pu(IV) concentrations in the U extraction step, and also agreed with the experimentally-measured U(VI) concentrations in the scrub step.