Extraction of uranium (VI) and plutonium (IV) from nitric acid solution bysubstituted cyclic amides

Eight substituted cyclic amides have been synthesized and the extraction of U(VI) and Pu(IV) by the amides was investigated under various conditions. From the results of distribution ratio measurement for U(VI) and Pu(IV) (D- U and D-Pu), as functions of nitric acid and cyclic amide concentrations, t he effects of the cyclic amide ring size and the structure of substituents attached to different positions in the cyclic ring on the extraction were d iscussed. N-(2-ethylhexyl)-buty rolactam (EHBLA), N-(2-ethylhexyl-valerolac tam (EHVLA) and N-(2-ethylhexyl)-caprolactam (EHCLA) at a concentration of 1 kmol/m(3) in dodecane have produced a third phase at relatively high HNO3 concentration in the aqueous phase. By introducing an octyl group to the r ing, the third phase disappeared. EHVLA extracted U(VI) and Pu(IV) more str onger than EHBLA and EHCLA. DU and D-Pu values for 2-octyl-N-(2-ethylhexyl) -caprolactam (2OEHCLA) were lower than for the mixture of 3-octyl-N-(2-ethy lhexyl)-caprolactam (3OEHCLA) and 5-octyl-N-(2-ethylhexyl)-caprolactam (5OE HCLA). Steric hindrance by an n-octyl group next to the C=O group was great er in the extraction of Pu(IV) than U(VI).