A solution of 0.1 M N,N-di-2-ethylhexyl-N´,N´-di-octyl-3-oxa-1,5-diamide (DEHDODGA)-0.5 M N,N-dihexyloctanamide (DHOA) in n-dodecane has been evaluated for the separation of trivalent actinides from high-level liquid waste (HLLW). The extraction and stripping behaviour of Am(III) and other metal ions present in HLLW was studied. The distribution ratio of various metal ions was measured as a function of concentration of nitric acid and interfering ion. The extraction of metal ions decreased in the order M4+ ≥ M3+ ≫ M2+ ∼ MO22+ ≫ M+. The extraction of Am(III), Eu(III), Y(III), and Zr(IV) was quantitative. However, the distribution ratio of unwanted metal ions such as Fe(III), Co(II), Sb(III), Mn(II), and Cs(I) was negligible. The distribution ratios of Cd(II), Ru(III), Pd(II), Mo(VI), Cr(VI), Ba(II), Ni(II), and Sr(II) were not insignificant, but were quite low. The conditions needed for the quantitative recovery of trivalents from the loaded organic phase were optimized with the use of diethylenetriaminepentaacetic acid (DTPA)-citric acid at pH 3 to facilitate the mutual separation of lanthanides-actinides in the subsequent step.
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