CATION-EXCHANGE BEHAVIOR OF ACTINIDES IN AQUEOUS-ORGANIC SOLUTIONS OFNITRIC-ACID CONTAINING TRIOCTYLPHOSPHINE OXIDE

A comparative study was carried out of cation-exchange behavior of Th, Pa, U, Np, Pu, Am, Cf, Zr, Nb, Eu, Sr, and Cs on Dowex-50 cation exch anger in aqueous-organic solutions of HNO3 depending on the solvent (C H3OH, C2H5OH, C4H9OH, CH3COOH, CH3COCH3, CH3CN, ethylene glycol, tetra hydrofuran, and dimethyl sulfoxide) and concentration of acid and trio ctylphosphine oxide in solution. The distribution coefficients of acti nides in higher oxidation states [Th(IV), Pa(V), U(VI), Np(V), and Pu( IV)] and of Zr(IV) and Nb(V), which form strong solvates with trioctyl phosphine oxide (TOPO) in nitric acid solutions, are several times sma ller than the distribution coefficients of elements in oxidation state s I, II, and III [Cs, Sr, transplutonium (TPEs), and rare-earth (REEs) elements] in the same systems. Experimental results permit selection of the optimal conditions of TPE separation from light actinides and f ission elements using a cation exchanger and aqueous-organic solutions of HNO3 as eluents.