Cation exchange behaviour of actinides in aqua-organic nitric acid solutions containing trioctylphosphine oxide

Comparative study of Th, Pa, U, Np, Pu, Am, Cf, as well as of Zr, Nb, Eu, Sr and Cs behaviour on the Dowex-50 cationite in mixed water-organic solutions of HNO3, depending on solvent nature, has been conducted acid concentration and TOPO content in the solution. It is shown that the values of actinide distribution factors in higher oxidation states [Th(4), Pa(5), U(6), Np(5), Pu(4)], as well as Zr(4) and Nb(5), forming strong solvates in nitric acid solutions with TOPO, are several orders lower than the distribution factors for mono-, bi- and trivalent elements (Cs, Sr, TPE, rare earths) in the systems. On the basis of the results obtained the optimal conditions for TPE separation from light actinides and fission fragments on the cationite using water-organic solutions of HNO3 as eluents have been chosen. 12 refs.; 4 tabs