Comparative study on the hydration states of Cm(III) and Eu(III) in solution and in cation exchange resin

The sorption behavior and hydration structure of Cm(III) and Eu(III) in the cation exchange resin-acid solution systems were studied by measurements of the distribution coefficient KD and the inner-sphere hydration number NH2O of the ions in acid solution and in resin phase. The differences in the KD and NH2O values for Cm(III) and Eu(III) above 5 M HCl are KD(Eu)>KD(Cm) and NH2O(Eu)>NH2O(Cm), while the NH2O of Cm(III) in the resin phase in 0.1-11 M HCl solution are approximately equal to those of Eu(III). The NH2O of Cm(III) in HNO3 or HClO4 solution and in the resin phase are similar to those of Eu(III), in agreement with the similarity in the KD of the ions. The separation and sorption mechanisms of Cm(III) and Eu(III) are discussed from the KD and NH2O values. (orig.)