Comparative study of self-diffusion of the trivalent ions Eu 3+(4f) and Am 3+ in aqueous solutions

Abstract

The self diffusion coefficients of the 152Eu 3+ ion aqueous nitrate solution and the 241Am 3+ ion in neodymium perchlorate solution are determined by the open end capillary method (OCM). The aim of this work is as follows: Verification of the Onsager limit law concerning the relative variation of the self diffusion coefficient with the ionic strength. Comparison of the behaviour of the europium ion 152Eu 3+ with that of the americium ion 241Am 3+ from the point of view of ionic transport. This work would be useful in elucidating the electrolytic behaviour of actinide and lanthanide ions, especially with respect to ion-ion and ion-solvent interactions under equilibrium and non-equilibrium conditions. The data show that there is a similarity in the ionic transport processes of the 152Eu 3+ and 241Am 3+ ions. Diffusion coefficient of lanthanide ion at infinite dilution: D i° × 10 6 cm 2 s: 6.10 ( 152Eu 3+)[1]. Diffusion coefficient of actinide ion at infinite dilution: D i° × 10 6 cm 2 s: 6.19 ( 241Eu 3+)[1]. The present work shows that the electrostatic relaxation effect for 152Eu 3+ in an aqueous solution of Eu(NO 3) 3 is responsible for a relatively important variation (20%) in the concentration range 0 to 10 −3 M for the self-diffusion of these ions. On the other hand , our results show that the ionic transport process for 152Eu 3+ is similar to that for 241Am 3+ at pH 2.5. Moreover, it may be provisionally argued that the Eu 3+ ion in solution at pH⩾ 6 has essentially the same structure as a tripositive 5f ion.