Self-diffusion coefficients and structure of the trivalent transplutonium ion berkelium in aqueous solution

Abstract

Self-diffusion coefficients D of the trivalent aquo ion Bk3+ have been determined in aqueous Nd(ClO4)3-HClO4 solutions (pH 2.5) at 25°C by the open end capillary method (O.E.C.M.). The variation of D versus the square root of the concentration of inactive solution is not linear in the studied range of concentration. The limiting value D0 at zero ionic strength is 5.95 ∗ 10−6 cm2s−1. The graph D = f(√C) for Bk3+ ion can be compared to those of 241Am3+ and 152Eu3+ obtained under the same conditions. Moreover, it may be argued that the Bk3+, Am3+ and Eu3+ aqueous ions in solution have the same hydration as other 5f and 4f tripositive ions in the absence of hydrolysis, complexing or ion pairing at pH 2.5. A semi-quantitative extension of the Debye-Onsager limiting law available in the range of concentrations up to 1M is proposed. The present study contributes to show the analogy of solvation structure of actinides ions in aqueous solution at pH 2.5 with that of the lanthanides trivalent ions as a help for predicting their transport properties.