An equation for self-diffusion coefficients of the trivalent lanthanide ion 152Eu (III) in concentrated asymmetrical 3:1 electrolyte aqueous solutions at pH 2.50 and at 298.15 K

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Ionic self-diffusion coefficients D of the trivalent ion 152Eu (III) have been determined in aqueous Gd(NO 3) 3–HNO 3 concentrated solutions (pH = 2.50) at 25 °C by the open-end capillary method (O.E.C.M.). The method measures the transportation time of ion across a fixed distance. We optimized the pH in order to avoid the hydrolysis, pairing and complexing trivalent 4f ions. The diffusion data obtained in large range of concentration as well as the physicochemical properties, allow to derive the following information: ( i) the limiting value D° at zero ionic strength, as 6.115 10 − 6 cm 2 s − 1 for 152Eu (III), ( ii) the validity of the Onsager limiting law, ( iii) the ionic self-diffusion coefficient as a function of the ionic strength for asymmetrical 3:1 electrolytes in dilute solutions, ( iv) a competition between ion–ion interaction and ion–solvent interaction and ( v) a more extended law available for an intermediate range of concentration up to 0.114 mol L − 1 and for a concentrated range up to 1.5 mol L − 1 . This study contributes to demonstrate similarities transport and structure properties between 4f and 5f trivalent ions explained by a similar electronic configuration, ionic radius and same hydration number.