Self-diffusion of cobalt and manganese ions in aqueous electrolyte solutions

Abstract

Self-diffusion coefficients of Co²⁺ ions labelled with ⁶⁰Co²⁺ in aqueous solutions of CoCl₂, Co(NO₃)₂ and CoSO₄, and of Mn²⁺ ions tagged with ⁵⁴Mn²⁺ in aqueous solutions of MnCl₂ and MnSO₄ have been measured over a concentration range of 0.005–2 mol dm^–3, using an open-ended capillary technique with stirring. The theoretical self-diffusion coefficients of Co²⁺ and Mn²⁺ ions in the respective salts are calculated using the Onsager–Gosting–Harned equation and compared with the experimentally determined diffusion coefficient values. The deviations observed between theoretical and experimental values are explained by taking into account viscosity changes, ion–water and ion–ion interactions.