Ion–solvent mutual transport in multicomponent solutions

Abstract

In a complete discussion of transport properties in terms of the formalism of irreversible thermodynamics, we have described the diffusion of ions in non-homogeneous solvent mixture; the ion–solvent coupling terms l_ij play an important role as a result of the preferential solvation phenomenon. Moreover, it is concluded that the determination of these coupling terms leads to the absolute values n₊ and n_– which are the excess of water molecules transported by anions and cations. The development of this formalism has been extended in order to obtain expressions of experimental quantities such as Washburn numbers W=n₊t₊–n_–t_– and generalized diffusion coefficients; D_ij in the case of ternary system (electrolyte and mixed solvent) in terms of Onsager l_ij coefficients; we then demonstrate that both the experimental quantity W and the D₁₂ cross coefficients of the electrolyte lead to absolute individual values, n^°₊ and n^°_–, in the case of highly dilute electrolytes.