Solvent extraction of some divalent metal cations into nitrobenzene by using a synergistic mixture of strontium dicarbollylcobaltate and hexaethyl calix[6]arene hexaacetate

Abstract

From extraction experiments and γ-activity measurements, the exchange extraction constants corresponding to the general equilibrium ${\text{M}}^{2 + } ({\text{aq}}) + {\text{SrL}}^{2 + } ({\text{nb}}) \Leftrightarrow {\text{ML}}^{2 + } ({\text{nb}}) + {\text{Sr}}^{2 + } ({\text{aq}})$ taking place in the two-phase water–nitrobenzene system (M²⁺ = Ca²⁺, Ba²⁺, Pb²⁺, Cd²⁺; L = hexaethyl calix[6]arene hexaacetate; aq = aqueous phase, nb = nitrobenzene phase) were evaluated. Moreover, the stability constants of the ML²⁺ complexes in nitrobenzene saturated with water were calculated; they were found to increase in the following order: Cd²⁺ < Ca²⁺ < Sr²⁺ < Pb²⁺ < Ba²⁺.