Synergistic extraction of some divalent cations into nitrobenzene by using dicarbollylcobaltate and substituted calix[5]arenes.

From extraction experiments and γ-activity measurements, the exchange extraction constants corresponding to the general equilibriums Sr²⁺ (aq) + 2 picrate (aq) + L (nb) ⇔ SrL²⁺ (nb) + 2 picrate (nb) and M²⁺ (aq) + SrL²⁺ (nb) ⇔ ML²⁺ (nb) + Sr²⁺ (aq) taking place in the two–phase water–nitrobenzene system (M²⁺ = Ca²⁺, Ba²⁺, Pb²⁺, Cu²⁺, Zn²⁺, Cd²⁺, Mn²⁺, Co²⁺, Ni²⁺, UO 2 2 + ; L = substituted calix[5]arenes; aq = aqueous phase, nb = nitrobenzene phase) were evaluated. Moreover, the stability constants of the ML²⁺ complexes in nitrobenzene saturated with water were calculated. Very high stability constants of pentaethyl p-tert-butylcalix[5]arene pentaacetate ligand with Ba²⁺ cation has been found. [ABSTRACT FROM AUTHOR]