Synergistic extraction of some divalent cations into nitrobenzene by using strontium dicarbollylcobaltate and hexaethyl p-tert-butylcalix[6]arene hexaacetate

From extraction experiments and γ-activity measurements, the exchange extraction constants corresponding to the general equilibrium M2+ (aq) + SrL2+ (nb) ↔ ML2+ (nb) + Sr2+ (aq) taking place in the two-phase water-nitrobenzene system (M2+ = Ca2+, Pb2+, Cu2+, Zn2+, Cd2+, UO22+, Mn2+, Co2+, Ni2+; L = hexaethyl p-tert-butylcalix[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+ < Mn2+ < Cu2+, Zn2+ < UO22+, Co2+ < Ni2+ < Sr2+ < Pb2+. (author)