Solvent Extraction of Ba2+, Pb2+ and Cd2+ into Nitrobenzene by Using Strontium Dicarbollylcobaltate in the Presence of Tetraethyl p-tert-Butylcalix4arene Tetraacetate

From extraction experiments and -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+ = Ba2+, Pb2+, Cd2+; L = tetraethyl p-tert-butylcalix4arene tetraacetate; aq = aqueous phase, nb = nitrobenzene phase) were evaluated. Further, the stability constants of the ML2+ complexes in water saturated nitrobenzene were calculated; they were found to increase in the order Ba2+ < Cd2+ < Pb2+.