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 Sr 2+ (aq) + 2 picrate (aq) + L (nb) ⇔ SrL 2+ (nb) + 2 picrate (nb) and M 2+ (aq) + SrL 2+ (nb) ⇔ ML 2+ (nb) + Sr 2+ (aq) taking place in the two–phase water–nitrobenzene system (M 2+ = Ca 2+ , Ba 2+ , Pb 2+ , Cu 2+ , Zn 2+ , Cd 2+ , Mn 2+ , Co 2+ , Ni 2+ , <m:math xmlns:m="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <m:mrow> <m:msubsup> <m:mtext>UO</m:mtext> <m:mn>2</m:mn> <m:mrow> <m:mn>2</m:mn> <m:mo>+</m:mo> </m:mrow> </m:msubsup> </m:mrow> </m:math> UO₂²⁺ ; L = substituted calix[5]arenes; aq = aqueous phase, nb = nitrobenzene phase) were evaluated. Moreover, the stability constants of the ML 2+ complexes in nitrobenzene saturated with water were calculated. Very high stability constants of pentaethyl p-tert-butylcalix[5]arene pentaacetate ligand with Ba 2+ cation has been found.