WATER-SOLUBLE CALIXARENES AS POSSIBLE METAL-ION EXTRACTANTS IN POLYETHYLENE GLYCOL-BASED AQUEOUS BIPHASIC SYSTEMS

The behavior of a water soluble calixarene ligand has been investigate d in an (NH4)(2)SO4/polyethylene glycol-2000 (PEG) aqueous biphasic sy stem. Spectroscopic measurements indicate that 4-sulfonic-calix-6-aren e partitions preferentially to the polymer-rich phase in this system. The utility of this ligand as a metal ion extractant was also investig ated. The addition of the calixarene (10(-2)M in initial PEG-rich stoc k solution) did not significantly enhance the partitioning of Na+, Cs, Sr2+, Ba2+, Co2+, Cd2+, or UO22+ from the (NH4)(2)SO4-rich to the PE G-rich phase. The partitioning behavior of these metal ions is depende nt, rather, on their Gibbs free energy of hydration (Delta G(hyd)).