Liquid membrane separations of metal cations using macrocyclic carriers

The selectivity in water and methanol solvents of macrocyclic crown ether ligands toward univalent and bivalent cations is well known. Incorporation of these ligands into chloroform liquid membranes separating water and salt solution phases results in a system showing selective cation transport. The cation transport rates of single cations across these liquid membranes have been correlated with equilibrium constant values for cation-macrocycle interaction in methanol. This correlation has been extended to binary cation mixtures of Cs+ with Li+, Na+, K+, and Rb+. A model for cation transport from these cation mixtures has been reduced to an equation which gives good agreement between measured and predicted transport rates across our liquid membranes. 11 figures, 3 tables