SILVER(I) ION-SELECTIVE TRANSPORT ACROSS POLYMER INCLUSION MEMBRANES CONTAINING NEW PYRIDINO-PODAND AND BIPYRIDINO-PODAND

A novel technique was developed for Ag+ ion separation from complex mi xtures including transition metal ions. Ag+ ion-selective transport is observed across polymer inclusion membranes (PIMs) containing several tridentate podands. These podands have three pyridine nitrogen atoms at tridentate coordinating positions and exhibit Ag+ ion selective bin ding. Using PIM systems, Ag+ ion could be selectively removed from a c omplex mixture containing high concentrations of Cd2+, Zn2+, Co2+, Ni2 +, Pb2+ and Cu2+ ions. The present study revealed remarkable effects o f stereochemically controlled substitution of the podand on Ag+ ion pe rmeability. Thus, design of podand-type carriers based on guest-target ed ligand geometry and stereochemically controlled substitution provid e a new, effective methodology in developing cation-specific membranes . The present type of PIMs was stable for long period experiments and showed high flux and selectivity for Ag+ ion at practical levels (j>2x 10(-5) mol/m(2) s). (C) 1998 Elsevier Science B.V. All rights reserved .