LIQUID-LIQUID-EXTRACTION OF METAL-IONS WITH A CYCLIC LIGAND CALIXARENE CARBOXYL DERIVATIVE

The extraction behavior of alkaline, alkaline-earth, and transition me tals in liquid-liquid extraction was systematically investigated with a cyclic host compound calixarene carboxyl derivative. Using a novel h ost ligand, an extraction equilibrium experiment was carried out and t he complexation mechanism between the metal ions and the cyclic ligand was investigated. Calixarene carboxyl derivatives showed high extract ability for all of the metal ions compared to that of the monomer anal og. The extraction behavior of alkaline and alkaline-earth metals is c losely related to the cavity size of the cyclic ligands; thus, the tet ramer selectively extracted sodium and calcium ions, while the hexamer did so for cesium and barium ions. On the other hand, the extractabil ity of transition metals could not be explained by a size effect, and increased in the order: monomer<tetramer<hexamer. Among transition met als, the higher the stability constant between a metal and the carboxy l group, the more preferential extraction was occurred. These results indicate that the cyclic structure is effective for the extraction of alkaline and alkaline-earth ions, rather than transition-metal ions. A ll of the metal ions were confirmed to be extracted with the cyclic li gands by forming a 1:1 complex in a toluene phase.