NOVEL LIQUID ANION-EXCHANGE EXTRACTANT

A new type of liquid anion-exchange extractant, ethylenebis-(trioctylphosphonium) (EBTOP), was developed, which is a lipophilic diphosphonium ion bearing two cation centers adjacently in a molecule. EBTOP exhibited a better extractability than Capriquat-type monocationic ion-exchange extractants, when MIIX42- type anionic complexes of divalent metal ions (zinc(II), cadmium(II), copper(II), lead(II)) were extracted. Conversely, in the extraction of trivalent metal ions such as iron(III) and indium(III), which is capable of forming monoanionic complexes of the type MIIIX4-, EBTOP was inferior to the monocationic extractants in extraction ability. By making use of such extraction behavior of EBTOP, selective extraction of zinc family-metal ions could be performed in the presense of excess iron-(III) and indium(III). The extraction equilibrium was discussed.