EXTRACTION OF RARE-EARTH-METALS BY LIQUID SURFACTANT MEMBRANES CONTAINING A NOVEL CYCLIC CARRIER

Extraction behavior of three rare-earth metals (He, Er and Y), was sys tematically studied by liquid surfactant membranes (LSMs) containing a novel host compound, a calixarene carboxyl derivative, which is a cyc lic compound connected to some phenol rings, as a mobile carrier in a stirred cell. Using the host compound, the extraction equilibrium of t he metals in liquid-liquid extraction was also investigated in order t o elucidate the complexation mechanism between the metal ions and the cyclic compound. The calixarene carboxyl derivative showed a high extr actability for all rare-earth metal ions compared with the analog mono mer compound. The extractability for the rare-earth metals was found t o increase in the following order: monomer < tetramer < hexamer. Howev er, the extraction rate of the tetramer was higher than that of the he xamer. The carboxyl derivative of calix[4]arene (tetramer) was an exce llent carrier for the permeation of rare-earth metals by LSMs. The eff ects of several operation factors on the extraction of the metals by L SMs were systematically examined with the calix[4]arene. The permeatio n mechanism of the rare-earth metals by LSMs containing the mobile car rier was explained with an interfacial reaction model.