Extraction of rare earth metals by calix[4]arene solubilized in AOT reversed micellar solution

Abstract

Abstract Extraction of rare earth metals (europium and yttrium) and their separation from zinc were investigated using a novel host compound, p - tert -octylcalix[4]arene carboxyl derivative as an extractant. Extraction behavior of the metals with a typical commercial extractant PC-88A or Versatic 10 was also examined. The cyclic ligand calixarene showed a high selectivity towards rare earth metals compared with PC-88A and Versatic 10. The addition of sodium ion into the feed aqueous solution enhanced the extractability of rare earth metals, and resultantly, improved the selectivity. The drawback of this promising extractant was the poor solubility in organic solvents, especially in nontoxic aliphatic solvents such as isooctane and kerosene. We attempted to solubilize the novel extractant calix[4]arene in isooctane by utilizing reversed micelles formed with an anionic surfactant AOT. p - tert -Butylcalix[4]arene could be dissolved in the AOT–isooctane reversed micellar solution by injecting an adequate amount of water. Furthermore, the extraction of metals from the aqueous solution dissolving sodium ion was conducted by the AOT–isooctane system containing p - tert -butylcalix[4]arene. The excellent extraction and separation of metals was achieved by using calixarene solubilized in the AOT-reversed micellar solution.