Enhanced extraction and separation of trivalent lanthanoids with 4,4,4-trifluoro-1-phenyl-1,3-butanedione and crown ether

Synergistic extraction of the trivalent lanthanoids Nd, Eu and Tm with mixtures of 4,4,4-trifluoro-1-phenyl-1,3-butanedione (Hbtfa) and 18-crown-6, dicyclohexano-18-crown-6 or dibenzo-18-crown-6 (CE) in 1,2-dichloroethane from perchlorate solutions was investigated. Characteristic ion-pair extraction of the Nd(III) or Eu(III) was observed with 1,2-dichloroethane containing Hbtfa and crown ether, in which the cationic complex, Ln(btfa)(2).CE+, was formed and extracted. On the other hand, the heavier lanthanoid, Tm(III), was extracted as Tm(btfa)(3).CE. The addition of a crown ether to the metal chelate system not only enhances the extraction efficiency of these trivalent metal ions but also improves the selectivities significantly among the lighter and middle lanthanoids. Hence, such a system would be of practical value in the mutual or group separation of trivalent lanthanoids.