To Separate a Particular Ln(III) Selectively Using Solvent Extraction

ABSTRACT

Since a particular trivalent lanthanide (Ln(III)) often plays a unique role in different industrial applications, the development of a selective separation method to get only the requisite Ln(III) would be most convenient. Synergistic extraction with β-diketone (HA) and Lewis base (B), which has been extensively used for the separation of lanthanides, relies on two processes: the extraction with HA as LnA₃ into the organic phase and the complexation of LnA₃ with B as LnA₃B in the organic phase. The variation in the pattern of the extraction constants of LnA₃ across the Ln series correlates with the number of CF₃- group in the β-diketones, and with the stability constants of LnA₃B of different Lewis bases. It is seen that the constants with bipyridyl increase with increasing atomic number, while those with POPO (methylenediphosphonate) and MePhPA (methylphenylphenanthroline carboxamide) decrease with increasing Ln atomic number. Using pivaloyltrifluoroacetone as the β-diketone and MePhPA, the best extractability appeared at Sm(III) among the series. As a conclusion, to get only a required Ln(III), the combination of β-diketone and Lewis base is very important. In addition, the separation of Lns(III) from other metals and the use of new extractants developed recently and reported in literature were referred to find out more effective extractants and selective separation methods.

KEYWORDS:

• Selective separation
• synergistic extraction
• β-diketone
• lanthanide
• Lewis base