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Lanthanides & Actinides
Lanthanides Separation

2/3 of world production is actually used mixed in the proportions occuring naturally in the ore

1. Cerium & Europium may be extracted Chemically:
  • Oxidize only Ce to M4+ by HClO or KMnO4, then precipitate as CeO2 or Ce(IO3)4
  • On action of Zn/Hg only Eu forms a stable M2+ that doesn't reduce H2O, then isolate by precipitation as EuSO4
2. Separation by Fractionation:

Small Scale methods used originally:

Fractional Crystallization of e.g. Ln(NO3)3.2NH4NO3.4H2O or Ln(BrO3)3

Fractional Thermal Decomposition of e.g. Ln(NO3)3

Current Small Scale Lab. Separation:

Ion-Exchange Displacement Column

  • Ln3+(aq) are strongly adsorbed by a cation-exchange resin
  • add an eluant ligand
    typically chelating ligands
    e.g. EDTA , or 2-hydroxy-EDTA

    e.g. HIB{[[alpha]]-hydroxyisobutyric acid}

  • Ligand binds most strongly to smallest ion
e.g. the binding constants of the Ln(EDTA) complexes

  • Elution order is Lu Æ La
  • The process of separation is indicated graphically
greater detail on these columns may be found in:-
  • Greenwood & Earnshaw, p. 1427-1428
  • Open University S304 Unit 27, p. 20-22


Current Large Scale Industrial Separation:

Solvent Extraction

  • Ln3+(aq) is extracted in a continuous counter-current process into a non-polar organic liquid (e.g. kerosene)
  • the kerosene contains ca. 10% of
    • bis(2-ethylhexyl)phosphinic acid (DEHPA)


    • tri-n-butylphosphine oxide (TBPO) (nBu3O)3PO
  1. solubility of Ln3+ in organic solvent increases with its RAM
  2. separation factor for adjacent rare earths = 2.5
  3. automatic multistep, counter-current conditions Æ 99.9% purity Ln
--Info & DownloadsBibliography  [textbook & online resources]

Source: Dr. S.J. Heyes; University of Oxford
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