Lanthanoids separation

Goto, M., Matsumoto, S., Uezu, K. et al. 1999. Development and computational modeling of novel bifunctional organophosphorus extractants for lanthanoid separation. Sep. Sci. Technol. 34 (11) 2125-2139. 

Of the remaining 26 undiscovered elements between hydrogen and uranium, 11 were lanthanoids which Mendeleev s system was unable to characterize because of their great chemical similarity and the new numerological feature dictated by the filling of the 4f orbitals. Only cerium, terbium and erbium were established with certainty in 1871, and the others (except promethium, 1945) were separated and identified in the period 1879 -1907. The isolation of the (unpredicted) noble gases also occurred at this time (1894-8). 

Difficulties in separating and isolating the lanthanoids delayed their widespread use in technology. However, today they are studied intensely, because superconducting materials often contain lanthanoids (Fig. 1.64). All the actinoids are radioactive. None of the elements following plutonium occurs naturally on Earth in any significant amount. Because they can be made only in nuclear reactors or particle accelerators, they are available only in small quantities. 

The discovery of Sc occurred separately from the above work. In 1840, C. J. A. Scheerer reported a new mineral euxenite which had been found near Jolster in Norway. An approximate analysis was made and many elements were detected including lanthanoids. Lars Fredrik Nilson in 1879 reported the isolation of2g of SC2O3 if om working up 10 kg of euxenite plus someresidues from several other minerals. 

Modolo, G., Seekamp, S., Nabet, S. 2002. Development of an extraction process for separation of actinoids(III)/lanthanoids(ni) with the aid of dithiophosphinic acids. Chem. Ing. Tech. 74 (3) 261-265. 

Dysprosium is one of 15 rare earth elements in Row 6 of the periodic table. The name rare earth is misleading because the elements in this group are not especially uncommon. However, they often occur together in the earth and were once difficult to separate from each other. A better name for the rare earth elements is lanthanoids. This name comes from the element lanthanum, which is sometimes considered part of the lanthanoids group in the periodic table. The periodic table is a chart that shows how chemical elements are related to one another. 

Dysprosium was discovered in 1886, but was not commercially available until after 1950. The reason for the long delay was that methods for separating dysprosium from other lanthanoids had not been developed. Dysprosium has few applications but is used in some hybrid cars. 

The first step in obtaining praseodymium is to treat monazite, basmasite, or another ore to separate the lanthanoids from each other. The various elements are then changed to compounds of fluorine, such as praseodymium fluoride (Prp3). Praseodymium metal can then be obtained by passing an electric current through molten (melted) praseodymium fluoride ... 

The classical chemical methods to separate lanthanoids were based upon the redox behavior of Ce, Sm, Eu, and Yb , Other classical methods (fractional crystallization) are essentially physical processes. Cerium is oxidized to the 4-I- state and separated from the 3+ rare earths by solvent extraction, iodate precipitation, or selective hydrolysis or precipitation of basic Ce(IV) compounds in weakly acidic solution. Europium is reduced and maintained in H2O as Eu " by Zn amalgam and precipitated as EUSO4. Sm and Yb are extracted from H2O by reduction into dilute Na or Li amalgam. 

Tributyl phosphate (TBP) is the traditional and still most widely used neutral organophosphorus extractant . The light trivalent rare earths can be separated in 10-14 extraction stages. Liquid-liquid extraction is used commercially to separate the lanthanoids. ... 

To a limited extent, lanthanoids are separated from each other by tertiary amine extractants and by quaternary ammonium salts with long (Cg and Cio) alkyl groups. Tertiary amines in an organic phase preferentially extract the trivalent actinoids better than the lanthanoids by salting out (dehydrating) the cations from the aqueous phase with high LiCl concentration, e.g., the TRAMEX (tertiary amine extraction) process for Cm isolation . Recent developments in trivalent f-element separations, such as chelating and bifunctional extractants have been reviewed . 

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