SIM² KU Leuven researchers have developed a novel approach to separate samarium from cobalt originating from SmCo magnets. Their newly published paper in Separation and Purification Technology (210 (2019) 209–218) introduces very simple and cheap-to-maintain solvent extraction processes. (Leuven, 14/08/2018)

End-of-life SmCo magnets are a valuable secondary source of cobalt and samarium

This article critically compares three solvent extraction systems with ionic liquids as the extracting phase. Ionic liquids were applied without the addition of any modifier or diluent. Undiluted quaternary ammonium ionic liquids with chloride, thiocyanate and nitrate anions were used to extract metals from aqueous feed solutions with high chloride concentrations in order to separate the main metals (Sm/Co/Cu) present in SmCo magnets.

A chloride/chloride extraction was compared with two split-anion extraction systems (i.e. chloride in the aqueous phase and either nitrate or thiocyanate in the organic phase). The advantage of split anion extraction is that it can be done from a chloride solution, but with the extraction behaviour of nitrate or thiocyanate solutions.

Sm/Co separation

Split-anion extraction was in this work applied to the separation of rare earth elements/transition metals instead of previous applications to the mixtures of rare earths. For all the systems, the selectivity of extraction, scrubbing and stripping from a multi-element solution were investigated. High separation factors (> 7500) were found for Co/Sm separations. Co(II) and Cu(II) extracted in the chloride/chloride and chloride/nitrate systems could be stripped simply by water. However, stripping of the loaded ionic liquid in the chloride/thiocyanate system with water was not feasible.

Sm/Co separation from SmCo magnets (graphical abstract)


The extraction mechanism for the different ionic liquids was studied by extended X ray absorption fine structure (EXAFS). A possible explanation on the extraction behaviour of samarium ions in the presence of transition metal ions is given.

Full reference paper

Simona Sobekova Foltova, Tom Vander Hoogerstraete, Dipanjan Banerjee, Koen Binnemans, Samarium/cobalt separation by solvent extraction with undiluted quaternary ammonium ionic liquids, Separation and Purification Technology, 210 (2019) 209–218,

Bio Simona Sobekova Foltova

Simona SobekovaSimona Sobekova Foltova is an environmental engineer graduated in Slovakia. She was awarded for her work on automotive shredder residue. Passion for the separation technologies brought her to Belgium, where she spread her knowledge in solvent extraction and upscaling to mixer-settler setup.


The research leading to these results has received funding from the European Community’s Horizon 2020 Programme (H2020/2014-2019) under Grant Agreement no. 674973 (MSCA-ETN DEMETER). This publication reflects only the author’s view, exempting the Community from any liability. Project website: TVDH acknowledges the FWO-Flanders for a postdoctoral fellowship. The authors would like to thank Dr. Jeroen Sniekers for taking night shifts at the DUBBLE beamline.