Title: From NdFeB magnets towards the rare-earth oxides: a recycling process consuming only oxalic acid
Authors: Vander Hoogerstraete, Tom
Blanpain, Bart
Van Gerven, Tom
Binnemans, Koen # ×
Issue Date: 2014
Publisher: RSC Publishing
Series Title: RSC Advances vol:4 issue:109 pages:64099-64111
Abstract: A chemical process which consumes a minimum amount of chemicals to recover rare-earth metals from NdFeB magnets was developed. The recovery of rare-earth elements from end-of-life consumer products has gained increasing interest during the last few years. Examples of valuable rare earths are neodymium and dysprosium because they are important constituents of strong permanent magnets used in several large or growing application fields (e.g. hard disk drives, wind turbines, electric vehicles, magnetic
separators, etc.). In this paper, the rare-earth elements were selectively dissolved from a crushed and roasted NdFeB magnet with a minimum amount of acid, further purified with solvent extraction and precipitated as pure oxalate salts. The whole procedure includes seven steps: (1) crushing and milling of the magnet into coarse powder, (2) roasting to transform the metals into the corresponding oxides, (3)
the selective leaching of the rare-earth elements with acids (HCl, HNO3) to leave iron behind in the precipitate, (4) extracting remaining transition metals (Co, Cu, Mn) into the ionic liquid trihexyl(tetradecyl) phosphonium chloride, (5) precipitating the rare earths by the addition of oxalic acid, (6) removing the precipitate by filtration and (7) calcining the rare-earth oxalates to rare-earth oxides which can be used as part of the feedstock for the production process of new magnets. The magnet dissolution process from the oxides utilized four molar equivalents less acid to dissolve all rare earths in comparison with a
dissolution process from the non-roasted magnet. Moreover, the less valuable element iron is already removed from the magnet during the dissolution process. The remaining transition metals are extracted into the ionic liquid which can be reused after a stripping process. Hydrochloric acid, the side product of the rare-earth oxalate precipitation process, can be reused in the next selective leaching process. In this way, a recycling process consuming only air, water, oxalic acid and electricity is developed to recover the rare earths from NdFeB magnets in very high purity.
ISSN: 2046-2069
Publication status: published
KU Leuven publication type: IT
Appears in Collections:Molecular Design and Synthesis
Sustainable Metals Processing and Recycling
Process Engineering for Sustainable Systems Section
× corresponding author
# (joint) last author

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