A novel
method to recover rare earth elements (REEs) from NdFeB
magnets was developed. This method involves three basic steps, i.e.,
the vacuum induction melting (VIM) process, the hydrolysis process
and the magnetic separation process (HMS). In the VIM process, the
NdFeB magnets were melted in a graphite crucible under vacuum (<1
Pa), in which way the rare earth carbides formed by the reaction of
REEs and carbon, and the carbon saturated NdFeBCsat alloy
was obtained. On the basis of the hydrolysis of rare earth carbides,
the REEs were separated from the NdFeBCsat alloy by the
reaction of the rare earth carbides phase with water. Thus, the rare
earth hydroxides and iron-based metal residues were produced. Magnetic
separation was further used to remove the iron residues from the rare
earth hydroxides. Through this method, the optimal recovery ratio
reached 93%, and the purity of the rare earth hydroxides was as high
as 99.7%. Along with the VIM-HMS process, the investigation of NdFeBCsat alloy, the morphology of the rare earth hydroxides and
the conversion of rare earth hydroxides to rare earth oxides are also
presented in this paper. In this research, the X-ray diffraction (XRD),
optical microscopy (OM), scanning electron microscopy (SEM), transmission
electron microscopy (TEM), inductive-coupled plasma spectroscopy (ICP),
mass spectrum analyses, CS analyses, magnetic properties analyses
and nitrogen physisorption analyses were applied.
In order to recover the rare earth elements (REEs) from neodymium permanent magnet scraps, Fe 2 O 3 , B 2 O 3 , and FeO-B 2 O 3 fluxes were designed to extract the REEs. The REEs containing oxides were successfully separated from the Fe-based metals at the temperatures of 1,673, 1,773, and 1,823 K. A mechanism for extraction of REEs has been proposed based mainly on the experimental observations using the flux of FeOÁB 2 O 3 at 1,573 K. Effects of temperature and reaction time were also investigated. The experimental results have shown that increasing temperature and prolonging holding time help the reduction of B 2 O 3 contents in the oxide phase. The FeO-B 2 O 3 fluxes show better extraction efficiency. The purity of rare earth oxide was 98.4 % produced by 2FeOÁB 2 O 3 and the extraction ratios were higher than 99.5 % after the FeO-B 2 O 3 fluxes treatment.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.