Recycling of NdFeB magnets employing oxidation, selective leaching, and iron precipitation in an autoclave

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dc.authoridFriedrich, Prof. Dr.-Ing. Dr. h.c. Bernd/0000-0002-2934-2034
dc.authoridEmil Kaya, Elif/0000-0002-9945-1199
dc.contributor.authorEmil-Kaya, Elif
dc.contributor.authorPolat, Buse
dc.contributor.authorStopic, Srecko
dc.contributor.authorGuermen, Sebahattin
dc.contributor.authorFriedrich, Bernd
dc.date.accessioned2025-02-20T08:42:17Z
dc.date.available2025-02-20T08:42:17Z
dc.date.issued2023
dc.departmentTürk-Alman Üniversitesien_US
dc.description.abstractThe increasing production of neodymium-iron-boron (NdFeB) magnets for technological applications results in disposal problems. NdFeB magnets contain a significant quantity of rare earth elements (REEs). China is the largest REEs producer, but it applies quotas and increases the export prices of REEs. To address this issue, this study aims at investigating the recovery process of REEs from scrap NdFeB magnets. After oxidation of NdFeB magnet powders, selective leaching with nitric acid was carried out to achieve high-purity REE-rich leaching liquor. First, the oxidation kinetics of NdFeB powders was studied in detail to determine the oxidation temperature and duration. Afterwards, the effects of selective leaching parameters, including acid concentration, leaching temperature, stirring speed and solid/liquid ratio, were examined by analysis of variance (ANOVA) analysis based on Taguchi method. The most substantial parameters were assigned to be the temperature and solid/liquid ratio. Eventually, the dissolution kinetics were studied to propose a model for REEs. Several universal equations for dissolution kinetics were tested, and (1 - (1 - x) = k x tn) gives the best results for REEs. The findings show that the leaching process follows the shrinking core model. Activation energy was calculated to be 40.375 kJ mol(-1) for REEs. As the last step, the iron dissolved during leaching was precipitated as hematite in the autoclave. The hematite precipitation experiments were performed based on the Box-Behnken design. The effect of precipitation parameters was investigated by ANOVA analysis, and the precipitation process was optimized using response surface methodology (RSM), which resulted in the minimum iron and maximum REEs content in the leach liquor.
dc.description.sponsorshipFederal Ministry for Economic Affairs and Climate Action [273 EN]; Scientific and Technological Research Council of Turkey [120N331]; project Sustainable recovery of rare earth elements (Nd, Pr, Dy) from spent magnets
dc.description.sponsorshipThis research was funded by the Federal Ministry for Economic Affairs and Climate Action, grant number 273 EN, and The Scientific and Technological Research Council of Turkey under grant agreement 120N331. The APC was funded by the project Sustainable recovery of rare earth elements (Nd, Pr, Dy) from spent magnets. Elif Emil-Kaya would like to thank TUBITAK 2214-A - International Research Fellowship Programme for PhD Students.
dc.identifier.doi10.1039/d2ra06883d
dc.identifier.endpage1332en_US
dc.identifier.issn2046-2069
dc.identifier.issue2en_US
dc.identifier.pmid36686927
dc.identifier.scopus2-s2.0-85146083947
dc.identifier.scopusqualityQ1
dc.identifier.startpage1320en_US
dc.identifier.urihttps://doi.org/10.1039/d2ra06883d
dc.identifier.urihttps://hdl.handle.net/20.500.12846/1628
dc.identifier.volume13en_US
dc.identifier.wosWOS:000907659100001
dc.identifier.wosqualityQ2
dc.indekslendigikaynakWeb of Science
dc.indekslendigikaynakScopus
dc.indekslendigikaynakPubMed
dc.language.isoen
dc.publisherRoyal Soc Chemistry
dc.relation.ispartofRsc Advances
dc.relation.publicationcategoryMakale - Uluslararası Hakemli Dergi - Kurum Öğretim Elemanı
dc.rightsinfo:eu-repo/semantics/openAccess
dc.snmzKA_WOS_20250220
dc.subjectRare-Earth-Elementsen_US
dc.subjectRecoveryen_US
dc.subjectWastesen_US
dc.subjectScrapen_US
dc.titleRecycling of NdFeB magnets employing oxidation, selective leaching, and iron precipitation in an autoclave
dc.typeArticle

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