Abstract
Over the last decade, rare-earth elements (REEs) have become critical in the European Union (EU) in terms of supply risk, and they remain critical to this day. End-of-life electronic scrap (e-scrap) recycling can provide a partial solution to the supply of REEs in the EU. One such product is end-of-life neodymium (NdFeB) magnets, which can be a feasible source of Nd, Dy, and Pr. REEs are normally leached out of NdFeB magnet waste using strong mineral acids, which can have an adverse impact on the environment in case of accidental release. Organic acids can be a solution to this problem due to easier handling, degradability, and less poisonous gas evolution during leaching. However, the literature on leaching NdFeB magnets waste with organic acids is very scarce and poorly investigated. This paper investigates the recovery of Nd, Pr, and Dy from NdFeB magnets waste powder using leaching and solvent extraction. The goal was to determine potential selectivity between the recovery of REEs and other impurities in the material. Citric acid and acetic acid were used as leaching agents, while di-(2-ethylhexyl) phosphoric acid (D2EHPA) was used for preliminary solvent extraction tests. The highest leaching efficiencies were achieved with 1 mol/L citric acid (where almost 100% of the REEs were leached after 24 h) and 1 mol/L acetic acid (where >95% of the REEs were leached). Fe and Co—two major impurities—were co-leached into the solution, and no leaching selectivity was achieved between the impurities and the REEs. The solvent extraction experiments with D2EHPA in Solvent 70 on 1 mol/L leachates of both acetic acid and citric acid showed much higher affinity for Nd than Fe, with better extraction properties observed in acetic acid leachate. The results showed that acetic acid and citric acid are feasible for the recovery of REEs out of NdFeB waste under certain conditions.
Highlights
Rare-earth elements (REEs) possess excellent physical and chemical properties, which is why they are used on a large scale in permanent magnets, lamp phosphors, NiMH batteries, catalysts, various mechanical and electric devices as well as electric motors and generators, which are important for transition to a greener economy
Citric acid and acetic acid leachates to determine the possible use for the recovery of REEs and other achieved using some bacteria like Shewanella putrefaciens [22]
The powderofbefore and aftermagnets roastingfound treatment wasmarket analyzed using were inthe accordance with the composition neodymium on the scanning electron microscopy coupled with energy dispersive
Summary
Rare-earth elements (REEs) possess excellent physical and chemical properties, which is why they are used on a large scale in permanent magnets, lamp phosphors, NiMH batteries, catalysts, various mechanical and electric devices as well as electric motors and generators, which are important for transition to a greener economy. Of NdCit, NdHCit, NdHCit, and NdCit was confirmed by the solution in the pH electronic This indicates that acetic acid could be used for the recovery of Nd and possibly other REEs from range 2–5, which proved thathave citricbeen acidpreviously could be used leaching. Investigated in detail the kinetics extraction complexes with REEs. the leaching of neodymium magnets with organic acids is very that Nd3+. The feasibility of further extraction of REEs out of leachates of complexes with In this of a high‐temperature‐treated neodymium magnet organic acids wasstudy, notleaching addressed. In this study,using leaching of a high-temperature-treated magnet powder was investigated out of NdFeB waste using acetic acid.recovery. The leaching process was optimized in order to achieve the Before the leaching experiments, the powder before and after roasting treatment was analyzed using maximum REEs recovery by varying leaching time, acids concentration, and S:L ratio.
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