Leaching of Rare Earth Elements from NdFeB Magnets without Mechanical Pretreatment by Sulfuric (H2SO4) and Hydrochloric (HCl) Acids

Anna Klemettinen,Anna Leśniewicz,Maja Wełna,Lassi Klemettinen,Andrzej Żak,Ida Chojnacka,Sabina Matuska,Zbigniew Adamski,Leszek Rycerz

doi:10.3390/min11121374

Anna Klemettinen, Anna Leśniewicz + Show 7 more

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https://doi.org/10.3390/min11121374

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Abstract

A simplified approach for rare earth elements leaching from NdFeB (neodymium-iron-boron) magnets was investigated. The possibility of simplifying the magnet recycling process by excluding grinding, milling and oxidative roasting unit operations was studied. Attempts to skip the demagnetization step were also conducted by using whole, non-demagnetized magnets in the leaching process. The presented experiments were conducted to optimize the operating conditions with respect to the leaching agent and its concentration, leaching time, leaching temperature and the form of the feed material. The use of hydrochloric and sulfuric acids as the leaching agents allowed selective leaching of NdFeB magnets to be achieved while leaving nickel, which is covering the magnets, in a solid state. The application of higher leaching temperatures (40 and 60 °C for sulfuric acid and 40 °C for hydrochloric acid) allowed us to shorten the leaching times. When using broken demagnetized magnets as the feed material, the resulting rare earth ion concentrations in the obtained solutions were significantly higher compared to using whole, non-demagnetized magnets.

Highlights

Between 20 and 25% of the worldwide mining output of rare earth elements (REEs) is used for the manufacturing of neodymium–iron–boron (NdFeB) permanent magnets [1]. These magnets contain approximately 30% of the REEs. All of these rare earth elements are considered as critical raw materials (CRMs) by the European Commission [2]
Magnets could account for up to 50% of the REE demand by 2035 [6,7]. These magnets are essential in energy saving and digital equipment such as hard disk drives (HDDs), highly efficient air conditioners, hybrid and electric vehicles as well as wind power generators [8,9]
As mentioned in the introduction, the goal of the study was to propose a simple leaching process that allowed the selective digestion of REEs and iron, while keeping nickel in the solid form

Summary

Introduction

Between 20 and 25% of the worldwide mining output of rare earth elements (REEs) is used for the manufacturing of neodymium–iron–boron (NdFeB) permanent magnets [1] These magnets contain approximately 30% of the REEs (mainly neodymium, praseodymium, dysprosium and terbium). It has been predicted that the manufacturing of NdFeB magnets could account for up to 50% of the REE demand by 2035 [6,7] These magnets are essential in energy saving and digital equipment such as hard disk drives (HDDs), highly efficient air conditioners, hybrid and electric vehicles as well as wind power generators [8,9]. Some of the aforementioned devices (hybrid and electric vehicles, wind power generators) will work for many years, while others reach end-of-life relatively quickly and can potentially be recycled.

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