Hydrometallurgical Recovery of Rare Earth Elements from NdFeB Permanent Magnet Scrap: A Review

Abstract

NdFeB permanent magnet scrap is regarded as an important secondary resource which contains rare earth elements (REEs) such as Nd, Pr and Dy. Recovering these valuable REEs from the NdFeB permanent magnet scrap not only increases economic potential, but it also helps to reduce problems relating to disposal and the environment. Hydrometallurgical routes are considered to be the primary choice for recovering the REEs because of higher REEs recovery and its application to all types of magnet compositions. In this paper, the authors firstly reviewed the chemical and physical properties of NdFeB permanent magnet scrap, and then carried out an in-depth discussion on a variety of hydrometallurgical processes for recovering REEs from the NdFeB permanent magnet scrap. The methods mainly included selective leaching or complete leaching processes followed by precipitation, solvent extraction or ionic liquids extraction processes. Particular attention is devoted to the specific technical challenge that emerges in the hydrometallurgical recovery of REEs from NdFeB permanent magnet scrap and to the corresponding potential measures for improving REEs recovery by promoting the processing efficiency. This summarized review will be useful for researchers who are developing processes for recovering REEs from NdFeB permanent magnet scrap.

Acid Dissolution of Neodymium Magnet Nd-Fe-B in Different Conditions

“…Table 3 shows the comparative composition of a neodymium magnet dissolved under different conditions in comparison with the works of other authors. According to the work [6] , the content of the main elements (neodymium, iron and boron) in the composition of magnet waste, three groups can be distinguished: waste with a low content of REM (REM < 20%), waste with an average content of REM (REM about 20-30%) and waste with a high content of REM (REM > 30%). Table 3 shows the content of magnet waste with average concentrations of REM.…”

“…At the same time, it is important to effectively separate REM. The dissolution of neodymium magnets and the separation of rare-earth metals from them are considered in the following works [2][3][4][5][6].…”

Advances in Mineral Processing and Hydrometallurgy

“…Zhang et al [28] provide a review of rare earth recycling entitled "Hydrometallurgical Recovery of Rare Earth Elements from NdFeB Permanent Magnet Scrap: A Review". NdFeB permanent magnet scrap is regarded as an important secondary resource that contains rare earth elements (REEs) such as Nd, Pr, and Dy.…”

Chain Entanglement of 2-Ethylhexyl Hydrogen-2-Ethylhexylphosphonate into Methacrylate-Grafted Nonwoven Fabrics for Applications in Separation and Recovery of Dy (III) and Nd (III) from Aqueous Solution

“…The technology for the separation and recovery of dysprosium and neodymium from used permanent magnets has been extensively studied [ 21 , 22 ]. The most common method of recovering dysprosium and neodymium from waste materials involves leaching them in an acid solution and purifying the leached ions by solvent extraction [ 11 , 12 , 13 , 23 ].…”

“…On the other hand, other methods such as chemical precipitation and ionic liquids extraction are also used for the separation and recovery of rare earths. Although the chemical precipitation process is simple and low in cost, the purity and recovery ratio of the resulting product are usually low, while the ionic liquid extraction cost is high for actual application [ 21 ]. Currently, the effective separation and recovery of rare earths from an aqueous solution requires relatively simple processes [ 27 , 28 ].…”