Selective Extraction and Recovery of Nd and Dy from Nd-Fe-B Magnet Scrap by Utilizing Molten MgCl 2
- PDF / 2,061,444 Bytes
- 11 Pages / 593.972 x 792 pts Page_size
- 93 Downloads / 146 Views
INTRODUCTION
NEODYMIUM-IRON-BORON (Nd-Fe-B) sintered magnets[1,2] are rare earth permanent magnets, which have extremely high magnetic intensity. When doped with dysprosium (Dy), Nd-Fe-B can sustain its high magnetic intensity even at high temperatures.[3] This feature makes Nd-Fe-B magnets suitable for wider applications, including the fabrication of motors for electronic vehicles (EVs), compressors in air conditioners, and power generators. In response to the increasing demand for these applications, the production of Nd-Fe-B magnets has increased significantly and is expected to increase further. However, Nd and Dy are rare earth elements (REEs) and are therefore difficult to procure. For example, Dy is scarce in the Earth’s crust and economically feasible ores of Dy are found only in limited regions (i.e., ion clay ore from the southern part of China). Accordingly, Dy is currently in short supply and is very expensive. Although Nd is rather abundant, radioactive wastes such as uranium (U) and thorium (Th) compounds are always present during the mining and smelting of Nd. In the near future, used magnet scrap discarded from EVs will be an important secondary source of a stable supply of these materials. In SAKAE SHIRAYAMA is with the Institute of Industrial Science, The University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo, 1538505, Japan. Contact e-mail: [email protected] TORU H. OKABE is with the Institute of Industrial Science, The University of Tokyo. Manuscript submitted December 21, 2016.
METALLURGICAL AND MATERIALS TRANSACTIONS B
order to ensure a reliable supply of valuable REEs and to save energy and natural resources consumed by the production of REEs from ores, it is important to develop an efficient recovery process for Nd and Dy from Dy-containing Nd-Fe-B magnet scrap materials. Currently, magnet scrap can be classified into two types: those generated during production processes, e.g., alloy fabrication, magnet shaping, and grinding; and those discarded from used industrial products. REEs are usually recovered from scrap produced in magnet manufacturing by a wet process using multistage hydrometallurgical methods that generate a large quantity of waste acid solutions. However, magnets from used industrial products are currently not recycled, with the exception of the large magnets used in medical magnetic resonance imaging (MRI) equipment. The large magnets used in motors for EVs are a good target for recycling, as they are disposed of within 10 years. To recycle a large quantity of magnet scrap, the pyrometallurgical method is advantageous from an environmental perspective. This technique is an alternative to the hydrometallurgical method, which produces a large amount of waste solution, including the very strong oxalic and hydrofluoric acids. In addition, the pyrometallurgical process is relatively simple with a fast processing time, which is suitable for large-scale operation. In order to develop an environmentally friendly recycling process for REEs with high efficiency, many studies ba
Data Loading...
