NdFeB magnet is one of the important rare earth functional materials. With the rapid development of new energy vehicles, wind power generation, electronic equipment and other industries, the demand for NdFeB magnets has been increased year by year. China is the largest producer of NdFeB in the world. The annual output is nearly 170 000 t, accounting for nearly 90% of world production. About 30% waste is produced during production process. In addition, a large number of magnets are discarded when the service life is reached. These wastes contain 20%-30% rare earth elements, which are valuable secondary resources. Waste recycling is not only conducive to environmental protection, but also contributes to the sustainable development of the rare earth industry. The composition characteristics of various NdFeB waste are quite different. Therefore, the treatment methods are also different. There are two research directions: (Ⅰ) recovery of rare earth elements from NdFeB waste; (Ⅱ) magnet regeneration manufacturing. The recovery method consists of hydrometallurgy and prometallurgy. How to achieve the organic unity of rare earth regeneration product quality, environmental friendliness and economy has become the hotspot and difficulty. The hydrometallurgy technologies include hydrochloric acid total solution method, hydrochloric acid optimal solution method, sulfate double salt precipitation method, etc. The general characteristics of these technologies are list as follows: the rare earth is separated from other elements by controlling the pH value. Single rare earth compound is obtained by multistage extraction. Then, the rare earth is converted into salt by precipitator, and the single rare earth oxide is obtained after calcination. These methods are highly adaptable to different raw materials, the purity of rare earth products is high. However, the process is long and environmentally unfriendly. The prometallurgy technologies include oxidation method, chlorinate method, liquid alloy extraction method, etc. The principle is based on the ability of rare earth elements and other elements to combine with oxygen, chlorine and alloying elements. These methods are short-process and relatively environmentally friendly, but mixed rare earth compounds are usually obtained. In addition, these methods are not industrialized. In recent years, new recovery methods have been developed at home and abroad, such as electrolysis method, ionic liquid method, hydrolysis method, etc., but they are still in their infancy. Mixed rare earth compound are obtained by electrolysis and hydrolysis method. Ionic liquid method has the advantages of good separation efficiency and high system stability, showing good prospect. Short-process regenerative manufacturing methods mainly include hydrogen detonation method, doping method, etc. These methods are short-process and relatively environmentally friendly. However, magnetic property usually decrease to a certain extent, which will further limit its application. How to ensure the property of regenerative magnets is the key point of regenerative manufacturing development in the future. This article briefly introduces the sources and characteristics of NdFeB waste, then summarizes the research status and problems of various recovery methods (hydrometallurgy, pyrometallurgy, new recycling methods, short-process regeneration manufacturing). The research development tendency is also prospected. The article is expected to provide a reference for the comprehensive utilization of NdFeB waste. © 2021, Materials Review Magazine. All right reserved.
