oa Effectiveness Evaluation of Pyrometallurgy and Hydrometallurgy Methods in The Recycling Process of Nd-Fe-B Permanent Magnet and Rare Earth Metals Recovery : A Review

Nd-Fe-B is a rare earth element (REE) based permanent magnet material which consist of main magnetic phase Nd2Fe14B and minor phase Nd-rich or α-Fe.  Nd-Fe-B permanent magnet has a remarkable maximum energy product (BHMax) reaching 474 kJ/m3 or nearly 60 MGOe, making Nd-Fe-B magnets as the ultimate permanent magnet material and widely used in various technological applications.  A commercial Nd-Fe-B magnet contains 22-32 wt% of rare earth elements such as Nd, Dy, Pr, and La, which causes an increasing demand for rare earth elements.  As a results, the availability of REE from natural resources are decreasing and several REE such as Nd, Dy, and Pr are in the critical category.  The recycling process of Nd-Fe-B magnet waste to recover the containing REE is one possible solution to provide raw materials for permanent magnet industry and minimizing electronical devices waste.  Pyrometallurgical and hydrometallurgical metal extraction process are commonly used for REE recovery process.  These two methods are excellent for REE recovery and relatively easy to conduct, allowing pyrometallurgical and hydrometallurgical methods to be adopted on industrial scale to the availability of raw materials for Nd-Fe-B magnet industry.