Recycling of NdFeB Magnets Using Sulfation, Selective Roasting, and Water Leaching

NdFeB magnets currently dominate the magnet market. Supply risks of certain rare earth metals (REMs), e.g., Nd and Dy, demand efficient recycling options that are applicable to different types and compositions with minimum use of chemicals and waste generation. In this study, a hydrometallurgical method is presented, which is adjustable to all NdFeB magnets, regardless of their composition. After completely transforming powdered samples into a sulfate mixture, a suitable selective roasting and water leaching treatment resulted in 95-100 % extraction efficiencies for Nd, Dy, Pr, Gd, Tb, and Eu, while Fe remained in the resultant residue forming a marketable hematitedominated by-product. Impurities other than Fe were also greatly separated from the leachate thereby enabling the production of a liquid with at least 98 % REM purity. Such a solution then can be directly treated with subsequent shortened downstream processes without pretreatments for impurity removal. Due to decomposition reactions of impurities, including Fe, during the selective roasting stage, the majority of consumed acid is recyclable resulting in an environment-friendly flow sheet.