Development and Assessment of Different Hydrometallurgical Processes for Sustainable Recovery of Rare Earths from Spent NdFeB Magnets

Abstract

The utilization of NdFeB magnets is extensive in cutting-edge technologies such as hybrid electric vehicles and wind turbines. These magnets possess a substantial REE (Rare Earth Elements) content, approximately 30%, which significantly surpasses the concentration found in natural REE ores. Due to their pronounced economic significance and the associated supply risks stemming from limited primary resources, REEs are classified as critical metals. With the NdFeB permanent magnet sector experiencing an annual growth rate of 20%, the recycling of end-of-life magnets emerges as a highly effective strategy for mitigating challenges related to the supply of essential raw materials. In the current investigation, three distinct processes have been developed to recover REEs from spent wind turbine magnets. These processes encompass (1) oxidation roasting-acid leaching, (2) chlorination roasting-water leaching, and (3) electrochemical dissolution. Optimization of process parameters has been meticulously undertaken for each of these methods to achieve the production of high-purity rare earth oxide (>99%). Furthermore, a comparative evaluation has been conducted, taking into account energy efficiency and environmental sustainability, to determine the most viable approach for the sustainable recovery of REEs from spent NdFeB magnets.