Comparative Leaching of Rare Earth Elements From Roasted and Unroasted End‐of‐Life HDDs Magnet and Kinetic Study Using Hydrochloric Acid

The increasing demand for rare earth elements (REEs) in advanced technological applications, combined with the limited availability of primary resources, has intensified efforts to recover REEs from secondary sources. Spent NdFeB magnets, commonly found in hard disk drives (HDDs), represent a rich and promising source, containing approximately 30% of REEs. This study focuses on the comparative leaching studies between roasted and unroasted NdFeB magnet samples using HCl as lixiviant. Leaching experiments were systematically conducted to evaluate the influence of key process parameters: acid concentration, temperature, and leaching duration on the recovery of valuable metals. The unroasted sample achieved 99.9% REEs recovery; however, high iron dissolution indicated poor selectivity. In comparison, the roasted sample demonstrated higher selectivity, with recoveries of 96.9% for Dy, 95.4% for Pr, and 93.2% for Nd, while iron dissolution was limited. Leaching kinetic analysis of roasted magnet powder indicated that rare earth leaching kinetics followed a mixed control mechanism, with the activation energy calculated as 39.35 kJ/mol within the temperature range of 30–60°C.