From magnet waste to rare earth oxides: A sustainable route for recovering neodymium and holmium from electric vehicle motors

Abstract

With the projected increase in electrification by 2050, the demand for rare earth elements (REE) is expected to rise. However, their extraction is complex, and resources are limited. Therefore, recycling emerges as a sustainable alternative. In this work, neodymium and holmium were successfully recovered and separated from end-of-life permanent magnets from electric vehicle motors by combining pyro- and hydrometallurgical methods. Initially, a chlorination roasting of the magnet powder, followed by a water leaching to dissolve the REE was carried out. Subsequent liquid-liquid extraction steps were consecutively carried out to remove iron, yielding a purified REE-rich solution. To achieve the separation of Nd and Ho, a liquid-liquid extraction was performed using 0.05 M di-(2-ethylhexyl) phosphoric acid (D2EHPA) as extraction agent, which enabled the extraction of holmium into the organic phase. The resulting Nd-rich aqueous phase was treated with oxalic acid to obtain neodymium oxalate. On the other hand, the Ho-loaded organic phase was stripped using an oxalic acid-saturated solution to recover holmium oxalate. Both oxalates were thermally treated to obtain the corresponding oxides, resulting in high-quality materials with final potential applications, as evidenced by using a wide range of complementary experimental characterization techniques. The developed process demonstrates an effective route for the recovery and separation of rare earth elements from real waste sources.