An Integrated Hydrometallurgical Treatment and Combustion Process for Sustainable Production of Sm2O3 Nanoparticles from Waste SmCo Magnets

Abstract

Samarium (Sm), as one of the rare earth elements (REEs), has gained significant attention in the production of SmCo magnets due to their high corrosion and oxidation resistance, as well as their high-temperature stability. SmCo magnets find applications in various industries, including but not limited to national defense, aerospace, military, and medical equipment. Sm and Co have been classified as a critical metal due to its economic importance and supply risk. Recovering Sm from SmCo magnets is an effective method to ensure a stable supply. The present study investigates an integrated hydrometallurgical treatment and combustion process for the preparation of rare earth oxide (Sm₂O₃) powders from SmCo. Initially, SmCo powders is exposed to nitric acid, and the resulting slurry is selectively oxidized at 250 °C to obtain Sm(NO₃)₃, Co₂O₃, and Fe₂O₃. Subsequently, the selectively oxidized powders are leached with water to extract Sm. Sm₂O₃ powders are produced from the obtained leaching solution using an energy- and time-efficient solution combustion process. In this process, once the ignition point of the leaching solution-citric acid complex is reached, combustion occurs and concludes within a short time. The combusted powders are then calcined at different temperatures to produce crystalline Sm₂O₃ powders. Finally, the optimal conditions for the production of Sm₂O₃ are identified, and the produced powder is characterized through XRD and FESEM analysis.