Extraction mechanism of rare earth elements contain in permanent magnets using molten bismuth

There is continuing interest to explore new and alternate extractants to molten magnesium to increase the extraction efficiency of rare earth elements from permanent magnets. We used molten bismuth as an extractant to study the extraction mechanism of rare earth elements from permanent magnets. To investigate the characteristics of diffusion in bismuth-rare earth element couples, we assessed the reaction and diffusion of neodymium and dysprosium in molten bismuth. The effects of the experimental parameters, such as temperature and time, were investigated to identify the reaction mechanism. The diffusion coefficient of rare earth elements from the permanent magnet into molten Bi was higher than that into molten magnesium, and the reaction rate varied with respect to temperature. The critical temperature for extraction and diffusion of rare earth elements by bismuth is 500 °C. Additionally, we determined that the diffusivity of neodymium is several orders of magnitude higher than that of dysprosium.