Extraction of rare earth elements from spent NdFeB magnets by supergravity-enhanced bismuth

Since NdFeB is the most widely used permanent magnet material, a large amount of spent NdFeB magnets will reach its service life every year. These wastes contain 20%~30% rare earth elements, which are valuable secondary resources. In this paper, bismuth(Bi) metal was used as extractant to recover the rare earth elements in spent NdFeB magnets by fire melting, to seperate the excess Bi by high-temperature supergravity technology, for recycling. The influence of Bi waste mass ratio on rare earth extraction efficiency in melting process, and the impact of temperature and gravity coefficient on Bi recovery rate in supergravity centrifugation process were investigated. The results show that when Bi waste mass ratio is over 1:1, the separation of Bi phase from iron phase is good, and almost all rare earth elements in spent NdFeB magnets entered Bi phase. At a better separation condition, i.e., T=500 ℃ and G=1 000, the recovery rate of rare earth elements reaches 99.6% and that of Bi 74.7%. The successful development of this process has opened up a new way for recycling rare earth elements in spent NdFeB magnets.