Article ID



Recycling of Rare Earth Magnet Scraps: Part II, Oxygen Removal by Calcium


R.O. Suzuki, A. Saguchi(Sumitomo Metals Industries, Ltd), W. Takahashi(Sumitomo Metals Industries, Ltd), T. Yagura and K. Ono


Mater. Trans., 42[12] pp.2492-2498 (2001).


Powder scraps of neodymium-iron-boron permanent magnet were deoxidized by using calcium vapor, liquid or CaCl2 melt at 1223-1273K. Because the scraps react with the acidic solutions during leaching of the byproduct CaO, the methods for removal of the excess amount of Ca and CaO were studied. When pH was controlled at about 8 during several times leaching, the dissolution of rare earth elements could be minimized. Ca vapor deoxidation could not supply enough amount of Ca through CaO layer. When a large amount of CaCl2 was added, the dissolution rate of CaO into the aqueous solution became faster, but some amounts of rare earth components were lost. The deoxidation by Ca liquid and 5mass%CaCl2 and the subsequent leaching in distilled water with pH larger than 8 gave the better result so that oxygen, even in heavily oxidized scraps, could be lowered to 0.7 mass%.