RECOVERY OF RARE METALS FROM SCRAP OF RARE-EARTH INTERMETALLIC MATERIAL BY CHEMICAL-VAPOR TRANSPORT

A dry process for recovery of rare metals from sludges of Sm2Co17, Nd2Fe14B and LaNi5 intermetallic compounds was investigated using chemical vapour transport along a given temperature gradient. Chlorine and aluminium chloride were used as a chlorinating agent and a transporting agent respectively, and the rare metal chlorides were chemically transported as vapour complexes, e.g. RAl(n)Cl(3+3n) (R=rare earth), MAl(n)Cl(2+3n) (M=Co, Ni). Rare earth chlorides were concentrated in the deposits in the higher temperature zone (800-900 degrees C) while cobalt and nickel chlorides were in the lower temperature zone (500-700 degrees C). Purity of each of the recovered chlorides was more than 99%. Chlorides of other metals, such as iron, copper, zirconium, and aluminium, were condensed at the outlet of the reactor (below 350 degrees C) without any contamination for the recoveries. After transport reaction for 6 h, yields of nickel and cobalt were more than 99%, whereas those of lanthanum, samarium, neodymium and dysprosium were lower, i.e. 27%, 39%, 59% and 68%, owing to the relatively low formation rate of RAl(n)Cl(3+3n) complexes. If the transport reaction lasts for a longer time, the yields of rare earths can be improved.