Recovery of rare metals from scrap of rare earth intermetallic material by chemical vapour transport

Abstract

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. RAlnCl3+3n (R = rare earth), MalnCl2+3n (M = Co, Ni). Rare earth chlorides were concentrated in the deposits in the higher temperature zone (800–900 °C) while cobalt and nickel chlorides were in the lower temperature zone (500–700 °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 °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 RAlnCl3+3n complexes. If the transport reaction lasts for a longer time, the yields of rare earths can be improved.