Comprehensive Recovery of Valuable Metals From Spent Magnesia–Chrome Refractories by Ferric Chloride–Hydrochloride Leaching

A large amount of spent magnesia–chrome refractories is produced every year from nonferrous metallurgy industry in China. These spent refractories contain not only Mg and Cr but also a large amount of Ag, Pb, Bi, Cu, Sb and other valuable metals. This study proposes a high-efficiency, low-cost and recyclable technology for the treatment of spent magnesia–chromium refractories. In the hydrochloric acid–ferric chloride leaching system, under the conditions of hydrochloric acid concentration of 4.0 mol/L, liquid–solid ratio of 7:1, ferric chloride dosage of 4%, leaching temperature of 70 °C, leaching time of 90 min and stirring intensity of 500 rpm, Cr, Fe and Al are enriched in the leaching residue, and the recoveries are 92.26%, 78.30% and 97.34%, respectively. The extraction rates of Mg, Pb, Bi, Sb, Cu and Ag are 89.04%, 98.88%, 99.82%, 91.48%, 92.64% and 96.38%, respectively. The residue can be used as chromium products, whilst metal ion in the leachate can be precipitated as metallurgical raw materials. According to thermodynamic calculation and experiments, ferric chloride can greatly improve the leaching rate of copper, silver and bismuth in the hydrochloric acid system, depending on its own oxidation ability and increase the concentration of chloride ion. Graphical Abstract