Recovery of molybdenum from copper slags

Slags as the by-product of copper making have been produced in large amounts in Chile, and about 5 million tons of slags are estimated to be disposed every year and about 50 million tons have been already accumulated near the mine site. Typical Chilean copper slag contains about 0.3 mass% Mo which is the same to the grade of primary mine production of molybdenite and the copper slags also contain about 40 mass% of Fe and 1 mass% Cu. Recovery of Mo from Chilean copper slags is quite attractive to secure a stable Mo supply. The feasibility of the recovery of Mo from copper slags as Fe-Mo alloys by carbothermic reduction is investigated in the present study. Mo in the copper slag is found to be fully recovered as Fe rich Fe-Mo alloy. The recovered alloy contains about 0.60 mass% Mo and 2.4 mass% Cu. To use the recovered Fe-Mo alloy effectively in the special steel industry, which is the most important market for molybdenum, Cu in the produced Fe-Mo alloy is successfully decreased from 2.4 mass% to 0.1 mass% by using FeS-Na₂S flux. Thus, Mo recovery from Chilean copper slag can be promising.