Recovery of molybdenum from copper slag

Slag as by-product of Cu making has been produced in large amounts in Chile, and around 5 million tons of slag are estimated to be disposed every year and 40 to 45 million tons have been accumulated. Typical Chilean Cu slag contains about 0.3 mass% Mo which is the grade of primary mine production of molybdenite and it also contains about 40 mass% of Fe and 1 mass% Cu. Recovery of Mo from Chilean copper slag is quite attractive to secure a stable Mo supply. The feasibility of the recovery of Mo from Cu slag as Fe-Mo alloys by carbon reduction is investigated in the present work. Mo in Cu slag is found to be fully recovered as Fe rich alloy. The recovered Fe rich alloy contains about 0.65mass% Mo and 2.4 mass% Cu. In addition, to use the recovered Fe-Mo alloy 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 Cu slag can be promising.