Molybdenite Processing

In molybdenite processing, the molybdenite is first heated to a temperature of 700 °C (1,292 °F) and the sulfide is oxidized into molybdenum(VI) oxide by air:

2 MoS2 + 7 O2 → 2 MoO3 + 4 SO

The oxidized ore is then either heated to 1,100 °C (2,010 °F) to sublimate the oxide, or leached with ammonia, which reacts with the molybdenum(VI) oxide to form water-soluble molybdates:

MoO3 + 2 NH4OH → (NH4)2(MoO4) + H2O

Copper, an impurity in molybdenite, is less soluble in ammonia. To completely remove it from the solution, it is precipitated with hydrogen sulfide.

Molybdenite 

Molybdenite 

Pure molybdenum is produced by reduction of the oxide with hydrogen, while the molybdenum for steel production is reduced by the aluminothermic reaction with addition of iron to produce ferro-molybdenum. A common form of ferro-molybdenum contains 60% molybdenum.