Removing molybdenum from tungstate solution with metal sulfides

The effect of removing molybdenum from tungsten solution by using metal sulfides, such as CuS, CoS, NiS, PbS, FeS, ZnS and HgS, was studied. After the molybdenum contained in Na_2WO_4 or (NH_4)_2WO_4 solution was sulfurized from MoO~(2-)_4 into MoS~(2-)_4 by using Na_2S or (NH_4)_2S, the metal sulfide was added into the solution to remove MoS~(2-)_4. It is shown that CuS, CoS and NiS are very effective for removing Mo from Na_2WO_4 or (NH_4)_2WO_4 solution. Considering the economic and environmental protection factors, CuS is considered as the proper reagent of removing Mo. The effects of the amount of metal sulfide used, the pH of solution and temperature on removing Mo from tungstate solution were studied. Under the optimum conditions, the Mo concentration can be reduced from 0.60.77 g/L to 0.0070.02 g/L, the efficiency of de-molybdenum is 96.0%98.5%, and the recovery of tungsten reaches 99.75% in this process.