Improved Method For The Purification Of Technical Grade Molybdenum Trioxide

Two design-of-experiments studies were carried out to investigate the leaching of technical grade molybdenum tri-oxide (TGM) in the presence of hydrochloric acid and the mother liquor of ammonium di-molybdate crystallization used as an ammonia source. Results indicated that leaching of TGM in HCl is possible only when used at about 1N concentration. In high concentrations of HCl, technical grade MoO3 had very high solubility (7.5 to 40 g/L Mo). The most suitable conditions for HCl leaching of TGM were obtained at a slightly elevated temperature of 80°C. Using about 1N HCl at 80°C, potassium in the leached solids (TGM) decreased to about 110 ppm, a value typically obtained in TGM leached in HNO3 - NH4NO3media (3.5 - 4.0 moles /L HNO3 + 0.5 ? 1.0 moles/L NH4NO3). Mo losses under these conditions were 0.8-0.9 g/L Mo. The HCl-leach method, presented here-in, has a significant advantage in chemical cost and environmental benefits over HNO3 ? NH4NO3 purification method.