Reaction behavior of low grade molybdenum concentrates in oxidation roasting process

Thermodynamics of oxidation roasting, phase evolution rules and roasting characteristics of low grade molybdenum concentrate with grade of 39.27% were studied. Thermodynamics analyses show that the oxidation tendency of MoS2 is second to that of FeS2, so it is easily oxidized and generates several oxide products. Furthermore, MoO3 could react with various metal oxides to generate molybdate in which calcium molybdate generates most easily. Roasting process contains three stages of incomplete oxidization of MoS2, stable existence of MoO3 and generation of molybdate. Molybdate and low valence molybdenum oxide, which go against subsequent leaching, will easily generate at over high temperature or for long time. The suitable temperature is 650-675℃ and the roasting time is 2 h. After roasting, ammonia leaching rate of molybdenum is only about 84.02%, residue of Mo in leaching residue reaches 13.93%. XRD analysis shows that calcium molybdate is the main component in leaching residue. When Na2CO3 is used as the leaching reagent, calcium molybdate can be extracted during leaching residue, and the ultimate recovery rate of Mo can reach 90.82%. ©, 2014, Central South University of Technology. All right reserved.