China Nonferrous Metallurgy

Molybdenum recovery ratecanbeover 95% in the treatment of molybdeniteby oxygenpressure and water leaching process. Subsequently, ammonia leachingofoxygen pressure and water leaching residue will lead to the presence of some insoluble molybdate in the ammonia leaching residue, which decrease the recovery of molybdenum. Oxygen pressure and water leaching residue of molybdenum concentrate as raw material with NaOH and Na₂CO₃ as leaching agents, the effects of leaching agent dosage, temperature, liquid-solid ratio, and leaching time on molybdenum leaching rate were investigated in this paper.The chemical composition analysis of oxygen pressure and water leaching residue and alkaline leaching residue were analysed to reveal the mechanism of alkaline leaching of oxygen pressure and water leaching residue.Results show thatthe oxygen pressure and water leaching residue contains CaMoO₄, which cannot be effectively leached by NaOH. In case of using Na₂CO₃ as leaching agent, spontaneous decomposition of CaMoO₄ occurs at temperature above 20℃, and the higher the temperatureis, the easier the decomposition is. The optimum conditions for using Na₂CO₃ as leaching agent are temperature of 90℃, Na₂CO₃ consumption coefficient of 1.2, liquid-solid ratio of 4∶1, time of 90 minutes, and stirring speed of 400 rpm, in which, the molybdenum leaching rate can reach 97.15%.Under the optimum conditions for using NaOHas leaching agent, themolybdenum leaching rateis 93.98%。Results indicatethat the leaching rate of Mo canbe effectively increased by using Na₂CO₃ as leaching agent.