Preparation of sodium molybdate from molybdenum concentrate by microwave roasting and alkali leaching

A new process for the efficient recovery of molybdenum from molybdenum concentrate by microwave roasting and sodium hydroxide leaching was proposed, as an environmentally benign and economical alternative. Thermodynamic analysis indicated the feasibility of oxidative roasting of molybdenum concentrates. The effects of roasting temperature, holding time and power to mass ratio on the oxidation and leaching process on the formation of sodium molybdate (Na₂MoO₄-2H₂O) were investigated. The optimal process conditions for oxidation roasting were found to be a roasting temperature of 700°C, a holding time of 110 min and a power to mass ratio of 110 W/g, while for leaching the optimal conditions correspond to sodium hydroxide concentration of 2.5 mol/L, a liquid to solid ratio of 2:1, a leaching temperature of 60°C and the leaching solution was terminated at pH 8. The optimum conditions result in the leaching rate of 96.24% for sodium molybdate with 94.08% content. A variety advanced characterization techniques such as XRF, XRD, SEM-EDS and FTIR were utilized to elucidate the conversion process.v