Selective extraction of molybdenum from copper concentrate by air oxidation in alkaline solution

Alkaline leaching of copper concentrate bearing molybdenite was investigated. Thermodynamic analysis of Mo-S-H2O and Cu-Fe-S-H2O indicates that alkaline leaching of copper concentrate is feasible for selective extraction of molybdenum. The oxidation mechanisms of sulfide ores in the copper concentrate were discussed based on the analysis results of X-ray diffraction (XRD) and scanning electron microscopy/energy-dipersive X-ray spectroscopy (SEM-EDS) of copper concentrate before and after leaching. The effects of leaching factors including sodium hydroxide concentration, temperature, leaching time and liquid to solid (L/S) ratio on the leaching rate were studied. The results show that molybdenite was oxidized and then dissolved selectively. The optimum parameters were as follows: temperature 80 °C, L/S ratio 6/1 mL/g, sodium hydroxide concentration 2 mol/L, air with ventilation volume 0.6 m3/h and leaching time 8 h. About 97.5% of Mo was selectively extracted and only 1.84% of Cu was dissolved into the solution under the conditions.