Co-volatilizing-water leaching process for efficient utilization of rhenium-bearing molybdenite concentrate

Rhenium-bearing molybdenite concentrate is a typical mineral resource to recover molybdenum and rhenium, but has long been poorly utilized via oxidative roasting-leaching route. In this work, a novel flowsheet consisting of chloride leaching, co-volatilization, selective condensation, and water leaching has been proposed and verified on the basis of both experimental and thermodynamic studies. Purification treatment was first performed using a solution of HCl and CaCl2, which increased the grades of Mo and Re from 43.6 wt% and 321 mg/kg to 51.3 wt% and 374 mg/kg, respectively, after leaching at 95 °C for 30 min. The purified concentrate was then roasted with air supply after being pelletized with the addition of SiO2 and Al2O3, which served as skeleton materials to prevent pellets from being broken. The results showed that over 99.9% of rhenium and 90.4% of Mo could be co-volatilized within 30 min when temperature was 1050 °C. The volatile material condensed above 500 °C was assayed to be highly pure MoO3 (99.9%) with almost no rhenium, while the volatile material collected at lower temperature was concentrated with high-content Re2O7. Furthermore, through water leaching at 25 °C for 30 min with liquid to solid ratio of 5 mL/g, 98.6% of Re was easily leached out from volatiles.