Separation and recovery of valuable metals from low-grade REE–Nb–Fe ore

• Fe, REE and Nb were separated and recovered from low-grade REE–Nb–Fe ore.
• Fe was separated from the ore by selective reduction and magnetic separation.
• The grade of Nb2O5 and (REE)O in magnetic separation tailings was notably elevated.
• Aeschynite was reduced to NbC at 1150 °C which was adverse for leaching.
• After reduction roasting, Nb and REE could be extracted by sulfuric acid leaching.

To recover valuable metals from Bayan Obo tailings, thermodynamic analysis and experiments were conducted to extract Fe, Nb, and rare earth elements (REE) from low-grade REE–Nb–Fe ore by reduction roasting, magnetic separation, and sulfuric acid (H2SO4) leaching. The separation efficiency of Fe increased with the increase in reduction roasting temperature to 1100 °C. Once the reduction roasting temperature reached 1150 °C, the aeschynite ((Ce,Nd)NbTiO6) as the main mineral phase of Nb was reduced to NbC. After a magnetic treatment, it was observed that ~ 79.1% of Fe was separated, and the grade of total Fe in the magnetic materials was 88.2 wt.% when the ores were reduced first at the optimum temperature of 1100 °C. As the Fe was removed, the content of Nb2O5 and REE oxides ((REE)O) in magnetic separation tailings also increased. A H2SO4 solution was used to separate Nb and REE from the magnetic separation tailings at 160 °C. The results showed that ~ 98.2% of Nb and 99.0% of REE were extracted; they could be used to obtain Nb or REE-bearing products by further purification.