Increase of iron concentration and reduction of impurities in red mud from the Wenshan area of Yunnan Province by segregation roasting-low intensity magnetic separation

摘要

Red mud is a solid waste produced during alumina extraction from bauxite. In this study, we pretreated red mud by segregation roasting to convert the iron from weak magnetic minerals to ferromagnetic minerals and then subjected the material to grinding and low intensity magnetic separation to obtain iron concentration. The effects of the chlorinating , agent type, chlorinating agent dosage, reducing agent dosage, temperature, reaction time, additive, grinding fineness and magnetic field strength on the iron concentrate grade and recovery rate are studied. At a red mud/KCl/coke/ Na_2S0_4mass ratio of 100:15:15:10, segregation roasting at 1100°C for 60 min, the roasted ore is ground to about 95 wt.% passing 0.045 mm and a magnetic field strength of 0.22 T, the final iron concentrate grade is 78.29% and the recovery is 84.08%, which is an efficient improvement of the valuable metal iron in red mud. The X-Ray Diffraction, Scanning Electron Microscopy and Energy Dispersive X-ray Spectroscopy analysis of the iron concentrate shows that before the segregation roasting, the precious metal iron in the red mud is mainly in the form of Fe_2O_3. After the segregation roasting, the iron is transformed into a new iron mineral phase mainly composed of metal Fe and Fe_3O_4. The main impurities in the iron concentrate are calcium, silicon and aluminum.