Activation Behavior and Mechanism of Sodium Sulfate for Iron Recovery from Red Mud through Magnetization Roasting-Magnetic Separation

It is a hot topic to recover iron from red mud in the research field of solid waste comprehensive utilization, but high-quality iron concentrate is always difficult to be obtained unless by high-temperature reduction roasting-magnetic separation. In this study, low-temperature magnetization roasting-magnetic separation has been conducted to recover iron from red mud, with carbon monoxide as the reducing agent, and the effect of Na2S04 as an additive and corresponding activation mechanism has been investigated, confirming that Na2S04 can significantly improve the quality of the iron concentrate. Under the optimum conditions, an iron concentrate with a total iron grade of 60.65% and a recovery of 94.01% could be obtained, increased by 3.46% and 2.76%, respectively, compared with that in the absence of Na2S04. This verified that weak-magnetic hematite was transformed into strong-magnetic magnetite by reductive roasting. The iron content in the magnetite was raised from 0.93% in red mud to 80% and 82%, respectively, for the roasted briquettes in the absence and presence of Na2S04. As Na2S04 contributed to not only the reduction and enrichment of iron minerals but also to the decomposition of iron-containing complex oxides, the separation of the iron and the magnetic property intensity of iron concentrate was enhanced.