Transformation Behavior of Iron Minerals in High-Iron Red Mud During High-Pressure Hydrothermal Reduction

Nowadays, the comprehensive utilization of red mud is still a difficult problem. Using starch as the reducing agent, the "high-pressure hydrothermal reduction method" is used to separate and recover sodium, aluminum, and iron in high-iron red mud in one step in an alkaline hydrothermal system. This article focuses on the hydrothermal reduction behavior of the iron ore phase. The results showed that starch formed a strong reduction system through degradation under alkaline hydrothermal conditions, in which Fe₂O₃ was first partially dissolved and reduced to form Fe[OH]⁺, then Fe[OH]⁺ further reacted with Fe₂O₃ to form Fe₃O₄. At a temperature of 260°C, a C/S (calcium to silicon ratio) of 3.5, a Na₂O concentration of 250 g/L, W_{high-iron red mud}/W_starch = 10, the Fe reduction rate was 98.46%, and the transformation slag at a magnetic field strength of 1800 Gs resulted in a magnetic iron concentrate powder with a TFe grade of 65.75%.