Conversion Behavior of Iron-Containing Minerals in the Process of Dissolving High-Iron Bauxite by Starch Hydrothermal Method

Abstract

The starch is used as a reducing agent to simultaneously reduce the iron oxide during the hydrothermal dissolution of the diaspore. Thermodynamic calculation and experiments studied the hydrothermal reduction behavior of iron oxide in alkaline solution, thermodynamic calculations show that Fe2O3 can be converted to Fe3O4 under appropriate redox conditions. Fe2O3 will dissolve in an alkaline aqueous solution to form FeO2−, and part of the FeO2− moiety will be converted to Fe(OH)4− in an alkaline aqueous solution having a temperature higher than 373 K. The starch is degraded under alkaline hydrothermal conditions, releasing an aldehyde group to form a strong reduction system, and reducing Fe3+ to Fe2+, and Fe3+ further reacts with Fe2+ to form Fe3O4. In this process, the temperature and alkali concentration in this process have a great influence on the hydrothermal reduction of Fe2O3. The experimental results show that when the treatment temperature is 260 °C, the alkali concentration is 210 g/L, the time is 60 min, the lime/dry ore is 7%, the starch/dry ore is 10%, and the magnetic separation strength is 0.08 T. At this point, the aluminum dissolution rate was 98.57%, the iron reduction rate was 98.41%, the magnetic separation rate was 97.0% or more, and the TFe grade was 73.5%.