China Nonferrous Metallurgy

The content of Fe₂O₃ and Al₂O₃ in red mud is relatively high. At present, there are some problems in the treatment process, such as low recovery rate, high cost and single metal element recovery. In this paper, based on the strong reducibility of biomass under alkaline conditions, the high-iron red mud was treated by calcified biomass transformation method. The effects of various process parameters on the reduction process of hematite in red mud and the dissolution process of sodium alkali and alumina were investigated. The main conclusions are as follows. The hematite in the red mud is transformed into magnetite through the transformation of calcified biomass into magnetite into the transformation slag, and some iron is used as isomorphism to replace the aluminum in the hydrogarnet to generate the iron-hydrogarnet; under the conditions of reaction temperature 280℃, caustic alkali concentration 240g/L, biomass addition amount of straw∶hematite=1∶2, liquid-solid ratio 4∶1 and reaction time 1h, hematite was transformed into magnetite and entered the transformation slag. The maximum reduction rate of Fe₂O₃ could reach 98.13%, and the dissolution rates of Na₂O and Al₂O₃ could reach 88.27% and 86.61%, respectively. The phase ratio of magnetite and iron hydrogarnet in red mud transformation slag can be controlled by calcified biomass transformation method, so as to achieve the ideal effect of alkali removal and aluminum dissolution, and create favorable conditions for the magnetic separation and recovery of subsequent iron. At the same time, the low alkali, low aluminum and low iron content after magnetic separation can be obtained.