Reaction Behavior of Aluminogoethite and Silica Minerals in Gibbsite Bauxite in High-Temperature Digestion

The digestion behavior of silica and iron minerals in gibbsite bauxites during 230–280 °C, which has great importance for the recovery efficiency of alumina, was studied in detail in this paper. The effects of digestion temperature, digestion time, and lime addition on aluminogoethite phase transition behavior were investigated. Furthermore, the reaction behavior of silica minerals in the gibbsite bauxite during the digestion process at high temperatures was also studied. It was determined that the phase transition of aluminogoethite is enhanced at 250 °C. By further raising the temperature and extending the digestion time, aluminogoethite transforms into hematite, from which more alumina can be recovered. Aluminogoethite completely transforms into hematite after digestion at 260 °C for 30 min. However, the reaction of nonreactive silica minerals is also enhanced at high temperatures. Quartz completely dissolves after digestion at 260 °C for 20 min. Adding lime to the digestion process has a positive effect on the phase change of aluminogoethite, but excess lime addition reduces alumina recovery due to hydrogarnet formation. Graphical Abstract