Effect of alumogoethite in Bayer digestion process of high-iron gibbsitic bauxite

The transformation law of goethite and its effect on the alumina recovery were investigated in order to determine the reason of low alumina recovery in Bayer digestion process of gibbsitic bauxite with high alumogoethite content.The results show that the goethite present in this kind of bauxite has no obvious change in the digestion temperature range of 110 ℃ to 240 ℃ with low alumina recovery.And alumogoethite can be transformed to hematite by increasing digestion temperature to 260 ℃ or adding lime of 3% of dry ores added at about 240 ℃,and the alumina digestion rate increases with the increase of the goethite conversion degree.Adding non-calcareous additives in the re-digestion process of red mud containing goethite can promote the structure transformation of alumogoethite and thus alumina almost reacts completely.The transition of alumogoethite into other forms in Bayer digestion process is important for alumina recovery for lateritic bauxite.