Investigating the effect of ferrous ion on the digestion of diasporic bauxite in the Bayer process

• Ferrous sulfate heptahydrate was added to the Bayer digestion of diasporic bauxite.
• Satisfactory digestion ratios of diasporic bauxite were obtained.
• The mechanism by which ferrous ion works was investigated.
• The product of the reaction between anatase and ferrous ion was Fe2TiO4.
• Fe2TiO4 was much less soluble than anatase and sodium titanate.

The effect of ferrous ion on the Bayer digestion of diasporic bauxite was studied under different conditions. Results showed that the digestion ratio of diasporic bauxite increased with increasing ferrous ion dosage, temperature, digestion time, and caustic alkali concentration. The product of the reaction between anatase and ferrous ion in synthetic Bayer liquor and the dissolution behavior of anatase in synthetic Bayer liquor in the presence of ferrous ion were further examined to probe the mechanism by which ferrous ion exerts its action. XRD results indicated that anatase reacted with the aluminate solution to form sodium titanate, which dissolved in solution and subsequently reacted with ferrous ion to form Fe2TiO4. Fe2TiO4 was found to be considerably less soluble than anatase or sodium titanate. Therefore, no re-precipitation of sodium titanate would coat the surface of diasporic bauxite, and the inhibitory effect of anatase on the digestion of diasporic bauxite was eliminated.