Effects of iron-containing phases on transformation of sulfur-bearing ions in sodium aluminate solution

Sulfides in the high-sulfur bauxite lead to serious steel equipment corrosion and alumina product degradation via the Bayer process, owing to the reactions of sulfur and iron-containing phases in the sodium aluminate solution. The effects of iron-containing phases on the transformation of sulfur-bearing ions (S2-, S2O32−, SO32− and SO42−) in sodium aluminate solution were investigated. Fe, Fe2O3 and Fe3O4 barely react with SO32− and SO42−, but all of them, particularly Fe, can promote the conversion of S2O32− to SO32− and S2- in sodium aluminate solution. Fe can convert to Fe(OH)3− in solution at elevated temperatures, and further react with S2- to form FeS2, but Fe2O3 and Fe3O4 have little influence on the reaction behavior of S2- in sodium aluminate solution. Increasing temperature, duration, dosage of Fe, mole ratio of Na2Ok to Al2O3 and caustic soda concentration are beneficial to the transformation of S2O32− to SO32− and S2-. The results may contribute to the development of technologies for alleviating the equipment corrosion and reducing caustic consumption during the high-sulfur bauxite treatment by the Bayer process.