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

Abstract

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.