Interaction of sodium sulfide with silica-containing minerals in sodium aluminate solution

• The sulfur in aluminate solution can be incorporated into lazurite and zeolite.
• Desilication product amount and temperature favor sulfur concentration decrement.
• Sulfur-containing desilication products have lower solubility.
• Calcium oxide addition causes sulfur content decrement of desilication products.

The divalent anion of sulfur (S2 −) from the digestion of sulfur-containing bauxite considerably harms Bayer alumina production. This study experimentally investigated the reaction behavior of sodium sulfide in the processes of formation and transformation of desilication products generated by the reaction of silica-containing minerals with sodium aluminate solutions. The formation of lazurite (Na7Al6Si6O24·S3) and sulfur-containing zeolite (Na8Al6Si6O24·S·4H2O) induce the incorporation of sulfur into the desilication products, resulting in a remarkable decrease of sulfur concentration in liquors, and the decrement of sulfur concentration increases with the increase in the amount of desilication products and temperature. The results of the treatment of sulfur-free desilication products prepared atmospherically with sodium aluminate solutions bearing S2 − indicate that sulfur can be incorporated into the residue by dissolving sulfur-free desilication products and subsequently transforming to less soluble sulfur-containing desilication products. Moreover, the presence of calcium oxide leads to the decrease in sulfur content of sulfur-containing desilication products because of hydrogarnet formation.

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