Sulfur removal by adding aluminum in the bayer process of high-sulfur bauxite

This paper proposes a novel approach to sulfur removal by adding aluminum in the bayer process of high-sulfur bauxite. The effects of aluminum dosage on the concentrations of different valence sulfur in sodium aluminate solution were investigated at length to find that high-valence sulfur (S2O32−, SO32−, SO42−) concentration in sodium aluminate solution decreases, but the concentration of the S2− in the sodium aluminate solution increases as aluminum dosage increases. This suggests that aluminum reacts with high-valence sulfur to generate low-valence sulfur at digestion temperature, which is consistent with our thermodynamic calculation results. As aluminum dosage increases, sulfur digestion rate decreases notably, and the alumina digestion rate decreases slightly, while sulfur content in red mud markedly increases. This suggests that high-valence sulfur in sodium aluminate solution can be converted to S2− and then enter red mud by adding aluminum during the digestion process.