Optimization of the treatment of red mud with sulfur dioxide

The SO₂ absorption ability of an aqueous suspension of red mud, which is waste from the Bayer process for bauxite, and the possibility of dissolution of metals using sulfurous acid are studied. It is found out that red mud can be used to neutralize sulfur dioxide of any concentration to an environmentally safe level. A statistical mathematical model is developed, and the absorption process is optimized. Under the optimal conditions, the mud is totally neutralized, and the sulfurous acid produced in the presence of an excess amount of SO₂ dissolves 35% of all the aluminum in one step. Since iron precipitates as FeSO₃, aluminum readily precipitates as hydroxide from solutions of iron-free aluminum salts.