Removal Of S^2- From Sodium Aluminate Solution With Sodium Ferrite

At present, the gradual decrease of high quality bauxite resource and the high foreign-trade dependence extremely limit the sustainable development of Chinese alumina industry. However, a large amount of high sulfur-containing bauxite has not been massively utilized, because of the limitation of technology and economy. Most of sulfur enters into the solution in the form of S " during Bayer digestion process. And the economical desulfuration method is sediment desulfuration in solution. Therefore, the research of removing S " from sulfur-containing sodium aluminate solution is the important process in utilizing high sulfur-containing bauxite.In this paper, the removal of S2" by forming insoluble sulfur ferric compounds in sulfur-containing sodium aluminate solution with sodium ferrite and the economical recycling of desulfuration slag were systematically studied. The study determined the best combining condition and the desulfurization law of sodium ferrite. Besides, the study also confirmed the factors affecting the separation of sulfur and iron in desulfurization slag. Based on this, the economical and efficient desulfuration process was proposed and the recycling scheme of desulfuration slag was explored. The main results are as follows:1) Thermodynamic analysis and experiment results indicate that sodium ferrate(IV) is formed by the reaction of ferric oxide and sodium carbonate which are fully mixed with mole ratio1:1at700℃, sodium ferrite begins to form at800℃and fully forms at900℃for80mins. The finer of the reactant particle, the faster sodium ferrite forms.2) Sodium ferrite can remove the S2-in aluminate solution. Sodium ferrite reacts to Fe(OH)4-by the interaction with solution, Fe(OH)4-can remove the S2-by forming insoluble sulfur ferric compounds. The desulfurization efficiency can reach70%under the following desulfurization conditions:reaction temperature is100℃, reaction time is1h, and dosage of sodium ferrite is NFe/S-1～2(NFe/s is the mole ratio of Fe to S). The desulfuration slag mainly is NaFeS2-3) The sulfide in low valence can easily transform to sodium sulfate with the presence of alkaline. The sulfur and iron can not be fully separated after pyrometallurgical treatment of the desulfurization slag, because of the presence of sodium. By exploring the hydrometallurgical treatment of desulfurization slag, we can get the sulfur concentrate and slag after the hydrometallurgical treatment of FeS. The sulfur concentrate mainly is S, and the slag mainly is amorphous iron products. The sulfur recovery of sulfur concentrate is76.92%.