Wet Oxidation Method Of Removal Of Industrial Sodium Aluminate Negative Bivalent Sulfur Ions In The Solution Of The Research

Our country is rich of high grade sulfur-containing bauxite, its sum accounts for 11.0% of total bauxite resources in China. However, when this kind of bauxite was used for alumina production by Bayer process, it may result to the raise of S2- in Bayer liquor, and then the concentration of Fe2O3 in final products may rise. So it is of great significance to develop an efficient process to remove S2- from sodium aluminate liquor for utilization of high grade sulfur-containing bauxite.In this paper, the transforming of sulfur in Bayer digestion process was studied. The research results confirm that more than 61.3% of sulfur in bauxite goes into Bayer liquor as S2-, and some of them are removed out of Bayer system with red mud. The red mud has some purifying capacity.The study confirms that the method of using Wet Air Oxidation to remove S2- in Bayer digestion process is effective. Adding proper air into digestion process, more than 85% of S2- in the liquor can be reduced.In the first part of this process, S2-is oxidized into S2O32- firstly, that makes the concentration of S2O32- rise up. As reaction goes on, S2O32-、SO32- will be transformed into SO42- when S2- is reduced to a low condition, and their concentration will be fall.The results revealed that the more O2 was added, the greater the removal effect of S2- can be got. Finally, S2-, S2O32-and SO32- all can be converted into SO42-. Besides, the temperature can accelerate the reaction. To get better effects of oxidation, the temperature should keep above at 220℃.Using Wet Air Oxidation method to remove S2- in digestion process, some of the organics in Bayer liquor can be also oxidized. Ordinary, organics will be converted into sodium oxalate, and it will continue to be oxidized into sodium carbonate when O2 is enough. After treated with Wet Air Oxidation process, settling and separating property of Bayer process red mud can be improved. Concentration of Fe2O3 in Bayer liquor can also be reduced significantly.