Behavior And Suppression, Of Iron In The Sodium Aluminate Solution

Presently in china, bauxite resources are consumedly insufficient with thedevelopment of alumina industry. So research on alumina production using non-highquality bauxite is extraordinarily urgent. Generally mineral containing iron does notaffect the alumina production. But when the diaspore with high content of sulfur wasadopted, iron would be dissolved into the sodium-aluminate solution and precipitatealong with aluminum tri-hydroxide with the temperature decreasing, which badlycontaminates the aluminum tri-hydroxide product. Therefore, studying the behavior ofiron during the digestion process and finding the method to restrain the iron content insodium-aluminate solution are great of practical significance.Results demonstrate that the iron concentration in sodium-aluminate solutionincreases with prolongation of the digestion time and S^2- can markedly improve theiron concentration in sodium-aluminate solution. During the high pressure digestionprocess using different bauxite containing iron, caustic soda concentration has greatinfluence on the iron concentration in sodium-aluminate solution, and Na₂CO₃ canevidently improve the iron concentration in sodium-aluminate solution while Na₂SO₄has no effect.Simultaneously, the effects of different additives on the iron content in sodium-aluminate solution are investigated. The results are as follows:Precipitant NP and weak reductant NS_x can greatly reduce the iron content of liquorin the high-pressure digestion process. The iron content was reduced by 71.5% and76.3% respectively after adding the two precipitant (5g/L) individually. Solidabsorbent RM can remarkably reduce the iron content of liquor in the normal-pressuretreatment process. The iron content was decreased by 60.9% when treatment time is120 min. In the sedimentation process, inorganic substance MSO can distinctly reducethe iron content of liquor. The decreased value of iron content is 77.3% with MSOaddition content of 2 g/L.