Study on the efficient removal of trace iron from sodium aluminate solution by the heterogeneous nucleation method

When treating high-sulfur bauxite by the high-temperature Bayer method, the obtained sodium aluminate solution typically has an iron concentration of more than 5 mg/L, rendering it unusable for the production of high-purity alumina. In this work, the sulfur ions from the sodium aluminate solution may formed strong coordination bonds with Fe(Ⅲ) or Fe(Ⅱ) to generate complex-ion with Fe(II)-S-OH - .Then, the ligand-metal bonds dissociated and reconfigured, and more stable nano-polycrystalline products such as FeSO 4 ·7H 2 O and FeS were formed. Iron in solution reacted with these iron-sulfur compounds via heterogeneous nucleation reactions to crystallize and agglomerate, and a simple filtration reduced the iron concentration in the sodium aluminate solution to below 5 mg/L. Under suitable conditions, the removal of iron from the sodium aluminate solution reached 86 % with an alumina loss of less than 2 %. The method of inducing crystallization and enrichment by the addition of Fe(Ⅲ) or Fe(Ⅱ) can effectively remove iron impurities.