Choi HY  Kim DH  Park NK  Lee TJ  Kang M  Lee WG  Kim HD  Park JW

Vol. 18,  No. 1, pp. 63-68, Mar.  2012

Bauxite Bayer process Aluminum hydroxide High purity alumina

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In this study, aluminum hydroxide (Al(OH)3) was synthesized by Bayer process and sodium contained in Al(OH)3 was removed with the acid solution such as HCl and acetic acid for the synthesis of high purity alumina. The bauxite produced in Queensland of Australia was used for the production of alumina by Bayer, and was crushed to a particle size of below 10 um by attrition mill. The crushed bauxite was treated in sodium hydroxide solution of 5 N for the elution of aluminum component. The elution of aluminum from bauxite was carried out at 140 ℃ and 3.4 atm in autoclave. The sample solution was separated to the red mud and liquid solution by filter paper. The elution of aluminum from bauxite was confirmed with changing a structure and aluminum content in both bauxite and red mud analyzed by XRD and EDX. Aluminum contained in the separated solution was crystallized to Al(OH)3 with the addition of aluminum hydroxide used as the seed material. Al(OH)3 powder obtained during the crystallization process was purified by several times washing with distillated water. It was also confirmed that the sodium remained in Al(OH)3 powder is removed with acid solution. The purity of Al(OH)3 powder produced in this study was 99.3% and the content of sodium was reduced to approximately 0.009% after the acid treatment.