Review on alumina trihydrate precipitation mechanisms and effect of Bayer impurities on hydrate particle growth rate

• Hydrate morphology ranges from lozenges to prisms and depends on polynucleation.
• Impurity on the crystal surface disrupts the birth and spread growth on the basal faces.
• Impurities mainly affect the alumina hydrate growth rate and agglomeration.
• Impurities reduce growth kinetics to about fifty percentage than that of pure liquor.

The Bayer process used for refining bauxite to smelting grade alumina serves as the linchpin of the Aluminum production industry worldwide. Even though the process is well established, the presence of impurities in the liquor affects the quality of product and imposes a major economic cost on the industry. This review article focuses on the issues pertaining to Gibbsitic (Al2O3.3H2O) precipitation. The comprehensive review provides a basic understanding of the aluminum trihydrate precipitation and agglomeration phenomena. Crystal growth rate and agglomeration play a significant role in determining the output particle size distribution (PSD) of agglomerates. Hence, the effect of certain thermodynamic and hydrodynamic parameters along with the impact of natural impurities and additives (artificial impurities) on hydrate growth has been reviewed.