Caustic aluminate liquors: Preparation and characterisation using static light scattering and in situ X-ray diffraction

Caustic aluminate liquors of several concentrations were prepared from different starting materials and varying methods. Static light scattering and in situ X-ray diffraction experiments were performed on these solutions. The results showed that there was a definite correlation between the liquor preparation, size of the initial species present in solution and the resulting crystalline phase. Liquors prepared by dissolution of gibbsite at atmospheric pressure crystallised only as gibbsite and contained species with radii > 25 nm in the initial solution. The identical solutions of dissolved gibbsite subsequently heated to 160 degrees C for 16h gave rise to a mixed crystalline product of gibbsite and bayerite and contained species of radius < 55 nm in the initial solution. Solutions made with aluminium metal behaved identically to the solutions prepared from gibbsite with the additional heating. The solutions prepared from gibbsite at atmospheric pressure were proposed to be self-seeding, providing gibbsite-like templates for the nucleation of the single crystalline phase. It is proposed that the different methods and materials used in preparation of synthetic Bayer liquors account for the variance in the physical properties determined by different researchers.