Nucleation and Morphology of Monosodium Aluminate Hydrate from Concentrated Sodium Aluminate Solutions

The induction time for monosodium aluminate hydrate (MAH) crystallization from supersaturated solution at 333 to 373 K is systematically investigated by experiment and the primary nucleation is also identified according to the classical nucleation theory. The truncated quadrangular orthopyramid and the twin/composite truncated pyramid crystals of MAH except for the tabular crystals and octagonal platelets obtained in the research are presented for the first time; furthermore, the supersaturation and temperature of the nucleation are experimentally studied. The interfacial free energies γ of truncated pyramid and octagonal platelet MAH crystals in the supersaturated sodium aluminate solution are conducted, and then the octagonal platelet MAH crystal is considered more stable in the solution than the truncated pyramid crystals. The two-dimensional (2D) mediated growth mechanism for MAH crystallization is suggested based on the regression of experimental data of nucleation.