Crystallization kinetics and crystallization process of pseudoboehmite from ammonium aluminum sulfate solution

In this work, the crystallization kinetics of pseudoboehmite was studied by intermittent crystallization method. The kinetic model of pseudoboehmite process was established based on particle number equilibrium. The results show that the nucleation is mainly caused by crystal collision, the main speed control step is diffusion process, and the enlargement of crystals mainly originates from the growth. Reducing the temperature of system can obtain pseudoboehmite crystals which have larger particle size and more uniform particle size distribution. Two parallel octahedral units connected by hydroxyl groups are preferentially stacked along the (020) crystal plane. Excessive interlayer water molecules between (020) crystal planes lead to an increase in the interlayer distance. The increased distance between (020) layers will weaken the hydrogen bond between layers, as well as the electrostatic forces and van der Waals forces, resulting in the formation of folded layers with holes. Finally, the irregularly sheets of pseudoboehmite are stacked to form porous spherical structures.

Automated summary

The crystallization kinetics of pseudoboehmite was investigated using intermittent crystallization method. A kinetic model based on particle number equilibrium was established for the pseudoboehmite process. It was found that crystal nucleation is mainly caused by crystal collision, diffusion process is the main speed control step, and crystal enlargement mainly originates from growth. Reducing the system temperature resulted in pseudoboehmite crystals with larger and more uniformly distributed particle sizes. Two parallel octahedral units connected by hydroxyl groups preferentially stack along the (020) crystal plane. Excessive interlayer water molecules between (020) crystal planes lead to an increase in interlayer distance. This increased distance weakens the hydrogen bonds, electrostatic forces, and van der Waals forces between the layers, resulting in the formation of folded layers with holes. Finally, the irregular sheets of pseudoboehmite stack together to form porous spherical structures.