Effect of calcium hydroxide concentration and stirring rate on the crystallization of the calcium carbonate on the surface of fly ash

To improve the whiteness of fly ash, fly ash was prepared using calcium hydroxide, water, and carbon dioxide as the reaction system to coat calcium carbonate crystals on the surface of the fly ash. This study investigated the effect of the calcium hydroxide content and stirring rate on the crystallization of the calcium carbonate on the fly ash surface. The results showed that the calcium carbonate nanoparticles prepared with a 7% calcium hydroxide concentration and stirring rate of 500 rpm were coated on the surface of the fly ash, and the whiteness of the modified fly ash reached a maximum of 59.7% ISO. The microscopic process of heterogeneous nucleation of calcium carbonate and the LaMer model were explored to explain the influence of the precursor reactant concentration and stirring rate on the nucleation and growth of the crystal. © 2018, BioResources.