Dispersion of TiO2 particles and preparation of SiO2 coating layers on the surfaces of TiO2

Fine TiO2 has been widely used as a white pigment, but the aggregation of TiO2 particles related to the high specific surface area makes it a challenge to modify its surface. In this paper, NaOH and Na2SO3 were adopted as regulators for the pH of TiO2 aqueous dispersion. It was discovered that when the pH is 12, the TiO2 particles have the maximum zeta potential and the repulsive force between two TiO2 particles is also at the maximum, which is favourable for the dispersion of TiO2. In terms of the modifying the surface, it was proved that a continuous and compact film of hydrous silica on the surface of TiO2 particles is produced by coprecipitation of Na2SiO3 and H2SO4 when the TiO2 particles are adequately dispersed by ultrasound at pH 12. Furthermore, it was found that the morphology of SiO2 is different when Na2SiO3 and H2SO4 solutions are added in different ways.