Sub-micro photocatalytic TiO₂ particles for a water depollution: Comparable removal efficiency to commercial P25 and easy separation via a simple sedimentation

The sub-micrometer sized TiO₂ particles (100–200 nm) were synthesized by a sol-gel and subsequent thermal annealing. The particle size, surface area, pore structure, and crystallinity were varied upon the annealing temperatures (450, 550, 650 °C). The photocatalytic activities of three TiO₂ particles annealed at various temperatures (450-, 550-, and 650-TiO₂) were examined by performing photocatalytic depollution of three organic model pollutants (methylene blue, methyl orange, and phenol) from aqueous solutions under the UV light irradiation. Among three samples, 550-TiO₂ (~200 nm) exhibited the highest photocatalytic activity towards the removals of all three model pollutants. Photocatalytic activity of the 550-TiO₂ was compared with a commercial TiO₂ (P25, Evonik) at various conditions of loading amounts of particles dispersed in MB solution. Light scattering by dispersed particles at high sample loading conditions was less pronounced in the case of 550-TiO₂. Therefore, the sub-micro 550-TiO₂ particles can exhibit comparable activity to P25 at high sample loading conditions (2–4 g/L). In addition, the bigger size of 550-TiO₂ made it possible to separate them via a simple sedimentation process, showing a potential of sub-micro TiO₂ particles as an efficient photocatalysts for water depollution.