The photocatalytic efficiencies of three commercially-available TiO2 samples were evaluated and compared for TiO2 powder dispersed systems with respect to several experimental variables such as pH, types and concentrations of cation and anion ions, dissolved oxygen, UV, and target organics to be photo-catalytically decomposed. All the TiO2 samples of P-25, NT-C, NT-20 showed a significant dependence of the photocatalytic efficiency on pH and exhibited higher photocatalytic efficiency in the pH range between 5 and 7. The water used for the preparation of the TiO2 slurry also affected the photocatalytic efficiency of the TiO2 samples presumably due to a few cation ions existing in the water. The degree of oxygen content dissolved in the slurry enhanced the photocatalytic efficiency by its role as an electron scavenger. The effect of several anions except Cl− and SO4 −2 on the photocatalytic efficiency varied depending on their concentrations and source of TiO2 powder. The photocatalytic properties of TiO2 samples varied significantly depending on the key experimental conditions applied to the TiO2 slurry. In the photocatalytic decomposition of organics, any particular TiO2 sample did not always show a better efficiency than other sources of TiO2 powder.

Keywords: Photocatalyst, TiO2, Organic decomposition, Dissolved oxygen, pH, Cation, Anion, UV.