Photo decomposition ability of ultra-fine rutile TiO2 powder was investigated using the photo-catalytic reaction in
aqueous 1.0 mmol 4-chlorophenol (4CP) solutions with pH-controlled conditions. Its photo-catalytic characteristics were
then compared with those of commercial P-25 powder having mainly anatase phase. When 4CP was completely
decomposed by the photo-catalytic reaction, HPPLTed TiO2 powder was more effective than the P-25 powder regardless
of the crystalline structures. As the photo-catalytic reaction time increased, the decomposition of 4CP in the aqueous
solution was accompanied with much consumption of OH- ions. However, in the case of the aqueous solution at pH=4
naturally obtained by mixing of water and 4CP, the photo-catalytic reaction of the HPPLTed TiO2 powder occurred more
actively, compared with in the cases of the more acidic and caustic aqueous solutions. Therefore, it is thought that the
decomposition of non-degradable 4CP would take place well at a certain amount of OH- ion concentration in the aqueous
solution, considering to show no difference in the adsorption of 4CP on the surface of TiO2 particle with various pHs of
the solution, when the HPPLTed TiO2 powder with high surface areas more than 180 m2/g was used.
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