Photocatalytic degradation of 4-chlorophenol by Pt/sol-gel and Ag/Sol-gel TiO2

Photocatalytic degradation of 4-chlorophenol (4-CP) was studied using TiO2, Pt/TiO2 prepared by the sol-gel methods and commercial TiO2 (Degussa P25) as photocatalysts. The influence of dissolved oxygen on the reaction rate and amount of intermediate products obtained from the 4-CP degradation were determined. In the experiments, a photocatalyst was suspended in the 4-CP solution which was then irradiated with an 11 W low pressure mercury lamp of wavelength of 200-280 nm. The results showed that, with TiO2 (sol-gel), a decrease in 4-CP concentration was much faster than that with Degussa P25. In contrast, the reduction rate of total organic carbon (TOC) with Degussa P25 was much higher than that with TiO2(sol-gel). The addition of a small amount of either Pt or Ag into TiO2 (sol-gel) improved significantly the catalyst activity. The highest degradation rate of 4-CP were found at 1.0% Pt/TiO2 and 0.5% Ag/TiO2. 0.5%/Ag/TiO2 showed the highest activity in terms of both 4-CP and TOC removals. Hydroquinone and hydroxyhydroquinone were identified experimentally as the main intermediate products under the presence of dissolved oxygen. The presence of dissolved oxygen played a significant role in enhancing the photocatalytic degradation of 4-CP for all prepared catalysts.