The pH influence on photocatalytic decomposition of organic dyes over A11 and P25 titanium dioxide

The photocatalytic removal (decomposition + adsorption) of four azodyes (Reactive Red 198, Acid Black 1, Acid Blue 7 and Direct Green 99) in water was investigated using Tytanpol A11 (Police Chemical Factory, Poland) and Degussa P25 (Degussa, Germany) as photocatalysts. The effect of pH of the reaction solution has been examined. The degree of the dye removal in the solution was measured by UV-Vis spectroscopy. Photodecomposition of dye on photocatalyst surface was monitored by FTIR spectroscopy. A11 photocatalyst has lower activity in the reaction of photocatalytic decomposition of organic dyes than Degussa P25. The photocatalytic decomposition of the dyes takes place on the photocatalyst surface at pH = 2 while at pH = 12 photocatalytic reaction proceeds via photogenerated hydroxyl radicals for both A11 and P25. (C) 2003 Elsevier Science B.V. All rights reserved.