Abstract
The effect of the support on photocatalytic degradation activity was investigated with three kinds of catalyst beads (TiO2/SiO2, TiO2/Al2O3 and TiO2/Zeolite) using phenol as a reactant. The rate constant of phenol degradation and the conversion to inorganic carbon were compared among three kinds of catalysts. The rate constant (k) for TiO2/Al2O3 was the largest (0.0448 min−1) followed by TiO2/SiO2 and TiO2/Zeolite at 0.0246 and 0.0235 min−1, respectively. The conversion to inorganic carbon after 120 min UV irradiation was the lowest for TiO2/Zeolite (22.4%) among three catalysts. Thus, the influence on the reaction mechanism of different supports was discussed from the time courses of concentration in phenol, intermediate products and also the amount of TOC changed to inorganic carbon. Based on the HPLC species analysis, the photocatalytic degradation mechanism was suggested to involve consecutive reactions. In addition, the pH value in the solution depended on the support used, i.e., around 6 for TiO2/SiO2 and TiO2/Al2O3, and around 7 for TiO2/Zeolite. GC/MS analyses showed that negatively charged compounds were produced in the reaction on TiO2/Zeolite Since the ζ-potential on the catalyst surface is considered to depend on the pH of the solution, adsorption of the charged compounds on the catalyst surface would be inhibited by an electrostatic effect. This phenomenon will affect the photocatalytic degradation activity of phenol on each catalyst.
