Enhancement of the photocatalytic degradation rate of aromatic pollutants: Investigation of the photocatalytic degradation kinteic of catechol in the presence Fe3+ doped TiO2

The anatase form of TiO2 is the most suitable photocatalyst used in heterogeneousphotocatalysis. However, the degradation rates for many organic pollutants have been foundto be too slow to be of practical interest. In recent years, attention has been directed towardstransition metal ion doping on TiO2 in order to improve its photocatalytic activity. Althoughthere are numereous investigations on the effects of metal ion doped TiO2, the roles of themetal dopants and the mechanism of the process is still uncertain.In this study, with the intent to determine the role of the metal ion dopant, Fe3+ ion, thekinetics of the photocatalytic degradation of catechol has been investigated experimentallyand theoretically. Catechol has been chosen as the model compound, sincedihydroxybenzenes are the toxic intermediate products of the photocatalytic degradationreactions of phenolic compounds which constitute an important class of water and aircontaminants. The reactions have been carried out in a constant temperature batch-typephotoreactor using pure and doped TiO2 P25 Degussa as the photocatalyst. The effects of thecatalyst loading, initial concentration of catechol and Fe3+ ion dopant on the degradation ratehave been determined. The new photocatalyst has been characterized by using structuralmethods such as FTIR, XRD and SEM.In the theoretical part, in order to investigate the effect of doping on the electronic structure ofanatase and to find models suitable for determining the electronic properties of TiO2, a clustermodel Ti9O18 cut from the anatase bulk structure has been modelled. Calculations have beencarried out using Density Functional Theory DFT at B3LYP/LANL2DZ level. The optimizedgeometries, the frontier-orbital energies, energy gaps, Mulliken charge distributions of theatoms on the surface have been determined. Finally, the product distribution for thephotocatalytic degradation of catechol has been determined by means of quantum chemicalmethods and the Transition State Theory calculations for all the possible reaction paths.Keywords: catechol, iron ion doping, photocatalytic degradation, titanium dioxide.JURY:1. Prof. Dr. Zekiye ÇINAR Date: 21.06.20062. Prof. Dr. Hüseyin YILDIRIM Pages: 1003. Prof. Dr. Miray BEKBÖLET