The influence of titanium dioxide phase composition on dyes photocatalysis

A comparative study of TiO2 powders prepared by sol-gel methods is presented. Titanium tetraisopropoxide was used as the precursor for the sol-gel processes. The effects of the annealing treatment on phase, crystallite size, porosity and photodegradation of dyes (methyl orange and methylene blue) were studied. The phase structure, microstructure and surface properties of the films were characterized by using X-ray diffraction (XRD) and Atomic Force Microscopy (AFM). The X-ray diffraction was used for crystal phase identification, for the accurate estimation of the anatase-rutile ratio and for the crystallite size evaluation of each polymorph in the samples. It was found that the only TiO2 anatase phase of the synthesized TiO2 develops below 500 A degrees C, between 600 and 800 A degrees C the anatase coexist with rutile and above 800 A degrees C only the rutile phase was found in the samples. Attention has been paid not only to crystal structures, but also to the porosity, the particle size and the photocatalytic properties. However, the annealing temperature was found to have significant influence on the photocatalytic properties. Different TiO2 doctor blade thin films were obtained mixing the sol gel powder (100% anatase) and TiO2 Aldrich with TiO2 Degussa P25. The surfactant (Triton X100 or sodium dodecyl sulfate) affects the packing density of the particles during deposition and the photocatalytic degradation efficiency of the dyes. The photocatalytic degradation kinetics of methyl orange and methylene blue using TiO2 thin film were investigated.