Surface Modification Of Titanium Dioxide And Its Photocatalytic Properties

With the improving of living standard, people require a healthy and clean living environment. Therefore, the "white pollution" problem has attracted more and more concern. Currently the treatment of waste plastic using semiconductor photocatalytic oxidation becomes one of the most promising ways. The process of the photocatalysis can decompose organic pollutants into water, carbon dioxide and non-toxic organic acids by chemical oxidation. Nano titanium dioxide photocatalyst is chemically stable, cheap, non-toxic and highly catalytic active. As an outstanding representative of the semiconductor photocatalyst, it has a very good prospect of application and has been studied extensively. However, titanium dioxide has some inherent flaws when it used as catalyst to photodegradate polymers. The nano-particles will easily aggregate to be cluster. Its surface is not oleophylic enough. Hence it is difficult to blend with polymer. Therefore, it is necessary for the nano titanium dioxide to be surface modified in order to achieve a comprehensively good performance. And the treatment should not damage the photocatalytic activity of TiO₂ nanoparticles.Seveal reagents were selected to modify nano titanium dioxide, inclusing toluene 2,4- diisocyanate, photosensitizer dyes, polyaniline, acetylacetonate rare earth complexes, ferric acetylacetone complex, ferrocene ferric benzoyl acetone complexes, ferric beta-tone imine complexes and so on. To evaluate the photocatalytic activities of modified catalysts, the degradation of methyl orange was tested as a probe reaction. It was found that TiO₂ modified by ferric acetylacetonate showed good performance. The ferric acetylacetonate modified TiO₂ was characterized by UV-Vis, IR, XRD, SEM, fluorescence and optical microscopy analysis. It demonstrated that the crystal structure of modified nano-TiO₂ has not changed. On the surface there is strong interaction between ferric acetylacetonate and TiO₂. This effectively prevented the agglomeration of nano particles.The composite of modified nano-TiO₂ and polyethylene glycol (PEG) was prepared. The photodegradation process was studied by understanding of the weight loss, the molecular weight and the morphology of the composite powder. It was found that ferric acetylacetonate modified nano TiO₂ shows good activity. The degradation reaction rate is relevant with the average molecular weight. The higher the PEG molecular weight, the lower the degradation rate is. As the degradation process going on, the polymer molecular weight of PEG decreases gradually and the molecular weight distribution broadens. In this thesis, a new and simple method is proposed to prepare modified nano-titanium dioxide photocatalyst. The modified nano-TiO₂ photocatalyst is good dispersed, rather oleophylic and highly catalytic active. These new effective modified nano-TiO₂ photocatalysts should have good future in the degradation of white pollutants.