Controllable Preparation Of TiO₂-based Nano-catalyst And Its Application In Photocatalytic Degradation Of Organic Wastewater

Although there has been much interest in photocatalysis for degradation of organic wastewater, there are currently few commercial applications of photocatalysis because of the following abstacles: 1) a relatively lower quantum efficiency, and 2) the requirement of near ultraviolet light energy (λ < 387.5 nm ).In this thesis, some methods of the quantum efficiency enhancement were investigated. The photocatalytic degradation of a kind of dye (Cationic Brilliant Red 5 GN ) was selected as a model reaction. The researches focused on the controllable preparation of nanotitania, the combination of titania and silica, and the modification of TiO₂/SiO₂ with silver. The main factors of photoreaction were also researched and some of kinetic rules were found.TiO₂ nanoparticles were prepared by a novel alkoxide sol precipitation method — controlled hydrolysis. The nanoparticles' structure and properties were characterized by XRD, TEM and UV-Vis measurements and their photocatalytic properties were investigated. The results indicated that the size of nanopaticles calcined at 500℃ was 15.8 nm, and the reaction rate of the same sample for 5GN photocatalytic degradation was 2.34 times of that of commercial nano-TiO₂.TiO₂/SiO₂ photocatalysts were prepared by sol-gel method, based on the complex reaction between Ti⁴⁺ and H₂O₂. The effects of preparation conditions such as calcined temperature, microwave promotion and the content of silica on photocatalytic activity were researched. The results showed that the TiO₂ particles doped with SiO₂ displayed the enhanced activity and excellent anti-sintered properties. The optimum content of silica doped was 25 mol. %. The calcination time of the TiO₂ powder can be shorten after the microwave treatment.Several preparation ways of TiO₂/SiO₂ modified with silver were researched. TheAg/TiO2/SiO2 particles prepared by impregnation and reduction methods displayed the best photocatalytic activity, which suggested that the Ag° was the main center capturing the photoelectron. The photocatalytic activity of samples as TiO2, Ag/TiO2, TiCVSiOj and Ag/TiO2/SiO2 particles were compared. The activity order was as follows:Ag/TiO2/SiO2>TiO2/SiO2>Ag/TiO2>TiO2.With the TiC>2 nanoparticles prepared by the controlled hydrolysis of alkoxide, the rule of Cationic Brilliant Red 5GN photocatalytic degradation under UV irradiation in fluidized photoreator were studied. The effects of light sources with different wavelength, catalyst content, initial substrate concentration, and oxygen concentration on reaction kinetics were investigated in detail. The total reaction followed the first-order kinetic rule.