Study On Preparation Of Nanosized Titanium Dioxide And Photocatalysis Of Phenol Aqueous Solution

Heterogeneous photocatalysis by semiconductors has unique advantages in water pollution control, especially in the treatment of waste water containing poisonous organic compounds which are hard to be destroyed. In this thesis, the preparation and characterization of photocatalysts of titanium dioxide and its composites have been carried out. Meanwhile, photocatalysis of phenol aqueous solution has been experimentally studied considering its strong application background in wastewater treatment. Besides, the possible synergetic effect between photocatalysis and sonolysis under ultrasound field has been investigated.First, Nano-sized titanium dioxide particles were prepared with precipitation method under alkaline condition, in which dilute ammonia gas was continuously introduced into titanium tetrachloride acidic solution. Effects of several influencing factors such as temperature, titanium concentration, solution PH, amount of dispersing agent added and the reaction time on the particle sizes, aggregation and photocatalytic performances were investigated experimentally, and the optimum preparation conditions were obtained. The photocatalysis experiments of phenol aqueous solution by titanium dioxide and/or its composites were carried out under UV-irradiation. It was found that in addition to the anatase crystal titanium dioxide, the non-crystal titanium dioxide hydrate also exhibits good photocatalytic performance.Sonolysis and photocatalysis are all of advanced oxidation technologies following the same free radical mechanism, on the other hand, ultrasonic cavitation can greatly improve the mass transfer between photocatalyst and liquid. Therefore, a synergetic effect may be expected by coupling these two technologies. In this paper, sonolysis, photolysis, and photocatalysis of phenol solution by titanium dioxide photocatalyst with/without ultrasound were studied, meanwhile, the temperature effect of photolysis and photocatalysis has also been investigated. It was shown that the ultrasound at 40KHz and 0.4W-cm"2 have no obvious effect on phenol degradation, and its promotion on photocatalysis is also marginal. The difference between photolysis and photocatalysis curves is of prominence which implies that photocatalyst can notably decrease the concentration of intermediate produced in the degradation process. Besides, temperature has a remarkable promotion on both photolysis and photocatalysis processes.