Study On Photocatalytic Properties Of TiO₂ Sol And Its Application

The degradation and treatment of printing and dyeing wastewater is a very difficult problem in the field of wastewater treatment. Titanium dioxide becomes very popular in science research in recent years. Titanium dioxide has been shown to be an excellent photocatalyst owing to its stable chemical characteristics and low price, etc.This dissertation describes a titanic dioxide sol containing anatase crystals and able to be excited by UV irradiation and visible irradiation, which is prepared through sol-gel method under low temperature. Based on the experimental results and theoretical analyse, a reactive mechanism for photocatalytic of TiO₂ sol has been proposed. The sol possesses direct photocatalytic property without the traditional high-temperature heat-treatment in the powder and film research.The parameters such as the amount of hydrolysis water, aging time, aging temperature, pH value have been studied on the photocatalytic activity of TiO₂ sol for degradation dyes. The tests reveal that the water amount determines the photocatalytic activities. The acidic amount influences the electrical environment. The preparing temperature and the aging time also affect the photocatalytic activates. The optimum conditions are aging 7d in the room temperature and the ratio of Ti(OC₄H₉)₄:H₂O is 1:100. The degradation rate of 97.5% is reached implying the sol has high photocatalytic activity.The sol is able to be excited by UV ray and visible ray, thus the sol can use solar energy. Also it can possess a better photocatalytic performance. The influences of concentration and solution volume are analyzed in the paper and reaction kinetics of the sol on methylene blue is studied in detail. The best conditions for maximum photocatalytic degradation are found to be pH 2.0 and 9.0. The photocatlytic degradation rate is high when the initial concentration of reactive orange 2 is 20mg/L. Using TiO₂ sol and comparison between photoactivity of TiO₂ sol and TiO₂ sol added H₂O₂ and Fe³⁺ reveal that, H₂O₂ and Fe³⁺ can be used as a suitable alternative to TiO₂ sol for water treatment.The results show that the mean particle diameter of TiO₂ sol was 18.04nm. The XRD result indicates that TiO₂ sol was nano-crystal sol. The kinetics analyst indicates that the mechanism of photocatalytic reaction of TiO₂ sol is different from that of powders and films widely which are simply simulated by zero order or first order simulation. The quantum effect, huge surface and the Brown activities of the anatase crystals in the sol make the Photocatalytic reaction much more complex than those of powder's and film's. The reaction of photocatalysis can be devided into two steps: sirstly slow first-order reaction of breaking up the congeries of Methylene Blue molecules, and the following fast complex reaction of breaking up the bonds inside Methylene Blue molecules.The color removal of wastewater is 99.9%, COD removal is 78.4% and TOC removal is 70.5% under UV irradiation for 120min.The photocatalytic degradation mechanism of the TiO₂ sol is briefly discussed. The mechanism and kinetics of photocatalytic decomposing dye has been preliminarily researched. UV/vis, IR analyzes the degradation process of Methylene Blue. The degradation process was to be speculated that Methylene Blue color groups are firstly destroyed into lower color organic intermediates. The intermediates are then degraded gradually even fully translated into Carboxylic acids and primary amines.