Photocatalytic Oxidation Process Of Methyl Orange Wastewater Preliminary Studies

With the quick development of science and technology, people's living standard rising ceaselessly, printing and dyeing industry also obtained a rapid development, leading to a large number of printing and dyeing wastewater discharge. Dye not only influences the people's lives, but also bring some changes to people and environment. If dyeing wastewater directly discharged to environment, would lead serious pollution to soil and natural water. So it must be processed before discharged. Printing and dyeing wastewater is known to have the character of huge water dischargement, deep chromaticity, high content of organic matter and non-biodegradable properties. Because the azo(-N=N-) dyes containing azo groups, has a character of high stability, so it is widely used in the industry of printing and dyeing, which is the main dye wastewater discharge of the species. In this paper, we have prepared photo-catalysts by different methods of Homogeneous precipitation and precipitation. Take methyl orange (MO) as simulated wastewater, the influence of photo-catalyst on color removal and COD removal of MO have been investigated.In the first part, firstly the classification, the nature, and the usage of dyes were introduced; Secondly we analyzed the harm of dye wastewater, and show dangerous of the dye wastewater to human survival and environmental:and then status of printing and dyeing wastewater treatment were reviewed, including physical, chemical and biological treatment methods:and the forth, we introduced the application of photo catalytic oxidation in the dyeing wastewater treatment; In the end of this part, the contents, the purpose and innovations of this research were introduced.In the second part, the experimental reagents, instruments and experimental methods were presented.In the third and fourth part, the degradation of MO was studied by photo catalytic oxidation process. The effects of catalyst amount, pH and the amount of hydrogen peroxide on the decolorization and COD removal of MO have been studied. We also investigated the reuse of catalysts. The experimental results show that, at the optimal operating conditions, the final color removal and COD removal from the wastewater reached99.9%and85%by ZnO/Kaolin photo catalyst which is prepared by Homogeneous precipitation method:the final color and COD removal from the wastewater reached98.7%and79.8%by ZnO/Kaolin-1photo catalyst which is prepared by precipitation process. The ZnO/Kaolin photo catalyst has higher activity and stability which can be reused5times. The result show that the ZnO/Kaolin photo catalyst with Homogeneous precipitation method is more efficiently than the ZnO/Kaolin-1photo catalyst with deposition method.In the fifth part, the behavior of ZnO/Kaolin on the adsorption of MO aqueous solution was investigated, which includes the factors that affect the adsorption, adsorption isotherms, adsorption kinetics and adsorption thermodynamics. The adsorption equilibrium experiments show that ZnO/Kaolin adsorption of MO is more in line with the Langmuir model, and the adsorption behavior are preferential adsorption; Kinetic studies showed that the adsorption process of MO on ZnO/Kaolin a is very suitable for the pseudo second order kinetic model, equilibrium adsorption capacity is reduced with temperature increasing. The adsorption thermodynamic behavior of the whole adsorption process is mainly physical adsorption.