Preparation Of Graphite / Nano - Titanium Dioxide Composites And Their Photocatalytic Degradation Of 2,4 - Dichlorophenol

TiO2 is used as photocatalyst in this article. During the process of photocatalysis, the value of pH was changed in solution. The reason of this change is the formation of organic acids which have small molecular weight in the reaction system. The photocatalytic reaction rate is extremely sensitive to the change of pH value. Therefore,the pH value of solution must be stable to get accurate results. By carrying out the photocatalysis in Na2CO3-NaHCO3 buffer system, this problem can be resolved perfectly. On this basis, the process of photocatalysis on the weakly alkaline environment(pH=9)was researched. And experimental results have shown that the rate of photocatalytic degradation in alkaline environment is higher than witch in acidic and neutral conditions.DCP wastewater that came from actual production generally have a high concentration of NaCl. The presence of NaCl will significantly reduce the catalytic activity of titanium dioxide. It has been suggested that the combination of TiO2 with graphene could reduce the level of electron-hole recombination. In order to improve the efficiency of photocatalysis, TiO2 and graphene that prepared by the method of Hummers and TiO2 were combined. By hydrothermal method, graphene- TiO2 composite photocatalyst with different weight ratios of graphene to TiO2(0,0.01,0.02, 0.05, 0.10 respectively) was prepared. Experiments about the photo catalytic performance of graphene- TiO2 composite photocatalyst show that catalytic activity of the composite photocatalyst compared to pure titanium was improved significantly in alkaline reaction system with high concentration of sodium chloride((pH = 9, Na2CO3-NaHCO3 buffer system, 20% NaCl). And the catalytic activity of composite photocatalyst was increased with the pace of the increase of graphene concentration when graphene level is less than 5%. The reason of this phenomenon is that the BET of graphene increased so that DCP would be adsorbed on the surface of photocatalyst rapidly and the separation of electron-hole pair was very efficient. When the graphite content is more than 5%, graphene would suppress the absorption of light and the content of titanium dioxide in composite photocatalyst would be reduced accordingly. Therefore, all of these factors repressed the catalytic activity of composite photocatalyst.