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A Study of Photocatalysis Degradation of Polybrominated Diphenyl Ethers (PBDEs)

Author: SunYan
Tutor: ChenLiang
School: Donghua University
Course: Environmental Engineering
Keywords: Polybrominated diphenyl ethers Titanium dioxide Photocatalytic Reductive debromination
CLC: X70
Type: Master's thesis
Year: 2012
Downloads: 82
Quote: 0
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Abstract


Polybrominated diphenyl ethers (PBDEs) are an important brominated flame retardants, lipophilic, chemically stable, is typical of refractory organic pollutants. Currently, electronics, appliances, furniture, building materials and other industries polybrominated diphenyl ether has a wide range of applications. With the increasing content of polybrominated diphenyl ethers in the environment has caused a global environmental pollution, serious harm to the ecosystem and human health. Therefore, polybrominated diphenyl ethers seek a reasonable treatment and repair technology is becoming increasingly important. Select decabromodiphenyl ether (BDE-209) is widely used as a research object, study its analog sunshine photocatalytic system degradation effects and degradation mechanism to provide the basis for theoretical research and practical application. data. In this study, the following three components. The first part: using high performance liquid chromatography (HPLC) as decabromodiphenyl ether detection method, see the relevant literature to determine the appropriate detection conditions; experiments to simulate sunlight as the light source, under a nitrogen atmosphere to study the TiO2 suspension ten Photocatalytic Degradation of PBDEs. The study found that the TiO2 suspension system can be effective catalytic degradation of BDE-209. Experiments to examine the various factors, such as light source, the dosage of catalyst, the initial concentration of BDE-209, the hole scavengers on the photocatalytic degradation. Based on this study the photocatalytic reaction kinetics. The results show that when TiO2 dosage of 1g / L BDE-209, the initial concentration of 20mg / L, the hole scavenger selected methanol degradation of BDE-209 is the most efficient, light reaction 150min after the degradation rate of up to 78.6%. The photocatalytic reaction order kinetics, reaction rate constant for 0.0103min. Part II: To further enhance the effect of photocatalytic degradation of BDE-209, 20W UV lamp as a light source in the the Ti02 suspension system in the photocatalytic reduction role in the nitrogen protecting and hole scavengers, the reduction of silver ions prepared Ag/TiO2. And use other means of transmission electron microscopy (TEM), X-ray diffraction (XRD), energy spectrum analysis (EDS) were characterized. The results found that the photocatalytic reduction of the Ag deposition to the Ti02 surface. Simulated sunlight as a light source, prepared Ag/TiO2 as the catalyst, an amount of 1g / L, and the initial concentration of the BDE-209 was 20mg / L, the selection of methanol hole scavenger for photocatalytic degradation experiments. The results show that, by simulated sunlight illumination within 30 minutes of BDE-209 degradation rate reached 96%, 60min all degradation, degradation rate than Ti02 suspension system greatly improve. Part III: the GC-EI/MS and GC-CI/MS two methods as photocatalytic degradation product detection method to determine the detection conditions, and the TiO2 suspension of photocatalytic degradation products of qualitative analysis. The results show that the degradation products detected the formation of a series of low-brominated products, reaction the hexabromodiphenyl ether after 1h appear reaction 2h five PBDEs, reaction 6h after a small amount of three PBDEs. As the reaction proceeded, the product number of the bromine contained in gradually reduced. By the to degradation products inference mechanism of photocatalytic reaction: step by step process of reductive debromination. Photogenerated holes and electrons, hole scavenger (methanol) hole oxidation catalyst by light excitation, decabromodiphenyl ether as an electron acceptor, get electronic hydrogenation, and stepwise debromination to form a low-brominated products .

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