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

Polybrominated diphenyl ethers (PBDEs) have been widely used as an important Brominated Flame Retardants (BFRs) in electrical apparatus, electronic product, furniture and building materials which is one kind of persistent organic compounds with toxic and lipophilic properties. With the increasing of PBDEs in the environment, they have affected wildlife and human populations and the research of removal technology of PBDEs has become increasingly important.Decabrominated diphenyl ether(BDE-209) has been choosen as the studying sample.Removal efficiency and Removal Mechanism was studied under simulated sunlight irradiation so as to make the contribution to theoretical research and engineering. This paper is consisted of three parts described below.First part:The High Performance Liquid Chromatography(HPLC) method was adopted for determination of BDE-209,and a set of detection methods was established on the basis of the reference literatures. In TiO2 suspension system, the photocatalytic reduction of BDE-209 was studied under simulated sunlight irradiation. Effects of the light source, dosage of TiO2, initial concentration of BDE-209, hole scavenger kind on photocatalytic reduction of BDE-209 have been investigated. The results showed that effect of photocatalytic degradation of BDE-209 was evident in TiO2 suspension system. When amount of TiO2 is 1g/L, hole scavenger is methanol, the degradation rate of BDE-209 was 78.6% under irradiation for 2.5h and the degradation course obeyed the one order kinetic equation, and had the rate constant of 0.0103min-1。Second part: To improve the removal efficiency of BDE-209. Ag/TiO2 was prepared by photo-reduction method and characterized by TEM, XRD, EDS. The results showed that Ag successfully deposited on the surface of TiO2. In Ag/TiO2 suspension system, the photocatalytic reduction of BDE-209 was studied under simulated sunlight irradiation. The results showed that the degradation rate of BDE-209 was 96% under irradiation for 0.5h and reached 100% in 1h.The removal efficiency was higher in Ag/TiO2 suspension system.Third part: GC-EI/MS and GC-CI/MS was adopted for determination the degradation products of BDE-209.A set of detection methods was established and the degradation products was analyzed. The results showed that the degradation products was lower bromo congeners.6-BDEs was detected in 1h,5-BDEs was detected in 2h,3-BDEs was detected in 6h.During the photocatalytic reaction, electrons are excited from VB into CB of TiO2 under irradiation which results in the generation of VB hole and CB electron. The VB hole is scavenged by methanol and the electron is accumulated in CB of TiO2 and BDE-209 was reductive by CB electrons.