Effect Of Dissolved Organic Matters On The Photolysis Of 2,4,4'-Tribromophenylphenyl Ether

In this study,we have investigated the photolysis of 2,4,4'-tribromophenylphenyl ether(BDE-28)in non-ionic surfactant triton X-100(TX-100)solutions,and discuss the degradation of BDE-28 under different light source,substrate concentration,pH and temperature.discussed the effect of TX-100 on the photodegradation of BDE-28.We also discussed the effects of two representative dissloved organic matters,anthraquinone-2,6-disulfonate(AQDS)and citrate on the photodegradation of BDE-28 and the mechanism,which provides a scientific basis and theoretical basis for the migration and transformation of low brominated diphenyl ethers in the environment The main conclusions are as follows:(1)The light source had a great effect on the degradation of BDE-28,and the degradation of BDE-28 was the fastest under UV irradiated compared with other light sources.The initial concentration of BDE-28 also had a great effect on the photodegradation of BDE-28.The photodegradation of BDE-28 was inhibited with initial concentration increasing.Under high pH and low pH conditions,BDE-28 was unstable and prone to photodegradation.The photodegradation of BDE-28 under neutral conditions was relatively slow.The temperature had little effect on the photodegradation of BDE-28.(2)The photo-sensitization of TX-100 promoted the photodegradation of BDE-28,and also produced competitive light absorption with BDE-28 molecule,which caused the light shielding effect to inhibit photodegradation of BDE-28.At the same time,dissolved oxygen showed a dual effect on the photodegradation of BDE-28,and apparently inhibited the photodegradation of BDE-28.On the one hand,the dissolved oxygen initiates the photo-sensitization of TX-100 and promotes the photodegradation of BDE-28.On the other hand,dissolved oxygen quenches the excited state of BDE-28 and inhibits its photodegradation,The final degradation of BDE-28 was dominated by inhibition.(3)AQDS exhibits a dual effect on the photodegradation of BDE-28: promoting photodegradation of BDE-28 at low concentrations and inhibiting photolysis at high concentrations.The effect of AQDS on BDE-28 photolysis is that AQDS can produce ROS under light sources irradiated to promote the photodegradation of BDE-28.The inhibitory effect is on the competitive light absorption of BDE-28,resulting in light shielding effect and BDE-28 molecules combine to produce a light quenching effect.Citrate has little effect on the photodegradation of BDE-28 because of the strong hydrophilicity of citric acid that does not react with BDE-28 in the hydrophobic chamber of the surfactant.(4)The degradation of BDE-28 was mainly due to the de-bromination reaction,and the bromination reaction of BDE-28 occurred mainly in the ortho position and the bromine atom in the ortho position is more easily removed than the bromine atom in the para position.