Photodegradation Of Dissolved Anthracene And Pyrene In A Mixture And The Effect Of Surfactant On The Photodegradation Of Dissolved Anthracene Or Pyrene

Polycyclic aromatic hydrocarbons(PAHs) are common persistent organic pollutants that are mainly produced by human activities in environment.They pose a potential threat to human health through bioaccumulation via food chains.In this dissertation the properties,hazards,sources and dominant environmental behaviors of PAHs in aquatic environment were presented firstly.Secondly,photodegradation of PAHs in liquid phase were reviewed.Thirdly,the structures,properties and applications of surfactants were introduced and their applications in environmental scientific were emphasized.Finally,the applications of fluorimetry in related studies of PAHs were summarized.On the basis of the discussions above,the proposals of this dissertation were illuminated.Anthracene(An) and pyrene(Py) were selected as the model molecules.Photodegradation of dissolved An and Py in a mixture in water, simulated seawater(SSW) and pretreated natural seawter(PNSW) which was filtered and sterilized before use was investigated,and the effect of surfactant on the photodegradation of dissolved An or Py was also studied.The mainly results were as follows:Firstly,photodegradation of dissolved An and Py in a mixture was investigated. Proper photodegradation apparatus was set up,then the photodegradation of dissolved An and Py in a mixture in water,SSW and PNSW was directly studied by synchronous fluorimetry.Several environmental factors such as radical inhibitor (HCO₃^-),humic acid(HA),acetone,hydrogen peroxide(H₂O₂),nitrate(NO₃^-) and heavy metal ions(Cu²⁺,Cd²⁺,Hg²⁺ and Zn²⁺) were selected,and the effects of these environmental factors on the photodegradation of dissolved An and Py in a mixture in water,SSW and PNSW were investigated,respectively.Some important results were as follows:The photodegradation rates of dissolved An and Py in a mixture increased with the increment of salinity of aqueous solution.The photodegradation rates of dissolved An and Py in water,SSW and PNSW decreased as this order:SSW＞PNSW＞water.The processes of photodegradation of dissolved An and Py in a mixture were enhanced when HCO₃^-,acetone,H₂O₂ or NO₃^- was introduced to water,SSW and PNSW,respectively.Whereas,the contrary results were obtained when HA was introduced to water,SSW and PNSW.The effects of different heavy metal ions on the photodegradation of dissolved An and Py in a mixture varied a lot in water,SSW and PNSW.Experimental results show that all the processes of photodegradation of dissolved An and Py investigated followed first-order reaction kinetics.The half-lives of photodegradation of dissolved An in water varied from 0.3 to 18.6 min,and the half-lives of dissolved An in a mixture in water,SSW and PNSW varied from 0.5 to 18.9 min,0.2 to 5.1 min and 1.5 to 10.7 min,respectively.Moreover,the half-lives of photodegradation of dissolved Py in water varied from 1.3 to 30.9 min.The half-lives of dissolved Py in a mixture in water,SSW and PNSW varied from 1.7 to 34.7 min, 1.2 to 29.1 min and 2.3 to 31.7 min,respectively.Secondly,photodegradation of dissolved An or Py in three kinds of surfactant (Brij35,SDS and DTAB) solutions were investigated by fluorimetry,according to the characteristic of water solubility enhancement of PAHs.These three kinds of surfactants contain different charges.It was found that the processes of photodegradation of dissolved An or Py were retarded in SDS and DTAB solutions, because An and Py resided in the micelles within the core of surfactants in these solutions.While in Brij35 solution the processes of photodegradation of dissolved An or Py were enhanced,and the reason is that An and Py resided in the micelles among the polyoxyethylene portion of Brij35.The processes of photodegradation of dissolved An in water and Brij35 solution followed first-order reaction kinetics,and their half-lives were 16.3 min^-1 and 8.9 min^-1,respectively.Experimental results show that the process of photodegradation of dissolved Py in water also followed first-order reaction kinetics,but the process of photodegradation of dissolved Py in Brij35 followed second-order reaction kinetic.The half-lives of photodegradation of dissolved Py in water and Brij35 solution were 24.8 min^-1 and 1.3 min^-1.In addition, the mechanism of photodegradation of dissolved An in Brij35 solution was explored preliminarily.The experimental results showed that HCO₃^- had no effect on the photodegradation of dissolved An in Brij35 solution,and the photodegradation rate of dissolved An in Brij35 solution increased a little with the present of magnetic field.In conclusion,in Brij35 solution An decomposed according to the mechanism with the excited triple state of An but without a radical cation,and this mechanism was homologous with the mechanism of photodegradation of dissolved An in water.