The Study Of Photochemical Behavior Of Polycyclic Aromatic Hydrocarbons(phe) On The Secondary Minerals

PAHs is one kind of the persistent organic pollutants(pops),which are mainly produced from fossil fuel deposits and incomplete combustion。With the development of industry and agriculture,more PAHs have been detected in naturally hydrophobic phases,such as in liquid、soil and air。Due to the circulation of environment,the pollution of PAHs in soils is much more serious than others,which threat to security,human health and the ecosystem structure of agricultural products。How to control and repair the pollution sites is becoming a hot topic。Phenanthrene is one of the most widespread PAHs,always used as a model to study the degradation and transportion of PAHs。It is difficult to control and repair the pollution of PAHs in soils,understand the relation of soils and PAHs is important to promote the degradation of PAHs in soils。Polycyclic aromatic hydrocarbons have large unsaturated bond,can absorb the ultraviolet light(290-400 nm)and visible light(400-700 nm),which is the basis of the photodegradation of polycyclic aromatic hydrocarbons。The photolysis of PAHs is a potentially important process which decide its fate in soil environment,and the soil components,such as metal oxide,humic acid,natural minerals,also significantly impact the photolysis。In this study,we choose Phenanthrene as the object to understand the photochemical behavior of PAHs at irradiated clay surfaces。Attempting to reveal the impact of clay type on photolysis,gain insight into the transformation pathway of PAHs and the fators affect photolysis process。(1)We analyze the appearance and structure characteristics of secondary minerals through XRD and SEM pictures,the results show that both smectite and kaolinite present massive and lamellar structure,goethite and water sodium manganese present needle and granular structure。Smectite and water sodium manganese water sodium manganese have larger internal porosity,adsorption ability of four minerals follow the order:water sodium manganese>smectite>goethite>kaolinite。(2)Photolysis experiments are conducted under 254 nm UV light,the removal rate of Phenanthrene is quantified by a UPLC,result shows that UV light can significant promote the degradation of Phennanthrene and conform to the First order reaction kinetics。The removal rate of Phenanthrene on four secondary minerals follow the order:smectite<kaolinite<goethite<water sodium manganese。We also detect the photoproducts of Phenanthrene by GC-MS,and Bis(2-ethylhexyl)phthalate,alkane,phenol are identified as the main intermediate products。The experiment provides valualbe insights on that Phenanthrene could change into low toxicity or non-toxic materials,and mineralization finally when under UV irradiation。(3)Photolysis experiments under different light condition are conducted under 254 nm、300 nm、365 nm UV irradiation,results show that removal capacity of three wavelength present like:254 nm>300 nm>365 nm。Three different concentration of low molecular organic acid are added into semples and compare the change of removal rate under 254 nm、365 nm UV irradiation。Vanillic acid in both wavelength can restrain the photodegradation of Phenanthrene,citric acid under the condition of 365 nm wavelength suppresses the photodegradation,but under the condition of 254 nm wavelength it promoted the removal rate of Phenanthrene。...