Analysis Of Hexabromocyclododecane And Photocatalytic Degradation Mechanism

Hexabromocyclododecane(HBCD)is a new type of persistent organic pollutants(POPs).Long-term accumulation may pose a potential long-term hazard to humans and the environment.There are two main ways to reduce HBCD in the environment,one is to control the source of HBCD emissions,and the other is to degrade and eliminate HBCD.At present,there are few studies on these two aspects,especially the research on packaging materials,which is one of the important emission sources of HBCD,is still blank in my country.Based on this,we have carried out the following research.First,one of the important emission sources of HBCD in daily life-the packaging box was carried out to study the content and characteristics of HBCD,and the detection method of HBCD in packaging materials by gas chromatography-mass spectrometry was established;secondly,different sources and different The effects of solvents and different catalysts on the degradation of HBCD,and the degradation mechanism of HBCD was discussed.This research is innovative and practical,and the research results can provide a reference for the supervision and treatment of HBCD.The main research content of the thesis and the results obtained are as follows:(1)Study on the content and characteristics of HBCD in expanded polystyrene(EPS)packaging boxes.The thesis first established a gas chromatography-mass spectrometry analysis method for HBCD in EPS samples based on the current situation that there is no standard detection method for HBCD in EPS packaging samples.Secondly,EPS packaging boxes are a source of HBCD emissions that people often come into contact with but ignored in life.After systematically investigating the characteristics of EPS packaging boxes on the Chinese market,we collected 71 typical samples of EPS packaging boxes and used the established gas chromatography Mass spectrometry has carried out research on the content characteristics and key influencing factors of HBCD.The study found that among the 71 samples collected,11.3%of the packaging boxes were deliberately added with HBCD,and the content of HBCD was about 0.8%.The content of HBCD was affected by the use of the packaging box,the place of production,and the density.This research has rarely been reported before.The results of this study and the proposed control plan played an important role in the special inspection of HBCD packaging boxes by the Ministry of Ecology and Environment.(2)Research on the degradation effect and mechanism of HBCD.In spite of the current situation that HBCD does not have a good degradation elimination method and that the degradation mechanism of HBCD is unclear,this project has carried out research on the degradation method and degradation mechanism of HBCD.First,the self-made graphite phase carbon nitride was used to photocatalyze the degradation of HBCD.Secondly,the photocatalytic degradation effect of three commercial materials of titanium dioxide,ferrous sulfide and graphene oxide on HBCD was studied.Finally,the degradation mechanism was analyzed and speculated.In this paper,the thesis uses thermal polymerization method to prepare graphite phase carbon nitride with urea and melamine as precursors respectively,and characterizes its structure,morphology and other characteristics,and uses it as a catalyst to degrade HBCD.The study found that the photocatalytic degradation of HBCD by graphite phase carbon nitride varies greatly with the composition of the solution system.Among the four systems of water plus toluene,acetone,methanol,or acetonitrile,the mixture of water plus methanol provides the best environment of the photocatalytic degradation effect.After 15 minutes of reaction,the degradation rate of HBCD is close to 100%.In the system of methanol plus water,the rank of the catalysts is:carbon nitride prepared by urea precursor>carbon nitride prepared by melamine precursor>ferrous sulfide>graphene oxide>titanium dioxide.Using liquid chromatography mass spectrometry to detect the degradation products,it was found that the degradation rate of the three isomers of HBCD:?-HBCD<?-HBCD<?-HBCD.The identification results of the photolysis products showed that the degradation process was dominated by direct debromination products,including tetrabromocyclododecene,dibromocyclododecadiene,cyclododecatriene,and some epoxy-based products.Debrominated products.