Study On The Adsorption Performance Of Acid-modified β Zeolite For Hydroxylated Polybrominated Diphenyl Ethers And Its Application In Environmental Testing

Persistent organic pollutants（POPs）refer to organic matter with the characteristics of persistence,bioaccumulation and high toxicity.as derivatives of polybrominated diphenyl ethers（PBDEs）,Hydroxylated polybrominated diphenyl ethers（OH-PBDEs）are a new type of POPs that destroy endocrine.Compared with PBDEs,OH-PBDEs have higher and stronger toxicity.OH-PBDEs exist in trace amounts in environmental.With the widespread use of PBDEs in daily necessities,OH-PBDEs have also begun to be frequently detected in different environmental media and organisms.Because OH-PBDEs have the characteristics of persistence,toxic effect and accumulation,they are difficult to be degraded in environmental and bring unpredictable risks to the ecosystem and humans.However,OH-PBDEs,which exist in trace form,have many homologues and are susceptible to matrix interference,have brought certain difficulties to current analysis techniques.Based on the characteristics of OH-PBDEs,most of the researches mainly use liquid-liquid extraction,solid-phase extraction,liquid-solid extraction,etc.combined with liquid chromatography tandem mass spectrometry（LC-MS/MS）,gas chromatography coupled with mass spectrometry（GC-MS/MS）and other analytical techniques detect OH-PBDEs in different environmental media and organisms.However,most of the reported methods require derivatization of OH-PBDEs.The derivatization process is not only complicated and easy to cause secondary pollution,but most importantly,the derivative product is the methoxy polybrominated diphenyl ether（Me O-PBDEs）,which will interfere with the accuracy of quantitative analysis;in addition,the high temperature of the GC-MS inlet will cause thermal decomposition of the thermally unstable OH-PBDEs.Therefore,it is of great significance to develop a simple,efficient,and environmentally friendly pretreatment technology,combined with a highly selective and sensitive analytical instrument to detect OH-PBDEs in environmental media.Based on previous studies,this paper established a method for pre-processing and enrichment of samples with Citric acid modifiedβzeolite,optimized the process of sample pre-processing,and combined it with UPLC-MS/MS to detect 11 kinds of OH-PBDEs in environmental water samples and aquatic products.The main contents are as follows:（1）According to the different physical and chemical properties of the adsorption materials,βzeolite,graphene oxide（GO）and carbon nanotubes（CNTs）were modified to prepare different types of adsorption materials:different acids（including nitric acid,oxalic acid,lemon Acid）and alkali（sodium hydroxide）modifiedβzeolite（NA-β,OA-β,CA-βand Na-β）and DL-1-（1-naphthyl）Functional GO（DGO）,nitric acid modified CNTs（NA-CNTs）and NA-CNTs-GO composite membranes grafted onto graphene oxide by ethylamine.Then,with OH-PBDEs as the target analyte,the adsorption experiment shows that CA-βzeolite modified with citric acid has the best adsorption performance for OH-PBDEs.On this basis,through the use of field emission scanning electron microscope（SEM）,scanning transmission electron microscope（STEM）,X-ray electron spectroscopy（XPS）,X-ray powder diffraction（XRD）,nitrogen physical adsorption-desorption and Fourier Infrared transform spectroscopy（FI-IR）characterizes the structure of CA-βzeolite before and after modification,and analyzes the changes in the surface properties of CA-βzeolite before and after modification.It was found that the dealumination of citric acid increased the number of pores in CA-βzeolite,and increased the silicon-to-aluminum ratio and hydrophobicity to a certain extent,which helped to improve the adsorption capacity of CA-βzeolite for the target analyte OH-PBDEs.（2）Adopt single-factor adsorption experiment to systematically investigate and optimize CA-βzeolite adsorption conditions for OH-PBDEs from six aspects:citric acid concentration,adsorbent dosage,extraction time,cleaning solution composition,eluent type and dosage,and the optimized results are as follows:0.1 mol L^-1 citric acid concentration,200.0 mg CA-βzeolite,8 min extraction time,100%ultrapure water washing and 18 m L acetone solution for elution.Experiments show that under the optimal adsorption conditions,the recovery rate of CA-βzeolite for all OH-PBDEs is above 80%.On this basis,an adsorption-desorption cycle regeneration experiment was carried out on CA-βzeolite,and it was found that the CA-βzeolite after 10 cycles of regeneration still has a satisfactory recovery rate,which proves that CA-βzeolite is used for processing,the feasibility and practicality of adsorbing actual samples containing OH-PBDEs.（3）On the basis of structure and morphology characterization,the adsorption mechanism of CA-βzeolite was further explored through ammonia temperature program desorption（NH₃-TPD）and pyridine infrared,and the results showed that the porous structure characteristics,high hydrophobicity and the increase of Lewis acid at the adsorption site has a significant impact on the adsorption of OH-PBDEs by CA-βzeolite.The adsorption behavior of CA-βzeolite to the target analyte was further investigated through the adsorption isotherm.The results showed that the adsorption behavior of CA-βzeolite was more in line with the Linear model,and its R²=0.998.The adsorption process of CA-βzeolite was investigated through adsorption kinetic experiments,and the results showed that the process followed a pseudo-second-order kinetic model,where R²=1 and K₂Q_e=1.96.（4）Under optimal adsorption conditions,CA-βzeolite and different adsorption materials（including:DL-1-（1-naphthyl）ethylamine grafted onto graphene oxide to prepare functional oxidation Graphene DGO,nitric acid modified carbon nanotube NA-CNTs,nitric acid modified NA-βzeolite,oxalic acid modified OA-βzeolite,NA-CNTs-GO composite membrane and different framework types of zeolite）for adsorption comparison,To verify the excellent adsorption capacity of CA-βzeolite for OH-PBDEs.（4）Using CA-βzeolite as a solid-phase extraction material,combined with ultra-high liquid chromatography-tandem mass spectrometry（UPLC-MS/MS）to separate and analyze OH-PBDEs in lakes and fish in Wuhan.The results showed that under optimized experimental conditions,all 11 OH-PBDEs peaked within 8 minutes,the isomers were completely separated,and the peak shape was good.The linear range of detection of 11 target analytes is 0.6～100μg m L^-1,the detection limit range is 0.007～0.251μg m L^-1,the recovery rate of lake water is91.99%～117.94%,and due to serious matrix interference,The fish recovery rate ranges from27.45%to 110.56%.The results show that CA-βzeolite as a solid-phase adsorbent can easily,accurately and efficiently separate the trace amounts of OH-PBDEs in environmental water samples and fish.This verifies the feasibility of the method established in this paper.