Adsorption And Determination Of Benzo[a]pyrene Based On Magnetic Covalent Organic Framework

Benzo[a]pyrene(Ba P)is a kind of polycyclic aromatic hydrocarbons(PAHs)formed by a benzene ring fused to pyrene,which has strong carcinogenic,mutagenic and teratogenic toxicity.Ba P widely exists in the environment and food,and can enter the human body through respiration or food intake,gradually posing threat to human health.Therefore,it is of great significance to establish an efficient Ba P removal and detection method.Covalent organic frameworks(COFs)are a family of emerging porous nanomaterial,which have the advantages of good chemical stability,adjustable porous structure,large specific surface area,large porosity,and?-conjugated system.COFs are widely used in sample pretreatment and have great potential for adsorption and removal of aromatic compounds.Magnetic COFs combine the advantages of COFs and magnetic nanoparticles,which can achieve rapid separation under external magnetic field,avoid the separation procedure such as centrifugation or filtration,and facilitate the recycling of materials.Therefore,in this paper,the magnetic covalent organic framework material(Fe₃O₄/COF-DQTP)was prepared.A method for fast-efficient adsorption and sensitive detection of Ba P was established based on magnetic COF-DQTP,and applied to the adsorption of environmental water and the detection of roast meat.The main research contents and results are as follows:(1)Preparation of magnetic COF-DQTP and its application for adsorption of Benzo[a]pyrene.The Fe₃O₄/COF-DQTP magnetic adsorbent was synthesized quickly and easily by the co-precipitation method.The magnetic adsorbent was characterized by Fourier Transform Infrared Spectroscopy(FT-IR),Nitrogen Adsorption(BET),Vibrating Sample Magnetometer(VSM),Transmission Electron Microscopy(TEM)and Energy Dispersive X-ray Spectroscopy(EDX),indicating magnetic adsorbent had been successfully synthesized and had a smaller particle size(about 20 nm),a larger specific surface area(80.2m²/g),and superparamagnetic properties(61.1 emu/g),which was conducive to adsorption and magnetic separation.The prepared Fe₃O₄/COF-DQTP was used as an adsorbent to test the adsorption performance for Ba P from water.The results showed that the adsorption efficiency of Ba P was above 98%with the optimal conditions(3 mg/m L adsorbents,10 min adsorption time,298 K).The maximum adsorption capacity of Ba P is up to 19.312 mg/g.Through desorption and regeneration,the adsorption efficiency of Fe₃O₄/COF-DQTP for Ba P remained about 90%after recycling 3 times.The study of adsorption kinetics showed that the adsorption of Ba P on Fe₃O₄/COF-DQTP conformed to the Pseudo-second-order model,indicating that it was mainly controlled by chemical adsorption mechanism.Meanwhile,the adsorption isotherm is more followed Freundlich model,indicating that the adsorption of Fe₃O₄/COF-DQTP to Ba P was the multilayer adsorption based on heterogeneous surface.Through the exploration of the adsorption mechanism,it was preliminarily speculated that was the result of the synergetic effect of?-?conjugation and pore size effect.On this basis,the method was applied to the removal of Ba P in environmental water(tap water,lake water and river water)and the adsorption efficiency of Ba P was above 98%.(2)Determination of Ba P in roast meats by magnetic solid-phase extraction(MSPE)-high-performance liquid chromatography-fluorescence detector(HPLC-FLD).The magnetic covalent organic framework Fe₃O₄/COF-DQTP was used as an adsorbent for MSPE and combined with HPLC-FLD to establish a method for detection of Ba P.The linear range of the MSPE-HPLC-FLD method was 0.5?100.0 ng/m L(R²=0.9998),the limit of detection(LOD,S/N=3)was 0.14 ng/m L,and the limit of quantification(LOQ,S/N=10)was 0.47 ng/m L by optimizing the experimental conditions such as adsorbent dose,extraction time,desorption solvent,desorption time and desorption volume.The relative standard deviations(RSDs)of the intra-day(n=5)and inter-day(n=5)were 3.5%and 3.9%,respectively.On this basis,this method was successfully applied to the determination of Ba P of roast meats(grilled fish,beef and mutton),the level of measured Ba P for three samples were 19.5 ng/g,17.3 ng/g,16.0 ng/g,respectively.The recoveries of standard addition were in the range from 76.0%to 123.4%at three spiked concentrations(10.0,20.0,30.0 ng/g)by standard addition method,and the relative standard deviation is 1.7%?10.6%.