Preparation Of Bimetallic Magnetic Porous Graphene Composites And Their Enrichment And Removal Of Antibiotics In The Environment

Environmental pollutants have posed a serious threat to the social environment and human life and health.The development of reliable and sensitive removal and detection methods based on effective adsorbents has always been the focus of researchers.Adsorption method is often used to remove refractory pollutants in the environment because of its advantages of simplicity,high efficiency,low cost and environmental protection.Magnetic solid phase extraction(MSPE),as a novel solid phase extraction method,has the advantages of simplicity,rapidity,time saving and easy recovery.It is often used in the sample pretreatment for the detection of trace pollutants in complex matrix.Porous graphene(PG)is often used in adsorption separation and other fields because of its large specific surface area and adjustable pore size.However,there are also some shortcomings in its application,such as single reaction site,low yield and strong hydrophobicity,which limit its further application.In addition,most of the preparation methods of magnetic adsorbents are complex and time-consuming.Based on the above research background,this study takes carbon material porous graphene as the carrier,solves the problems existing in the application of PG by doping different metal compounds and non-metal atoms,improves the preparation efficiency of magnetic adsorbent by one-step combustion method,and uses the prepared magnetic porous graphene composite as an adsorbent for the removal and detection of antibiotics in environmental water samples.The specific research contents are as follows:1.Iron-nickel bimetallic oxide porous graphene composite material(Fe/Ni-PG)was prepared by a simple partial combustion method,which can be used to effectively remove sulfonamides(SAs)in aqueous solution.The adsorption performance of Fe/Ni-PG,Fe-PG and Ni-PG on six kinds of SAs were compared,and the influence of time,temperature,p H and initial concentration of SAs on the adsorption behavior of SAs of Fe/Ni-PG in aqueous solution were studied.Langmuir model and pseudo-second-order kinetic model can describe the adsorption isotherm and kinetics.The maximum adsorption capacities of sulfadiazine(SD),sulfamerazin(SM),sulfamethazine(SDM),sulfathiazole(STZ),sulfapyridine(SPD),and sulfisoxazole(SIZ)calculated by Langmuir model were 26.3,50.3,42.2,27.3,34.5 and41.7 mg/g respectively,which exceeded most reported adsorbents.In the adsorption process,hydrogen bonding,?-?electron donor-acceptor,electrostatic interaction,and bimetallic synergies plays a major role,and the entire adsorption process is spontaneously endothermic.In addition,the material has excellent stability,and the Fe/Ni-PG after desorption is consistent with the raw material.2.In order to further improve the hydrophilicity and action sites of the materials,iron nickel bimetallic nitrogen doped porous graphene(Fe/Ni-NPG)nano materials with rich pores,strong magnetism and good reusability were prepared.The introduction of nitrogen increased the dispersion and active sites of the materials.It was used as a magnetic solid phase extraction(MSPE)agent for the determination of 5-nitroimidazoles(5-NDZs)in environmental water samples by HPLC.The adsorption behavior of 5-NDZs on Fe/Ni-NPG was investigated,which accorded with the quasi second-order kinetics and Langmuir isotherm model.The?-?electron donor-acceptor interaction,hydrogen bond and electrostatic interaction between Fe/Ni-NPG and 5-NDZs are the main help to obtain excellent adsorption properties.Several important conditions of MSPE are systematically optimized.Under the optimal MSPE condition,the linear range of DMZ is 0.6-500?g/L,the linear range of TNZ and ONZ is 0.7-500?g/L,and the correlation coefficient R~2?0.9991.The limit of detection is 0.18-0.2?g/L,the limit of quantification is 0.6-0.7?g/L,the RSDs of intraday and interday precision are 1.58%-4.66%and 3.77-9.69%,respectively.In the three spiked actual environmental water samples,the recovery was 78.05-107.05%(RSDs<7.82%).3.In order to further increase the active sites of the material,a bimetallic magnetic nitrogen sulfur Co doped porous graphene(Fe/Ni-N/S-PG)was prepared in this chapter to remove ciprofloxacin(CIP)from environmental water samples.The introduction of nitrogen and sulfur through ammonium sulfate helps to improve the dispersion and pore size of the material.Compared with Fe/Ni-NPG and Fe/Ni-PG prepared in the previous two chapters,they showed better adsorption performance for CIP(q_e=94.83 mg/g).Electrostatic interaction,pore filling effect,hydrogen bond and?-?EDA interaction are important factors to promote the adsorption of Fe/Ni-N/S-PG and CIP.The whole adsorption process is spontaneous,reversible and exothermic,and conforms to Freundlich and quasi second-order kinetic model.After the Fe/Ni-N/S-PG was reused for 5 times,the adsorption capacity remained at the initial 83.94%,and the removal rate reached 84.99-95.15%in the actual water sample.In this study,the combustion method used to prepare magnetic porous graphene composites is simple,rapid and high yield.It shows excellent adsorption properties for SAs,5-NDZs and CIP in environmental water samples.It opens up a new way and provides a new technology for the preparation of bimetallic magnetic adsorbent and the efficient removal of antibiotics,and lays a foundation for the purification of social environment.Combined with MSPE-HPLC,it can accurately and efficiently detect the residue of 5-NDZs in the Yellow River water and fish culture water.It has the advantages of simple operation,environmental protection and low cost.It provides a new method for the analysis of trace targets in complex actual samples,and provides a reference for environmental safety and human life and health.