The Preparation Of A New Type Of Carbon-based Solid Phase Extraction Material And Its Application In Water Samples

Solid phase extraction has been widely used in the environmental samples preparation as a sample preparation technique.The solid phase extraction materials play an important role in solid phase extraction technique.It is significant to develop new solid phase extraction materials with high selectivity as well as sorbents that can be applied to a wide range of matrices and analytes.Carbon-based materials have become one of the research hotspots in the preparation of solid phase extraction materials owing to their wide varieties,unique structures and abundant raw material resources.Based on the above points,rice husk-based activated carbon and multi-walled carbon nanotubes are modified by chemical process to prepare new carbon-based solid phase extraction sorbents with high performance and rapid pretreatment for samples preparation in this thesis.1.Biomass materials are the common raw materials of activated carbon?AC?with the advantages of abundant source,low cost.In this paper,rice husk is selected as biomass materials to prepare AC.The silica in rice husk,as the natural template,is removed by hydrofluoric acid to prepare porous activated carbon precursors.Then the zinc chloride is used as the activator to prepare the rice husk-based activated carbon.Factors affecting the preparation of AC,including the mass ratio of ZnCl₂ and rice husk carbon?RHC?,activation temperature and time are investigated.The optimal conditions for the preparation of activated carbon from rice husk are obtained.Then,magnetic activated carbon?mag-AC?is synthesized by in situ co-precipitation of rice husk-based activated carbon and Fe₃O₄.The microstructures of the materials are characterized by XRD,SEM,FT-IR spectrometry and nitrogen adsorption/desorption.Based on the Brunauer-Emmett-Teller?BET?results,the specific surface area of AC prepared under optimized conditions is as high as 1673 m²/g and the average pore size is 2.27 nm.The specific surface area and average pore size of mag-AC are 987 m²/g and 3.62 nm,respectively.2.Mag-AC is used as a magnetic solid phase extraction material for adsorption of 3 kinds of tetracycline antibiotics?oxytetracycline,chlortetracycline and tetracycline?in water samples,combined with high performance liquid chromatography tandem mass spectrometry for qualitative and quantitative analysis.Several factors affecting the extraction efficiency,including the pH of the extraction system,the amount of magnetic activated carbon,the extraction time and the type of eluent are discussed.The results show that mag-AC is a viable sorbent for the analysis of tetracycline antibiotics in water at trace levels.The limits of detection and quantification are 0.10-0.95?g/L and 0.35-2.85?g/L,respectively.The reproducibility of the method is measured by standard deviations,the range is1.5-9.4%.In addition,the extraction process is simple,fast and efficient by magnetic separation technology,and it can avoid the time-consuming steps of traditional solid phase extraction,such as filtration,sedimentation and centrifugation.3.Multi-walled carbon nanotubes are coated with sodium carboxymethyl cellulose by a simple cross-linking reaction.And sponge-like multi-walled carbon nanotubes composites are prepared by freeze-drying technique.The structures of spongy multi-walled carbon nanotubes are characterized by SEM and FT-IR.The results indicate that the composites have three-dimensional network structure,and the multi-walled carbon nanotubes have been successfully coated in carboxymethyl cellulose.Due to the the?-?interaction between multi-walled carbon nanotubes and the molecules with benzene ring structure,the composites are used as the solid phase extraction adsorbents for the extraction of polycyclic aromatic hydrocarbons in water and analyzed by gas chromatography-mass spectrometry.