Mesoporous Silica-Modified Multi-Walled Carbon Nanotubes And Its Application In Determination Of Organic Pollutants In Aqueous Samples

As important nanomaterials, due to their layered and hollow structure, large surface area, high mechanical strength, excellent chemical stability, good electrical conductivity and absorption properties, carbon nanotubes (CNTs) are widely used in electronics, field emission materials, catalysis, and so on. However, the application of CNTs has been limited in many fields because there are usually held in big bundles and difficult to disperse homogeneously in different solvents. Therefore, to improve the dispersion property and adsorption ability of CNTs by some modifications has become a research hotspot.In this thesis, a kind of solid-phase extraction (SPE) adsorbent was synthesized by coating mesoporous SiO2on multi-walled CNTs. With small particle size, big surface area, high stability and good dispersion property, the prepared adsorbents were applied for the preconcentration and removal of organic pollutants in aqueous samples.(1)Preparation and characterization of mesoporous SiO2-coated multi-walled CNTs(mSiO2@MWCNTs)A SiO2layer was coated on MWCNTs with the aid of the cationic surfactant CTAB. Mesoporous structure was obtained by extracting CTAB via an ion-exchange procedure. A number of advanced techniques, including FT-IR, TEM and N2adsorption-desorption were used to characterize the structure and surface properties of mSiO2@MWCNTs. The results showed that the dispersibility of mSiO2@MWCNTs was improved greatly, and mesoporous SiO2layer was coated on the surface of MWCNTs uniformly.(2) Application of mSiO2@MWCNTs as SPE adsorbentmSiO2@MWCNTs was first adopted as SPE adsorbent in this thesis for the enrichment and separation of phthalate esters (dimethyl phthalate ester, dibutyl phthalate ester and dioctyl phthalateester), phenolic compounds (p-nitrophenol,1-naphthol and2-naphthol) and nitroanilines (o-nitroaniline,m-nitroanilineand p-nitroaniline), and coupled with HPLC to quantitative analysis the nine kinds of substances. In the SPE optimization experiments, several factors that affected the SPE efficiency were investigated, including amount of mSiO2@MWCNTs, pH of the sample solution, eluent type and volume. And the optimum conditions were finally obtained. The method of mSiO2@MWCNTs SPE-HPLC established in this paper was proved successfully to determine the nine kinds of organic pollutants in Xiangjiang River water, pond water, well water and tap water.