Development Of Novel Separation And Enrichment Approaches Based On Carbon Nanomaterials

Carbon based-materials are an integral part of materials. Carbon nanomaterials,0Dfullerenes,1D canbon nanotube and2D graphene, have attracted considerable attentionfrom both the experimental and theoretical scientific communities. Among these,fullerenes and graphene, whose discovery won the Nobel Prize, respectively. Theadvantages of carbon nanotube and graphene include high surface area, low toxicity,good chemical stability, environmentally friendliness, etc. The extraordinary propertiesof carbon nanotube and graphene make them promising candidates for practicalapplications, such as adsorbing material, sensitized material and conductive material.Porous polymer monolithic column, which possesses advantages of easy preparation,excellent permeability, low backpressure, large capacity for samples, and pH stabilityprovides great potential applications in sample preparation. The aim of the presentthesis is the design and synthesis functionalized carbon nanotube and the compositematerials of the graphene and porous polymer monolith. Furthermore, we developednovel methods of separation and enrichment based on functionalized carbon nanotubeand polymer monolith materials modified with graphene. We not only developed simpleand rapid synthetic routes and summarized its mechanism, but also explored thesematerials application in the field of separation and preconcentration. The main points ofthis thesis are described as follows: 1. The development and application of carbon nanotube and graphene, and thepreparation, modification, and application of polymer-based monolithic column werereviewed in Chapter1.2. Modified multi-walled carbon nanotubes (MWCNTs) were chosen as adsorbentsfor the adsorption of rare earths. Nitric acid, sodium hypochlorite (NaClO), hydrogenperoxide, and potassium permanganate were used for the modification of MWCNTs.The concentrations of rare earths were determined with UV-Vis spectrometry. Theadsorption capacities of rare earths on MWCNTs treated with different modificationmethods were compared with each other. The experimental results indicated thatMWCNTs modified with NaClO had highest adsorption capacity of rare earths. Asrepresentatives, the adsorption of samarium (Sm), gadolinium (Gd), and ytterbium (Yb)with the MWCNTs modified with NaClO was investigated in detail. Effects of variousparameters such as the concentration of rare earths, pH, ion strength, amount ofMWCNTs, and experimental temperature were investigated. Furthermore, Theadsorption isotherm (Langmuir and Freundlich isotherm models) and kinetics had alsobeen studied.3. We prepared an environmental friendly sorbent by modifying multi-walled carbonnanotubes with tannic acid (TA-MWCNTs). The adsorption of La (III), Tb (III) and Lu(III) as a function of contact time, initial solution pH, and quantity of adsorbent wasstudied using a batch technique. Both Langmuir and Freundlich isotherms were used todescribe the process. The major adsorption mechanisms were attributed to ion exchangeand surface complexation. The kinetics of the adsorption followed apseudo-second-order model. The thermodynamic functions H, G, and S indicatedthat the sorption was endothermically driven. The adsorbed ions could be readilydesorbed from the surface with1mol L–1hydrochloric acid. TA-MWCNTs were simple,convenient and inexpensive adsorbents for removing of rare earth, showing the potentialutilization of functionalized carbon nanotubes.4. Novel monolithic capillary columns with embedded graphene were developed and used for polymer monolith microextraction (PMME) coupled to LC MS analysis.The column was prepared inside fused silica capillaries (320μm, i.d.) using thermallyinitiated free-radical polymerization with butyl methacrylate (BMA) as monomer,ethylene dimethacrylate (EDMA) as cross-linker, and1,4-butanediol and1-propanol asporogens. Graphene (GN) was incorporated into the poly(BMA-co-EDMA) monolith toenhance the loading capacity. The extraction performance of the monolithic column wasevaluated by glucocorticoids as the analytes. The operation parameters of PMMEincluding desorption solvent, sample flow rate, sample volume, sample pH, and eluentflow rate were studied and optimized. Finally, the PMME method, based on thedeveloped monolithic capillary as the extraction media, was applied to thedetermination of nine glucocorticoids in cosmetics.5. We designed and synthesized a new type of graphene oxide (GO)/graphene (GN)nanosheets coated-poly(glycidyl methacrylate-co-ethylene dimethacrylate) monolithicbed (GO/GN@GMA-co-EDMA) via a simple procedure. They synthesized inside thecapillary in order to prepare a promising polymer monolith microextraction (PMME)material. Some technologies, containing atomic force microscopy, Fourier transforminfrared spectroscopy, transmission electron microscopy, X-ray photoelectronspectroscopy, and scanning electron microscopy, were employed to characterize thesynthesized GO/GN@GMA-co-EDMA monoliths, confirming that GO/GN waseffectively functionalized on the poly(GMA-co-EDMA) monolithic materials.Furthermore, a new method was developed for the analysis of sarcosine (identified as apotential prostate cancer biomarker) using PMME coupled with liquidchromatography-tandem mass spectrometry (LC-MS/MS).