Application Of Titanium Dioxide Nanotube Materials In The Trace Analysis Of Environmental Pollutants

Titanium dioxide nanotubes, a new type of TiO2 materials, have mainly used in many fields such as sensors, dye sensitized solar cells, photoelectric catalysis and photocatalysis, etc. They were widely used for photoelectric catalysis and photocatalysis in environmental field. They have larger specific surface area than that of titanium dioxide nanoparticles, titanium dioxide nanotubes should have much better adsorption ability. Recently, highly ordered TiO2 nanotube array was introduced as a new kind of TiO2 materials. In contrast, it has better physical and chemical properties, much larger specific surface area than that of TiO2 nanotube powders. Except these, TiO2 nanotube is connected with the substrate directly and tightly, and not easy to be desquamated. Because of the highly ordered structure and non-agglomeration, it is very easy to realize stable and cycled application of TiO2 nanotube array. So TiO2 nanotube array absorbed much more attention. However, there are very few reports on the application of TiO2 nanotube array in environmental analytical field. Due to their special physical and chemical properties, TiO2 nanotube array should play an important role in environmental field, especially in preconcentration and detection of environmental pollutants, and have a great prospect.In this thesis, a series of new analytical methods were developd to determine environment pollutants with TiO2 nanotubes and TiO2 nanotube array, and a novel enrichment technique micro-solid phase equilibrium extraction was well established. Further a preliminary study on the sorption mechanism was carried out. This thesis consists, of the following four parts:In the first part, the research progress of solid phase extraction and TiO2 nanotubes were reviewed.In the second part, the feasibility of TiO2 nanotubes as solid phase extraction absorbents for organophosphorus and benzoylurea pesticides was investigated. The experimental results showed that organophosphorus pesticides such as chlorpyrifos, phorate and methyl parathion could be quantitatively absorbed onto TiO2 nanotubes packed cartridge, and these compounds retained on the cartridge can be desorbed quantitatively with suitable amounts of n-hexane. The detection limits of the proposed method for the determination of chlorpyrifos, phorate and methyl parathion were 0.11,0.014,0.0025μgL-1 respectively. The analysis of real water samples demonstrated that satisfied spiked recoveries were achieved in the range of 86.5%-115.1%. The experimental results indicated that TiO2 nanotubes had good adsorption capacity for diflubenzuron, chlorbenzuron, triflumuron, flufenoxuron and chlorfluazuron in environmental water samples. A new, sensitive, and rapid method was developed for determination of such compounds with TiO2 nanotubes cartridge in combination with high performance liquid chromatography, and the detection limits were in the range of 0.0.62-0.21μgL-1. Four real water samples were used to validate the developed method, and the spiked recoveries were in the range of 82-100.2%.The potential of TiO2 nanotube array as absorbent for some organic pollutants was investigated in the third part. A new method micro-solid phase equilibrium extraction (μSPEE) procedure was established. The experimental results show that some organic pollutants such as pyrethroid pesticides, organochlorine pesticides and polychlorinated biphenyls can be quantitatively absorbed on TiO2 nanotube array sheet, then these compounds retained on the TiO2 nanotube array sheet can be desorbed quantitatively with little amounts of organic solvent, finally the analytes can be detennined by gas chromatography-electron capture detector. This method has been applied to determine pyrethroid pesticides, organochlorine pesticides and polychlorinated biphenyls in several environmental water samples. The detection limits of the developed method were 0.018-0.070μgL-1,0.10-0.0076μgL-1,0.020-0.10μgL-1 respectively. The spiked recoveries from real environmental water samples were in the range of 81.9-110.6%,78-102.8% and 95.8-110.5% respectively.In the last part, ordered TiO2 nanotube array which was modified with cetyltrimethylammonium bromide was used to preconcentrate polycyclic aromatic hydrocarbons (PAHs) based on micro-solid phase equilibrium extraction. The experimental results show that the modified ordered TiO2 nanotube array has good enrichment ability to PAHs. The detection limits of the developed method were in the range of 0.026-0.82μgL-1. The spiked recoveries from real environmental water samples were in the range of 75.0-114%. A primary study on the absorption mechanism was carried out with pyrene and fluoranthene as the model targets.