Application Of Nanometer Sized Metal Oxides In Pollutant Treatment And Environmental Analysis

Nanometer science & technology has been rapidly developing ever since 1980's, which means recognizing and reconstructing the nature on the level of nanometer size, and also creating new substances through directly driving atoms and molecules. Nanometer sized materials, as the basis of nanometer science & technology, are considered as the most promising materials in the 21^th century. Generally speaking, nanometer sized materials refer to those particles sized between 1-100 nm, which falls into the interface area of atom clusters and macroscopical substances. Nanometer sized material is classified into two levels: nanometer particles and nanometer sized solid materials, the former refers to ultra-micro particles sized in l-100nm, and the later is just the solid material made from such particles. The special structure of nanometer particles has resulted in many unique properties of nanometer sized solid materials. That is to say, the volume effect, surface effect, quantum effect and macroscopical tunnel effect have lead to its special characteristics in mechanics, electrics, magnetics, optics and chemical activity, and thus decided the wide application foreground in many fields.Environment pollution is an issue attracted the scientists all over the world. Whether environment pollution can be controlled effectively or not is very significant in protecting environment, maintaining zoology balance and achieving sustained development. Nanometer-sized semiconductor materials are characterized with photochemical reaction activity, double electrical layers hydroxide conjugate adsorption and higher specific surface area, which have attracted many researchers. In recent years, metal oxides semiconductors, such as nanometer-sized TiO₂ and CdS, have been applied widely in photo-degradating the environmental pollutants. However, this kind of methods based on nanometer-sized TiO₂ which has high photo- catalyzing activity is always faced with some problems, i.e., a manual light source is needed, photons efficiency is rather poor, immobilization of the photo catalyzer is difficult, strong acid reaction medium is needed, additional introduction of O₂ or N₂ into the system is necessary and the taken system must be light-pervious. Hence the application of the methods is limited. Therefore, to deal with the environmental pollutants with using nanometer-sized materials under relatively simple technical conditions has all the times been a challenging and innovative subject.Dealing with the dye pollution is one of the difficult matters that confront scholars all over the world. Dye pollution mainly comes from the azo dyes and rhodamine dyes.During recent years, nano-TiO2 has been applied widely in photodegradation of the environmental pollutions due to its specific characteres, whereas the studied objects are usually the azo dyes and reports on the treatment and degradation mechanism of rhodamine dyes are relatively less seen.Environmental analysis is the eye of environmental pollutants control, which is very important. However, in the practical work, the environmental samples are very complex and difficult to analyze because of the background interference and restriction of sensitivity of analysis methods. Solid-phase micro-extraction is an effective technique for separating and concentrating. The property of the adsorption materials used is a crucial factor affecting the analytical sensitivity and the selectivity. Thus, to find the new excellent adsorption materials is a significant job.The elemental chemical speciation points at the actual forms of elements and compounds existmg in certain ionic or molecular formation. Various form of an element will present quite different environmental behaviors and biological toxicity as well as different availability. So, it is much more significant to study the form of trace element than to analyze its concentration. Obviously, it is highly depended on new methods of form analysis.It is always demanded a quite high sensitivity and selectivity in form analysis, what is more, the formation of the object should be kept unchanged during the sampling and analyzing procedure. Therefore, form analysis is usually more difficult than quantitative determination of an element or a compound, and it is always connected with separation and concentrating operations.Nowadays, various of separation techniques have been applied in form analysis, which include HPLC, IC, SFC, GC, CZE, and so on. However, these separation techniques always need particular instruments with high cost.Adsorption materials have also been applied in form analysis today. On basis of the difference in adsorbing ability of the materials between different forms, some formation is concentrated or eliminated so as to facilitate the subsequent determination.In this thesis, the work is focused on the application of nanometer sized metal oxides in the fields described above, which mainly includes the following aspects.1. Three kinds of nanometer metal oxide powder were synthesized with Sol-Gel method. The diameter of powder was controlled with surfactants. The average diameter and specific surface area were measured. The synthesis condition, average diameter, specific surface area, stability and photo-catalyzing activity of the three oxides werecompared systematically.2. The photo-chemical reactivity of nanometer ZnO was applied in photo-degradation of Rhodamine dye. Dynamic molecular spectroscopy was used to trace the kinetics and mechanism of dye on the surface of ZnO. The applicability of nanometer sized ZnO in photo-degradation of rhodamine dye is studied.3. Adsorption behaviors of several metal ions, to say, V(V),Cr(VI),Mo(VI) and W(VI) on nanometer ZrO2 and Fe2O3 were studied systematically. Factors affecting the adsorption and diluting of these ions were examined. Special emphasis was put on the study of Cr(VI), a kind of highly toxic pollutant, thus a new method for treating Cr(VI) ion was built up based on the adsorption power ofZrOi and Fe2O3.4. Adsorption behaviors of V(V) on nanometer ZrO2 was studied and a separation and pre-concentration method for trace amount of V(V) in environmental samples was proposed. The sensitivity and selectivity of the method was much higher than existing methods.5. Adsorption behaviors of three kinds of azo dyes on nanometer ZrO2 were studied. Experimental conditions were optimized and the possibility of eliminating pollution of dyes with nanometer ZrO2 was discussed.6. Adsorption behaviors of As(III)/As(V) on Z1O2 as well as affecting factors including the diluting conditions were studied with spectrophotometry, hence the application of ZrO2 in form analysis was looked in.7. Based upon the above work, the adsorption mechanism of these nanometer sized metal oxides was discussed preliminarily. And the possibility of reusing these metal oxides was studied.