【作者】 林龙利；

【导师】 刘国光；

【作者基本信息】 广东工业大学 ， 应用化学， 2012， 博士

【摘要】 Ti0：光催化技术是目前被广泛关注的一项催化新技术。Ti0：在受光照后会产生电子-空穴对,光生电子具有很强的还原能力,光生空穴具有很强的氧化能力,当污染物种(如有机物或金属离子)吸附到半导体Ti02表面时,就会分别得到电子或空穴,发生相应的氧化还原反应。利用电子-空穴的协同作用,同时去除环境中的氧化态和还原态的污染物成为当前催化和环境保护研究领域的一个研究热点。本课题在以下几个方面做了一些研究工作,为开拓TiO2纳米管催化剂在同步处理有毒有机废水和含重金属离子的废水方面提供了理论基础。1.以纳米Ti02为原料,采用水热合成法制得Ti0：纳米管。采用红外光谱(FT-IR)分析、X衍射(XRD)分析和电镜扫描分析进行表征。表明用水热合成法制备的纳米管不会改变其晶型,同样主要为锐钛矿型,含有少量金红石型；相比纳米Ti02,制得的Ti02纳米管晶粒尺寸较小,增大了比表面积和孔体积、具有相对较好的分散性能,克服了纳米Ti02颗粒容易团聚的现象,制备出来的Ti0：纳米管在理论上具有良好的光催化活性。2.在总体积为500 mL、反应物浓度为2×10-mol/L、300W紫外光照射下(体系中的光密度为8 MW/cm2)、温度控制在26±0.5℃、空气曝气(300 mL/min)、TiO2纳米管的浓度为2.0 g/L实验条件下,用所制备的TiO2纳米管进行光催化降解EDTA、酒石酸、柠檬酸和DTPA的研究。实验发现尽管紫外光也能直接光解EDTA.酒石酸、柠檬酸和DTPA,但Tj0：纳米管的加入,可以促进四种有机物的降解,使反应速率更快,反应更彻底。1小时后,采用高效液相色谱(HPLC)很难检测到体系中的有机物。表明Ti02纳米管光催化法非常适合于含EDTA、柠檬酸、酒石酸和DTPA废水的处理。3.用所制备的Ti02纳米管进行光催化还原Cu(Ⅱ)和Ag(Ⅰ)的实验。1小时后Cu(Ⅱ)和Ag(Ⅰ)的去除率分别达到了83.7%和88.1%。表明Ti02纳米管光催化法是一种很有效的处理含金属离子废水的方法。用X射线光电子能谱(XPS)表征金属离子的还原产物,Cu(Ⅱ)能被Ti0：纳米管光催化还原为相应的金属单质。这表明Ti02纳米管光催化法也是一种很有优势和前景的资源回收的方法。4.研究了有机添加物的氧化还原电位与有机物对Ti02纳米管光催化Cu(Ⅱ)的还原速率的影响之间的相关性。发现并不是添加所有的有机物都能明显促进金属离子的光催化还原。酸类(甲酸和乙酸)能加快金属离子的还原反应,而醇类(甲醇和乙醇)作用不明显；有机物对金属离子的反应速率的影响与有机物本身的氧化还原电位之间具有一定的相关性。X射线光电子能谱(XPS)结果表明添加有机物,只是影响金属离子的光催化反应速率,而对金属Cu(Ⅱ)还原产物的形态则没有影响。5.对Ti02纳米管光催化处理含络合铜废水的处理进行了研究。实验发现尽管Cu(Ⅱ)能与EDTA、DTPA、柠檬酸和酒石酸形成稳定的配合物,但Cu(Ⅱ)的存在对有机配体的光催化氧化还是具有促进作用,但配合物的稳定性的大小会影响这种促进作用。同样地,有机物的存在,即使能与Cu(11)稳定配合,对Cu(Ⅱ)的光催化还原也具有促进作用,同时体系的pH变化、有机物本身的光催化氧化的难易程度和配合物稳定性的大小都会影响到这种作用。X射线光电子能谱(XPS)结果表明络合铜还原产物仍然为单质铜。说明Ti0：纳米管光催化法适合含络合铜废水的处理。6.同样条件下,研究EDTA、DTPA对Ag(Ⅰ)光催化还原速率的影响和柠檬酸、酒石酸对Ag(Ⅰ)光催化还原速率的影响。EDTA和DTPA与Ag(1)能配合为稳定的配合物；而柠檬酸和酒石酸与Ag(Ⅰ)很难配合。实验发现不管Ag(Ⅰ)能否与有机体配合,Ag(Ⅰ)的光催化还原和有机体的光催化氧化之间存在明显的协同作用;但是如果金属离子能与有机体稳定配合,这种配合作用将会使有机体对金属离子光催化还原的促进作用有所降低；同样配合物的产生也会降低金属离子对有机体的光催化降解的促进作用。不管有没有添加有机体,Ag(Ⅰ)还原后的体系的pH都会降低;但下降的程度不一样。添加有机体之后,体系的pH变化更小一些；添加四种有机体反应后体系的pH的变化区别不是很明显。更多还原

【Abstract】 Recently, it has been demonstrated that photocatalysis is a promising technology applicable for the treatment of pollutants. Electron-hole pairs will be consistently generated from semiconducting TiO2 under irradiation, with electron’strong reducing power and the holes’strong oxidizing power, when electron-hole pairs are trapped by the contaminant (e.g., organic pollutants and/or metal ions) on surface, redox reactions will be initiated. Thus, the electron-hole synergy has been used to remove pollutants of oxidation and reduction state of the environment synchronously, becoming a hot topic in catalytic and environmental research. We have done some research work in the following areas, which provides a theoretical basis for the development of using TiO2 nanotubes photocatalysis to remove synchronously toxic organics and heavy metal ions in the wastewater.TiO2 nanotube was successfully synthesized by a hydrothermal method. The TiO2 nanotube photocatalytic material were characterized by using FT-IR spectrum, scanning electron microscope, X-Ray diffraction and BET surface area analysis etc. The results showed that the TiO2 nanotubes prepared by hydrothermal synthesis method are also primarily anatase and contain a small amount of rutile, not changing its crystal form. Compared to nano-TiO2, TiO2 nanotube grain sizes are smaller, while its surface area and pore volume are larger. Furthermore, TiO2 nanotubes are relatively good dispersion properties and can’t easily reunion, which proves to prossess excellent photocatalytic activity.The experiments were carried out under the following conditions:magnetic stirrer; initial concentration.2×10-5mol/L; temperature, fixed at 26±0.5℃; TiO2 nanotubes concentration,2.0 g/L; the suspensions 500 mL; aerated at a flow rate of 300 mL/min; the average light intensity, about 8 MW/cm2; under 300W ultraviolet light irradiation. The persent study is targeted on using TiO2 nanotubes photocatalytic degradation of EDTA, citric acid, tartaric acid and DTPA. It was found that the photolysis of organics exsist to a certain extent, but the reaction rate is much faster and more efficient in the case of TiO2 nanotubes. An hour later, it’s difficult to detect organics in the system through HPLC. Therefor, TiO2 nanotubes photocatalysis is very suitable for removing the wastewater containing EDTA, citric acid, tartaric acid and DTPA.The experiment using TiO2 nanotube photocatalysis to remove Cu (Ⅱ) and Ag (Ⅰ) was carried out under the same condition. An hour later, the removal efficiency of Cu (Ⅱ) and Ag (Ⅰ) were 83.7%,88.1% respectively. The results show that TiO2 nanotube photocatalysis is effective for removing dissolved transition metal ions from aqueous solution. Cu (Ⅱ) and Ag (Ⅰ) can be reduced to the corresponding metal elemental and its reductive products were characterized by XPS.The experiments were performed under the same condition using aqueous systems containing Cu(Ⅱ) with formic acid, acetic acid, methanol, ethanol and TiO2 nanotubes, respectively. The current work aims to know the correlation between organic standard redox potentials and the reduction rate of Cu(Ⅱ) and how the organics will affect the treatment of Cu(Ⅱ). It’s found that not all organics can promote the photocatalytic reduction of metal ions. Carboxylic acids can catalyze the removal of Cu (Ⅱ), while it’s not obvious in the case of alcohols. The influence of organic addictives on the reduction rate of Cu(Ⅱ) depends crucially on its potentials. Cu(Ⅱ) reductive product was analyzed by using XPS. The results indicated that organic addictives have no influence on Cu(Ⅱ) reductive product.UV/TiO2 photocatalysis of chelated copper in aqueous solutions has been performed starting from Cu (Ⅱ)-tartaric acid, Cu (Ⅱ)-citric acid, Cu (Ⅱ)-EDTA and Cu (Ⅱ)-DTPA, in the presence of oxygen and at acidic pH. The photocatalytic reaction obeys first-order kinetic equation. The influence of Cu (Ⅱ) on photocatalytic oxidation of organic ligands and how the various organics will affect the treatment of Cu (Ⅱ) were described. The result indicates that the stability constant, the photocatalytic oxidation rate of organic ligands and the solution pH are three major factors controlling the accelerating effect between the reduction of Cu (Ⅱ) and oxidation of organic ligands. It also proves that TiO2 photocatalysis is an effective approach for removing chelated copper from wastewater.The present study is targeted on the simulated wastewater containing Ag(Ⅰ), organics and TiO2 under UV illumination in the presence of oxygen and at acidic pH. The results indicated that photocatalytic oxidation of organics can catalyze the removal of Ag(Ⅰ), and conversely, Ag(Ⅰ) can also catalyze the photocatalytic oxidation of organics. A significant synergistic effect was observed between the reduction of Ag(Ⅰ) and simultaneous oxidation of organics. However, organic complexes with Ag(Ⅰ) would weaken the synergistic effect between Ag(Ⅰ) and organics.更多还原