【作者】 郭森；

【导师】 吴忠标；

【作者基本信息】 浙江大学 ， 环境工程， 2009， 博士

【摘要】 光催化技术具有条件温和、不产生二次污染等优点,在环境净化尤其是室内气相污染物去除方面具有极佳的应用前景。TiO2性能优良,性质稳定,价廉易得,是理想的光催化材料。其实际应用中存在着光生电子-空穴复合率高、负载困难等问题。本文以提高TiO2的实用性为目的,针对TiO2紫外光催化剂开发中的结构化、负载化等热点问题,重点开发改进了高性能一维TiO2光催化剂的制备工艺,并探讨了贵金属沉积、原位金属掺杂工艺对一维TiO2光催化剂光催化性能的影响；并针对本文开发的一维TiO2光催化剂,以甲苯为探针污染物进一步研究了TiO2光催化降解甲苯的反应动力学。本文研究为新型高效TiO2基紫外光催化剂的开发提供了理论支持。首先,以钛片为原料,采用阳极氧化法制备了直接负载于钛片的TiO2阵列纳米管结构,考察了乙二醇有机电解液体系中氧化电压、氧化时间等制备参数对TiO2阵列纳米管长度、直径等的影响。在此基础上,通过控制氢氟酸及水的浓度,获得了直接负载的TiO2一维线管复合结构。该材料底部为纳米管、顶部为纳米线,直接负载于钛片上,具有良好的光催化性能和负载性能。其次,为开发简易、价廉的一维结构TiO2紫外光催化剂制备工艺,通过强碱水热处理工业钛粉的方法制备了一维TiO2纳米管,并采用简单浸渍法对所得一维TiO2纳米管分别进行了银、铂、钯等贵金属的沉积改性。其中,贵金属银和铂具有较好的改性效果,其光催化活性分别为同等测试条件下P25的2.2、2.1倍。为进一步简化TiO2一维结构的制备、改性工艺,本文改进强碱水热工艺,实现了金属原位掺杂一维TiO2纳米管的一步法制备,并系统研究了掺杂源种类、源物质比例等对催化剂活性的影响,研究结果表明,镧、锶原位掺杂的一维TiO2纳米管具有较好的光催化活性。强碱水热工业钛粉制备TiO2一维结构的工艺制备高性能紫外光催化剂的过程中需要高温高压的环境,反应条件要求较高。为此,本文进一步开发了超声辅助的强碱氧化工艺。该工艺以工业钛粉为原料,在低温常压条件下即可制备大比表面积的一维介孔TiO2纳米棒。超声辅助的强碱氧化工艺经济成本低,制备过程简单,所得一维TiO2纳米棒的孔结构以介孔为主,光催化活性达商用P25 TiO2的2.8倍。结合强碱水热法制备一维TiO2的机理,提出了以钛粉为原料,超声氧化法制备一维介孔Ti02纳米棒的OSRS机理(即Oxidation-Shaking off-Rolling up-Shrinkage mechanism)。最后,以超声氧化法制备的一维介孔Ti02纳米棒为典型催化剂,采用自制连续流反应器对低浓度气相甲苯的降解进行了动力学研究。综合考虑氧气浓度、水蒸气浓度的影响,提出了改进的L-H污染物降解模型,得到了一维介孔Ti02纳米棒光催化降解甲苯的动力学参数。更多还原

【Abstract】 Photocatalytic reaction has advantages of mild reactive conditions, no secondary pollutants, etc.Photocatalytic technology has broad application prospects in environmental purification, especially in the removal of gas phase pollutants. TiO2 is one of the most promising photocatalytic materials due to its excellent photocatalytic performance, stable chemical property and low cost. However, there are still challenges for inhibiting the recombination of photo-induced hole-electron pairs and improving the coating methods. This paper focuses on improving the synthesis methods of high activity TiO2 photocatalysts, such as one-dimensional TiO2 and mesoporous TiO2 with high surface area. Novel modification process for the parapration of noble metal deposited TiO2 and in-situ metal doped TiO2 are also discussed.The reaction kinetics of one typical TiO2 photocatalyst is studied, using continuous toluene flow as target pollutants.The study provides theoretical supports for the preparation of high performance UV-induced TiO2Firstly,TiO2 nanotube arrays are prepared by anodization method in ethylene glycol electrolyte with titanium foils as starting material.The effects of anodic voltage and time on the TiO2 nanotube arrays’morphology and photocatalytic activity are studied. Furthermore, immobilized composite TiO2 nanostructure of nanowires covered nanotubes are synthesized by adjusting the concentration of H2O and HF.The higher activity of this novel catalyst for photocatalytic removal of gaseous toluene is also demonstrated. The reproducible simple synthesis route for efficient immobilized photocatalysts shows great application potential in air purification.Secondly, TiO2 nanobubes are synthesized by hydrothermal treating of industrial titanium powder in alkali solution. Then, the TiO2 nanobubes are further modified by Ag, Pt and Pd deposition, which is carried out by a simple dip-coating process. The diameter and length of the Ag-TNTs are about 20 nm and 100 nm, respectively. The porous structure of Ag-TNTs is characterized to be hierarchical micro-meso porous structure. The optimum photocatalytic activities of the samples are 2.2 and 2.1 times that of P25 for Ag-TNTs and Pt-TNTs, respectively. To simplify the preparation and modification process of UV-induced TiO2 a simple one-step hydrothermal method is developed to synthesize In-situ metal doped TiO2 nanotubes.The influences of doping metal type and doping ratio on the photocatalytic activity are studied. The as prepared photocatalysts are tested by the photodegradation of gas phase toluene. It is found that the apparent reaction rates are 1.2 and 1.5 times that of P25,respectively.To avoid the high temperature and pressure in the hydrothermal route, a mild template-free sonochemical method is developed to synthesize mesoporous TiO2 nanorods using industrial bulk Ti powder. The sonochemical synthesis process was carried out under normal atmospheric pressure and relative low temperature. The as prepared TiO2 nanorods contain numerous irregular olive-like nanorods aggregates. The photocatalytic degradation of gas phase toluene shows that the activity of the sample is 2.8 times that of P25.Compared with normal hydrothermal technique, this novel sonochemical method is simple and low cost. A mechanism of Oxidation-Shaking off-Rolling up-Shrinkage (OSRS) is proposed to explain the crystal growth.Finally, the reaction kinetics of photocatalytic degradation of gas phase toluene is studied in a homemade continuous flow reactor. The sample made by sonochemical oxidation method is chosed as typical photocatalyst. Carefully considering the influnce of humidity and oxygen concentration, a kinetics model with multifactors is built and solved by amending the L-H model.更多还原