【作者】 徐甦；

【导师】 雷乐成；

【作者基本信息】 浙江大学 ， 环境工程， 2004， 硕士

【摘要】 本文从研制和改进催化剂材料入手，制备新型负载型纳米TiO₂催化剂，并在其结构表征和吸附性能考察的基础上，对对氯苯酚的降解开展了系统的研究。并通过对催化剂的改性来考察其对甲基橙染料废水降解效率的提高。 采用常压金属有机物化学气相沉积（Metal Organic Chemical Vapor Deposition）技术在活性炭表面沉积构成纳米TiO₂催化剂。对该负载型纳米TiO₂催化剂进行表征，XRD图谱表明煅烧温度为773K时负载的TiO₂晶型结构为锐钛矿，873K时出现金红石相。TEM分析表明负载量为8％（wt）时负载的TiO₂颗粒的粒径为10～20nm；载体负载前后BET面积改变仅为6％，表明负载TiO₂后对活性炭结构影响不大。在光催化反应体系下，加入负载型TiO₂后降解对氯苯酚（4-cp），实验结果表明负载型TiO₂具有较高的光催化效率。 由于TiO₂半导体的禁带宽度较大，且量子效率相对较低，对某些有机污染物（如甲基橙）光催化活性不明显。为改善负载型纳米TiO₂催化剂的性能，对采用MOCVD技术制备出的TiO₂／沸石催化剂，通过硝酸银溶液浸渍—紫外光照还原沉积的方法将银沉积在TiO₂表面，获得载银的改性TiO₂／沸石催化剂。通过对甲基橙光照降解的实验表明，光催化性能较改性前可提高1倍。最佳硝酸银浸渍液浓度为10^-3M，此时该催化剂的光催化性能接近纳米TiO₂粉末（Degussa P25），但进一步提高硝酸银浸渍液浓度，催化剂光催化性能又降低。实验通过XRD和TEM对载银TiO₂／沸石催化剂的表征，进一步分析了其催化机理。 对该催化剂对对氯苯酚（4-cp）的吸附行为进行了分析，发现催化剂对4-cp的吸附较好的符合Langmuir吸附等温方程，4-cp在催化剂上以表面单分子形式吸附。在紫外光照情况下对4-cp进行催化降解实验，并利用Langmuir-Hinshelwood动力学模型探讨了TiO₂／活性炭催化剂对4-cp的吸附行为和光催化降解之间的关系，求出4-cp降解反应速率常数K_r。实验结果显示暗吸附和光照吸附条件下的吸附常数K_b存在差异，发现在紫外光照条件下催化剂对4-cp的吸附明显增强，对4-cp的吸附不再完全是表面单分子吸附形式。更多还原

【Abstract】 In this work, a new type of nanometer TiO2/AC catalyst was prepared. The structure characteristics and adsorption behavior of this novel catalyst were investigated. The photodegradation of p-chlorophenol by using this catalyst was studied. The silver-modified TiO2/zeolite catalyst was also prepared in order to improve the photodegradation efficiency of methyl orange waste water.The atmospheric pressure metal-organic chemical vapor deposition (MOCVD) technology was used to load TiO2 onto the surface of active carbon. XRD results showed that TiO2 calcined at 773K is in anatase phase and rutile phase at 873K. The results of TEM suggested that TiO2 particles were in the range 10 to 20 nm when the amount of titania supported was 8%(wt). BET surface area was only reduced by 6% with the loading amount was 8%(wt), so it can be concluded that the framework of active carbon was not destructured strongly. The degradation of 4-CP was enhanced with the samples of TiO2-AC added to the photocatalytic system.To some organic contaminations such as methyl orange, the photodegradation performance of supported TiO2 catalyst is not satisfied. Catalysts of silver-modified TiO2/zeolite containing different amounts of Ag via a two-step dipping of AgNO3 solution and UV-irradiation process were examined for their improved catalytic activity towards photodegradation of methyl orange. The silver modified TiO2/zeolite catalysts present enhanced photocatalytic efficiency one time more than non-silver modified TiO2/zeolite catalysts did. The optimum silver nitrate concentration of the dipping solution was found to be 10-3M, whose photodegradation efficiency is approximate to that of titanium dioxide powder (Degussa P25). While with the Ag+-ion concentration further increased in dipping solution, the photocatalyst efficiency of the silver-modified catalysts decreased. The silver-modified catalysts were characterized with XRD and TEM. In addition, the presence of metallic silver always produces an increase in activity in comparison with Ag+ ions. This can be explained by the increase in the electron-hole pair separation efficiency induced bytrapping of electrons by metallic silver.The adsorption characteristics of 4-cp on TiO2/AC catalyst system have been investigated. The result shows that The adsorption isotherm forms of 4-cp adsorbed on TiO2/AC catalyst follows Langmuir adsorption model. The relationship of the photodegradation of 4-cp and the adsorption behavior of 4-cp on TiCVAC catalyst can be described by the Langmuir-Hinshelwood kinetics model, we can conclude the reaction rate of the photodegradation of 4-cp by this model. The adsorption equlibrium constant calculated by Langmuir adsorption isotherms under dark adsorption conditions is smaller than calculated by L-H kinetics model under UV-light photodegradation, which shows that the adsorption of 4-cp on TiO2/AC catalyst has increased when under UV-light photodegradation.更多还原