【作者】 周爱娟；

【导师】 陈兆波；

【作者基本信息】 哈尔滨工程大学 ， 环境工程， 2010， 硕士

【摘要】 多环芳烃(PAHs)是一类典型的持久性有毒物质,具有致畸、致癌、致突变“三致”毒性,是目前已知环境中最大量的具有致癌性的单一化学物种。以水溶性最强的PAHs——萘为原料,合成邻苯二甲酸酐、染料、杀虫剂的过程中产生的萘系废水,具有排放量大、浓度高、色泽深、酸或碱性强、成分复杂等特征,属于典型的有毒有害难降解的工业废水。研究开发此类难降解有机污染物的处理技术对我国的萘系有机中间体生产有着重要的意义。光催化氧化法是处理难降解萘系化合物优先考虑和重点研究的发展方向。近年来纳米Ti02作为一种新型环境功能材料被广泛用于难降解废水处理中。但是由于悬浮态Ti02与废水分离困难,使废水处理的成本提高。本论文以稳定的超顺磁性Fe304纳米粒子作为磁核,应用StOber法在Fe304纳米粒子表面包覆Si02,制成超顺磁性Fe3O4-SiO2载体,通过溶胶-凝胶法在Fe3O4-SiO2载体表面担载纳米Ti02催化剂,制备出单分散的具有“核-壳”结构的磁可分TiO2/Fe3O4-SiO2(TFS)复合型光催化剂。通过XRD、FTIR、TEM等表征手段,对最佳条件下制备的TFS复合型光催化剂的物性进行分析,证实制备出磁可分的纳米级复合型Ti02光催化剂。为了探讨TFS复合型光催化剂对污染物的催化降解效果,本论文选择多环芳烃的代表性污染物——萘进行降解试验,并通过响应曲面法的中心组合设计方法对实验操作条件进行优化,确定各个实验操作条件对萘降解率的影响顺序,同时采用数值求导、Matlab及遗传算法三个方法求得更精确的最佳操作参数数值,使萘的降解率达到最大值。试验结果表明,TFS复合型光催化剂对萘均具有高效的降解能力,且表观反应速率快。光催化对萘的最佳操作条件为光照时间97.1min、pH值2.1、复合型催化剂投加量96.2mg/L,在此条件下优化的萘降解率高达97.39%。通过模型验证,该模型预测值与实验值的最大相对误差不超过4%,说明模型对实验结果具有良好的预测效果,对于实验具有较好的指导意义。应用GC-MS分离分析方法在萘光催化降解反应过程中检测到12种确定的中间产物及3种未确定的中间产物,并推测出能够解释这些化合物形成和转化的光降解途径。更多还原

【Abstract】 Polycyclic aromatic hydrocarbons (PAHs) are typical persistent poisonous matters known for their toxic, mutagenic and carcinogenic properties which are the largest number of carcinogenic single chemical species in the current known environment. The naphthalene series wastewaters are produced during the course of synthesize phthalic anhydride, dyestuffs and pesticides using the most water soluble PAHs-naphthalene as raw material.The wastewaters are characterized with component complex, higher concentrations, toxicity, darker color, acidity or alkalinity and toxicity, and are difficult to be degraded under natural environment. Therefore it is very meaningfulness to study and look for the practical technology that is used for processing wastewater of our countrvy’s naphthalene series.In recent years, TiO2 nanocatalysts are widely used in wastewater treatment as a kind of new environmental function materials. However, because suspended TiO2 is hard to be separated from wastewater, the cost of this treatment is raised much higher. In this paper, superparamagnetic Fe3O4 nanoparticle in the form of ferrofluid (supplied by Harbin Normal University) was selected as the magnetic nanocore to produce homogeneous coated Fe3O4-SiO2 support using the well-known stober method. Then immobilizing TiO2 nanocatalyst on Fe3O4-SiO2 magnetic nanocores the monodispersed TiO2/Fe3O4-SiO2 (TFS) nanocatalyst with typical "coreshell" structrue was successfully obtained through sol-gel process. The prepared magnetic separable TiO2 nanocatalysts were characterized by scanning electron microscopy (SEM), Xray diffraction (XRD) and Fourier-transform infared spectroscopy(FTIR) methods which confirming that has synthesized a magnetic separable nano-scale composite TiO2 photocatalyst.To study the effect of the TFS composite photocatalyst’s catalyzing and dagrading the contamination, this paper chooses the representational contamination of polycyclic aromatic--naphthalene to conduct the degradation experiment, and optimizes the experimental operating conditions through the method of central composite design of the response surface methodology, makes sure the influencing sequence of these experimental operating conditions. In the meanwhile,it takes three methods:numerical derivation,matlab simulation and genetic algorithm to get the more precise optimal values of operating parameters, so as to make the dagradation rate of naphthalene reach the maximum.The experiment result indicates that the TFS composite photocatalysts behave a high efficient ability of degradation,and its apparent reaction rate is fast. The optimal experimental condition which photocatalysis acts to naphthalene is:illumination time is 97.1min, pH-value is 2.1, the amount of compound catalyst is 96.2mg/L. In the conditon above, the optimized naphthalene degradation rate is high to 97.39%. Though model verification, the maximum relative error between this model predictive value and the experiment value is no more than 4% which illustates that this model has a good prediction effect to the results of experiment and shows a relatively fine guiding significance. It detects 12 kinds of determined intermediates and 3 kinds of uncertain intermediates in the progress of photocatalysis degradation reaction by using the GC-MS separation and analysis method, and conjectures the degradation pathway which can explain these compounds’ formation and transformation.7更多还原