【作者】 卜聃；

【导师】 庄惠生；

【作者基本信息】 东华大学 ， 环境工程， 2011， 硕士

【摘要】 摘要环境污染和能源短缺问题是国际社会普遍面临的问题,如何利用太阳能治理环境污染问题已经引起了世界各国的广泛关注。半导体光催化氧化技术作为一种深度氧化技术具有氧化效率高、反应速度快、绿色环保、可利用太阳能等优点,因而备受瞩目。以Ti02为代表的半导体光催化材料更是重要的绿色环保材料。世界范围内,对金属半导体光催化材料的改性研究已经进行了几十年。研究认为,光催化剂催化性能受到晶型、晶粒大小、焙烧温度、金属离子负载量、不同半导体材料复合等因素的影响。其中,光催化材料的微观形貌也是一个重要的影响因素。材料不同的微观形貌通过改变表面吸附量、吸附方式、光照路径等因素来提高光催化性能。空心球型光催化剂的制备研究是该研究方向的一个重要分支。传统的空心球型光催化剂的制备方法是利用各种可牺牲性材料作模板,使金属半导体微粒吸附在模板的表面,再通过高温焙烧、溶剂溶解等方式去除模板,称为模板法。本课题研究中,利用花粉作为生物模板,控制制备了Cu掺杂的Ti02空心微球光催化剂。生物模板法具有形貌多样化(筛状、网状、球形、筒形等)、尺寸小(纳米级)、自组装、生物模板形貌重复性高、制备产物结构性能可预期等特点,以及廉价、丰富、可再生、容易得到、环境友好等优点。本论文中,应用改进溶胶-凝胶法制备铜掺杂Ti02光催化剂。相比传统的溶胶-凝胶法,不在反应体系中加入水,水的生成来自醇和酸的酯化作用和钛酸四正丁酯水合产物-Ti(OR)3(OH)之间缩合脱水两个途径。该方法可有效地避免凝胶形成过程中缩合过快,凝胶迅速长大聚团,不能在花粉模板表面较好地覆盖,球体破裂,成球性差的缺点。水解凝胶过程温度、pH变化规律明显,其中温度在300min时达到最大值,随后逐渐降低,这说明反应过程在300min左右达到平衡。改变醇钛比、pH、铜离子掺杂量等制备条件,制备了一系列Cu/Ti02空心球光催化剂。研究认为醇钛比为1：4：4、水解pH为3、Cu掺杂量为2wt.%时制备的光催化剂催化性能最好。SEM、XRD、BET等仪器表征表明,空心球光催化剂的平均直径为20μm,壁厚为0.6μm,呈球形好；半导体材料的晶型随着焙烧温度的升高而呈现不同的结果,焙烧温度为500℃时,以锐钛矿相为主并伴有一定的金红石相,表现出混晶效应；比表面积在141.80-172.51 m2/g之间,与微粒型和p-25光催化剂的51.85 m2/g、50m2/g相比,有明显的提高,因此有更强的表面吸附能力。在光催化剂催化降解盐酸金霉素的过程中,空心球型光催化剂表现出较高地催化活性。反应120min后,金霉素降解率最高可达99.66%, COD、TOC降解较为完全,降解率均在95%以上。光照反应1h后BOD5/COD>0.3,明显改善了水质地可生化性能。降解过程的最佳工艺条件为：催化剂投加量1.2g/L金霉素初试浓度50mg/L,体系pH=2。当加入H202浓度达到300mg/L时,可缩短一半的反应时间。金霉素在光催化过程中,发生了一系列光氧化和光催化过程,其中间产物包括多种双环、三环化合物,多环化合物进一步开环生成醛、醌、烯醇等较小分子化合物,最终生成CO2、H2O、NH4+等无机物。光催化剂的良好性能与模板的作用密不可分。花粉在制备空心球型光催化剂的过程中起到了硬模板的作用,其作用过程包括包覆和模板去除两个过程。花粉参与反应提供吸附活性位,是第一层吸附发生的必要条件；花粉表面反应活性位的多少也决定了吸附量的多少,可控制空心球的壁厚。包覆好的花粉在高温下逐渐燃烧去除,留下良好的空心结构。综上所述,本课题研究制备了具有较好三维空间形貌和结晶特点的半导体光催化材料,其性能超越p-25,有良好的应用前景。对金霉素抗生素废水的降解工艺条件研究和降解产物分析,对日后的科研工作有一定的帮助。但研究中还有很多工作需进一步完善,以求精益求精。更多还原

【Abstract】 ABSTRACTEnvironmental pollution and energy crisis are the common problem in all of the countries. Effective utilization of solar energy to solve pollution problems has become of great interest in the world. The photocatalytic technology, which is a kind of advanced oxidation technology, has the advantages of high efficiency, fast, green, utilization of solar energy. And TiO2 photocatalyst is the most important environmental material.The research of metal semiconductor photocatalystic materials has been lasted for many years. It has been pointed out that the property of photocatalyst is affected by factors-crystal form, crystal size, temperature, quality of loaded mental ion, coupled semiconductor materials and so on. Meanwhile, morphology is also a important factor, which will affect the quality of surface absorption, absorbed ways, light path, et al. The synthesis of hollow sphere structure is a part of morphology research. The traditional synthesized method of hollow sphere is to use varies of templates which is cheap and removed easily. Mental ion semiconductor particulars absorb onto the surface of templates firstly, then the templates removed by high temperature or solvent. In our research, pollens have been employed to synthesize copper loaded TiO2 hollow spheres photocatalysts. Biotemplates has so many shapes (griddle shape, reseau, sphere, cylinder, et al.) and advantages such as small size, easy control, cheap, green, no-pollution and so on.Copper-loaded titania hollow microspheres were synthesized using the pollen grains as a natural biotemplate via an improved sol-gel method and a succedent calcinations process. In the synthesized process, the water was provided by two processes, esterification of normal butanol and acetic acid, as well as Ti(OR)3(OH) condensation reaction, unlike the conventional sol-gel procedure of adding water directly. This synthesized method can obviously avoid the rapid condensation reactive speed and gel reunion. In the experiment, the temperature and pH changes regularly. Temperature doesn’t reach the maximum value until 300min reaction; meanwhile, reaction equilibrium will also be attained.A series of photocatalysts has been synthesized through the distinct processes-different molar ratio, pH, and quality of copper loaded. The best synthesized condition is Ti (OC4H9)4:n-C4H9OH:CH3COOH=1:4:4, pH=3,2 wt.% copper loaded quality. Knowing from SEM, XRD, BET equipment analysis, average diameter of hollow spheres is 20μm and thickness of cell is 0.6μm. The crystal form of semiconductor material is changed with the temperature. When the calcination temperature is at 500℃, the samples crystal forms are anatase, as the main crystal phase, coupled with rutile. BET values are ranging from 141.80m2/g to 172.51m2/g, compared with values of particular and p-25 photocatalyst,51.85 m2/g and 50 m2/g, respectively. The hollow sphere photocatalysts have higher BET surface area so that it will, have stronger absorption ability.The hollow sphere photocatalyst has exhibited a high photocatalytic activity when it is employed to degrade chlortetracycline hydrochloride (CTC) solution. After 120min irradiation, the maximum degradation ratio of CTC is 99.66%, COD removal efficiency could reach up to 95%, as well. Meanwhile, chemical and biologic properties of waster water will be improved, when the value of BOD5/COD> 0.3. The best technological conditions of degradation process are as follow:dosage of catalysts is 1.2g/L, initial concentration of CTC is 50mg/L, pH=2. When the concentration of H2O2, added into the reaction system, exceeds 300mg/L, the reaction time will be cut down in half. During the photocatalytic processes, chemical mechanism on degradation of CTC involves series of photooxidation processes and subsequent chemical reactions. Intermediate products of Chlortetracycline included a variety of bicyclic, tricyclic compounds. Polycyclic compounds will be opened up, and then aldehydes, quinones, enolase and other small molecular compounds were produced. Ultimately, CO2, H2O, NH4+ and other inorganic products were investigated.We can come to the conclusion that the pollen has played three important roles in the process. Firstly, it serves as a hard template to form the morphology of the products. Secondly, the abundant functional groups on the surface of pollen gains are active sites to absorb the reactants. And the groups are also critical factor to control the first-step encapsulation process. Thirdly, the bimolecular on the cell walls exert an influence on restraining the growth of nanoparticles.In summary, Cu/TiO2 photocatalysts with good three dimensional morphology and crystal characteristics have been synthesized successfully, which have better activity and utilization prospect than p-25. The analysis of degradation process conduction of CTC antibiotic waster water, as well as degradation product can be helpful to further research. However, there is a lot of work to be improved in order to strive for excellence.更多还原