【作者】 陈善斌；

【导师】 李海涛；

【作者基本信息】 湖南师范大学 ， 高分子化学与物理， 2008， 硕士

【摘要】 固液光催化体系的发展和推广应用一直以来存在两个关键点：一是如何提高催化活性；二是催化剂的分离和回收以及重复使用性。具有金属对金属电子转移metal-to-metal charge transfer（MMCT）性能的杂双金属氧化物复合材料是一种高效的光吸收激发材料，可以在可见光激发下催化有机化合物的氧化还原反应。因此，根据实际需要和金属的氧化还原电势，选择合适的金属物种和适宜的制备方法，在双金属或多金属氧化物复合材料上构建金属-金属电子转移（MMCT）中心，制备出在可见光激发下能够催化有机污染物氧化还原降解反应的新型催化剂，成为了一个新的热点研究领域。将光诱导催化活性中心固载于磁性纳米粒子上，可以采用用磁分离方法，十分便利地解决纳米催化剂的分离和回收的问题。本文在大量调研文献的基础上，采用Stober法制备了核壳结构的SiO₂-Fe₃O₄纳米复合粒子，并将Ti⁴⁺／Mⁿ⁺（MMCT）固载在SiO₂-Fe₃O₄粒子上，用XRD、TEM、UV-Vis和IR等手段对制备的磁性纳米复合材料样品进行了表征，并以苯酚和亚甲基蓝的氧化降解为模型反应，考察了材料在可见光下的催化性能。主要内容如下：1、综述了纳米材料的制备和特性、光催化材料的发展及其在有机污染物催化降解领域中的应用。2、采用Stober法制备了核壳结构的SiO₂-Fe₃O₄磁性纳米复合材料，并将Ti⁴⁺／Sn²⁺（MMCT）固载在SiO₂-Fe₃O₄上制备得到了Sn／Ti-SiO₂-Fe₃O₄纳米复合材料，对样品进行了表征，考察了其在苯酚的光降解反应中的催化性能，以及外界条件对样品催化效能的影响。研究发现样品磁响应性好，呈纳米形态（粒径约为80nm），在可见光区表现出MMCT吸收。在通氧气和常温条件下，当pH为4，以Sn含量为4 wt％的Sn／Ti-SiO₂-Fe₃O₄的磁性纳米催化剂，在可见光激发下催化苯酚的氧化降解反应，苯酚降解率达到了83．96％。3、把Ti⁴⁺／Ce³⁺（MMCT）固载在纳米SiO₂-Fe₃O₄上，制备了磁性纳米复合材料，考察了Ce／Ti-SiO₂-Fe₃O₄纳米复合材料在不同条件下对苯酚氧化降解反应的催化性能。研究发现所得的磁性纳米复合材料磁响应性好，在可见光区表现出很强的MMCT吸收，对苯酚光降解反应具有良好的可见光催化降解活性。常温通氧条件下，当pH为4时，以Ce含量为2 wt％的Ce／Ti-SiO₂-Fe₃O₄为催化剂，在可见光下对苯酚光降率达到了91．43％。催化剂易回收，重复使用性好。4、将Ce／Ti-SiO₂-Fe₃O₄磁性纳米复合材料作为催化剂，应用到模拟染料废水处理当中，催化氧化分解亚甲基蓝染料。研究了染料浓度，pH值，添加H₂O₂含量等因素对亚甲基蓝脱色率的影响，并对反应机理进行了探讨。结果表明，pH=8，初始浓度为60 mg／L的亚甲基蓝溶液，外加H₂O₂的投加量为1．5 mL／L时，复合Ce／Ti-SiO₂-Fe₃O₄磁性纳米材料对亚甲基蓝氧化降解的催化效率最高，且在循环使用三次后催化活性依然保持良好。更多还原

【Abstract】 In the development and application of solid-liquid photocatalytic systems,two key problems should be paid attention to.One is the enhancement of the photocatalytic activity and the other is the separation,recovery,and reuse of the catalysts.Composites of two metal oxides,which are of metal-to-metal charge transfer character（MMCT）,areconsidered to be effective photo absorbent and photo-inducing agents which can be used as catalysts for redox reaction of organic compounds in visible light.It is newly developed hot field to prepare novel catalyststo meet the actual demands of the degradation of organic pollutants by choosing a suitable pair of metals for constructing MMCT.Immobilization of photo-induced catalytic species onto nano-magnetic particles will facilitate the separation of catalysts with the utilization ofmagnetic feature and the recovery of the catalytic activity.On the basis of related literatures,SiO₂-Fe₃O₄ nanoparticle composite with core-shell structure was prepared in Stober way.And Ti⁴⁺/Mⁿ⁺（MMCT）was assembled on the magnetic SiO₂-Fe₃O₄ nanoparticles.The resultant magnetic nanocomposites were characterized with XRD、TEM、UV-Vis spectrum and IR spectrum.The photocatalyticperformance of the resultant materials was investigated by using thedegradation of phenol and methylene blue under visible light as themodel reactions.Concrete contents of this work are as follows:1、This dissertation reviewed the properties and thesynthetic methods of nanoparticles,the developments ofphoto-induced catalytic materials and their applications inthe field of the degradation of organic pollutants.2、SiO₂-Fe₃O₄ nanoparticle composite with core-shell structure was prepared in Stober way.And Ti⁴⁺/Sn²⁺（MMCT）was assembled on the magnetic SiO₂-Fe₃O₄ nanoparticles.The resultantnanocomposite was characterized XRD、TEM、UV-Visspectrum and IR spectrum..The photo-catalyticperformances of the materials were characterized byphenol degradation.The results show that the obtainedcomposites have the nanoparticle morphology（80 nm）and respond well to the magnetic field.Under visiblelight,the composite exhibits relative strong MMCT absorption.When Sn/Ti-SiO₂-Fe₃O₄ composite with Sncontent of 4 wt% was used as catalyst,83.96% of phenolin aqueous solution of pH=4 was degraded whileirradiated with sunlight at room temperature inpresenting of O₂.3、Ti⁴⁺/Ce³⁺ was assembled on the magnetic SiO₂-Fe₃O₄ nanoparticle.The obtained nanocomposites were characterized in the same way as above.The Thephoto-catalytic performances of the materials in theoxidation degradation of phenol under differentconditions were examined.The research shows that the obtained composites respond well to magnetic field andare highly capable to catalyze the oxidation degradationof phenol in aqueous solution under visible light.Byusing Ce/Ti-SiO₂-Fe₃O₄ composite with Ce content of 2wt%,91.43% of phenol in aqueous solution of pH=4 wasdegraded while irradiated with sunlight at room temperature in presenting of O₂.The catalytic activity ofnanocomposites are easy to be recoveried and thus thecatalyst could be reused. 4、The Ce/Ti-SiO₂-Fe₃O₄ nanocomposites was also used as a catalyst in the photodegradation of methylene blue under visible light.The effects of the initial concentration of methylene blue,the concentration of H₂O₂ and the pH value on the photodegradation of methylene blue performance were studied.The results show that theoptimum conditions for the visible light induceddegradation of methylene blue in aqueous solution arepH=8,the initial concentration of methylene blue is 60mg/L,and the concentration of H₂O₂ is 1.5 mL/L.The catalytic activity retained well after the catalyst beingreused for 3 times.更多还原