【作者】 夏淑梅；

【导师】 张密林；

【作者基本信息】 哈尔滨工程大学 ， 材料学， 2009， 博士

【摘要】 纳米二氧化钛以其价廉、无毒、催化活性高、稳定性好、耐光腐蚀等优点而受到了广泛关注。但是由于TiO2的量子产率低,光响应范围窄,太阳能利用率低,催化剂分离回收困难等缺点限制其实际应用。本文针对纳米二氧化钛粉体催化剂分离回收难的问题,选择具有大的比表面积和易于磁分离的磁性纳米粉体为载体,采用溶胶凝胶法制备了一系列磁性纳米光催化剂,并通过碱土金属离子掺杂改性来拓展TiO2的光谱响应范围,提高对太阳光的利用率。以磁性颗粒负载的锐钛矿纳米二氧化钛为原料采用水热法制备了具有大比表面积的钛酸盐纳米管磁性复合材料。利用VSM、XRD、TEM、DRS、SEM等技术,研究了磁性光催化剂的结构与催化性能之间的关系,以亚甲基蓝为模拟污染物考察了催化剂的光催化性能。采用溶胶-凝胶法制备了磁性颗粒SiO2/MeFe2O4(SM, Me=Ni、Co、Co0.64Zn0.36)负载的复合光催化剂TiO2/SiO2/NiFe2O4(TSN)、TiO2/SiO2/CoFe2O4(TSC)和TiO2/SiO2/Co0.64Zn0.36Fe2O4(TSCZ).研究表明,TSN、TSC、TSCZ均具有亚铁磁性,易于通过磁场分离,具有良好的回收性能和重复使用性。SiO2中间层的引入极大地提高了复合光催化剂的光催化性能。光催化结果显示,TSN的紫外光催化性能最佳,TSCZ的可见光催化性能最佳。采用溶胶-凝胶法制备了碱土金属离子(M2+)掺杂的磁载复合光催化剂M2+-TSN(M2+=Mg2+、Ca2+、Sr2+、Ba2+),系统研究了碱土金属离子掺杂对TSN催化性能的影响。实验发现,M2+掺杂引起TiO2吸收边带红移,M2+掺杂进入晶格后引起晶格畸变,使粒径变小,Mg2+、Ca2+、Sr2+、Ba2+的最佳掺杂量分别为1.0%、1.0%、0.8%、0.8%。光催化实验显示,碱土金属离子掺杂提高了TiO2的可见光催化活性,Ba2+掺杂后样品在可见光区对亚甲基蓝的降解率比TSN提高近2倍。采用水热法合成了负载磁性颗粒的钛酸盐纳米管磁性复合材料(MTNT),考察了制备条件对MTNT形貌、组成、磁性和催化性能的影响。研究发现,水热反应温度和NaOH浓度对MTNT的形成有着显著的影响。MTNT主要组成为Na0.8H1.2Ti3O7。由于SiO2在强碱溶液中的溶解,MTNT的磁性比原料有所增强。在400～500℃煅烧后,钛酸盐纳米管转化为TiO2纳米管。光催化结果显示,煅烧后的MTNT活性增强。在可见光催化降解亚甲基蓝废水时,受体系pH的影响很小,MTNT的加入量为原料的1／3时,对亚甲基蓝的脱色率提高近2倍。采用水热法合成了Ba2+掺杂的钛酸盐纳米管磁性复合材料(Ba2+-MTNT)。考察了Ba2+掺杂对MTNT的性能的影响。Ba2+掺杂对MTNT的形貌没有明显影响,Ba2+掺杂加速了水热反应速率,提高了MTNT的热稳定性。Ba2+掺杂增大了纳米管的比表面积,提高了纳米管的可见光催化性能。Ba2+-MTNT具有良好催化性能,在可见光催化降解亚甲基蓝废水时,受体系pH的影响很小,催化剂加入量少,易于通过磁场分离,具有较好的应用前景。更多还原

【Abstract】 In recent years, TiO2 has been studied extensively in the photocatalytic field because of its advantages comparing to other semiconductor photocatalysts, such as inexpensive, non-toxic, high photocatalytic activity, chemical inertness, strong oxidizing power. However, the practical application of TiO2 is limited due to its low quantum yield, narrow range of light responding, low utilization rate of solar energy, difficulty in separation and recovery. In this paper, aiming at the disadvantages of TiO2 powder, such as difficulty in separation and recovery and low utilization rate of solar energy, magnetic photocatalysts have been prepared by the sol-gel processing using magnetic nano-powder with a large surface area and easy magnetic separation property as the carrier. Through the doping of alkaline-earth metal ions expands the scope of TiO2 the spectral response and improves the utilization of sunlight. Magnetic composite materials of titanate nanotubes were prepared by a hydrothermal method using TiO2 coated on magnetic nanoparticles as the precursor. The relationship between the magnetic photocatalyst structure and catalytic properties was studied by scanning electron microscopy (SEM), X-ray diffraction (XRD), vibration sample magnetometer (VSM), transmission electron microscopy (TEM) and diffuse reflectance spectra (DRS). Photocatalytic activities of the products were evaluated by measuring the decolorization rates of methylene blue(MB) solution.The magnetic nanocomposite photocatalysts TiO2/SiO2/NiFe2O4(TSN)、TiO2/SiO2/CoFe2O4(TSC) and Ti02/Si02/Co0.64Zn0.36Fe2O4(TSCZ) was prepared by the sol-gel processing with the magnetic particles SiO2/MeFe2O4 (SM, Me= Ni, Co, Co0.64Zn0.36) as the carrier. TSN, TSC and TSCZ are ferrimagnetism, easy to recycle through the magnetic separation and with good recovery performance and reusability. The thin SiO2 layer gave rise to the increase in photocatalytic activity. The photocatalytic results showed that the TSN has the best Photocatalytic activity under the UV irradiation and The TSCZ has the best Photocatalytic activity under visible light.Alkaline earth metal ions (M2+) doped magnetic photo-catalyst Ba2+-TSN was prepared by the sol-gel method. The effect of M2+ on photo-catalytic activity of TSN was systematic studied. It was found that the doping of M2+ causes the absorption spectrum to red-shift, leads to the distortion of lattice and restrains the increase of the particle size of TiO2. The optimum doping of Ca2+, Mg2+, Sr2+ and Ba2+is 1.0%,1.0%,0.8%, and 0.8%. The photocatalytic results show that the doping of M2+ remarkably gives rise to the remarkable increase in visible-light photo-catalytic activity. The decolorization rate of MB improved near two times using the Ba2+-TSN as the catalyst in the visible area.Magnetic composite materials of titanate nanotubes coated on magnetic particles (MTNT) were prepared by a hydrothermal method using TSN as the precursor. The effects of preparation conditions on their properties of MTNT were studied. The results show that the hydrothermal temperature and concentration of NaOH has a significant impact on the formation of the products. The main components of MTNT are Na0.8H1.2Ti3O7. The magnetism of MTNT has improved than raw materials because the SiO2 was dissolved by NaOH solution. MTNT was changed to TiO2 when it was calcined at high temperature with the heat-stable range of 400-500℃. The photocatalytic results show that the catalytic activity of MTNT was enhanced after calcined. In the visible-light photo-catalytic degradation of MB, the pH value of the system has little effect. The decolorization rate of MB improved near two times when the dosage of MTNT is only 1/3 of raw materials.Ba2+ dopeded magnetic composite materials of titanate nanotubes coated on magnetic particles (Ba2+-MTNT) were prepared by a hydrothermal method using Ba2+-TSN as the precursor. Doping of Ba2+ had no obvious impact on the morphology of MTNT. Doping of Ba2+ accelerated the reaction rate and improved the thermal stability of MTNT. Doping of Ba2+ increased the specific surface area and enhanced the visible-light catalytic properties of MTNT. In the visible-light photo-catalytic degradation of MB, the pH value of the system has little effect, catalyst dosage is less. Ba2+-MTNT had good recovery, reuse performance and good applied outlook.更多还原