【作者】 储金宇；

【导师】 吴春笃；

【作者基本信息】 江苏大学 ， 环境工程， 2011， 博士

【摘要】 水环境中的有机污染物(如酚类、卤代烃、芳烃及其衍生物、杂环化合物等)具有成份复杂、毒性大等特点,用传统的治理理技术很难处理。光催化氧化具有很强的氧化性,在有机污染物的降解中发挥着非常重要的作用。目前所研究的催化剂主要是TiO2,该催化剂的局限性在于其禁带较宽,在可见光照射下无光催化活性。同时由于其在光反应中电子和空穴复合率较高,催化效率较低,并且在实际应用中TiO2颗粒回收较难。论文以开发禁带宽度较窄的新型纳米可见光催化剂、TiO2改性、固载及磁负载研究为目标,设计并合成一系列新型可见光催化剂,并进行表征分析,研究催化剂表面结构和活性组元对降解有毒有机污染物效果的影响,并对其作用机理进行分析。主要研究内容和结论如下：(1)采用含铋前驱体合成禁带宽度较窄的新型纳米可见光催化剂钨酸铋和钒酸铋,并通过金属Ag表面修饰对钒酸铋表面改性以提高其光催化能力；采用溶胶-凝胶法制备MoS：纳米管表面修饰TiO2光催化剂,并将其负载于粉煤灰微珠,形成负载型TiO2光催化剂；以溶胶-凝胶法制备了TiO2/SrFe12O19、TiO2/SiO2/γ-Fe2O3纳米复合颗粒磁性光催化剂。(2)以空气中的O2作氧化剂,分别在紫外光和可见光下考察Ag-BiVO4的光催化活性以及对亚甲基蓝(MB)染料的降解效果。对比实验发现：Ag对BiVO4催化剂的修饰明显提高MB的降解率,最佳Ag掺杂量为3 wt%；经100℃热处理后得到的Ag-BiVO4光催化剂对MB的去除率最高,2 h后降解率可达95%以上；可见光条件下Ag-BiVO4降解MB的程度要比紫外光下的要深。同时考察了Bi2WO6催化刺对MB降解率的影响。结果表明：催化剂用量为0.2g/L,pH值为9.30,MB的初始浓度为10 mg/L时,对MB降解的效果最佳,4h后MB的降解率达到80%。(3)考察了Ti02复合MoS2及负载粉煤灰的负载量、催化剂用量、热处理温度等不同条件下催化剂的光催化活性。实验表明：在复合量为0.4 wt%,用量为0.02wt%,溶液初始浓度为15mg/L, pH为碱性条件,曝气量为1 L/min时可见光下复合MoS2纳米管TiO2光催化剂2h后MB的降解率达到最大,为70%；负载一次,热处理温度为500℃时,改性MoS2-负载粉煤灰的纳米Ti02对MB的降解率达80%。(4)纳米钙钛矿型TiO2包覆型磁性复合光催化剂TiO2/SrFe12O19,具有较好的可见光催化活性,且当铁氧体修饰量为20%,催化剂用量1.5g/L,MB初始浓度10mg/L以及溶液pH值6.8时,在可见光照射条件下,5h后MB的降解率达到95%以上。催化剂回收及重复实验表明：TiO2/SrFe12O19的每次回收率都在90%以上,而且回收后的催化剂的催化效率每次变化不大,在第5次使用时,5h后的降解率仍保持在90%左右,重现性较好。以y-Fe2O3为磁基体,制备了TiO2/SiO2/γ-Fe2O3,表征结果表明,TiO2/SiO2/γ-Fe2O3材料不但增强了对紫外光的吸收能力,更进一步拓宽了其在可见光区的光谱范围；磁性测试证明了该催化剂保留了γ-Fe2O3的顺磁性能,有利于提高其水相中的分散性,并能通过外加磁场有效地进行固液分离。在紫外光下TiO2/SiO2/γ-Fe2O3对MB的降解率最高达到98%以上,在可见光下达到65%；催化剂回收及重复实验表明：TiO2/SiO2/γ-Fe2O3具有较好循环重复使用性能,循环使用三次后,对MB的降解率保持在95%以上。经过两次的分离循环使用后,TiO2/SiO2/γ-Fe2O3催化剂的平均回收率为97%,说明该催化剂有良好的磁分离性能,是一种易于分离且光催化效果明显的磁载型光催化剂。更多还原

【Abstract】 Organic pollutants in water environment (Such as phenols, halogenated hydrocarbons, aromatic hydrocarbons and their derivatives, heterocyclic compounds, etc.) with the characteristics of complicated composition, toxicity are difficult to treat by the traditional environmental controlling technology. Photocatalytic chemistry has a strong oxidbillity, so it plays a very important role in the degradation of organic pollutants. Current researches about catalyst are mainly TiO2.The limitations of the catalyst is its wide band gap, so it has no photocatalytic activity in the visible light. The photocatalytic efficiency is lower because of difficult separation of electron and holes. It is difficult to recycle this catalyst.In this paper, new catalysts with high efficiency photocatalytic activity in the visible light, TiO2 modification and immobilization, magnetic carrier catalyst were studied. A series of new visible light catalysts were designed and synthesized. The catalytic activity of the degradation of toxic organic pollutants was tested. It was focused on the catalyst surface structure and the active component of the degradation activity of organic pollutants. And the principle was analyzed. The main research contents and results are as follows:(1) The new nano visible light photocatalysts, BiVO4 and Bi2WO6 were prepared with the Bi contained precursor. And the photocatalytic activity of BiVO4 was improved by the surface modification with Ag. The MoS2 NAno-tube mingled Nano-TiO2 micro-sphere catalyst and loaded fly ash micro-sphere photo-catalyst were prepared by sol-gel method.The new coated magnetic photocatalysts TiO2/SrFe12O19 and TiO2/SiO2/γ-Fe2O3 were prepared by sol-gel method.(2) The MB degradation by Ag-BiVO4 was examined under the UV irradiation and visible light irradiation using the O2 in the atmosphere. The compare experiments show that:The presence of Ag significantly enhanced the MB degradation and the optimal content of Ag was 3 wt%. It is confirmed that the calcination temperature on Ag-BiV04 is very important for the photocatalytic activity and the highest removal of MB was obtained by calcination at 100℃. The MB degradation is 95% after 2h. The UV-Vis spectral analysis showed that blue shift resulting from N-demethylation of MB occurred accompanied with oxidative degradation. On the same time, the MB degradation by Bi2WO6 was researched. The results demonstrated that the activity of catalyst which were prepared by hydrothermal process much better than prepared by solid-state reaction method. In the MB/ Bi2WO6 system, MB was effectively degraded by about 80% within 4 h, when the dosage of catalyst was 0.2 g/L, the initial concentration of MB was 10 mg /L and pH was 9.30.(3) The photocatalytic activity of the MoS2 NAno-tube mingled Nano-TiO2 micro-sphere catalyst and loaded fly ash micro-sphere photo-catalyst was examined in different conditions, such as loading volume, catalyst volume, temperature of the heat treatment, and so on. The experimental results show that:The MB degradation ratio is 70% after 2h while the loading volume is 0.4wt%, the catalyst volume is 0.02wt%, the original concentration is 15mg/L, pH>7, the aeration is 1L/min. The MB degradation ratio with TiO2 loaded fly ash micro-sphere photo-catalyst is 80% while it is loaded one time and prepared in 500℃(4) The catalysts, the ferrite coated by a layer of nano-anatase TiO2 (TiO2/SrFe12O19) still had excellent magnetic property and showed strong absorptive property under visible light irradiation. At the conditions of the doped content of barium ferrite of the photocatalyst, initial concentration of MB and pH value being 20 wt%,1.5 g·L-1,10 mg·L-1 and 6.8, respectively, the degradation of MB reached to above 95% in five hours under visible light. Furthermore, the degradation of using the two photocatalysts followed the first-order reaction kinetic model at different conditions in the reaction system. Finally, after magnetic separation of the catalysts for four times, the recovery rate of the catalyst was above 90%, the photocatalytic degradation rate of MB was around 90%. So the magnetic photocatalyst is very easy to recycle. The composite material of TiO2/SiO2/γ-Fe2O3 was synthesized via sol-gel technology, and theγ-Fe2O3 was the magnetic core. The characterization results indicate thatγ-Fe2O3 was red-brown, and the spectrum lines position of X-ray diffraction of TiO2 were in agreement with the standard spectrum of anatase TiO2. VSM results show that the composite has good magnetic property after loaded. The degradation of MB reached to above 98% under UV light, while the degradation is above 65% under visible light. After magnetic separation of the catalysts for two times, the recovery rate of this catalyst was above 97%. After magnetic separation of the catalysts for three times, the photocatalytic degradation rate of MB was around 95 %. Based on it s properties of high photocatalytic activity and easy separation and recovery, the photocatalyst will have a promising application.更多还原