不同稀土（Er、Gd、Te）掺杂氧化锌光催化剂的制备及其降解水中有机污染物

发布时间：2018-03-13 12:48

本文选题：稀土掺杂　切入点：ZnO　出处：《内蒙古农业大学》2017年硕士论文　论文类型：学位论文

【摘要】：木材加工工业废水中含有大量难降解、有毒的有机污染物,已经严重威胁着人类的生存发展,治理工业废水污染问题势在必行。光催化技术在常温、常压条件下可以有效的降解废水中的有机污染物,且不会造成二次污染。半导体光催化材料氧化锌(ZnO)相比其他催化剂,具有着较好的物理和化学稳定性,且无毒无害,价格低廉。过渡金属、碱土金属、稀土金属等掺杂能够改变ZnO的禁带宽度、晶体形貌结构等,是有效提高光催化性能的重要途径。很多稀土氧化物如氧化镧,氧化钕等可以有效提高和改善催化剂的稳定性和活性。本论文主要从稀土元素铒(Er)、钆(Gd)、铽(Te)着手,分别通过共沉淀法和溶胶-凝胶法制备了一系列稀土掺杂的ZnO光催化剂,分别探究了不同制备方法下不同焙烧温度、不同稀土元素掺杂和不同掺杂量对ZnO光催化剂的结构、形貌和活性影响。并通过扫描电镜(SEM)、X-射线粉末衍射(XRD)、比表面积(BET)、紫外可见漫反射(UV-Vis DRS)等技术对制备的光催化剂进行分析表征。主要内容简述如下:(1)利用共沉淀法制备稀土掺杂ZnO光催化剂,以紫外光下催化降解亚甲基蓝(MB)和甲基橙(MO)作为反应探针,研究了不同稀土(Er、Gd、Te)掺杂ZnO光催化剂,对稀土掺杂ZnO光催化剂的结构、形貌和光催化活性进行分析表征。研究结果表明:随着焙烧温度和稀土掺杂量增加,催化剂的结晶性和纯度都比较好,稀土掺杂有效引起ZnO平均晶粒尺寸的改变,比表面积和孔径大小发生改变,比表而积大的样品其光催化活性均比较强,UV-Vis DRS说明不同稀土元素掺杂对ZnO的带隙影响较小,与未掺杂ZnO对比,吸收带边无变化或略微蓝移。SEM图像分析可知不同掺杂量的光催化剂其形貌有着显著的变化。通过筛选优化影响光催化体系的因素,在500℃焙烧温度下,相比于未掺杂ZnO的降解率MB(MO)92.6%(42.4%),0.5at%Er/ZnO、0.5at%Gd/ZnO和3at%Te/ZnO展现出较好的光催化活性,在紫外光照射 2h 后,MB(MO)的降解率分别达到了 94.5%(60%)、95.9%(56%)、98.4%(57.7%)。(2)利用溶胶-凝胶法制备稀土掺杂ZnO光催化剂,以紫外光下催化降解MB和MO作为反应探针,研究了不同稀土(Er、Gd、Te)掺杂ZnO光催化剂,对ZnO的结构、形貌和光催化活性进行分析表征。研究结果表明:随着焙烧温度和稀土掺杂量增加,XRD各图谱中的衍射峰强度变化并不明显,均没有杂相产生,样品结晶度良好。BET数据表明,催化剂的比表面积均呈现不同变化趋势。SEM分析可知,相比于未掺杂,稀土掺杂氧化锌对光催化剂的形貌有明显的影响,UV-vis DRS说明不同稀土元素掺杂对ZnO的带隙影响较小。由光催化活性测试可知,对比于未掺杂ZnO,稀土掺杂ZnO对有机污染物亚甲基蓝和甲基橙的降解效果均有不同程度的改善提高。在三种稀土(Er、Gd、Te)掺杂ZnO催化剂中,50℃焙烧温度下,相比于未掺杂ZnO的降解率MB(MO)42.7%(22.1%),lat%Er/ZnO、0.5at%Gd/ZnO和1at%Te/ZnO分别具有较高的光催化活性,光催化对MB(MO)的降解率分别为 90.7%(40.3%)、91.7%(49.1%)、68.9%(29.5%)。
[Abstract]:Wood processing industry wastewater contains large amounts of refractory, toxic organic pollutants, has been a serious threat to human survival and development, it is imperative to waste water treatment of industrial pollution. The photocatalytic technology at room temperature, can effectively degrade organic pollutants in the atmospheric conditions, and will not cause two pollution. (Zinc Oxide semiconductor photocatalytic materials ZnO) compared with other catalysts, has good physical and chemical stability, non-toxic and harmless, low price. Transition metal, alkaline earth metal, rare earth metal doping can change ZnO bandgap, crystal morphology and structure, is an important way to improve the photocatalytic performance. Many rare earth oxides such as lanthanum oxide, neodymium oxide can effectively improve the stability and activity of the catalyst. This paper mainly from the rare earth Er (Er), gadolinium (Gd), terbium (Te) with hand, respectively by co precipitation method and solution A series of rare earth doped ZnO photocatalyst prepared by sol gel method, we studied the different preparation methods under different calcination temperature, the structure of different rare earth element doping and doping amount of ZnO photocatalyst. The effect of morphology and activity. By scanning electron microscopy (SEM), X- ray diffraction (XRD). The specific surface area (BET), UV Vis diffuse reflectance (UV-Vis DRS) to analyze the properties of the photocatalyst was technology. The main contents are described as follows: (1) the preparation of rare earth doped ZnO photocatalyst by coprecipitation method, the photocatalytic degradation of methylene blue (MB) and methyl orange (MO) as the reaction probe of different rare earth (Er, Gd, Te) doped ZnO photocatalyst, the structure of rare earth doped ZnO photocatalyst, the characterization of morphology and photocatalytic activity. The results show that with the calcination temperature and doping amount of rare earth catalyst, crystalline and pure Are relatively good, rare earth doped effectively by ZnO the average grain size, specific surface area and pore size change, surface area of large samples of their photocatalytic activity was relatively strong, UV-Vis DRS shows little effect on the band gap of ZnO doped with different rare earth elements, the UN doped ZnO contrast, absorption band while no change or slightly blue shift of the image analysis of.SEM photocatalyst shows different doping amount the morphology changes significantly. Through factor screening optimization effects on photocatalytic system, calcination temperature at 500 DEG C, compared to the undoped ZnO degradation rate of MB (MO) 92.6% (42.4%), 0.5at%Er/ZnO, 0.5at%Gd/ZnO and 3at%Te/ZnO show good photocatalytic activity under UV irradiation, 2h, MB (MO) degradation rate reached 94.5% (60%), 95.9% (56%), 98.4% (57.7%). (2) prepared by the sol-gel method of rare earth doped ZnO photocatalyst with UV light catalytic The degradation of MB and MO as probe reaction, effects of different rare earth (Er, Gd, Te) doped ZnO photocatalyst, the structure of ZnO, the characterization of morphology and photocatalytic activity. The results show that with the calcination temperature and doping amount increase, the diffraction peak of XRD of the intensity of the change is not obvious, no impurity phase, the sample was well crystallized.BET data show that the specific surface area of the catalyst showed a different trend in.SEM analysis, compared to the undoped, have obvious effect on the morphology of photocatalyst doped with rare earth UV-vis DRS Zinc Oxide, that gap has little effect on ZnO of different rare earth doped by photocatalysis. Activity test showed that compared to the undoped ZnO, were improved the degradation of organic pollutants in rare earth doped ZnO methylene blue and methyl orange. In three kinds of rare earth (Er, Gd, Te) doped ZnO catalyst, 50 C Under the calcination temperature, the degradation rate of MB was (MO) 42.7% (22.1%) compared with the undoped ZnO, and lat%Er/ZnO, 0.5at%Gd/ZnO and 1at%Te/ZnO had higher photocatalytic activity respectively. The degradation rate of photocatalytic MB (MO) was 90.7% (40.3%), 91.7% (49.1%), 68.9% (29.5%), respectively.

【学位授予单位】：内蒙古农业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：X798;O643.36

【参考文献】