过渡金属掺杂氧化钛催化材料的设计合成及其Fenton催化性能研究

发布时间：2018-08-30 20:36

【摘要】：过渡金属离子掺杂型异相Fenton催化剂在有机污染物催化降解中具有显著优势,能够有效克服均相Fenton催化剂在应用中受pH的限制、难以回收、容易造成二次污染等弊端,同时可以解决负载型异相Fenton催化剂活性组分易脱落的问题。但在催化过程中,过渡金属离子容易失活,即难以从氧化态形式有效转化为还原态形式,导致催化剂的循环使用性能较差。针对此,本论文提出利用掺杂基底来促进过渡金属离子还原恢复的设想,即通过掺杂基底与过渡金属离子之间可能的电荷传递,促进过渡金属离子的有效再生,从而获得长效稳定的异相Fenton催化剂。本论文首先采用密度泛函方法对Mn(II)掺杂的锐钛型TiO2进行模拟计算,从理论角度揭示出TiO2基底对锰离子的还原再生具有明显的促进作用。然后,通过“溶胶凝胶—氨水刻蚀—离子交换—灼烧”法合成出Mn掺杂的花状TiO2纳米材料(Mn-fTiO2),并证实Mn-fTiO2在催化降解多种染料的应用中显示出优异的催化活性和稳定性。在此基础上,我们进一步设计合成了系列过渡金属离子(Mn2+、Cu2+、Co2+、Ni2+)掺杂的花状氧化钛材料,并探究其对有机染料的催化降解效果,通过与均相催化体系进行对比研究,也证实了TiO2基底对于这些过渡金属离子催化活性具有明显的促进效果。主要研究内容及结论如下:1、建立了锰离子掺杂TiO2催化剂的结构模型,通过密度泛函方法,模拟H2O2在其表面的的反应路径(以甲醇为底物)。结果表明TiO2基底可促进Mn的还原再生,同时基底自身也易于恢复。进一步,采用“溶胶凝胶—氨水刻蚀—离子交换—灼烧”方法合成出Mn-fTiO2纳米材料,通过SEM、XRD、UV-DRS、XPS、BET等表征分析方法确定其物理化学性质,进一步考察了其对亚甲基蓝(MB)等有机染料的Fenton催化降解性能。结果证实Mn-fTiO2为单分散、球形、花状形貌,具有良好的锐钛矿晶型、较大的比表面积、Mn的掺杂形态为+2价;催化降解MB时表现出优异的Fenton催化性能;通过设计对照实验,确认了基底对Mn氧化还原存在明显的促进作用;另外,该材料对多种有机染料均表现出高效的催化降解性能,在多次循环使用之后仍保持稳定的催化活性。2、基于上述研究结果,我们以无定型TiO2(pTiO2)、乙二醇(EG)、乙二胺(EDA)、过渡金属盐等试剂为原料,发展出制备不同过渡金属离子掺杂TiO2的一种简单且通用性方法,合成出Mn2+、Cu2+、Co2+、Ni2+等掺杂的花状TiO2纳米材料。采用SEM、XRD、UV-DRS、XPS、BET等技术手段表征材料的物理化学性质。选用MB为模型降解底物,探究所合成的系列过渡金属离子掺杂氧化钛材料对有机染料的催化降解效果。表征结果显示,四种过渡金属离子掺杂材料均表现为单分散的球形花状形貌,具有结晶性优良、比表面积大等特点,四种离子的掺杂形态均为+2价;催化降解实验结果表明,四种材料对MB均表现出良好的催化活性,且活化能较小,反应容易进行;经设计对照实验,证实基底TiO2对四种过渡金属离子的还原再生均存在一定的促进作用;选取其中Mn2+、Co2+掺杂的两种材料分别考察其催化稳定性,发现循环使用5次之后其催化效率无明显衰减。
[Abstract]:Transition metal ion doped heterogeneous Fenton catalyst has obvious advantages in catalytic degradation of organic pollutants. It can effectively overcome the shortcomings of homogeneous Fenton catalyst which is limited by pH, difficult to recover and easy to cause secondary pollution in application. At the same time, it can solve the problem that active components of supported heterogeneous Fenton catalyst are easy to fall off. In the catalytic process, transition metal ions are easy to deactivate, that is, it is difficult to effectively convert from oxidized to reduced forms, resulting in poor recycling performance of the catalyst. In this paper, the density functional theory (DFT) method is used to simulate the Mn(II)-doped anatase titanium dioxide. It is revealed that the substrates of titanium dioxide can promote the reduction and regeneration of manganese ions. Mn-doped flower-like titanium dioxide nanomaterials (Mn-fTiO2) were synthesized by gel-ammonia etching-ion exchange-burning method. It was confirmed that Mn-fTiO2 exhibited excellent catalytic activity and stability in the catalytic degradation of various dyes. On this basis, we further designed and synthesized a series of transition metal ions (Mn2+, Cu2+, Co2+, Ni2+). The doped flower-like titania and its catalytic degradation effect on organic dyes were investigated. By comparing with homogeneous catalytic system, the catalytic activity of these transition metal ions on the titania substrate was also confirmed. The main research contents and conclusions are as follows: 1. The junction of Mn-doped titania catalyst was established. The results show that the TiO2 substrate can promote the reduction and regeneration of Mn, and the substrate itself can be easily restored. Furthermore, Mn-fTiO2 nano-materials were synthesized by sol-gel-ammonia etching-ion exchange-burning method. The Mn-fTiO2 nano-materials were characterized by SEM, X-ray diffraction. RD, UV-DRS, XPS, BET and other characterization methods were used to determine its physical and chemical properties, and the Fenton catalytic degradation of methylene blue (MB) and other organic dyes was further investigated. In addition, the material exhibits high catalytic degradation performance for various organic dyes and remains stable catalytic activity after repeated recycling. 2. Based on the above results, we have no definite conclusion. A simple and universal method for preparing different transition metal ions doped titanium dioxide was developed. Mn2+, Cu2+, Co2+, Ni2+ doped flower-like titanium dioxide nanomaterials were synthesized. The physical and chemical properties of the materials were characterized by SEM, XRD, UV-DRS, XPS and BET. The catalytic degradation of organic dyes by a series of transition metal ions doped titanium oxide materials was investigated. The results showed that all the four transition metal ions doped materials exhibited monodisperse spherical flower-like morphology, good crystallinity, large specific surface area and four kinds of ions doped. The results of catalytic degradation experiments show that the four materials have good catalytic activity for MB, and the activation energy is small, and the reaction is easy to proceed. The comparison experiments prove that the substrates of titanium dioxide can promote the reduction and regeneration of four transition metal ions to a certain extent. It was found that the catalytic efficiency of the catalyst was not attenuated after 5 cycles.
【学位授予单位】：中国地质大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：O643.36

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