碳纳米管增强金属卟啉催化活性的研究

发布时间：2017-12-28 15:56

本文关键词：碳纳米管增强金属卟啉催化活性的研究　出处：《浙江理工大学》2017年硕士论文　论文类型：学位论文

【摘要】：持久性自由基(Persistent Free Radicals,PFRs)因寿命长、毒性大作为一类新型环境危害物质被广泛关注,但国际上对PFRs环境危害机制的研究相对匮乏,其环境有益探索更是空白。我们从PFRs危害机制出发探索其环境有益应用。利用碳纳米管和金属卟啉具有优异电化学性能以及碳材料含有PFRs的特点,本论文尝试将铁卟啉(hemin)通过共价键的方式负载到碳纳米管(MWCNTs)上,制备得到一种新型催化剂(hemin-MWCNTs)。以H_2O_2为氧化剂,染料为探针化合物,考察该催化剂的催化性能。实验结果表明,与小分子铁卟啉相比,PFRs的引入显著改善了铁卟啉的催化性能,并拓宽了其pH适应范围。我们进一步将抗坏血酸(AA)引入上述催化体系,并与以活性碳纤维(ACF)为载体的催化体系(hemin-ACF/AA/H_2O_2)进行对照实验,发现碳纳米管为载体的体系具有更高的催化性能。本论文不仅为应用金属卟啉作为催化剂降解有机污染物提供了新思路,而且为持久性自由基应用到环境催化领域打下了坚实的基础。主要研究内容分为以下两部分:将铁卟啉嫁接到碳纳米管上,制得碳纳米管负载铁卟啉催化剂(hemin-MWCNTs),通过X射线光电子能谱(XPS)对其结构进行表征。以染料亚甲基蓝(MB)为探针化合物,以H_2O_2为氧化剂,考察了该催化剂的催化性能。研究结果表明,相比于hemin/H_2O_2体系,碳纳米管(PFRs)的引入显著增强了hemin的催化性能,hemin-MWCNTs/H_2O_2体系能在60 min内将98%的MB降解,同时其降解速率(k1=0.04195 min-1)是hemin/H_2O_2(k1=0.00068 min-1)体系的61倍。除MB以外,该体系还能有效降解其他不同结构的染料,如AO 7、AR 1、BG等。该体系在较广的pH(3-11)范围内能够有效降解染料,并且具有较好的温度适应性。以异丙醇为捕获剂,结合电子顺磁共振波谱(EPR)等测试手段,表明在催化降解过程中生成了·OH和高价铁(Fe(IV)),其中·OH对染料的降解起到了主导作用。为了构筑更加高效的催化体系,我们在hemin-MWCNTs/H_2O_2的基础上引入了抗坏血酸(AA)。以染料RR M-3BE为探针化合物,并与hemin-ACF/AA/H_2O_2催化体系的催化性能进行了对比。实验结果显示,与hemin-ACF/AA/H_2O_2催化体系相比较,hemin-MWCNTs/AA/H_2O_2表现出更高的催化活性,在相同条件能在6 min内能将RR M-3BE降解完全,其降解速率(k1=0.022 min-1)是hemin-ACF/AA/H_2O_2(k1=0.011 min-1)体系的2倍。该催化体系具有良好的pH以及温度适应性,并且催化剂在循环使用7次后依旧能够有效降解RR M-3BE。我们采用乙醇、三乙醇胺等捕获剂,并结合EPR技术、电化学实验等方法研究染料降解机理,结果表明,hemin-MWCNTs/AA/H_2O_2体系染料降解的是因为产生了空穴,不同于hemin-ACF/AA/H_2O_2机理(自由基机理)。此外,通过EPR技术对MWCNTs和ACF中的PFRs进行检测,实验结果表明MWCNTs和ACF中的不同的电子状态是导致该两个催化体系产生两种不同催化机理的重要原因。
[Abstract]:Persistent Free Radicals (PFRs) has attracted widespread attention as a new type of environmental hazardous substances due to its long life and high toxicity. However, the research on the environmental hazards mechanism of PFRs is relatively scarce in the world, and its environmental beneficial exploration is still blank. We start from the PFRs hazard mechanism to explore the beneficial application of its environment. Using carbon nanotubes and metalloporphyrins has excellent electrochemical performance and carbon materials containing PFRs, this paper tries to load iron porphyrin (hemin) onto carbon nanotubes (MWCNTs) by covalent bonds, and prepare a new type of catalyst (hemin-MWCNTs). The catalytic performance of the catalyst was investigated by using H_2O_2 as an oxidant and a dye as a probe compound. The experimental results show that, compared with the small molecular iron porphyrin, the introduction of PFRs significantly improves the catalytic performance of iron porphyrin and broadens its pH adaptation range. We further introduced the ascorbic acid (AA) into the above catalytic system, and compared it with the catalytic system (hemin-ACF/AA/H_2O_2) with active carbon fiber (ACF) as carrier. It was found that the carbon nanotubes as carrier system had higher catalytic performance. This paper not only provides a new idea for the application of metalloporphyrins as a catalyst for the degradation of organic pollutants, but also lays a solid foundation for the application of persistent free radicals to the field of environmental catalysis. The main research contents are divided into two parts: grafting iron porphyrin onto carbon nanotubes, and preparing carbon nanotube loaded iron porphyrin catalyst (hemin-MWCNTs). The structure is characterized by X ray photoelectron spectroscopy (XPS). The catalytic performance of the catalyst was investigated with the dye methylene blue (MB) as the probe compound and H_2O_2 as the oxidant. The results show that, compared to the hemin/H_2O_2 system, the introduction of carbon nanotubes (PFRs) significantly enhanced the catalytic performance of hemin, the hemin-MWCNTs/H_2O_2 system can be within 60 min 98% MB degradation, while its degradation rate (k1=0.04195 min-1) is hemin/H_2O_2 (k1=0.00068 min-1) 61 times system. In addition to MB, the system can effectively degrade other dyes of different structures, such as AO 7, AR 1, BG and so on. The system can effectively degrade dyes in a wide range of pH (3-11), and has good temperature adaptability. Isopropyl alcohol as a capture agent combined with electron paramagnetic resonance spectroscopy (EPR) and other testing methods showed that OH and high valent iron (Fe (IV)) were generated during the catalytic degradation process, and OH played a leading role in the degradation of dyes. In order to build a more efficient catalytic system, we have introduced ascorbic acid (AA) on the basis of hemin-MWCNTs/H_2O_2. The dye RR M-3BE was used as a probe compound and its catalytic performance was compared with that of the hemin-ACF/AA/H_2O_2 catalytic system. The experimental results show that compared with the hemin-ACF/AA/H_2O_2 catalytic system, hemin-MWCNTs/AA/H_2O_2 showed higher catalytic activity, in the same conditions in 6 min RR M-3BE can be degraded completely, the degradation rate (k1=0.022 min-1) is hemin-ACF/AA/H_2O_2 (k1=0.011 min-1) 2 times system. The catalytic system has good pH and temperature adaptability, and the catalyst can still effectively degrade RR M-3BE after 7 cycles. We used ethanol, triethanolamine as capture agent, and the combination of EPR technology and electrochemical experimental methods of dye degradation mechanism, the results show that the hemin-MWCNTs/AA/H_2O_2 system is due to the degradation of the dye hole is different from the mechanism of hemin-ACF/AA/H_2O_2 (free radical mechanism). In addition, EPR technology is used to detect PFRs in MWCNTs and ACF. The experimental results show that the different electronic states in MWCNTs and ACF are the important reasons for the two catalytic mechanisms of the two catalytic systems.
【学位授予单位】：浙江理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：O643.36;TB383.1

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