本文關(guān)鍵詞：碳納米管增強(qiáng)金屬卟啉催化活性的研究　出處：《浙江理工大學(xué)》2017年碩士論文　論文類型：學(xué)位論文

  更多相關(guān)文章： 持久性自由基 金屬卟啉 碳納米管 增效機(jī)理 降解污染物

【摘要】：持久性自由基(Persistent Free Radicals,PFRs)因壽命長(zhǎng)、毒性大作為一類新型環(huán)境危害物質(zhì)被廣泛關(guān)注,但國(guó)際上對(duì)PFRs環(huán)境危害機(jī)制的研究相對(duì)匱乏,其環(huán)境有益探索更是空白。我們從PFRs危害機(jī)制出發(fā)探索其環(huán)境有益應(yīng)用。利用碳納米管和金屬卟啉具有優(yōu)異電化學(xué)性能以及碳材料含有PFRs的特點(diǎn),本論文嘗試將鐵卟啉(hemin)通過(guò)共價(jià)鍵的方式負(fù)載到碳納米管(MWCNTs)上,制備得到一種新型催化劑(hemin-MWCNTs)。以H_2O_2為氧化劑,染料為探針化合物,考察該催化劑的催化性能。實(shí)驗(yàn)結(jié)果表明,與小分子鐵卟啉相比,PFRs的引入顯著改善了鐵卟啉的催化性能,并拓寬了其pH適應(yīng)范圍。我們進(jìn)一步將抗壞血酸(AA)引入上述催化體系,并與以活性碳纖維(ACF)為載體的催化體系(hemin-ACF/AA/H_2O_2)進(jìn)行對(duì)照實(shí)驗(yàn),發(fā)現(xiàn)碳納米管為載體的體系具有更高的催化性能。本論文不僅為應(yīng)用金屬卟啉作為催化劑降解有機(jī)污染物提供了新思路,而且為持久性自由基應(yīng)用到環(huán)境催化領(lǐng)域打下了堅(jiān)實(shí)的基礎(chǔ)。主要研究?jī)?nèi)容分為以下兩部分:將鐵卟啉嫁接到碳納米管上,制得碳納米管負(fù)載鐵卟啉催化劑(hemin-MWCNTs),通過(guò)X射線光電子能譜(XPS)對(duì)其結(jié)構(gòu)進(jìn)行表征。以染料亞甲基藍(lán)(MB)為探針化合物,以H_2O_2為氧化劑,考察了該催化劑的催化性能。研究結(jié)果表明,相比于hemin/H_2O_2體系,碳納米管(PFRs)的引入顯著增強(qiáng)了hemin的催化性能,hemin-MWCNTs/H_2O_2體系能在60 min內(nèi)將98%的MB降解,同時(shí)其降解速率(k1=0.04195 min-1)是hemin/H_2O_2(k1=0.00068 min-1)體系的61倍。除MB以外,該體系還能有效降解其他不同結(jié)構(gòu)的染料,如AO 7、AR 1、BG等。該體系在較廣的pH(3-11)范圍內(nèi)能夠有效降解染料,并且具有較好的溫度適應(yīng)性。以異丙醇為捕獲劑,結(jié)合電子順磁共振波譜(EPR)等測(cè)試手段,表明在催化降解過(guò)程中生成了·OH和高價(jià)鐵(Fe(IV)),其中·OH對(duì)染料的降解起到了主導(dǎo)作用。為了構(gòu)筑更加高效的催化體系,我們?cè)趆emin-MWCNTs/H_2O_2的基礎(chǔ)上引入了抗壞血酸(AA)。以染料RR M-3BE為探針化合物,并與hemin-ACF/AA/H_2O_2催化體系的催化性能進(jìn)行了對(duì)比。實(shí)驗(yàn)結(jié)果顯示,與hemin-ACF/AA/H_2O_2催化體系相比較,hemin-MWCNTs/AA/H_2O_2表現(xiàn)出更高的催化活性,在相同條件能在6 min內(nèi)能將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)體系的2倍。該催化體系具有良好的pH以及溫度適應(yīng)性,并且催化劑在循環(huán)使用7次后依舊能夠有效降解RR M-3BE。我們采用乙醇、三乙醇胺等捕獲劑,并結(jié)合EPR技術(shù)、電化學(xué)實(shí)驗(yàn)等方法研究染料降解機(jī)理,結(jié)果表明,hemin-MWCNTs/AA/H_2O_2體系染料降解的是因?yàn)楫a(chǎn)生了空穴,不同于hemin-ACF/AA/H_2O_2機(jī)理(自由基機(jī)理)。此外,通過(guò)EPR技術(shù)對(duì)MWCNTs和ACF中的PFRs進(jìn)行檢測(cè),實(shí)驗(yàn)結(jié)果表明MWCNTs和ACF中的不同的電子狀態(tài)是導(dǎo)致該兩個(gè)催化體系產(chǎn)生兩種不同催化機(jī)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.
【學(xué)位授予單位】：浙江理工大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：O643.36;TB383.1

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