鐵基氧化物降解DDT性能的研究
發(fā)布時間：2018-07-14 14:07
【摘要】：以DDT(雙對氯苯基三氯乙烷)為代表的有機農藥的廣泛使用滿足了人們對于農業(yè)生產效率的追求,而且DDT作為一種控制以蚊蟲為傳播媒介的傳染病的有效農藥,曾經幫助人類成功防治了瘧疾等疫病。然而,由于DDT分子的穩(wěn)定性,長期大規(guī)模的使用造成了DDT在自然界中大量的累積。DDT親脂性的特點使其在食物鏈中發(fā)生富集效應并最終累積于食物鏈頂端的高等動物體內,直接威脅人類的身體健康。由于DDT對人類生存環(huán)境造成的諸多危害,近年來,國內外許多研究者就DDT的降解方法及機理進行了研究。在本論文中,我們設計并合成了三種鐵基化合物及其復合物材料,探究這三類材料在催化降解DDT方面的性能以及機理。主要內容如下：(1)通過簡單的水熱法,以FeCl3·6H2O為前驅體合成了Fe3O4微球,然后通過不同溫度的熱處理,分別得到了α-Fe2O3,γ-Fe2O3與α-/γ-Fe2O3兩相共存的納米結構復合物。XRD和HRTEM結果證明所合成的復相氧化鐵樣品為α與γ兩相氧化鐵復合而成。在相同的催化降解條件下,α-Fe2O3或者γ-Fe2O3僅能降解～20%的DDT分子,而由α-和γ-Fe2O3組成的兩相納米復合物則能夠將降解率顯著地提高到65%。這是由于兩相相互作用導致的畸變會形成高反應活性區(qū)域,非常適合作為催化反應的活性位點來支撐DDT的催化降解。此外,通過氣相色譜-質譜聯(lián)用儀進一步分析了降解產物的組成,并由此推測α-/γ-Fe2O3納米復合物催化降解DDT可能通過脫氯作用與脫氯化氫作用兩個途徑進行。(2)通過水熱法合成了花狀的鐵醇鹽前驅體,然后通過熱處理和表面羥基化的方法,分別得到了花狀的α-/γ-Fe2O3納米復合物和γ-FeOOH,將后者經過進一步熱處理得到了γ-Fe2O3樣品。通過三者的降解性能的比較,研究了不同因素對催化性能的影響。在相同的降解條件下,γ-Fe2O3可以降解70%的DDT,略高于γ-FeOOH樣品(65%),而表面羥基濃度較低的γ-Fe2O3僅降解了15%。這充分說明了兩相界面和表面羥基濃度對催化降解DDT具有非常明顯的促進作用。此外,花狀結構的大比表面積使得材料的活性位置得到更充分的利用,進一步提高了催化活性。降解產物的分析表明花狀α-/]-Fe2O3納米復合物催化降解DDT主要為脫氯作用,而脫氯化氫作用在本降解體系中受到了抑制。(3)通過溶劑交換的方法,獲得了大比表面積的CoFe2O4凝膠,之后通過液相還原的方法,在CoFe2O4凝膠基體上原位還原獲得Co單質顆粒形成復合結構,之后采用SEM、XRD、TEM、BET以及紅外光譜等表征手段對樣品進行了分析表征。Co單質/CoFe2O4凝膠復合結構展現(xiàn)了良好的催化降解DDT的性能,這主要是由于Co單質的還原電位有利于進行DDT分子的催化還原,且凝膠基體的孔道結構和較高的比表面積也非常有利于單質Co降解特性的發(fā)揮。降解產物的分析結果顯示CoFe2O4凝膠負載Co單質顆粒復合結構催化降解DDT的反應途徑主要是脫氯作用。
[Abstract]:The widespread use of DDT (bis (p chlorophenyl) trichloroethane) as an organic pesticide satisfies the pursuit of agricultural production efficiency, and DDT is an effective pesticide for the control of mosquito-borne infectious diseases. It has helped humans successfully prevent and treat diseases such as malaria. However, because of the stability of DDT molecules, the long-term and large-scale use of DDT resulted in the accumulation of DDT in nature, which led to the accumulation of DDT in the food chain and eventually accumulated in the higher animals at the top of the food chain. It is a direct threat to human health. In recent years, many researchers at home and abroad have studied the degradation method and mechanism of DDT because of the harm to human living environment caused by DDT. In this thesis, we have designed and synthesized three kinds of Fe-based compounds and their complex materials, and explored the catalytic degradation of DDT and the mechanism of the three kinds of materials. The main contents are as follows: (1) Fe _ 3O _ 4 microspheres were synthesized by a simple hydrothermal method with FeCl _ 36H _ 2O as precursor, and then heat treated at different temperatures. The nanostructural complexes of 偽 -Fe _ 2O _ 3, 緯 -Fe _ 2O _ 3 and 偽-/ 緯 -Fe _ 2O _ 3 were obtained. The results of XRD and HRTEM show that the composite of 偽 -Fe _ 2O _ 3, 緯 -Fe _ 2O _ 3 and 偽 -Fe _ 2O _ 3 is composed of 偽 and 緯 phase ferric oxide. Under the same catalytic degradation conditions, 偽 -Fe _ 2O _ 3 or 緯 -Fe _ 2O _ 3 can only degrade 20% DDT molecules, while the two-phase nanocomposites composed of 偽-and 緯 -Fe _ 2O _ 3 can significantly increase the degradation rate to 65%. This is because the distortion caused by the two-phase interaction will form a highly reactive region, which is very suitable for supporting the catalytic degradation of DDT as an active site for catalytic reaction. In addition, the composition of the degradation products was further analyzed by gas chromatography-mass spectrometry. It is inferred that the degradation of DDT catalyzed by 偽-/ 緯 -Fe _ 2O _ 3 nanocomposites may be carried out by dechlorination and dehydrochlorination. (2) Flower ferric alcohol precursors were synthesized by hydrothermal method, and then by heat treatment and surface hydroxylation. The flower-like 偽-/ 緯 -Fe _ 2O _ 3 nanocomposites and 緯 -FeOOH were obtained, and the 緯 -Fe _ 2O _ 3 samples were obtained by further heat treatment. The effects of different factors on the catalytic performance were studied by comparing the degradation properties of the three factors. Under the same degradation conditions, 緯 -Fe _ 2O _ 3 can degrade 70% of DDT, slightly higher than 緯 -FeOOH sample (65%), while 緯 -Fe _ 2O _ 3 with lower surface hydroxyl concentration only degrades 15%. This fully shows that the two-phase interface and the concentration of surface hydroxyl groups can promote the catalytic degradation of DDT. In addition, the large specific surface area of the flower-like structure makes the active sites of the materials more fully utilized, and further improves the catalytic activity. The analysis of the degradation products showed that the catalytic degradation of DDT by flower-like 偽-/] -Fe _ 2O _ 3 nanocomposites was mainly dechlorination, while the dehydrochlorination was inhibited in this degradation system. (3) Cofe _ 2O _ 4 gel with large specific surface area was obtained by solvent exchange. After that, Co particles were prepared by in situ reduction on CoFe2O4 gel matrix by liquid phase reduction. After that, the composite structure of Co / CoFe2O4 gel showed good catalytic degradation of DDT by means of SEMX XRDX Tem BET and IR spectra. This is mainly due to the fact that the reduction potential of Co is favorable to the catalytic reduction of DDT, and that the pore structure and the high specific surface area of the gel matrix are also beneficial to the Co degradation characteristics. The analysis of the degradation products showed that the main way of catalytic degradation of DDT was the dechlorination of CoFe _ 2O _ 4 gel supported Co particle composite structure.
【學位授予單位】：山東大學
【學位級別】：碩士
【學位授予年份】：2015
【分類號】：X592;O643.36
本文編號：2121887
[Abstract]:The widespread use of DDT (bis (p chlorophenyl) trichloroethane) as an organic pesticide satisfies the pursuit of agricultural production efficiency, and DDT is an effective pesticide for the control of mosquito-borne infectious diseases. It has helped humans successfully prevent and treat diseases such as malaria. However, because of the stability of DDT molecules, the long-term and large-scale use of DDT resulted in the accumulation of DDT in nature, which led to the accumulation of DDT in the food chain and eventually accumulated in the higher animals at the top of the food chain. It is a direct threat to human health. In recent years, many researchers at home and abroad have studied the degradation method and mechanism of DDT because of the harm to human living environment caused by DDT. In this thesis, we have designed and synthesized three kinds of Fe-based compounds and their complex materials, and explored the catalytic degradation of DDT and the mechanism of the three kinds of materials. The main contents are as follows: (1) Fe _ 3O _ 4 microspheres were synthesized by a simple hydrothermal method with FeCl _ 36H _ 2O as precursor, and then heat treated at different temperatures. The nanostructural complexes of 偽 -Fe _ 2O _ 3, 緯 -Fe _ 2O _ 3 and 偽-/ 緯 -Fe _ 2O _ 3 were obtained. The results of XRD and HRTEM show that the composite of 偽 -Fe _ 2O _ 3, 緯 -Fe _ 2O _ 3 and 偽 -Fe _ 2O _ 3 is composed of 偽 and 緯 phase ferric oxide. Under the same catalytic degradation conditions, 偽 -Fe _ 2O _ 3 or 緯 -Fe _ 2O _ 3 can only degrade 20% DDT molecules, while the two-phase nanocomposites composed of 偽-and 緯 -Fe _ 2O _ 3 can significantly increase the degradation rate to 65%. This is because the distortion caused by the two-phase interaction will form a highly reactive region, which is very suitable for supporting the catalytic degradation of DDT as an active site for catalytic reaction. In addition, the composition of the degradation products was further analyzed by gas chromatography-mass spectrometry. It is inferred that the degradation of DDT catalyzed by 偽-/ 緯 -Fe _ 2O _ 3 nanocomposites may be carried out by dechlorination and dehydrochlorination. (2) Flower ferric alcohol precursors were synthesized by hydrothermal method, and then by heat treatment and surface hydroxylation. The flower-like 偽-/ 緯 -Fe _ 2O _ 3 nanocomposites and 緯 -FeOOH were obtained, and the 緯 -Fe _ 2O _ 3 samples were obtained by further heat treatment. The effects of different factors on the catalytic performance were studied by comparing the degradation properties of the three factors. Under the same degradation conditions, 緯 -Fe _ 2O _ 3 can degrade 70% of DDT, slightly higher than 緯 -FeOOH sample (65%), while 緯 -Fe _ 2O _ 3 with lower surface hydroxyl concentration only degrades 15%. This fully shows that the two-phase interface and the concentration of surface hydroxyl groups can promote the catalytic degradation of DDT. In addition, the large specific surface area of the flower-like structure makes the active sites of the materials more fully utilized, and further improves the catalytic activity. The analysis of the degradation products showed that the catalytic degradation of DDT by flower-like 偽-/] -Fe _ 2O _ 3 nanocomposites was mainly dechlorination, while the dehydrochlorination was inhibited in this degradation system. (3) Cofe _ 2O _ 4 gel with large specific surface area was obtained by solvent exchange. After that, Co particles were prepared by in situ reduction on CoFe2O4 gel matrix by liquid phase reduction. After that, the composite structure of Co / CoFe2O4 gel showed good catalytic degradation of DDT by means of SEMX XRDX Tem BET and IR spectra. This is mainly due to the fact that the reduction potential of Co is favorable to the catalytic reduction of DDT, and that the pore structure and the high specific surface area of the gel matrix are also beneficial to the Co degradation characteristics. The analysis of the degradation products showed that the main way of catalytic degradation of DDT was the dechlorination of CoFe _ 2O _ 4 gel supported Co particle composite structure.
【學位授予單位】：山東大學
【學位級別】：碩士
【學位授予年份】：2015
【分類號】：X592;O643.36
【參考文獻】
相關期刊論文 前1條
1 楊喜云,龔竹青,劉豐良;Kinetics of Fe_3O_4 formation by air oxidation[J];Journal of Central South University of Technology(English Edition);2004年02期
，本文編號：2121887
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