铁基氧化物降解DDT性能的研究
发布时间：2018-07-14 14:07
【摘要】：以DDT(双对氯苯基三氯乙烷)为代表的有机农药的广泛使用满足了人们对于农业生产效率的追求,而且DDT作为一种控制以蚊虫为传播媒介的传染病的有效农药,曾经帮助人类成功防治了疟疾等疫病。然而,由于DDT分子的稳定性,长期大规模的使用造成了DDT在自然界中大量的累积。DDT亲脂性的特点使其在食物链中发生富集效应并最终累积于食物链顶端的高等动物体内,直接威胁人类的身体健康。由于DDT对人类生存环境造成的诸多危害,近年来,国内外许多研究者就DDT的降解方法及机理进行了研究。在本论文中,我们设计并合成了三种铁基化合物及其复合物材料,探究这三类材料在催化降解DDT方面的性能以及机理。主要内容如下：(1)通过简单的水热法,以FeCl3·6H2O为前驱体合成了Fe3O4微球,然后通过不同温度的热处理,分别得到了α-Fe2O3,γ-Fe2O3与α-/γ-Fe2O3两相共存的纳米结构复合物。XRD和HRTEM结果证明所合成的复相氧化铁样品为α与γ两相氧化铁复合而成。在相同的催化降解条件下,α-Fe2O3或者γ-Fe2O3仅能降解～20%的DDT分子,而由α-和γ-Fe2O3组成的两相纳米复合物则能够将降解率显著地提高到65%。这是由于两相相互作用导致的畸变会形成高反应活性区域,非常适合作为催化反应的活性位点来支撑DDT的催化降解。此外,通过气相色谱-质谱联用仪进一步分析了降解产物的组成,并由此推测α-/γ-Fe2O3纳米复合物催化降解DDT可能通过脱氯作用与脱氯化氢作用两个途径进行。(2)通过水热法合成了花状的铁醇盐前驱体,然后通过热处理和表面羟基化的方法,分别得到了花状的α-/γ-Fe2O3纳米复合物和γ-FeOOH,将后者经过进一步热处理得到了γ-Fe2O3样品。通过三者的降解性能的比较,研究了不同因素对催化性能的影响。在相同的降解条件下,γ-Fe2O3可以降解70%的DDT,略高于γ-FeOOH样品(65%),而表面羟基浓度较低的γ-Fe2O3仅降解了15%。这充分说明了两相界面和表面羟基浓度对催化降解DDT具有非常明显的促进作用。此外,花状结构的大比表面积使得材料的活性位置得到更充分的利用,进一步提高了催化活性。降解产物的分析表明花状α-/]-Fe2O3纳米复合物催化降解DDT主要为脱氯作用,而脱氯化氢作用在本降解体系中受到了抑制。(3)通过溶剂交换的方法,获得了大比表面积的CoFe2O4凝胶,之后通过液相还原的方法,在CoFe2O4凝胶基体上原位还原获得Co单质颗粒形成复合结构,之后采用SEM、XRD、TEM、BET以及红外光谱等表征手段对样品进行了分析表征。Co单质/CoFe2O4凝胶复合结构展现了良好的催化降解DDT的性能,这主要是由于Co单质的还原电位有利于进行DDT分子的催化还原,且凝胶基体的孔道结构和较高的比表面积也非常有利于单质Co降解特性的发挥。降解产物的分析结果显示CoFe2O4凝胶负载Co单质颗粒复合结构催化降解DDT的反应途径主要是脱氯作用。
[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 伪 -Fe _ 2O _ 3, 纬 -Fe _ 2O _ 3 and 伪-/ 纬 -Fe _ 2O _ 3 were obtained. The results of XRD and HRTEM show that the composite of 伪 -Fe _ 2O _ 3, 纬 -Fe _ 2O _ 3 and 伪 -Fe _ 2O _ 3 is composed of 伪 and 纬 phase ferric oxide. Under the same catalytic degradation conditions, 伪 -Fe _ 2O _ 3 or 纬 -Fe _ 2O _ 3 can only degrade 20% DDT molecules, while the two-phase nanocomposites composed of 伪-and 纬 -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 伪-/ 纬 -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 伪-/ 纬 -Fe _ 2O _ 3 nanocomposites and 纬 -FeOOH were obtained, and the 纬 -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, 纬 -Fe _ 2O _ 3 can degrade 70% of DDT, slightly higher than 纬 -FeOOH sample (65%), while 纬 -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 伪-/] -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.
【学位授予单位】：山东大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：X592;O643.36
本文编号：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 伪 -Fe _ 2O _ 3, 纬 -Fe _ 2O _ 3 and 伪-/ 纬 -Fe _ 2O _ 3 were obtained. The results of XRD and HRTEM show that the composite of 伪 -Fe _ 2O _ 3, 纬 -Fe _ 2O _ 3 and 伪 -Fe _ 2O _ 3 is composed of 伪 and 纬 phase ferric oxide. Under the same catalytic degradation conditions, 伪 -Fe _ 2O _ 3 or 纬 -Fe _ 2O _ 3 can only degrade 20% DDT molecules, while the two-phase nanocomposites composed of 伪-and 纬 -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 伪-/ 纬 -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 伪-/ 纬 -Fe _ 2O _ 3 nanocomposites and 纬 -FeOOH were obtained, and the 纬 -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, 纬 -Fe _ 2O _ 3 can degrade 70% of DDT, slightly higher than 纬 -FeOOH sample (65%), while 纬 -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 伪-/] -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.
【学位授予单位】：山东大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：X592;O643.36
【参考文献】
相关期刊论文 前1条
1 杨喜云,龚竹青,刘丰良;Kinetics of Fe_3O_4 formation by air oxidation[J];Journal of Central South University of Technology(English Edition);2004年02期
，本文编号：2121887
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