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题名: 零价铁基复合材料构建与强化还原含氧阴离子机理研究
作者: 韩陆超1
学位类别: 博士
答辩日期: 2017-12
授予单位: 中国科学院大学
授予地点: 北京
导师: 胡春
关键词: 零价铁,二价铁,还原氧化石墨烯,微生物,腐殖酸 ; Zero valent iron, Ferrous iron, Reduced graphene oxide, Microorganism, Humic acid
其他题名: Construction and Mechanism of the new Fe0-based composites for Enhancement of Oxo-anions Reduction
学位专业: 环境科学
中文摘要: NO3-,BrO3-和ClO3-等是一类由人类工业农业生产活动产生的能够极大威胁人体健康的污染物。它们十分容易在水体中迁移并影响人类正常生产生活。而Fe0作为一种成本低廉的强还原剂,已经有大量研究将其用于还原去除多种含氧阴离子污染物。但随着Fe0与污染物之间的反应,Fe0表面会形成的铁氧化物钝化层极大的减弱Fe0的还原活性。因此本研究通过表面改性的方法构建新型Fe0基复合材料来增强其还原活性,并使用改性Fe0来进一步提高微生物降解含氧阴离子的活性,主要研究结果如下: 1.研究溶解态Fe2+加速Fe0还原NO3-的机理发现,调节溶液初始pH会改变溶液中的Fe2+含量和Fe0表面铁氧化物的形态特征,而这两个特征对NO3-还原均起到了关键的作用。研究NO3-在不同条件下的还原反应动力学发现,溶液中Fe2+的消耗和NO3-还原具有相似的反应动力学,并且两者相互促进,而这种促进关系还与Fe0表面铁氧化物的种类有关。穆斯堡尔谱的研究结果证实了吸附态Fe2+通过表面Fe3+与Fe2+的自发的外层电子转移源源不断的转化成无定形Fe3+,然后再转化成Fe3O4。电化学研究的结果证实了吸附态Fe2+与Fe3+氧化物之间的自发的电子转移能够加速Fe物种与NO3-之间的界面电子传递。此外,NO3-还原过程会在Fe0表面产生更多的铁氧化物,使得Fe2+与Fe3+氧化物之间自发电子转移机会更多,从而进一步加速NO3-还原。为此通过事先将Fe2+吸附在Fe0表面的方法制备了改性的N-Fe0+2。研究发现这种改性材料对于BrO3-降解也具备很高的还原活性和稳定性。 2.运用在厌氧条件下使用Fe0还原氧化石墨烯(GO)的方法成功制备了还原氧化石墨烯包覆的Fe0(rGO/Fe0)。表征分析证实rGO/Fe0具有 Fe0核和铁氧化物结合rGO壳结构。与Fe0相比,rGO/Fe0具有很高的还原NO3-,BrO3-和ClO3-的活性。对实验结果进行分析可知rGO/Fe0表面铁氧化物中的Fe原子与rGO缺陷位点上的C原子之间形成的Fe-O-C键是提高rGO/Fe0界面电子转移的关键因素。Fe-O之间形成的键和rGO碳平面内的大键之间的-超共轭同时提高了rGO/Fe0表面铁氧化物和rGO的极性,使得Fe0的电子更容易传递给含氧阴离子,从而提高Fe0降解活性。 3.研究rGO/Fe0对Pseudomonas stutzeri LF-7(一种从管垢中分离出的Fe物种耐受脱氮微生物)脱氮性能的影响。与Fe0相比,rGO/Fe0促进了LF-7将NO3-快速转化为N2的能力,减少反应过程中NO2-的积累。探究不同因素对LF-7脱氮性能的影响证实了rGO/Fe0表面的rGO是rGO/Fe0促进LF-7转化NO2-的主要原因。通过XRD和红外光谱对能促进转化的GO反应前后进行表征可以发现,材料表面羰基和环氧基在与LF-7结合的过程中被氧化为羧基,然而其表面含氧基团的总量却减少了,表明GO在此过程中同时被还原了,证实了GO是LF-7与NO2-之间进行电子传递的电子穿梭体。探究LF-7反应前后的变化发现,rGO/Fe0表面的rGO激活了LF-7细胞外膜上的细胞色素C增强了其胞外电子传递能力,从而促进了NO2-的还原。 4.研究 HA对LF-7与rGO/Fe0结合降解NO3-的能力的影响发现,HA能够通过对胞外电子传递的促进进一步增强LF-7降解NO2-的能力,也能够极大的促进结合了rGO/Fe0的LF-7降解NO3-。HA通过与rGO/Fe0表面rGO的π-π非极性相互作用和含氧基团间的极性相互作用吸附在rGO/Fe0表面,减少了rGO表面非极性C=C双键的暴露,降低了rGO非极性C=C双键对细菌细胞膜的破坏,减少了细菌的吸附,降低了rGO/Fe0表面rGO在反应之初对细菌生长的抑制,使得LF-7能够快速降解NO3-
英文摘要: Nnitrate (NO3-), bromate (BrO3-) and chlorate (ClO3-), which originate from many agricultural and industrial processes, can pose potential threats to human health. Oxo-anions will transfer and diffuse in water and significantly disturb the producing and living environments. As a strong reducing agent, zero valent iron (Fe0) has been extensively studied to reduce different oxo-anions. However, the oxidation of Fe0 results in the formation of an oxide layer, leading to a reduction in the reactivity of Fe0. In this study, the modified Fe0 was prepared to solve this problem. Moreover, the modified Fe0 could also increase the activity of denitrifying bacteria. The main research contents and results are as follows: 1. The mechanism of the effects of Fe2+ on the reduction of NO3- by Fe0 was investigated. The effects of initial pH on the rate of NO3- reduction and the Fe0 surface characteristics revealed Fe2+ and the characteristics of minerals on the surface of Fe0 played an important role in NO3- reduction. Both NO3- reduction and the decrease of Fe2+ exhibited similar kinetics and were promoted by each other. This promotion was associated with the types of the surface iron oxides of Fe0. Using the isotope specificity of 57Fe Mossbauer spectroscopy, it was verified that the Fe2+ was continuously converted into Fe3+ oxides on the surface of Fe0 and then converted into Fe3O4 via electron transfer between Fe2+ and the pre-existing surface Fe3+ oxides. Electrochemistry measurements confirmed that the spontaneous electron transfer between the Fe2+ and structural Fe3+ species accelerated the interfacial electron transfer between the Fe species and NO3-. Additionally, further reduction of NO3- produced more surface iron oxides, supplying more active sites for Fe2+, resulting in more electron transfer between Fe2+ and surface iron oxides and a higher reaction rate. According to the reaction mechanism research, the modified N-Fe0+2 was prepared by the pre-reaction between N-Fe0 and Fe2+. It exhibited the highly efficient and stable performance for the removal of BrO3-.2. Reduced graphene oxide-coated Fe0 (rGO/Fe0) was prepared via the reduction of graphene oxide (GO) by Fe0 under anaerobic conditions. Based on characterization, the rGO/Fe0 had a Fe0 core surrounded with an rGO/iron oxide shell. The rGO/Fe0 exhibited much higher activity than Fe0 for the reduction of three oxo-anions (NO3-, BrO3- and ClO3-). It was verified that the Fe-O-C between the carbon defects of rGO and Fe atom of iron oxides enhanced the interfacial electron transfer on rGO/Fe0. Orbital interactions involving σ-π electron transfer would increase the electronic polarizability of iron oxides and the in-plane sp2 carbon atoms in rGO, which was responsible for its higher reduction activity. 3. The effect of rGO/Fe0 on the performance of denitrification by Pseudomonas stutzeri strain LF-7, which is a Fe tolerant NO3 reducing bacteria isolated from pipe scale, was investigated. The denitrification process was investigated in rGO/Fe0 + Pseudomonas stutzeri strain LF-7 aqueous suspensions, where the enhancement of conversion of NO3- to N2 was obtained with lower NO2- formation. The effect of GO on the performance of denitrification by LF-7 demonstrated that the acceleration of NO2- reduction was ascribed to rGO on the surface of Fe0. The carbonyl group and epoxy group on the surface of GO were oxidized to carboxyl, while the amount of the oxygen-containing groups was decreased, indicating that GO was reduced simultaneously. The GO can act as electron shuttle between the denitrifying bacteria and NO2-. The rGO on the surface of Fe0 activated the C-type cytochromes on the outer membrane of LF-7 and enhanced the extracellular electron transfer of LF-7, resulting in the acceleration of NO2- reduction. 4. The effects of humus acid (HA) on the reduction of NO3- by LF-7 + rGO/Fe0 was investigated. It was found that the reduction of NO2- by LF-7 was promoted by HA, which was attributed to the acceleration of the extracellular electron transfer of LF-7 by HA. HA could also greatly promote the reduction of NO3- by LF-7 + rGO/Fe0. HA was adsorbed on rGO/Fe0 through π-π interactions and polar interactions between the O-containing functional groups on the surface of HA and rGO, resulting in the decrease of the exposed C=C on the surface of rGO/Fe0. The C=C could adsorb the cell of LF-7 and damage the cell membrane by the destructive extraction of lipid V molecules. The antibacterial property of rGO/Fe0 would fail by the adsorption of HA on the surface of rGO/Fe0, resulting in the acceleration of NO3- reduction by LF-7.
内容类型: 学位论文
URI标识: http://ir.rcees.ac.cn/handle/311016/38627
Appears in Collections:环境水质学国家重点实验室_学位论文

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作者单位: 1.中国科学院生态环境研究中心

Recommended Citation:
韩陆超. 零价铁基复合材料构建与强化还原含氧阴离子机理研究[D]. 北京. 中国科学院大学. 2017.
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