水溶液中几种酚类污染物在石墨烯上的转化与降解行为研究
文献类型：学位论文
| 作者 | 李春梅 |
| 学位类别 | 硕士 |
| 答辩日期 | 2015-05 |
| 授予单位 | 中国科学院研究生院 |
| 授予地点 | 北京 |
| 导师 | 裴志国 |
| 关键词 | 石墨烯，对苯二酚，酚类污染物，转化，降解，reduced graphene oxide, hydroquinone, phenolic contaminants, transformation, degradation |
| 其他题名 | Transformation of several phenolic compounds mediated by reduced grphene oxide in aqueous solution |
| 学位专业 | 环境科学 |
| 中文摘要 | 石墨烯纳米材料是近年来兴起的一种二维碳纳米材料，由于其大的比表面积和强的可修饰能力，在环境领域中主要被用作吸附剂或催化剂的载体，富集或去除环境中的污染物。但是随着研究的不断深入，人们逐渐发现石墨烯纳米材料除了能够强烈地吸附污染物外，其本身也具有催化活性，可以使一些被吸附的污染物发生转化与降解，从而改变它们在自然界中的赋存形态和环境行为。这种现象的存在一方面会导致石墨烯纳米材料的吸附实验数据出现偏差，另一方面也会给石墨烯纳米材料的应用和环境风险评价带来不确定因素。但由于石墨烯纳米材料出现的时间较晚，目前关于自然环境中石墨烯纳米材料促进有机污染物降解的研究还非常少。 本论文采用Hummers和热还原的方法分别制备了氧化石墨烯和石墨烯。利用批实验方法研究了它们对几种酚类污染物转化与降解行为的影响。通过污染物性质的对比、溶解氧实验和电子顺磁共振光谱，初步总结出了石墨烯纳米材料促进酚类污染物转化与降解的规律，并探讨了产生这种现象的微观机理。本论文主要取得了以下研究成果： 1. 考察了对苯二酚在石墨烯上的转化与降解行为，结果显示石墨烯可以显著促进对苯二酚转化成对苯醌。36 h内对苯二酚的降解率为76 %，其降解动力学符合拟一级动力学方程。石墨烯的浓度和溶液pH值都会影响对苯二酚的降解。石墨烯的活性边缘和缺陷位点以及其优良的电子传递能力是导致对苯二酚降解的关键因素，溶解氧可以与石墨烯的边缘和缺陷位点作用生成活性氧中间体，这些活性氧中间体与对苯二酚反应生成半醌自由基，半醌自由基则进一步与溶解氧反应生成对苯醌； 2. 酚类污染物在石墨烯上氧化降解的难易程度与其取代基团的电子效应密切相关。所选五种酚类污染物在石墨烯上降解从易到难的顺序为：4-甲氧基酚 > 4-甲基酚 > 苯酚 > 4-氯酚 > 4-硝基酚。由于酚的氧化反应是一个失电子过程，因此取代基的供电子能力越强，酚类污染物越容易被氧化降解；反之，如果取代基的吸电子能力越强，酚类污染物越难被氧化降解。该降解顺序与这些酚类污染物Hammett常数的大小呈负相关关系，因此Hammett常数可以作为 一个指示因子来反映酚类污染物的降解趋势。另外，环境中的Fe3+ 与石墨烯存在协同作用，它能显著促进五种酚类化合物在石墨烯上的降解。 |
| 英文摘要 | Graphene is an ideal two-dimensional structural carbonaceous material with thickness of only one atomic layer. Due to their large theoretical specific surface area and high ability of modification, potential environmental applications of graphene-based nanomaterials (GBNs) as superior adsorbents have been realized for removal of organic and inorganic contaminants from environment. To our knowledge, few people recognized the fact that GBNs can accelerate the transformation or degradation of some organic contaminants in the adsorption process. But relative knowledge is very important for the risk assessment of both GBNs and organic contaminants in the environment. In this dissertation, we prepared reduced graphene oxide (rGO) by thermal exfoliation/reduction. Then the mediation effect of rGO on the oxidative transformation of 1,4-hydroquinone (H2Q) and other five phenolics in aqueous solution were investigated using a batch method. Combined with dissolved oxygen experiments and electron paramagnetic resonance (EPR), we revealed the mechanisms of rGO in accelerating the oxidation of several phenolics. The main conclusions of this dissertation included: 1. It is found that the presence of rGO can mediate the transformation of H2Q in aqueous solution. In the presence of 33.3 mg L-1 rGO, more than 76.0 % of H2Q was oxidized to 1,4-benzoquinone (BQ) within 36 h. The degradation kinetics fitted the pseudo-first order kinetic model well. Both rGO concentration and solution pH will affect the oxidation efficiency of H2Q. The strong mediation efficiency of rGO can be attributed to the combined contribution of the high chemical reactivity of graphenic zigzag edges and defects on rGO and the high electron conductivity of graphene basal surface of rGO. Dissolved oxygen can react with graphenic edges and defects of rGO to produce surface-bound oxygen intermediates, which facilitated the generation of semiquinone radical (SQ●―). The generated SQ●― continued to react with molecularoxygen to yield BQ. 2. The degradation behavior of five phenolics in rGO system significantly depended on the electronic effect of their substituted groups. The degradation trend of five phenolics decreased in the order: 4-methoxyphenol > 4-methylphenol > phenol > 4-chlorophenol > 4-nitrophenol. It was shown that the stronger of electron-donoring of the substituted group, the easier of the phenolic compound to degrade, and vice versa. This trend was negatively related to the Hammett constants of these phenolics. In addition, the presence of Fe3+ can dramatically accelerate the degradation of phenolics in rGO system. |
| 源URL | [http://ir.rcees.ac.cn/handle/311016/34336]  |
| 专题 | 生态环境研究中心_环境化学与生态毒理学国家重点实验室 |
| 推荐引用方式 GB/T 7714 | 李春梅. 水溶液中几种酚类污染物在石墨烯上的转化与降解行为研究[D]. 北京. 中国科学院研究生院. 2015. |
入库方式： OAI收割
来源：生态环境研究中心
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