| 题名 | 可溶性有机质在石墨烯纳米材料上的吸附特征及其对重金属Cr3+和Cu2+吸附影响的研究 |
| 作者 | 杨爽 |
| 学位类别 | 硕士 |
| 答辩日期 | 2014-05 |
| 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 氧化石墨烯 可溶性有机质 吸附 Cr3+ Cu2+ Graphene Graphene oxide Dissolved organic matter Adsorption Cr3+ Cu2+ |
| 其他题名 | Interaction of dissolved organic matter with graphene-based nanomaterials and subsequent effects on heavy metal Cr3+ and Cu2+ adsorption |
| 学位专业 | 环境科学 |
| 中文摘要 | 石墨烯是具有单原子厚度的碳的二维晶体，由于其比表面积较大和可修饰能力较强，在环境领域中石墨烯纳米材料通常被用作吸附剂来去除环境中的污染物。此外自然界中可溶性有机质是无处不在的，它们不但可以和石墨烯纳米材料相互作用，改变其部分物理化学性质，而且还可以和重金属离子键合，改变它们在石墨烯纳米材料表面的吸附行为。因此研究可溶性有机质在石墨烯纳米材料表面的吸附特征及其对共存重金属离子吸附的影响，对正确认识石墨烯纳米材料和重金属的环境行为具有较强的理论和实践意义。 本论文选用性质差别比较大的石墨烯和氧化石墨烯作为研究对象，利用批平衡吸附方法，研究了可溶性有机质（胡敏酸和富里酸）在吸附剂上的吸附特征及其对重金属离子（Cr3+和Cu2+）吸附行为的影响，运用大量微观表征方法如傅立叶变换红外光谱（FTIR）和扩展X-射线吸收精细结构光谱（EXAFS）等技术，在分子水平上讨论了可溶性有机质、重金属在石墨烯纳米材料上的吸附位点和配位环境，探讨了可溶性有机质影响重金属离子在石墨烯纳米材料表面吸附行为的机理。论文取得了以下研究成果： 1.由于石墨烯和氧化石墨烯的结构和性质差异，可溶性有机质（胡敏酸和富里酸）在石墨烯和氧化石墨烯上的吸附机理不尽相同。其中可溶性有机质主要通过π-π共轭作用吸附在石墨烯表面，而在氧化石墨烯的表面则是主要通过含氧官能团之间的极性作用进行吸附的。 2.Cr3+在氧化石墨烯纳米材料上的吸附能够很快达到表观吸附平衡。Cr3+的吸附动力学更符合拟二级动力学，而吸附等温线符合Langmuir模型。实验结果表明，Cr3+在氧化石墨烯上的吸附是自发的吸热反应。Cr3+在氧化石墨烯上的吸附几乎不受溶液离子强度影响和胡敏酸的影响，而是主要取决于溶液pH。红外光谱表明Cr3+主要与氧化石墨烯表面的含氧基团键合。 3.胡敏酸的存在促进了Cu2+在石墨烯上的吸附。吸附胡敏酸后，增加了石墨烯表面含氧官能团和负电荷的数量，使得Cu2+可以通过化学络合和静电吸附的方式吸附于石墨烯的表面，因此促进了Cu2+的吸附。胡敏酸的存在对于Cu2+在氧化石墨烯上的吸附影响很小。这是由于胡敏酸主要通过极性作用吸附于氧化石墨烯的表面，胡敏酸在遮蔽氧化石墨烯表面极性吸附位点的同时，也给氧化石墨烯带去了大量的含氧官能团。两者相抵，最终对Cu2+的吸附有很小的影响。 4.扩展X-射线吸收精细结构光谱表明，Cu2+在石墨烯和氧化石墨烯上主要通过含氧官能团的极性作用进行吸附。与氧化石墨烯相比，石墨烯表面含氧基团数量较少，因此在pH = 8.0时，部分Cu2+在石墨烯表面形成沉淀，而在氧化石墨烯的表面则还是以吸附为主。胡敏酸存在条件下， Cu2+主要吸附在石墨烯表面包裹的胡敏酸上。当pH = 8.0时，胡敏酸的存在则使得Cu2+在石墨烯的表面形成了石墨烯-胡敏酸-铜的三元表面络合物。 |
| 英文摘要 | Graphene (G) 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 recognized for removal of organic and inorganic contaminants from environment. Dissolved organic materials (DOM) are ubiquitous in natural waters and have been found to interact with nanomaterials in the environment. The interactions between DOM and nanomaterials not only alter the surface properties and environmental behavior of these nanomaterials, but also affect the adsorption of coexisting contaminants. Therefore, it is necessary to study the interactions between DOM and GBNs with different structures and properties, and to examine their effects on the adsorption of coexisting contaminants. In this dissertation, we choose G and graphene oxide (GO) with different π-electron density and O-containing functional groups as adsorbents to examine the interactions of DOM (humic acid (HA) and fulvic acid (FA)) with G and GO and their effects on the adsorption of metal ions (Cr3+ and Cu2+) using a batch equilibration technique. Combined with X-ray photoelectron spectroscopy, Raman spectroscopy, micro-Fourier transform infrared spectroscopy and extended edge X-ray adsorption fine structure spectroscopy, we reveal the mechanisms of DOM adsorption and sequent effects on heavy metals adsorption on G and GO. The main conclusions of this dissertation included: 1. It is found that DOM is adsorbed on G and GO through different adsorption mechanisms due to the property difference between G and GO. Except for hydrophobic partition interaction, DOM is adsorbed on G mainly through π-π interaction. In contrast, DOM is adsorbed on GO surface mainly through polar interactions due to its rich O-containing functional groups. 2. The adsorption of Cr3+ on GO is a rapid process. The adsorption kinetic data were well described with pseudo-second-order model and the equilibrium data were well fitted by Langmuir model. The calculated thermodynamic parameters indicate that the adsorption of Cr3+ on GO is spontaneous and endothermic. It is found that Cr3+ adsorption on GO is strongly dependent on solution pH, but weakly dependent on ionic strength. Fourier transform infrared spectra suggest that Cr3+ is adsorbed on GO mainly through the formation of inner-sphere complexes with the O-containing functional groups on GO surface. 3. The presence of HA increases the adsorption of Cu2+ on G significantly. It is because the adsorbed HA introduced O-containing functional groups and negative charges to G surfaces, increasing Cu2+ adsorption through chemical complexation and electrostatic attraction. Compared to G, the adsorbed HA had little effect on Cu2+ adsorption onto GO. HA was adsorbed on GO through polar interactions. On the one hand, these adsorbed HA shielded the surface of GO and occupied parts of surface sites on GO, which would decrease the adsorption of Cu2+. On the other hand, the adsorbed HA can introduce new adsorption sites for Cu2+ adsorption onto the GO surface. The combined result is that the adsorption of Cu2+ is independent on the presence of HA. 4. EXAFS results suggest that O-containing functional groups of G and GO are the main adsorption sites for Cu2+. Compared to GO, G has fewer O-containing functional groups on its surfaces, which led to a portion of Cu2+ precipitate on G surfaces at pH 8.0. The addition of HA increased the amount of adsorption sites on G, causing most of Cu2+ to be adsorbed on G surfaces as G-HA-Cu ternary surface complexes at the examined pH range. |
| 公开日期 | 2015-06-15 |
| 内容类型 | 学位论文 |
| 源URL | [http://ir.rcees.ac.cn/handle/311016/13463]  |
| 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 | 杨爽. 可溶性有机质在石墨烯纳米材料上的吸附特征及其对重金属Cr3+和Cu2+吸附影响的研究[D]. 北京. 中国科学院研究生院. 2014. |
| 个性服务 |
| 查看访问统计 |
| 相关权益政策 |
| 暂无数据 |
| 收藏/分享 |
除非特别说明，本系统中所有内容都受版权保护，并保留所有权利。
修改评论