碳纳米管吸附海水中氯化盐的理论计算研究

发布时间：2018-04-26 21:29

本文选题：碳纳米管 + 吸附　；参考：《中国海洋大学》2014年博士论文

【摘要】：纳米材料领域的研究热点——碳纳米管，因其特有的一维几何结构，具有独特的物理化学性能，其对金属的吸附在能源和水资源等领域具有广阔的应用前景，吸引了很多研究者的关注。本论文运用第一性原理计算方法研究了碳纳米管对碱土金属原子、碱金属氯化物及碱土金属氯化物的吸附特性，分析了吸附的机理，得到了如下主要结果： 1．碳纳米管对碱土金属原子的吸附。碳纳米管对碱土金属原子的吸附主要依赖于碳纳米管的手性、位置以及碱土金属的特性。完整盖帽的(9,0)碳纳米管对碱土金属的吸附能大于完整盖帽的(5,5)碳纳米管对碱土金属的吸附能。碱土金属原子在碳纳米管五元环和六元环两个位置处的吸附存在明显的不同，碱土金属原子在六元环上的吸附能明显大于在五元环上的数值，并与碳纳米管的手性无关。碳纳米管吸附碱土金属原子后功函数明显降低，并与被吸附碱土金属原子的电负性成线性关系。碱土金属原子的电负性越大，吸附后碳纳米管功函数降低的越小。碳纳米管的功函数可以通过其吸附不同金属原子来进行调控。 2．碳纳米管对碱土金属氯化物、碱金属氯化物的吸附。碳纳米管对碱土金属氯化物、碱金属氯化物的吸附能小于600meV，属于物理吸附。吸附能大小主要与氯化物的电偶极矩、吸附距离两个参量有关，同族金属氯化物的吸附能和偶极矩与吸附距离的平方之比成线性关系。利用差分电荷密度、态密度和Bader电荷分析了碳纳米管与金属氯化物间的吸附机理，两者之间并没有发生电荷的转移，，吸附主要是通过偶极相互作用来完成的。 3．水分子对碳纳米管吸附金属氯化物的影响。碳纳米管基本不吸附水分子，因此在氯化物与水分子共存的环境中，碳纳米管将优先吸附氯化物；吸附了金属氯化物的碳纳米管对水分子的吸附能明显增大，说明金属氯化物修饰后的碳纳米管与水分子相互作用增强。这一结果对碳纳米管应用于海水资源提取提供了理论依据。
[Abstract]:Carbon nanotubes (CNTs), a research hotspot in the field of nanomaterials, have unique physical and chemical properties because of their unique one-dimensional geometry. The adsorption of metals on carbon nanotubes has a broad application prospect in the fields of energy and water resources. It has attracted the attention of many researchers. In this paper, the adsorption characteristics of alkali earth metal atom, alkali metal chloride and alkali earth metal chloride were studied by first principle calculation method. The adsorption mechanism was analyzed and the main results were obtained as follows: 1. Adsorption of alkali earth metal atoms by carbon nanotubes. The adsorption of alkali earth metal atoms by carbon nanotubes mainly depends on the chirality, location and characteristics of alkali earth metals. The adsorption energy of carbon nanotubes to alkaline earth metals is higher than that of complete capped carbon nanotubes to alkaline earth metals. The adsorption energy of alkali earth metal atom on the six-member ring is higher than that on the five-member ring, and it is independent of the chirality of carbon nanotube. The work function of carbon nanotubes after adsorption of alkali earth metal atoms decreases obviously and is linearly related to the electronegativity of the adsorbed alkali earth metal atoms. The larger the electronegativity of alkali earth metal atoms, the smaller the work function of carbon nanotubes after adsorption. The work function of carbon nanotubes can be regulated by their adsorption of different metal atoms. 2. Adsorption of Alkali Earth Metal Chloride and Alkali Metal Chloride by carbon Nanotubes. The adsorption energy of alkali earth metal chloride and alkali metal chloride by carbon nanotubes is less than 600meV, so it belongs to physical adsorption. The adsorption energy is mainly related to the electric dipole moment and the adsorption distance of chloride, and the adsorption energy and the ratio of dipole moment to square of adsorption distance are linear. The adsorption mechanism between carbon nanotubes and metal chloride was analyzed by differential charge density, density of states and Bader charge. There was no charge transfer between them. The adsorption was mainly accomplished by dipole interaction. 3. Effects of Water molecules on adsorption of Metal Chloride by carbon Nanotubes. Carbon nanotubes do not adsorb water molecules, so carbon nanotubes will preferentially adsorb chlorides in the presence of chloride and water molecules, and carbon nanotubes that adsorb metal chlorides have a significantly higher adsorption energy for water molecules. The results show that the interaction between carbon nanotubes modified by metal chloride and water molecules is enhanced. This result provides a theoretical basis for the application of Yu Hai in the extraction of water resources in carbon nanotubes (CNTs).
【学位授予单位】：中国海洋大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：P746

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