【作者】 高占明；

【导师】 邱介山；

【作者基本信息】 大连理工大学 ， 化学工艺， 2009， 博士

【摘要】 碳纳米管具有独特结构和性质，不仅在微电子元器件、场发射材料、催化等领域应用前景广阔，而且作为吸附材料在储氢、污染物消除等方面的应用潜能也值得关注。本文系统研究了碳纳米管及煤基微米碳纤维对水溶液中低浓度金属离子镉、铁、镍、铜、锌的吸附性能，考察了吸附时间、吸附温度、溶液pH值以及离子浓度等参数对吸附的影响，综合运用扫描电镜、透射电镜、液氮物理吸附、傅立叶变换红外光谱、X射线光电子能谱、电位滴定等技术手段研究碳纳米／微米吸附材料的结构及表面化学性质，将吸附材料的孔隙结构、表面物理化学性质与其吸附性能进行了关联，探讨了一维纳米材料碳纳米管吸附金属离子的热力学和动力学特征。考察了镉离子在电弧放电及化学气相沉积两种碳纳米管上的吸附特征。发现氧化处理对化学气相沉积制备的碳纳米管吸附能力有显著影响。镉离子在两种碳管上的吸附行为可用Langmuir和Freundlich模型进行描述。碳纳米管的吸附量对碳表面pH值呈指数关系。不同pH下的q_m和K_F对在对应pH值下解离的官能团数量呈线性关系。以单位比表面积为单位进行比较，氧化后两种碳纳米管的吸附能力高于活性炭。研究了化学气相沉积法制备的碳纳米管吸附Fe（Ⅱ）和Fe（Ⅲ）离子的行为发现pH值对Fe（Ⅲ）离子在碳纳米管上的吸附影响比Fe（Ⅱ）大。相同的平衡浓度下，碳管对Fe（Ⅲ）离子的吸附能力高于Fe（Ⅱ）。动力学研究表明，两种吸附质在碳纳米管上的吸附均可用准二级吸附动力学模型加以描述。热力学研究表明，Fe（Ⅱ）和Fe（Ⅲ）离子在氧化碳纳米管上吸附是一个自发的、吸热、熵增过程。研究了多组分体系中镍、铜、锌及镉离子在碳纳米管表面竞争吸附规律，发现对于单组分和双组分体系，吸附量遵从如下顺序：Cu²⁺>Ni²⁺>Cd²⁺>Zn²⁺；这和基于标准电极电势的离子氧化能力顺序一致。对于双组分、三组分和四组分体系，Langmuir模型可以较好地描述吸附剂对Cu²⁺离子的吸附行为，而对于其他三种离子，吸附量出现了极大值。在三组分和四组分体中，除了Cu²⁺离子外，其他三种离子的吸附量顺序如下：Cd²⁺>Zn²⁺>Ni²⁺。多组分体系竞争吸附规律与离子的氧化还原特性及离子交换密切相关。考察了煤基微米碳纤维吸附水溶液中镉离子的性能，研究表明氧化处理可大幅度增加煤基微米碳纤维的表面含氧官能团数量，其吸附能力和氧化前比增加显著。以单位重量和单位比表面积为基准进行比较，其吸附能力都很大，明显高于文献报道中的活性炭、甘蔗飞灰、碳纳米管等。动力学吸附数据遵从准二级速率方程。酸性条件下，等温吸附数据均能用Langmuir和Freundlich模型拟合，而沉淀发生条件下可用表面沉淀模型描述。更多还原

【Abstract】 Carbon nanotubes （CNTs）, with unique morphologies and surface characteristics not only have great potential applications in electronics, field emission materials, catalysis, but also are of potential in hydrogen storage or wastewater treatment. This dissertation focuses on the investigation of adsorption of cadmium, iron, nickel, copper, and zinc ions from low concentration solution on the CNTs and coal-derived micro-size carbon fibers （CCFs）. The effects of the adsorption time, temperature, pH value, and ion concentration on adsorption were investigated. A number of advanced techniques such as SEM, TEM, adsorption of nitrogen, FTIR, XPS, and potentiometric titration were used to characterize the structure and surface chemistry of adsorbents. The relationship between the surface properties of adsorbents and the adsorption capacity was analyzed. The kinetics and thermodynamics of adsorption were also studied.The comparative study of cadmium adsorption on different CNTs was carried out. Oxidation could significantly increase the cadmium adsorption capacity of the CNTs obtained from chemical vapor deposition （CVD） method. Both Langmuir and Freundlich models showed good agreement with the experimental data. The exponential relationship was found between the capacity of adsorbents for cadmium ions and their surface pH values, while the linear dependence was observed between the amounts adsorbed at certain pH on the number of groups dissociated at that pH. When the adsorption was analyzed based on the unit surface area of the adsorbents, the adsorption amounts were found to be comparable with those obtained on activated carbons.The adsorption of Fe （Ⅱ） and Fe （Ⅲ） ions using the oxidized CNTs obtained from CVD method was also studied. The results showed that the adsorption of Fe （Ⅲ） is more pH dependent than that of Fe （Ⅱ）. The uptakes of Fe （Ⅲ） at the same equilibrium concentration were higher than those of Fe （Ⅱ）. The study of kinetics showed that the pseudo-second-order kinetic adsorption model is suitable for describing the adsorption of Fe （Ⅱ） and Fe （Ⅲ） ions on the CNTs. The study of thermodynamics revealed that the adsorption process of Fe （Ⅱ） and Fe （Ⅲ） ions on the oxidized CNTs was spontaneous, endothermic and with an increase in entropy.The competitive adsorption of nickel, copper, zinc and cadmium ions from aqueous solutions was studied in single, binary, ternary and quaternary systems with the oxidized CNTs as an adsorbent. The uptakes in the single and binary systems at the same equilibrium concentration varied in the following order: Cu²⁺（aq） > Ni²⁺（aq） > Cd²⁺（aq） > Zn²⁺（aq）. This order agreed with that of oxidation ability of ions based on the standard electrode potential. For the binary, ternary and quaternary system, the isotherms of the copper ions followed the Langmuir model while for the isotherms of other ions, a decrease in the amount adsorbed was observed at certain concentration. For the ternary and quaternary system, except copper ions, the order in the amount adsorbed was following: Cd²⁺（aq） > Zn²⁺（aq） > Ni²⁺（aq）. This particular behavior can be related to the complex redox properties and ion exchange processes.CCFs were also used to remove cadmium ions from the aqueous solution. Oxidation introduced a large quantity of functional groups which caused a remarkable increase in adsorption capacity. If compared based on the unit weight and the unit surface area, the adsorption ability of oxidized CCFs was higher than that of activated carbon, bagasse fly ash and carbon nanotubes reported in literature. The kinetic study showed that the adsorption followed the pseudo-second order kinetic adsorption model. Both Langmuir and Freundlich models described the adsorption isotherms well at pH<7.00, while the surface precipitation model showed good agreement with the experiment data when deposition occurred.更多还原