类沸石咪唑骨架材料吸附去除水中砷锑污染物性能与机制研究
文献类型：学位论文
| 作者 | 刘豹 |
| 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 | 刘锐平 ; 张西旺 |
| 关键词 | 类沸石咪唑骨架材料，砷，锑，吸附，竞争吸附，Zeolitic imidazolate framework-8，arsenic, antimony, adsorption, competitive adsorption. |
| 其他题名 | Adsorption behaviors and mechanisms of arsenic and antimony on Zeolitic Imidazolate Frameworks |
| 学位专业 | 环境工程 |
| 中文摘要 | 砷和锑在元素周期表中同属于第 VA主族，具有相似的化学性质和生理毒性。砷在地壳中的丰度要远高于锑且分布更为广泛，砷污染较锑污染更为普遍更加严峻，因此长期以来对砷污染及其控制技术的研究远多于锑。我国不少省区存在较为严重的锑污染。事实上，我国锑矿已探明储量位居世界第一（70%以上），而被称为“世界锑都”的湖南冷水江市年锑产量占全球 60%，这导致资江沿线不少城镇存在饮用水源锑超标问题。进一步地，由于砷锑往往会在矿物晶相中共存，在锑矿开采过程中可能导致砷锑共存污染。研究开发除砷除锑新材料是推进砷锑污染控制技术发展的重要方向。 类沸石咪唑骨架材料（ZIFs）是一种由金属原子和咪唑配体杂化而成、具有与沸石相似结构的多维金属有机骨架材料。ZIFs具有开放的孔道、可调节的内表面性质和结构、巨大的比表面积、丰富的表面活性位点，这使得其在气体分离、催化、吸附等领域具有良好的应用前景，并成为近年来的研究热点。本文围绕砷锑污染控制问题，以稳定性较好的 ZIF-8为对象，研究并优化其在水中的制备工艺方法、形貌转化过程，并在此基础上系统研究其吸附砷锑性能与机理。 为优化 ZIF-8制备工艺、减少原料消耗、降低制备成本，本研究实现了在不添加任何模板剂、且较低的咪唑消耗条件下 ZIF-8晶体的成功制备。研究结果表明，2-甲基咪唑(2-Hmim)分子的脱质子化是影响 ZIF-8结构生成的关键，而成核速率则影响着颗粒的尺寸；采用 Zn(OAc)2作为 Zn源合成ZIF-8时，CH3COO能够竞争配位部分的Zn2+、降低成核速率，从而获得尺寸较大、晶型较好的菱形十二面体 ZIF-8。对比而言，采用 Zn(NO3)2、ZnCl2和 ZnI2作为前驱体时得到的 ZIF-8形貌较差，尺寸也比较小。此外，水的比例对 ZIF-8形貌形成也有显著影响，最佳的 Zn：Hmim：H2O比为 1：10：310。 分别制备了立方体状 ZIF-8（C-ZIF-8）、叶片状 ZIF-8（L-ZIF-8）和十二面体 ZIF-8（D-ZIF-8）等三种形貌各异的 ZIF-8，研究其对水中 As(III)的吸附性能。结果表明,ZIF-8的表面形貌、比表面积等特性对其吸附As(III)的性能影响不大。C-ZIF-8、L-ZIF-8和D-ZIF-8的比表面积分别为958.4，12.7和1151.2m2 /g，而对 As(III)的最大吸附容量分别为 122.6，108.1和117.5 mg/g。FTIR和XPS分析显示，As(III)在 ZIF-8表面主要与 Zn-OH结合，而 Zn-OH可通过表面未饱和配位的 Z原子或者断裂的 Zn-N基团进行补充。此外，D-ZIF-8对As(V)同样表现出良好的吸附性能，在 5min内可将 As(III)和 As(V)浓度从初始200μg/L降低至10 μg/L以下，显示其卓越的除砷性能和潜在的应用前景。水中常见的阴离子对 ZIF-8除砷性能有一定影响，且影响程度大小排序依次为磷酸根>碳酸根>硫酸根。 D-ZIF-8对Sb(V)也具有良好的吸附性能，最大吸附容量为 0.86 mmol/g，远高于国内外报导的铁基、铝基金属（复合）氧化物。pH值对Sb(V)在ZIF-8表面的吸附有明显影响；此外，对于砷锑共存体系，As(III)或 As(V)也会对Sb(V)的吸附产生明显抑制作用。在较低 pH条件下，随着吸附时间的延长，在吸附后期 Sb(V)可置换出部分已吸附在 ZIF-8表面的砷。此外，吸附质引入先后顺序会对 As与 Sb(V)之间的竞争吸附产生显著的影响：优先吸附的污染物可在ZIF-8上形成稳定的结构，并抑制后续引入污染物的吸附。FTIR分析显示，Sb(V)、As(III)和 As(V)的吸附都是与 ZIF-8结构中的锌原子结合，彼此之间竞争配位体从而表现出竞争吸附作用。 |
| 英文摘要 | Arsenic (As) and antimony (Sb) are metalloids belonging to VA in periodic table, and exhibit similarity in chemical and bio-accessibility in environment. However, in the past decade, much more attention has been attributed to As pollution than that of Sb,for its greater abundance and mobility in earth crust. Antimony pollution is very serious in many provinces in China. In fact, China occupied the world first on the antimony ore (more than 70%). In addition, Lengshuijiang City in Hunan which is famous for the “Capital of Antimony” occupies more than 60% of the antimony,leading to excess of antimony in the water of the Zijiang river. Furthermore, owing to the As and Sb are always intergrowth, co-pollution of As and Sb are observed in some Sb mining areas. Thus, the development of new materials for As and Sb removal plays vital roles on the control of As and Sb pollution. Zeolitic imidazolate frameworks (ZIFs), are subclass of the metal organic frameworks (MOFs), which are characterized by the resemble zeolite structure combined by metal atom and imidazole ligand. ZIFs are widely investigated and applied in gas separation,catalysis and adsorption for its opening porous structure, adjustable inner surface properties and structure and high surface area. In this pare, we investigated the synthesized method and mechanism of a kind of water stable ZIF-8, and focused on the adsorption behavior and mechanism of arsenic and antimony on the synthesized ZIF-8. In order to optimize the synthesis of ZIF-8, reduce the consumption of raw materials,lower the cost, the high crystallized ZIF-8 was successfully synthesized in aqueous solution via a green method at lower consume of imidazole without ant addition of modulates. The results shows that the deprotonating of 2-methylimidazole (2-Hmim)is the key of formation of ZIF-8 structure, while the particle size is influenced by the nucleation rate. When Zn(OAc)2 was adapted as zinc source, a part of Zn2+ was coordinated by the CH3COO- competitively, thus lowering the nucleation rate, leading to a high crystallized rhombic dodecahedral ZIF-8 with perfect morphology and large size. However, when the Zn(NO3)2、ZnCl2 and ZnI2 were used as precusor, poorly crystallized products were obtained. In addition, the ratio of water also plays an important role on formation of ZIF-8 and the best Zn/Hmim/H2O ratio was determined to 1/10/310. The morphology and surface are found to exert limited effects on adsorption of As(III) on ZIF-8 based on the capacities and vilocity. The ZIFs are all high crystalline, and with a BET surface area of 958.4, 12.7 and 1151.2 m2/g for cubic ZIF-8(C-ZIF-8),leaf-shaped ZIF-8(L-ZIF-8) and dodecahedral ZIF-8(D-ZIF-8), respectively while maximum adsorption capacities were 122.6, 108.1, 117.5 mg/g fitted by Langmuir model, respectively at pH 8.5. FTIR and XPS results indicate that As(III) species was combined with the Zn-OH on the surface of ZIF-8, which can be generated from unsaturated zinc atom and supplied by the broking of Zn-N. In addition, ZIF-8 shows considerable adsorption abilities towards As(V). As(III) and As(V) rapidly decreased to below 10 µg/L within 5min in water by the D-ZIF-8 at initial concentration of 200 µg/L, indicating a promising future in water treatment. The order of effect of anions on As adsorption by ZIF-8 is determined to phosphate > carbonate > sulfate. The maximum adsorption of Sb(V) on ZIF-8 was determined to be 0.86 mmol/g,which is competitive to many other metal based adsorbents. The adsorption of Sb(V)on ZIF-8 is pH depended and greatly influenced by the existence of As(III) and As(V). However, Sb(V) could partly replace the As(III) or As(V) species at low pH and initial As concentrations at an extend time in As-Sb coexistence system. Moreover, the adsorption also can be affected by the adsorption sequence. Generally, the prior adsorbed species could occupied the active sites strongly, then inhibit the latter species, i.e., The ZIF-8 with previously-adsorbed Sb(V) also showed remarkably decreased efficacy towards As(III) and As(V). QAs(III) and QAs(V) were respectively determined to be as low as 0.13 and 0.19 mmol/g. FTIR analysis indicates that the zinc hydroxyl group on ZIF-8 dominates in the adsorption of As(III), As(V), and Sb(V) These results shows that competitive adsorption should be well considered to achieve the simultaneous removal. |
| 源URL | [http://ir.rcees.ac.cn/handle/311016/34347]  |
| 专题 | 生态环境研究中心_环境水质学国家重点实验室 |
| 推荐引用方式 GB/T 7714 | 刘豹. 类沸石咪唑骨架材料吸附去除水中砷锑污染物性能与机制研究[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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