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题名: 溶解性有机质对纳米二氧化硅颗粒溶液稳定性和吸附金属离子特性的影响
作者: 梁亮
学位类别: 博士
答辩日期: 2011
授予单位: 中国科学院研究生院
授予地点: 北京
导师: 张淑贞
关键词: 纳米二氧化硅 ; Nano SiO2 ; 溶解性有机质 ; Dissolved organic matter ; 吸附 ; Adsorption ; 金属阳离子 ; Metal cations ; 集聚 ; Aggregation
其他题名: The interaction of nano-SiO2 with dissolved organic matter (DOM) and its effect on the nano-SiO2 stability and metal adsorption
中文摘要:
      纳米二氧化硅是当今世界生产和应用规模最大的一种工业纳米材料。由于其尺寸极小,因而具有极大的比表面积和众多的活性点位,极易与环境中广泛存在的溶解性有机质结合,影响纳米颗粒的性质和环境行为。 本论文研究了不同粒径纳米二氧化硅颗粒对溶解性有机质的吸附解吸、影响因素和作用机理。在此基础上,考察了纳米颗粒在不同电解质条件下的集聚动力学。运用X-射线精细结构光谱等现代光谱学手段,探讨了纳米颗粒与重金属元素间的界面反应和溶解性有机质对反应的影响。获得了如下主要研究成果: 1. 以三种不同粒径的二氧化硅颗粒为吸附剂,研究了其对胡敏酸和富里酸的吸附解吸特性。研究发现,三种粒径的颗粒对胡敏酸和富里酸的吸附动力学行为表现出很大的相似性,拟二级动力学方程可以较好的拟合吸附动力学实验数据。Langmuir吸附模型可以较好的拟合等温吸附的实验数据,结果表明,20nm的二氧化硅颗粒对胡敏酸和富里酸的吸附容量远大于其他两种粒径颗粒的吸附容量;二氧化硅颗粒对胡敏酸的吸附量大于对富里酸的吸附量。随着pH值的增加,二氧化硅颗粒对胡敏酸和富里酸的吸附量都呈下降趋势,尤其是对胡敏酸吸附的影响更为明显。值得注意的是,当离子强度较高时,二氧化硅颗粒对胡敏酸的吸附量大大提高而对富里酸的吸附量无显著地影响。进一步结合电位和傅里叶红外光谱的实验结果,可以推断,二氧化硅颗粒,尤其是粒径较小的20nm的颗粒可能是通过阳离子键桥的作用与胡敏酸和富里酸发生吸附反应。对胡敏酸和富里酸的解吸实验表明,吸附反应表现出了明显的解吸滞后效应,且胡敏酸比富里酸更难于解吸。 2. 采用时间分辨动力光散射方法对纳米二氧化硅颗粒在不同电解质溶液中的集聚动力学行为进行了研究,考察了pH值(2-9)、电解质种类(10-400mmol/L的NaNO3和0.2-5mmol/L Ca(NO3)2)和腐殖酸吸附对集聚行为的影响。研究表明,纳米颗粒的稳定性随体系pH值的增长而极大地提高。以NaNO3为背景电解质时,纳米颗粒的临界集聚浓度远大于以Ca(NO3)2为背景电解质时的浓度。实验还发现,由于被吸附的腐殖酸分子间的空间位阻作用力,胡敏酸能极大地提高纳米颗粒在一价电解质溶液中的悬浮稳定性。但由于高价态的钙离子可能与胡敏酸分子发生了络合作用,破坏了胡敏酸分子间的空间位阻作用。胡敏酸的吸附对纳米颗粒在二价电解质溶液中的稳定性没有明显影响。本部分研究的结果对于控制纳米颗粒在电解质溶液中的集聚行为具有一定的参考意义。 3.探讨了吸附/未吸附富里酸和胡敏酸的纳米二氧化硅颗粒与重金属元素Cu、Pb和Zn的界面反应过程。研究发现,吸附和未吸附腐殖酸的纳米颗粒对Cu、Pb和Zn的吸附反应都进行的非常迅速,拟二级动力学方程可以较好的描述吸附动力学实验数据。等温吸附的实验数据可以用Langmuir模型较好的拟合,其结果表明,吸附了腐殖酸,尤其是吸附了胡敏酸后,纳米颗粒对金属离子的亲和力有了显著地提高,饱和吸附量大大提升;对三种重金属离子吸附量的大小顺序遵循:Pb>Cu>Zn。进一步结合离子强度效应、傅里叶红外光谱和X-射线精细结构光谱等手段的结果,研究发现,重金属离子与纳米二氧化硅颗粒吸附生成内层配合物;在吸附样品的第一壳层,金属原子与氧原子结合。纳米二氧化硅颗粒在吸附富里酸或胡敏酸后,吸附样品第一壳层中金属原子仍然是与氧原子结合,但第二壳层配位情况发生了变化。未吸附时,金属离子与表面的硅原子结合,吸附后,金属离子与颗粒表面吸附的来自于腐殖酸的含碳有机官能团中的碳原子结合。研究证明,富里酸或胡敏酸在纳米颗粒上的吸附能显著改变颗粒对金属离子的吸附能力和吸附机理,从而影响这些物质在自然环境中的行为。
英文摘要:       Nanoparticles are a new group of materials with rapidly growing production and application. Owing to their extremely small size, nanoparticles have a much greater surface area and abundant surface reactive sites, which make them highly reactive to dissolved organic matter (DOM) and thereby inevitably change the properties and behaviors of the nanoparticles in the environment. In this dissertation, the adsorption and desorption of DOM on SiO2 particles in size of 20, 100 and 500 nm were investigated. Meanwhile, a time-resolved dynamic light scattering (DLS) was used to examine the aggregation behaviors of SiO2 particles with the effect of DOM adsorption. Furthermore, influences of surface coated fulvic acid (FA) and humic acid (HA) on the adsorption of metal cations of Cu(II), Pb(II) and Zn(II) on SiO2 nanoparticles were investigated. X-ray absorption spectroscopy (XAS) including X-ray absorption near-edge structure (XANES) and extended X-ray absorption fine-structure (EXAFS) spectroscopy was employed to interpret the coordination characteristics of metal cations adsorbed on SiO2 particles. The main experiments and conclusions are as follows: 1. The dsorption of HA and FA on SiO2 showed very similar kinetic behaviors for the different size particles. The pseudo-second-order equation fitted the adsorption kinetics much better than the pseudo-first-order equation for the adsorption. Meanwhile, the adsorption of HA and FA were fitted much better to Langmuir equation than Freundlich equation, particularly for the 20 nm SiO2 particles. It is interesting to note that the adsorption capacities of HA and FA were much higher for 20 nm particles than the other two sizes. On the other hand, adsorption of HA was much higher than FA adsorption on SiO2 particles. The adsorption of HA and FA decreased significantly with increasing pH and the trend was more obvious for HA. It is noteworthy that the influence of ionic strength was contrasting for HA and FA in their adsorption. The adsorption of HA was significantly higher at higher ionic strength, while no obvious difference was observed for FA adsorption between the two ionic strengths in the pH range investigated. It can be concluded with the FTIR results that, the strong adsorption of the HA and FA on the SiO2 particles could be attributed to the cation bridges. The desorbed amounts of both HA and FA were relatively small even after three desorption operations, and HA was more difficult to be desorbed than FA. 2. The stability of SiO2 nanoparticles in the presence of HA and different electrolytes (i.e., NaNO3 and Ca(NO3)2 ) was investigated and compared. An increase in solution pH from 2 to 9 resulted in a substantial decrease in nanoparticle aggregation kinetics. The critical coagulation concentration (CCC) of nanoparticle suspensions in NaNO3 background electrolyte was much higher than that in the Ca(NO3)2 solution. The presence of HA enhanced the stability of nanoparticles in NaNO3 solution, which can be ascribed to the reason that the adsorption of HA generated a greater steric repulsion and therefore, colloidal stability of the particles was markedly enhanced. However, the impact of HA on the aggregation of nanoparticles was negligible in the presence of Ca(NO3)2, possibly due to the complaxition of Ca2+ with HA which will eliminate the effects of HA adsorption on steric repulsion . 3. The influence of FA/HA on the interaction of heavy metals with nano-oxides was explored by examining and comparing the adsorption of metal cations Cu(II), Pb(II) and Zn(II) on nano-SiO2 and FA- and HA-coated nano-SiO2. The adsorption obviously entailed a very rapid process of about 30 min followed by a slow adsorption process. The adsorption data can be satisfactorily described by the pseudo-second-order kinetic model. The Langmuir model fit well with the equilibrium data either. The adsorption capacities exhibited the following sequence: Pb(II) > Cu(II) > Zn(II), and the FA/HA coated nanoparticles, particularly the SiO2-HA, exhibited higher adsorption capacities for the cations than the original SiO2 nanoparticles. With the results of XAS and Fourier Transform infrared spectroscopy (FTIR), it can be found that, inner-sphere complexation could be the adsorption mechanism for the metal cations. The XAS analysis indicated that, in the second shell of the adsorption samples, different from the direct bonding to SiO2 on the original nanoparticles, metal cations was adsorbed on FA/HA coated SiO2 through complexing with the hydroxyl moieties and organic functional groups of FA/HA as bridges.
内容类型: 学位论文
URI标识: http://ir.rcees.ac.cn/handle/311016/35084
Appears in Collections:环境化学与生态毒理学国家重点实验室_学位论文

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Recommended Citation:
梁亮. 溶解性有机质对纳米二氧化硅颗粒溶液稳定性和吸附金属离子特性的影响[D]. 北京. 中国科学院研究生院. 2011.
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