纳米铁与天然有机质相互作用研究

发布时间：2018-06-10 20:40

本文选题：纳米零价铁 + 天然有机质　；参考：《中国地质大学(北京)》2017年硕士论文

【摘要】：纳米零价铁(nano zero valent iron,nZVI)原位注射是近年用于地下水污染修复的新技术,天然有机质(natural organic matter,NOM)是水体中普遍存在的一种有机大分子混合物。应用纳米铁处理水体污染时,NOM会与其相互作用,导致纳米铁的一些物理性质如分散性、稳定性和团聚效应等发生改变,从而影响其迁移性及对污染物降解的能力,其活性与归宿行为也将受到NOM的影响。然而目前有关NOM对纳米铁性质,尤其是团聚效应的定量研究还鲜有报道。另外,NOM作为不均一混合物,会被纳米零价铁选择性吸附,而不同分子量组分所具有的化学性质也不同,因而在实际应用中会影响纳米铁的行为和使用效果。本文通过研究NOM对纳米铁性质的影响,并探讨相互作用机理,获得主要成果如下:1、相比于液相还原法制得的普通纳米零价铁,羧甲基纤维素包覆或膨润土负载改性使得纳米铁颗粒的分散稳定性提高,有效抑制了团聚和沉降。天然有机质腐殖酸HA会吸附在纳米铁颗粒表面,从而增加静电排斥力,提高了分散性,减缓了团聚效应。其中,HA对膨润土负载纳米零价铁的影响最为显著,其团聚体粒径能降至100 nm以下,沉降速率也极大减缓,分散稳定性表现最佳。2、两种天然有机质SRHA和SRFA在纳米零价铁与纳米四氧化三铁表面的吸附过程符合准二级吸附反应动力学;热力学Langmuir等温吸附过程可以很好的拟合吸附过程。纳米零价铁的对NOM的吸附能力要强于纳米四氧化三铁(最大吸附量约是三倍的关系)。造成吸附量差异之大的原因是两种纳米铁的表面性质不同,这也说明纳米零价铁表面不是致密的四氧化三铁。3、纳米零价铁对SRHA中间组分优先吸附,而对SRFA的大组分优先吸附,这种不同的选择性吸附现象很可能与其不同分子量组分的芳香性以及疏水性有关。相关认识在实际应用纳米零价铁修复时有重要参考意义。
[Abstract]:Nano zero valent ironn ZVI in situ injection is a new technique used in groundwater remediation in recent years. Natural organic matterNOM) is a common organic macromolecule mixture in water. NOM interacts with nano-iron when it is used to treat water pollution, which results in changes of physical properties such as dispersion, stability and agglomeration, thus affecting its mobility and ability to degrade pollutants. Its activity and fate behavior will also be affected by NOM. However, there are few reports on the quantitative study of nano-iron properties, especially the agglomeration effect of NOM. In addition, as a heterogeneous mixture, NOM can be selectively adsorbed by nanometer zero-valent iron, and the chemical properties of different molecular weight components are also different, so it will affect the behavior and application effect of nano-iron in practical application. In this paper, we studied the effect of NOM on the properties of nanometer iron and discussed the mechanism of interaction. The main results are as follows: 1, compared with ordinary nanometer zero-valent iron prepared by liquid-phase reduction method. Carboxymethyl cellulose coating or bentonite modification improved the dispersion stability of iron nanoparticles and effectively inhibited agglomeration and sedimentation. Humic acid HA of natural organic matter is adsorbed on the surface of iron nanoparticles, which increases electrostatic repulsion, improves dispersity and slows down the agglomeration effect. The effect of HA on bentonite supported iron nanoparticles is most significant. The particle size of the agglomerates can be reduced to less than 100 nm, and the sedimentation rate is also greatly slowed down. The adsorption process of SRHA and SRFA on the surface of nano-zero-valent iron and nano-iron trioxide accords with the kinetics of quasi-second-order adsorption, and the adsorption process of thermodynamic Langmuir isothermal adsorption can fit the adsorption process well. The adsorption capacity of nano-Fe _ 2O _ 4 to NOM is stronger than that of nano-Fe _ 2O _ 3 (the maximum adsorption capacity is about three times). The difference in adsorption amount is due to the different surface properties of the two kinds of nanocrystalline iron, which also indicates that the surface of nano-zero-valent iron is not the dense Fe _ 2O _ 3. 3, the nanometer zero-valent iron preferentially adsorbs the intermediate component of SRHA, while the large component of SRFA preferentially adsorbs. The different selective adsorption phenomena may be related to the aromaticity and hydrophobicity of different molecular weight components. The related knowledge has important reference significance in the practical application of nano-zero-valent iron repair.
【学位授予单位】：中国地质大学(北京)
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：X523

【相似文献】