三种有机物对纳米银在饱和多孔介质中沉降释放过程的影响

发布时间：2018-01-13 15:07

本文关键词：三种有机物对纳米银在饱和多孔介质中沉降释放过程的影响　出处：《四川农业大学》2015年硕士论文　论文类型：学位论文

【摘要】：由于纳米银拥有良好的催化、导电、传感及广谱抗菌活性,被广泛应用于医疗、食品、纺织、化妆品、水质净化等领域。随着纳米银的大量使用,其在生产、使用以及废弃过程中,难免会以“三废”的形式进入环境,并最终进入到地下水中。地下水的健康状况直接影响到人类生命安全。已有研究报道,纳米银对植物、细菌等将产生不同程度的毒副作用,并可能对人体产生肝毒性、肾毒性、神经毒性等毒性反应。而纳米银毒性效应的发挥与其在环境中的迁移能力有直接的联系。地下水有机物对纳米银的迁移有着复杂的影响机制,会改变污染域的尺寸与分布形状,使得预测纳米银对地下水生态环境的影响极具挑战性。不同有机物对纳米银迁移能力的影响机制不同,系统评价典型环境有机物对纳米银沉降释放等关键迁移过程的控制作用,对饮用淡水、水生生态环境及水质保护均具有重要意义。本文选取聚乙烯吡咯烷酮(Polyvinylpyrrolidone,PVP)涂层包覆的纳米银颗粒(PVP-Ag NPs)为研究对象,探索其在石英砂(Quartz sand,QS)及铁氧化物涂层砂(Iron-oxide-coated sand,IOCS)中的吸附迁移特性和相关作用机制,并通过静态混合实验及动态柱实验重点考察了N-乙酰-L-半胱氨酸(N-Acetyl-L-Cysteine,NAC)、十二烷基苯磺酸钠(Sodium dodecylbenzenesulphonate,SDBS)、乙二胺四乙酸(Ethylenediaminetetraacetic acid,EDTA)对纳米银在饱和多孔介质中沉降释放过程的影响,得到的主要研究结果如下：(1)纳米银在多孔介质中的沉降过程受纳米银内核(Ag core)及PVP涂层共同控制,以PVP涂层的控制作用为主。石英砂带负电,与同样带负电的纳米银内核相互排斥,但纳米银可通过PVP涂层与石英砂表面的Si-O-H键连而发生不可逆沉积；铁氧化物涂层砂带正电,与纳米银内核相互吸引,但由于铁氧化物涂层减少了供PVP键连的石英砂表面,使纳米银沉降效率降低,并且由于静电相互作用产生的沉积是可逆的,所以沉积在铁氧化物表面的纳米银会因为溶液的化学扰动而发生释放。(2)含硫的有机物SDBS/NAC与络合剂EDTA均能破坏纳米银与聚合物涂层之间的键连,使纳米银与涂层分离,粒径减小。但由于SDBS/NAC/EDTA均无法使纳米银表面的涂层完全脱落,所以涂层剥离机制并不能引起沉降在多孔介质表面纳米银的释放。(3)SDBS/NAC可诱导沉降在铁氧化物涂层砂(可逆沉降)表面纳米银的释放。其释放机理为SDBS/NAC通过吸附至铁氧化物涂层表面,中和甚至逆转介质表面电性,增强双电层排斥力,从而诱发纳米银的释放行为。(4)表面活性剂的胶束结构有利于提高SDBS对介质表面的电性调节能力,提高纳米银的释放效率。同时,胶束态SDBS比分子态SDBS更能有效阻塞多孔介质表面供纳米银吸附的点位,使其沉降效率降低。
[Abstract]:Due to its good catalytic, conductive, sensing and broad-spectrum antibacterial activity, nano-silver has been widely used in medical, food, textile, cosmetics, water purification and other fields. In the process of use and waste, it is inevitable to enter the environment in the form of "three wastes" and eventually into the groundwater. The health of groundwater directly affects the safety of human life. Nano-silver will produce toxic side effects to plants, bacteria and so on, and may produce hepatotoxicity and nephrotoxicity to human body. Neurotoxicity and other toxic reactions. The toxic effects of silver nanoparticles are directly related to their ability to transport in the environment. Groundwater organic matter has a complex mechanism of influence on the migration of silver nanoparticles. It will change the size and distribution of the pollution zone, which makes it very challenging to predict the impact of nano-silver on the groundwater ecological environment. Different organic matter has different influence mechanism on the migration ability of nano-silver. The effects of organic compounds in typical environment on the key migration processes such as the deposition and release of silver nanoparticles were systematically evaluated, and the effects of organic compounds on drinking fresh water were also systematically evaluated. In this paper, polyvinylpyrrolidone (Polyvinylpyrrolidone) is selected as a kind of polyvinylpyrrolidone. PVP coated silver nanoparticles (PVP-Ag NPs) were investigated in quartz sand Quartz sand. QS) and Iron-oxide-coated and IOCSs (Iron-oxide-coated and IOCSs). The N-Acetyl-L-Cysteine NAC (N-Acetyl-L-Cysteine NAC) was investigated by static mixing experiment and dynamic column experiment. Sodium dodecyl benzenesulphonate (SDBs). The effect of ethylenediaminetetraacetic EDTAA on the deposition and release of silver nanoparticles in saturated porous media. The main results obtained are as follows: (1) the deposition process of silver nanoparticles in porous media is controlled by Ag core (Ag core) and PVP coating. The control effect of PVP coating is dominant. The quartz sand belt has negative charge, and the nano-silver core with the same negative charge repel each other. However, the silver nanoparticles can be deposited irreversibly by the Si-O-H bond on the quartz sand surface through the PVP coating. The positive charge of the iron oxide coated belt is attracted to the nano-silver core, but the deposition efficiency of the nano-silver is decreased because the iron oxide coating reduces the quartz sand surface for PVP bond connection. And the deposition due to electrostatic interaction is reversible. Therefore, nano-silver deposited on the surface of iron oxides will be released as a result of the chemical disturbance of the solution. Both sulfur-containing organic matter SDBS/NAC and complex agent EDTA can destroy the bond between nano-silver and polymer coating. The nano-silver was separated from the coating, and the particle size decreased, but the coating on the surface of nano-silver could not be completely removed because of SDBS/NAC/EDTA. Therefore, the mechanism of coating stripping can not cause the release of silver nanoparticles on porous media surface. SDBs / NAC can induce deposition in iron oxide coated sand (reversible deposition). The release mechanism of silver nanoparticles on the surface is that SDBS/NAC is adsorbed to the surface of iron oxide coating. Neutralizing or even reversing the electrical properties of the dielectric surface, enhancing the repulsive force of the double layer, thus inducing the release behavior of nano-silver. 4) the micelle structure of the surfactants is beneficial to improve the ability of SDBS to regulate the electrical properties of the dielectric surface. At the same time, micellar SDBS can effectively block the sites on the surface of porous media for adsorption of silver nanoparticles, and the sedimentation efficiency of micellar SDBS is lower than that of molecular SDBS.
【学位授予单位】：四川农业大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：X131.2

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