溶液性质对金属纳米颗粒在多孔介质中迁移持留行为的影响机制研究

发布时间：2018-04-22 11:18

本文选题：氧化铜纳米颗粒 + 多孔介质　；参考：《浙江大学》2017年硕士论文

【摘要】：金属纳米颗粒(MNPs)是一类非常重要的纳米材料,在其生产、运输、使用和处置过程中不可避免地进入环境,对生态环境和人类健康产生潜在危险。金属纳米颗粒在以土壤和地下水为代表的多孔介质中的迁移扩散能力决定着其环境风险,探索金属纳米颗粒在多孔介质中的迁移持留行为对准确预测其环境风险有着非常关键的作用。因此,本文以纯净石英砂填充的多孔介质为研究载体,以氧化铜纳米颗粒(CuO NPs)为研究对象,研究常见溶液性质(pH、离子强度、天然有机质(NOM)、渗流流速)对CuO NPs在多孔介质中迁移持留行为的影响,并结合胶体稳定性理论(DLVO)和胶体过滤理论探讨CuO NPs的迁移持留特性和相关作用机制。主要研究结论如下:(1)弄清了溶液性质的变化对CuO NPs团聚行为的影响:CuO NPs的团聚程度随着离子强度的增加而增加。低浓度NOM(0.1mg-C/L HA和0.01 mg-C/L Cit)通过其长链组分间的非极性反应加剧了 CuO NPs的团聚行为,高浓度NOM(0.25-10mg-C/L HA 和 0.025-1 mg-C/L Cit)通过增加 CuO NPs 之间的双电层静电斥力和空间位阻斥力,抑制了 CuO NPs的团聚行为,抑制程度随着NOM浓度的增加而增加。(2)揭示了不同流速条件下pH和离子强度对CuO NPs迁移持留行为的影响机制:pH和离子强度对CuO NPs迁移持留行为的影响与渗流流速有关。0.375cm/min条件下,pH和离子强度对CuO NPs迁移持留行为的影响不明显,CuO NPs迁移过程中因受到的水流拖拽力小于自身重力而沉积在石英砂表面是控制CuO NPs迁移持留行为的主导机制。0.750 cm/min条件下,pH 6时,CuO NPs-石英砂之间以斥力为主,离子强度对CuO NPs迁移持留行为的影响不明显;pH 8和pH 9时,CuO NPs-CuO NPs势能能障小于CuO NPs-石英砂势能能障,新进入的CuO NPs易在已沉积的CuO NPs表面发生团聚行为而引起的阻滞现象(Straining)是控制CuO NPs在多孔介质中迁移持留行为的主导机制。3.000 cm/min条件下,pH和离子强度对CuO NPs迁移持留行为的影响不明显,CuO NPs迁移过程中因受到的水流拖拽力大于CuO NPs-石英砂之间DLVO势能能障而沉积在石英砂表面是控制CuO NPs在多孔介质中迁移持留行为的主导机制。(3)揭示了 NOM初始浓度对CuO NPs迁移持留行为的影响机制:低浓度HA(0.1 mg-C/L)存在下,CuO NPs迁移过程中因阻滞现象(Straining)而使沉积速率系数逐渐增大;随着HA浓度的增加,CuO NPs的迁移能力先增加后减小,0.5mg-C/L HA时迁移能力最好(Ce/C=0.59))与与CuO NPs-石英砂之之间XDLVO势能能障的变化趋势一致。低浓度Cit(0.01 mg-C/L)存在下,CuO NPs迁移过程中因熟化现象(Ripening)而使沉积速率系数逐渐增大;随着Cit浓度的增加,CuO NPs的迁移能力先增加后变化不明显,与CuO NPs-石英砂之间XDLVO势能能障的变化趋势一致。
[Abstract]:Metal nanoparticles (MNPs) are a kind of very important nanomaterials, which inevitably enter the environment in the process of production, transportation, use and disposal, resulting in potential risks to the ecological environment and human health. The transport and diffusion ability of metal nanoparticles in porous media, represented by soil and groundwater, determines their environmental risks. It is very important to explore the migration and retention behavior of metal nanoparticles in porous media to accurately predict their environmental risks. Therefore, in this paper, the porous media filled with pure quartz sand is used as the carrier, and the copper oxide nanoparticles CuO NPs are used as the research object to study the properties of common solutions, such as pH and ionic strength. The effect of natural organic matter (CuO) on the migration and retention behavior of CuO NPs in porous media was studied. The migration and retention characteristics of CuO NPs and its related mechanism were discussed in combination with colloid stability theory and colloid filtration theory. The main conclusions are as follows: (1) the influence of the change of solution properties on the aggregation behavior of CuO NPs is clarified. The aggregation degree of NPs increases with the increase of ionic strength. The agglomeration behavior of CuO NPs was aggravated by the nonpolar reaction between its long chain components at low concentrations of NOM(0.1mg-C/L HA and 0.01 mg-C/L Citr. High concentration of NOM(0.25-10mg-C/L HA and 0.025-1 mg-C/L Citr increased the electrostatic repulsion force and steric steric repulsive force between CuO NPs. Inhibited the agglomeration behavior of CuO NPs, The inhibition degree increased with the increase of NOM concentration. 2) the mechanism of the effect of pH and ionic strength on the transport retention behavior of CuO NPs under different flow rates was revealed. The effects of pH and ionic strength on the transport retention behavior of CuO NPs and the percolation velocity were investigated. The effect of pH and ionic strength on the migration and retention behavior of CuO NPs at 0.375 cm / min is not obvious. The surface of quartz sand deposited on the surface of quartz sand is the main factor controlling the migration and retention behavior of CuO NPs due to the fact that the drag force of flow is less than its own gravity during the migration of CuO NPs. The repulsive force between CuO NPs- quartz sand was dominant at pH 6 at 0. 750 cm/min. The effect of ionic strength on the transport and retention behavior of CuO NPs was not obvious. The potential energy barrier of CuO NPs-CuO NPs at pH 9 and pH 8 was smaller than that of CuO NPs- quartz sand. The agglomeration behavior of newly entered CuO NPs on the surface of deposited CuO NPs is the dominant mechanism controlling the migration and retention behavior of CuO NPs in porous media. The pH and ionic strength of CuO NPs hold CuO NPs migration under the condition of 3. 000 cm/min. The effect of retention behavior is not obvious. The deposition on the surface of NPs is the dominant mechanism to control the migration and retention behavior of CuO NPs in porous media due to the fact that the drag force of flow is greater than that of DLVO potential energy barrier between CuO NPs- quartz sand. (3) the effect of initial concentration of NOM on the migration and retention behavior of CuO NPs is revealed: the deposition rate coefficient increases gradually due to the blocking phenomenon during the migration of CuO NPs in the presence of low concentration HA(0.1 mg-C / L). With the increase of HA concentration, the migration ability of CuO NPs firstly increases and then decreases at 0.5 mg 路C / L HA. The best migration ability is CeR / C ~ (0.59)) and the trend of XDLVO potential energy barrier between CuO NPs- quartz sand is the same. In the presence of low concentration Cit(0.01 mg-C / L), the deposition rate coefficient increased gradually due to ripening phenomenon during the migration of CuO NPs, and the migration capacity of CuO NPs increased at first and then did not change obviously with the increase of Cit concentration. The change trend of XDLVO potential energy barrier is consistent with that of CuO NPs- quartz sand.
【学位授予单位】：浙江大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：X132

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