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首页> 外文期刊>Environmental Science & Technology >Role of the Air-Water Interface in the Retention of TiO_2 Nanoparticles in Porous Media during Primary Drainage
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Role of the Air-Water Interface in the Retention of TiO_2 Nanoparticles in Porous Media during Primary Drainage

机译：一次排水中空气-水界面在多孔介质中保留TiO_2纳米颗粒中的作用

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The increasing use of nanomaterials in commercial products has resulted in increased concerns about their potential environmental impacts. The overall mobility of nanomaterials in the environment may depend in part on their mobility in the unsaturated zone of the subsurface, which may provide a sink for nanomaterials, preventing their spread, or a long-term contaminant source. The objective of this work was to study the dynamic unsaturated transport of titanium dioxide (TiO_2) during primary drainage to examine the role of air-water interface formation on nanomaterial retention. A specialized automated system was used to track depletion of TiOz in the pore solution of a porous medium during dynamic drainage, while simultaneously measuring capillary pressure (P_c) and saturation (S). A continuous mass balance was used to calculate the mass of retained TiC_2 nanoparticles. Experiments were specifically designed to minimize TiO_2 interactions with solid surfaces to allow direct assessment of the role of the air-water interface. Results indicate that the mass of retained TiO_2 increases as saturation decreases at all drainage rates, with slower drainage rates corresponding to greater retention at a given saturation. Normalizing the retained mass (M) by the measured air-water interfacial area (A) shows near-constant M/A values at high saturations (S > 0.4) and increasing M/A values With decreasing saturation as saturation drops below 0.4. This result may indicate air-water interfacial adsorption at high saturations, with increasing contributions from film straining at lower saturations.
机译：纳米材料在商业产品中的使用越来越多，导致人们对其潜在的环境影响越来越关注。纳米材料在环境中的总体迁移率可能部分取决于其在地下不饱和区域中的迁移率，这可能会为纳米材料提供沉没，防止其扩散或长期污染源。这项工作的目的是研究初次排水过程中二氧化钛（TiO_2）的动态不饱和迁移，以研究空气-水界面形成对纳米材料保留的作用。使用专门的自动化系统跟踪动态排水过程中多孔介质孔隙溶液中TiOz的消耗，同时测量毛细管压力（P_c）和饱和度（S）。使用连续的质量平衡来计算保留的TiC_2纳米颗粒的质量。专门设计了实验，以最大程度地减少TiO_2与固体表面的相互作用，从而直接评估空气-水界面的作用。结果表明，在所有排水速率下，保留的TiO_2的质量均随饱和度的降低而增加，而较低的排水速率对应于给定饱和度下的较大保留率。通过测得的气-水界面面积（A）对保留质量（M）进行归一化，可以显示在高饱和度（S> 0.4）下接近恒定的M / A值，随着饱和度下降到0.4以下，随着饱和度的降低，M / A值会增加。该结果可能表明在高饱和度时空气-水界面吸附，而在较低饱和度时膜应变的贡献增加。

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