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Morphology of Shear-Induced Colloidal Aggregates in Porous Media: Consequences for Transport, Deposition, and Reentrainment

机译:多孔介质中剪切诱导胶体聚集体的形态:运输,沉积和再夹带的后果

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摘要

Colloid deposition in granular media is relevant to numerous environmental problems. Classic filtration models assume a homogeneous pore space and largely ignore colloid aggregation. However, substantial evidence exists on the ubiquity of aggregation within porous media, suggesting that deposition is enhanced by it. This work studies the deposition process in relation to aggregate size and structure, We demonstrate that aggregation is induced at typical ground water velocities by comparing the repulsive DLVO force between particle pairs to the hydrodynamic shear force opposing it. Column experiments imaged with high-resolution X-ray computed tomography are used to measure aggregate structure and describe their morphology probability distribution and spatial distribution. Aggregate volume and surface area are found to be power-law distributed, while Feret diameter is exponentially distributed with some flow rate dependencies caused by erosion and restructuring by the fluid shear. Furthermore, size and shape of aggregates are heterogeneous in depth, where a small number of large aggregates control the concentration versus depth profile shape. The range of aggregate fractal dimensions found (2.22-2.42) implies a high potential for restructuring or breaking during transport. Shear-induced aggregation is not currently considered in macroscopic models for particle filtration, yet is critical to consider in the processes that control deposition.
机译:胶体在颗粒介质中的沉积与许多环境问题有关。经典的过滤模型假定均匀的孔隙空间,而在很大程度上忽略了胶体聚集。但是,大量证据表明多孔介质中存在普遍的聚集现象,这表明沉积会增强聚集作用。这项工作研究了与聚集体大小和结构有关的沉积过程。我们通过比较颗粒对之间的排斥DLVO力和与之相对的流体动力剪切力,证明了聚集是在典型的地下水速度下诱发的。使用高分辨率X射线计算机断层扫描成像的柱实验用于测量聚集体结构并描述其形态概率分布和空间分布。发现骨料的体积和表面积呈幂律分布,而费雷特直径呈指数分布,并且由于流体剪切作用引起的侵蚀和重组而引起一定的流速依赖性。此外,聚集体的尺寸和形状在深度上是不均匀的,其中少量的大聚集体控制浓度与深度分布的形状。发现的总分形维数范围(2.22-2.42)意味着在运输过程中有很大的重组或破坏的可能性。目前,在颗粒过滤的宏观模型中并未考虑剪切诱导的聚集,但在控制沉积过程中必须考虑到剪切诱导的聚集。

著录项

  • 来源
    《Environmental Science & Technology》 |2020年第9期|5813-5821|共9页
  • 作者单位

    Department of Civil and Environmental Engineering University of California Davis California 95616 United States;

    Department of Chemical Engineering University of Chemistry and Technology Prague 166 28 Czech Republic;

  • 收录信息 美国《科学引文索引》(SCI);美国《工程索引》(EI);美国《生物学医学文摘》(MEDLINE);美国《化学文摘》(CA);
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

  • 入库时间 2022-08-18 05:27:33

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