University of Colorado Denver , Department of Civil Engineering, Campus Box 113, PO Box 173364, Denver, Colorado 80217-3364, United States.
Lawrence Berkeley National Laboratory , Earth Sciences Division, Mail Stop 74R316C, 1 Cyclotron Road, Berkeley, California 94720, United States.
Environ Sci Technol. 2015 Oct 20;49(20):12263-70. doi: 10.1021/acs.est.5b03212. Epub 2015 Oct 5.
Experiments reveal a wide discrepancy between the permeability of porous media containing colloid deposits and the available predictive equations. Evidence suggests that this discrepancy results, in part, from the predictive equations failing to account for colloid deposit morphology. This article reports a series of experiments using static light scattering (SLS) to characterize colloid deposit morphology within refractive index matched (RIM) porous media during flow through a column. Real time measurements of permeability, specific deposit, deposit fractal dimension, and deposit radius of gyration, at different vertical positions, were conducted with initially clean porous media at various ionic strengths and fluid velocities. Decreased permeability (i.e., increased clogging) corresponded with higher specific deposit, lower fractal dimension, and smaller radius of gyration. During deposition, fractal dimension, radius of gyration, and permeability decreased with increasing specific deposit. During flushing with colloid-free fluid, these trends reversed, with increased fractal dimension, radius of gyration, and permeability. These observations suggest a deposition scenario in which large and uniform aggregates become deposits, which reduce porosity, lead to higher fluid shear forces, which then decompose the deposits, filling the pore space with small and dendritic fragments of aggregate.
实验揭示了含有胶体沉积物的多孔介质的渗透性与可用预测方程之间存在广泛差异。有证据表明，这种差异部分源于预测方程未能考虑胶体沉积物形态。本文报道了一系列使用静态光散射（SLS）在通过柱体流动过程中对折射率匹配（RIM）多孔介质内胶体沉积物形态进行表征的实验。在不同的离子强度和流速下，使用最初清洁的多孔介质在不同的垂直位置进行了实时渗透率、特定沉积物、沉积物分形维数和沉积物转动惯量半径测量。渗透率降低（即堵塞增加）与特定沉积物增加、分形维数降低和转动惯量半径减小相对应。在沉积过程中，分形维数、转动惯量半径和渗透率随特定沉积物的增加而降低。在用不含胶体的流体冲洗时，这些趋势发生了逆转，分形维数、转动惯量半径和渗透率增加。这些观察结果表明，一种沉积情景是，大而均匀的聚集体成为沉积物，降低了孔隙率，导致更高的流体剪切力，然后分解沉积物，用聚集体的小而树枝状碎片填充孔隙空间。
