Pore-scale visualization of colloid straining and filtration in saturated porous media using micromodels
Pore-scale visualization of colloid straining and filtration in saturated porous media using micromodels
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DOI：
10.1029/2005wr004639
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发表时间：
2006-10-20
影响因子：
5.4
通讯作者：
Keller, Arturo A.
中科院分区：
文献类型：
--
作者：
Auset, Maria;Keller, Arturo A.
为了深入了解控制颗粒去除的微观过程，我们在孔隙尺度上研究了胶体输运。采用单分散胶体悬浮液和水饱和微模型。对不同粒径、颗粒表面粗糙度、溶液离子强度和流速进行了实验研究。通过光学显微镜跟踪单个胶体的轨迹和命运，观察和测量拉伸和附着。经典过滤理论证明适用于大于2.5的喉道与胶体比（T/C），但没有考虑到应变的可能性，而应变成为较小T/C比的重要捕获机制。从空间上看，在多孔介质中，前1-2个孔喉内发生了应变，而从入口到前6-10个孔喉处出现了拦截和附着，具体取决于颗粒大小。一旦粒子通过初始区域，附着的概率非常小。胶体附着随溶液离子强度的增大或流速的减小而增加，而应变主要与流速无关。晶粒的表面粗糙度在胶体捕获中也起着重要作用，使碰撞效率提高了2-3倍。随着T/C比的变化，胶体的去除机制和空间分布存在显著差异。微观模型可视化清楚地表明，在预测饱和多孔介质中胶体的输运时，应考虑物理应变和表面粗糙度的影响。
[ 1] Colloid transport was studied at the pore scale in order to gain insight into the microscale processes governing particle removal. Monodisperse suspensions of colloids and water-saturated micromodels were employed. Experiments were carried out for different particle sizes, grain surface roughness, solution ionic strength, and flow rates. Straining and attachment were observed and measured by tracking the trajectory and fate of individual colloids using optical microscopy. Classical filtration theory proved appropriate for throat to colloid ratios ( T/C) larger than 2.5 but did not take into account the possibility of straining that becomes an important capture mechanism for smaller T/C ratios. Spatially within the porous medium, straining occurred within the first 1-2 pore throats, while interception and attachment was seen from the inlet to the first 6-10 pore spaces, depending on particle size. Once a particle passed the initial region, the probability of attachment was very small. Colloid attachment increased with increasing solution ionic strength or decreasing flow rate, whereas straining was mainly independent of flow rate. Surface roughness of the grains also played a significant role in colloid capture, increasing collision efficiency by a factor of 2-3. The mechanisms of removal and the spatial distribution of colloid retention differed noticeably as a function of the T/C ratio. Micromodel visualizations clearly showed that physical straining and the effect of surface roughness should be taken into account when predicting the transport of colloids in saturated porous media.