A theoretical analysis of colloid attachment and straining in chemically heterogeneous porous media.
A theoretical analysis of colloid attachment and straining in chemically heterogeneous porous media.
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DOI：
10.1021/la4011357
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发表时间：
2013-05
期刊：
影响因子：
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通讯作者：
S. Bradford;S. Torkzaban;A. Shapiro
中科院分区：
文献类型：
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作者：
S. Bradford;S. Torkzaban;A. Shapiro
在含有高度h（r）的随机粗糙度的化学非均质多孔介质上进行施加的流体动力学（T（H））和抵抗粘附（T（A））扭矩的平衡，以确定在不利的附着条件下有助于胶体固定的固体表面积的分数（S（f）*）。该模型考虑了由于变形和粘附力的水平分量（F（AT））引起的阻力、孔隙尺度速度分布的空间变化以及hr对T（H）和T（A）的杠杆臂的影响。计算了各种理化性质的S（f）* 值，以深入了解影响胶体固定化的机制和因素。胶体附着过程被证明取决于溶液离子强度（IS），胶体半径（r（c）），杨氏模量（K），化学不均匀性（P+）的量，和达西速度（q）。胶体固定也被证明发生在粗糙的表面上的附件的情况下。在这种情况下，S（f）* 取决于IS、r（c）、粗糙度分数（f0）、h（r）和q。粗糙度有增加T（A）和减少T（H）的趋势。因此，IS对S（f）* 的影响相对于附着被h（r）增强。与此相反，与附着相比，r（c）和q对S（f）* 的影响被hr减弱。宏观粗糙度位置附近的胶体固定与颗粒-颗粒接触点有许多相似之处，可以被视为一种应变过程。在一般情况下，附件是更重要的较高的IS和方差的次最小值，并为较小的r（c），q和K，但扩散降低这些值。相反，应变是占主导地位的相反的条件。文献中关于胶体保留机制的不一致性可能是由于缺乏对所有这些因素的考虑。
A balance of applied hydrodynamic (T(H)) and resisting adhesive (T(A)) torques was conducted over a chemically heterogeneous porous medium that contained random roughness of height h(r) to determine the fraction of the solid surface area that contributes to colloid immobilization (S(f)*) under unfavorable attachment conditions. This model considers resistance due to deformation and the horizontal component of the adhesive force (F(AT)), spatial variations in the pore scale velocity distribution, and the influence of hr on lever arms for T(H) and T(A). Values of S(f)* were calculated for a wide range of physicochemical properties to gain insight into mechanisms and factors influencing colloid immobilization. Colloid attachment processes were demonstrated to depend on solution ionic strength (IS), the colloid radius (r(c)), the Young's modulus (K), the amount of chemical heterogeneity (P+), and the Darcy velocity (q). Colloid immobilization was also demonstrated to occur on a rough surface in the absence of attachment. In this case, S(f)* depended on IS, r(c), the roughness fraction (f0), h(r), and q. Roughness tended to enhance T(A) and diminish T(H). Consequently, the effect of IS on S(f)* was enhanced by h(r) relative to attachment. In contrast, the effects of r(c) and q on S(f)* were diminished by hr in comparison to attachment. Colloid immobilization adjacent to macroscopic roughness locations shares many similarities to grain-grain contact points and may be viewed as a type of straining process. In general, attachment was more important for higher IS and variance in the secondary minimum, and for smaller r(c), q, and K, but diffusion decreased these values. Conversely, straining was dominant for the opposite conditions. Discrepancies in the literature on mechanisms of colloid retention are likely due to a lack of consideration of all of these factors.