Seetha N, Mohan Kumar M S, Majid Hassanizadeh S, Raoof Amir
Department of Civil Engineering, Indian Institute of Science, Bangalore 560012, India.
Department of Civil Engineering, IFCWS, Indian Institute of Science, Bangalore 560012, India.
J Contam Hydrol. 2014 Aug;164:163-80. doi: 10.1016/j.jconhyd.2014.05.010. Epub 2014 Jun 5.
A mathematical model is developed to simulate the transport and deposition of virus-sized colloids in a cylindrical pore throat considering various processes such as advection, diffusion, colloid-collector surface interactions and hydrodynamic wall effects. The pore space is divided into three different regions, namely, bulk, diffusion and potential regions, based on the dominant processes acting in each of these regions. In the bulk region, colloid transport is governed by advection and diffusion whereas in the diffusion region, colloid mobility due to diffusion is retarded by hydrodynamic wall effects. Colloid-collector interaction forces dominate the transport in the potential region where colloid deposition occurs. The governing equations are non-dimensionalized and solved numerically. A sensitivity analysis indicates that the virus-sized colloid transport and deposition is significantly affected by various pore-scale parameters such as the surface potentials on colloid and collector, ionic strength of the solution, flow velocity, pore size and colloid size. The adsorbed concentration and hence, the favorability of the surface for adsorption increases with: (i) decreasing magnitude and ratio of surface potentials on colloid and collector, (ii) increasing ionic strength and (iii) increasing pore radius. The adsorbed concentration increases with increasing Pe, reaching a maximum value at Pe=0.1 and then decreases thereafter. Also, the colloid size significantly affects particle deposition with the adsorbed concentration increasing with increasing particle radius, reaching a maximum value at a particle radius of 100nm and then decreasing with increasing radius. System hydrodynamics is found to have a greater effect on larger particles than on smaller ones. The secondary minimum contribution to particle deposition has been found to increase as the favorability of the surface for adsorption decreases. The sensitivity of the model to a given parameter will be high if the conditions are favorable for adsorption. The results agree qualitatively with the column-scale experimental observations available in the literature. The current model forms the building block in upscaling colloid transport from pore scale to Darcy scale using Pore-Network Modeling.
建立了一个数学模型，以模拟病毒大小的胶体在圆柱形孔隙喉道中的输运和沉积，该模型考虑了诸如平流、扩散、胶体-收集器表面相互作用和流体动力壁效应等各种过程。基于在这些区域中起主导作用的过程，孔隙空间被划分为三个不同的区域，即主体区域、扩散区域和势区域。在主体区域，胶体输运由平流和扩散控制，而在扩散区域，由于扩散导致的胶体迁移率受到流体动力壁效应的阻碍。胶体-收集器相互作用力在发生胶体沉积的势区域中主导输运。控制方程被无量纲化并进行数值求解。敏感性分析表明，病毒大小的胶体输运和沉积受到各种孔隙尺度参数的显著影响，如胶体和收集器上的表面电势、溶液的离子强度、流速、孔径和胶体大小。吸附浓度以及表面对吸附的有利程度随着以下因素增加：(i) 胶体和收集器上表面电势的大小和比值减小；(ii) 离子强度增加；(iii) 孔径增加。吸附浓度随着佩克莱数（Pe）的增加而增加，在Pe = 0.1时达到最大值，此后减小。此外，胶体大小显著影响颗粒沉积，吸附浓度随着颗粒半径的增加而增加，在颗粒半径为100nm时达到最大值，然后随着半径的增加而减小。发现系统流体动力学对较大颗粒的影响大于对较小颗粒的影响。已发现随着表面对吸附的有利程度降低，颗粒沉积的二级最小值贡献增加。如果条件有利于吸附，模型对给定参数的敏感性将很高。结果与文献中可用的柱尺度实验观察结果在定性上一致。当前模型构成了使用孔隙网络模型将胶体输运从孔隙尺度放大到达西尺度的基础。
