Transport properties and size exclusion effects in wide-pore superficially porous particles.
Transport properties and size exclusion effects in wide-pore superficially porous particles.
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DOI：
10.1016/j.ces.2018.03.041
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发表时间：
2018-03
影响因子：
4.7
通讯作者：
R. Maier;M. Schure
中科院分区：
文献类型：
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作者：
R. Maier;M. Schure
利用孔隙尺度模拟研究了水动力半径对大孔表面多孔颗粒（SPP）填充床中溶质分子输运的影响。自由分子扩散速率通过斯托克斯-爱因斯坦关系随半径变化。格子玻尔兹曼和朗之万方法用于模拟流体运动和流体中溶质分子整体的传输，提供有关溶质浓度、通量、分子年龄和停留时间的统计数据，作为 SPP 中深度的函数。计算颗粒内有效扩散和床分散系数，并将其与流体动力学半径和可及孔隙率相关联。发现对流和扩散的相对重要性通过扩散速率取决于分子（示踪剂）尺寸，并且对流效应对于较大、扩散较慢的分子更为显着。当使用较大的分子时，颗粒内浓度与局部颗粒孔隙率成比例降低，从而自然定义了尺寸排阻色谱 (SEC) 中使用的可及孔隙率。尽管孔隙形状复杂，但可以直接通过模拟计算SEC常数K。模拟表明，有效扩散系数在颗粒外壳附近升高，颗粒外壳很大程度上对间隙流开放，并且随着颗粒深度的增加而减小。这里研究的所有分子都可以传输到整个粒子深度，尽管给定深度的可访问体积取决于它们的大小。扩散速率可以很好地预测进入颗粒的首次通过时间，但停留时间会受到对流的影响，从而缩短平均访问持续时间。这些结果对“灌注”色谱很有意义，其中对流被认为可以提高大生物分子的分离效率。
The effects of hydrodynamic radius on the transport of solute molecules in packed beds of wide-pore superficially porous particles (SPP) are studied using pore-scale simulation. The free molecular diffusion rate varies with radius through the Stokes-Einstein relation. Lattice Boltzmann and Langevin methods are used to model fluid motion and the transport of an ensemble of solute molecules in the fluid, providing statistics on solute concentration, flux, molecule age and residence time, as a function of depth in the SPP. Intraparticle effective diffusion and bed dispersion coefficients are calculated and correlated with the hydrodynamic radius and accessible porosity.The relative importance of convection and diffusion are found to depend on the molecule (tracer) size through the diffusion rate, and convection effects are more significant for larger, slower-diffusing molecules. When larger molecules are utilized, the intraparticle concentration is reduced in proportion to the local particle porosity, leading to a natural definition of the accessible porosity used in size exclusion chromatography (SEC). Although the pore shape is complex, the SEC constantKcan be calculated directly from simulation. Simulation demonstrates that the effective diffusion coefficient is elevated near the particle hull, which is largely open to interstitial flow, and decreases with depth into the particle. All molecules studied here have transport access to the entire particle depth, although the accessible volume at a given depth depends on their size. The first passage time into the particle is well predicted by the diffusion rate, but residence time is influenced by convection, shortening the average visit duration. These results are of interest in “perfusion” chromatography where convection is thought to increase separation efficiency for large biomolecules.