Li Ke, Ma Huilian
Department of Geology and Geophysics , University of Utah , Salt Lake City , Utah 84112 , United States.
Langmuir. 2019 Apr 23;35(16):5471-5483. doi: 10.1021/acs.langmuir.9b00748. Epub 2019 Apr 12.
Colloid surface charge heterogeneity was incorporated into a three-dimensional trajectory model, which simulated particle translation and rotation via a force/torque analysis, to study the transport and retention dynamics of rod-shaped colloids over a wide size range in porous media under unfavorable conditions (energy barriers to deposition exist). Our previous study Li , K. ; Ma , H. Deposition Dynamics of Rod-Shaped Colloids during Transport in Porous Media under Favorable Conditions , Langmuir , 2018 , 34 , 9 , 2967 - 2980 , 10.1021/acs.langmuir.7b03983 for rod transport under favorable conditions (lacking energy barriers) demonstrated that particle rotation due to the coupled effect of flow hydrodynamics and Brownian rotation governed rod transport and retention. In this work, we showed that the shape of a colloid affected both transport process and colloid-collector interactions, but shape alone could not make rods to overcome energy barriers of over tens of kT for attachment under unfavorable conditions. The location of colloid surface heterogeneity did not affect transport but predominantly affected colloid-surface interactions by influencing the likelihood of heterogeneity patches facing the collector due to particle rotation. For surface heterogeneity located on the end(s) of a colloid, rods displayed enhanced retention compared with spheres; for surface heterogeneity located on the middle band, rods showed less retention compared with spheres. It was more effective to arrest a traveling rod when surface heterogeneity was located on the end relative to the side, because the tumbling motion greatly increased the likelihood of the end to intercept collector surfaces, and also because a rod would experience less repulsion with an end-on orientation relative to the collector surface compared to a side-on orientation due to the curvature effect. The influences of the particle aspect ratio on retention strongly depended upon the location of colloid surface heterogeneity. Our findings demonstrated that rods had distinct rotation and retention behaviors from spheres under conditions typically encountered in the environment; thus, particle rotation should be considered when studying the transport process of nonspherical colloids or spherical particles with inhomogeneous surface properties.
将胶体表面电荷非均一性纳入三维轨迹模型，该模型通过力/扭矩分析模拟颗粒的平移和旋转，以研究在不利条件下（存在沉积能垒）宽尺寸范围内棒状胶体在多孔介质中的输运和滞留动力学。我们之前关于在有利条件下（不存在能垒）棒状颗粒输运的研究（Li, K.; Ma, H. Deposition Dynamics of Rod-Shaped Colloids during Transport in Porous Media under Favorable Conditions, Langmuir, 2018, 34, 9, 2967 - 2980, 10.1021/acs.langmuir.7b03983）表明，由于流体动力学和布朗旋转的耦合作用导致的颗粒旋转控制着棒状颗粒的输运和滞留。在这项工作中，我们表明胶体的形状既影响输运过程，也影响胶体与收集器之间的相互作用，但仅形状本身并不能使棒状颗粒在不利条件下克服数十kT的附着能垒。胶体表面非均一性的位置并不影响输运，但主要通过影响由于颗粒旋转而异质性斑块面向收集器的可能性来影响胶体与表面的相互作用。对于位于胶体端部的表面非均一性，与球体相比，棒状颗粒表现出增强的滞留；对于位于中间带的表面非均一性，与球体相比，棒状颗粒的滞留较少。当表面非均一性位于端部而非侧面时，阻止移动的棒状颗粒更有效，这是因为翻滚运动极大地增加了端部拦截收集器表面的可能性，还因为与侧面朝向收集器表面相比，棒状颗粒端部朝向收集器表面时由于曲率效应所经历的排斥力更小。颗粒纵横比对滞留的影响强烈依赖于胶体表面非均一性的位置。我们的研究结果表明，在环境中通常遇到的条件下，棒状颗粒与球体具有不同的旋转和滞留行为；因此，在研究非球形胶体或具有不均匀表面性质的球形颗粒的输运过程时，应考虑颗粒旋转。
