Gansu State Farms Academy of Agricultural Research, Wuwei, Gansu 733006, China.
J Environ Qual. 2010 Feb 19;39(2):500-8. doi: 10.2134/jeq2009.0100. Print 2010 Mar-Apr.
Colloidal particles of environmental concern often have nonspherical shapes. However, theories and models such as the classical filtration theory have been developed based on the behavior of spherical particles. This study examined the effect of particle shape on colloid retention (e.g., attachment and straining) and release in saturated porous media. Two- and three-step transport experiments were conducted in water-saturated glass bead columns using colloids dispersed in deionized water and an electrolyte solution. The particles used in the experiments were carboxylate-modified latex colloids of spherical (500 nm diam.) and rod (aspect ratio, 7.0) shapes. The rod-like particles were prepared by stretching the spherical particles. Analysis of the colloid breakthrough curves indicates that particle shape affected transport behavior, but retention did not increase with increasing aspect ratio. Retention of the spherical particles occurred mainly in the secondary energy minimum, whereas retention of rod-like particles occurred in primary and secondary energy minima. There was less straining of rod-like particles compared with spherical ones, indicating that the minor axis was the critical dimension controlling the process. Release of spherical particles on elution was instantaneous, whereas release of rod-like particles was rate limited, giving rise to long tails, implying an orientation effect for rod-like colloids. The results suggest that the differences in electrostatic properties and shape contributed to the observed different retention and release behaviors of the two colloids.
环境关注的胶体颗粒通常具有非球形形状。然而，基于球形颗粒的行为，已经开发出了诸如经典过滤理论等理论和模型。本研究考察了颗粒形状对胶体在饱和多孔介质中保留（例如，附着和挤压）和释放的影响。在使用去离子水和电解质溶液分散的胶体的水饱和玻璃珠柱中进行了两步和三步传输实验。实验中使用的颗粒是球形（500nm 直径）和棒状（纵横比，7.0）的羧酸修饰乳胶胶体。棒状颗粒是通过拉伸球形颗粒制备的。胶体突破曲线的分析表明，颗粒形状影响传输行为，但保留率不会随纵横比的增加而增加。球形颗粒的保留主要发生在二次能量最小值中，而棒状颗粒的保留发生在一次和二次能量最小值中。与球形颗粒相比，棒状颗粒的挤压程度较小，这表明较小的轴是控制该过程的关键尺寸。洗脱时球形颗粒的释放是瞬时的，而棒状颗粒的释放是速率限制的，导致长尾，这意味着棒状胶体存在取向效应。结果表明，静电特性和形状的差异导致了两种胶体观察到的不同保留和释放行为。
