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    Transport and Retention of Colloids in Porous Media: Does Shape Really Matter?

    Year: 2013

    Journal: Environ. Sci. Technol., 2013, 47 (15), pp 8391–8398, 20140104

    Authors: Megan B. Seymour 1, Gexin Chen 2, Chunming Su 3, and Yusong Li *1

    Last authors: Yusong Li

    Organizations: 1 Department of Civil Engineering, University of Nebraska-Lincoln, Lincoln, Nebraska 68583, United States 2 National Research Council Resident Research Associate, 919 Kerr Research Drive, Ada, Oklahoma 74820, United States 3 Ground Water and Ecosystems Restoration Division, National Risk Management Research Laboratory, Office of Research and Development, United States Environmental Protection Agency, 919 Kerr Research Drive, Ada, Oklahoma 74820, United States

    Country: USA, US, United States, United States of America, America

    The effect of particle shape on its transport and retention in porous media was evaluated by stretching carboxylate-modified fluorescent polystyrene spheres into rod shapes with aspect ratios of 2:1 and 4:1. Quartz crystal microbalance with dissipation (QCM-D) experiments were conducted to measure the deposition rates of spherical and rod-shaped nanoparticles to the collector (poly-l-lysine coated silica sensor) surface under favorable conditions. The spherical particles displayed a significantly higher deposition rate compared with that of the rod-shaped particles. Theoretical analysis based on Smoluchowski–Levich approximation indicated that the rod-shaped particles largely counterbalance the attractive energies due to higher hydrodynamic forces and torques experienced during their transport and rotation. Under unfavorable conditions, the retention of nanoparticles in a microfluidic flow cell packed with glass beads was studied with the use of laser scanning cytometry (LSC). Significantly more attachment was observed for rod-shaped particles than spherical particles, and the attachment rate of the rod-shaped particles showed an increasing trend with the increase in injection volume. Rod-shaped particles were found to be less sensitive to the surface charge heterogeneity change than spherical particles. Increased attachment rate of rod-shaped particles was attributed to surface heterogeneity and possibly enhanced hydrophobicity during the stretching process.