Transport of colloidal particles in a packed bed of collector beads are affected by the hydrodynamic and colloidal interactions between particles as well as between particle and collector. The colloidal interaction depends on the surface charging of collectors and particles. While many researchers have studied on the colloid deposition and transport as a function of ionic strength, experimental investigations examining the effect of surface charge are scarce. To figure out the effect of surface charge on colloid transport in porous media, we have performed the colloid transport experiment in a packed bed of spherical beads. In the present experiment, we used sulfate latex with a constant negative charge and carboxylate latex having pH-dependent negative charge [1, 2] as colloidal particles. Zirconia beads with pH-dependent charge and an isoelectric point around pH 7 were adopted as collectors [2]. The colloid transport experiment was carried out in 1 mM KCl as a function of pH and breakthrough curves of colloid were obtained. Experimental breakthrough curves were analyzed by a convection-dispersion equation including colloid deposition [3], where colloid filtration and dynamic blocking are considered. The results of experiments and analysis show that the maximum surface coverage of sulfate latex is constant against pH change. On one hand, the maximum coverage of carboxyl latex decreases with increasing pH, indicating that increased particle-particle repulsion enhances blocking in later stage of deposition. Hydrodynamic interaction also affects the maximum coverage.
References
[1] Sugimoto, T., et al., Colloids Surfaces A 443 (2014): 418-424.
[2] Kobayashi, M., et al., Colloids Surfaces A 347 (2009): 2-7.
[3] Kuhnen, F., et al. J. Colloid Interface Sci. 231 (2000): 32-41.
Kobayashi.moto.fp@u.tsukuba.ac.jp
