The Effects of Surface Charging Properties on Colloid Transport in Porous Media

Abstract

Transport properties of colloidal particles in a packed bed of collector beads are affected by hydrodynamic and colloidal interactions between particles as well as between the particle and the collector. The colloidal interaction depends on the surface charging of collectors and particles. While many researchers have studied on the colloid deposition and transport in porous media 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 the colloid transport in porous media, we have performed colloid transport experiments 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 as colloidal particles. Zirconia beads with pH-dependent charge and an isoelectric point around pH 7 were adopted as collectors. Colloid transport experiments were carried out in 1 mM KCl as a function of pH and breakthrough curves of colloid were obtained. The experimental breakthrough curves were analyzed by a convection-dispersion equation including colloid deposition, where colloid filtration and dynamic blocking are considered. The results of experiments and analysis show that the maximum surface coverage of sulfate latex on the collector surface is constant against pH change. On the one hand, the maximum coverage of carboxyl latex decreases with increasing pH, indicating that the lateral particle-particle repulsion increased by high charge enhances blocking in later stage of deposition. The result suggests that electro-hydrodynamic interaction also affects the maximum coverage.

Effect of electrostatic interaction on the retention and remobilization of colloidal particles in porous media

“…The formation of the external filter cake could occur due to electrostatic retention of positively charged hematite particles by negatively charged quartz matrix. Although at later stages of deposition, when quart surfaces got considerably covered by hematite particles, they could produce lateral repulsion effects (Kobayashi et al, 2014) screening the electrostatic attraction of quartz surfaces. At this stage size-exclusion interception of hematite micro-aggregates, formed in the suspension, could become dominant.…”