Initial deposition rate of latex particles in the packed bed of zirconia beads

Transport of colloidal particles in porous media depends on the deposition kinetics of particles onto collector surfaces. The deposition is governed by hydrodynamic as well as colloidal interactions between the particle and the collector. While many experiments have been carried out on the deposition with repulsive electric double layer (EDL), not so many studies have been conducted on the deposition in a packed bed in the presence of attractive EDL, where collector beads and colloidal particles are oppositely charged. Also, systematic experiments to examine the effect of surface potential on the deposition with attractive EDL are still lacking. In this context, we have decided to carry out the deposition experiment of sulfate latex particles, bearing a constant negative charge, in a packed bed of zirconia beads, having pH-dependent surface charge and an isoelectric point around pH 7. Deposition experiments were performed as a function of KCl concentration and pH to clarify the influence of surface potential on deposition in the presence of attractive EDL. Dimensionless deposition rates were evaluated from the breakthrough of latex suspension from the packed bed of zirconia. Experimental results demonstrated that deposition rates increase with decreasing salt concentration, and that the values of pH, that is, surface potential, have minor effect on deposition kinetics. Theoretical calculations also Supported this trend. The thickness of diffuse part of EDL is more important in the presence of attractive EDL force. (C) 2008 Elsevier B.V. All rights reserved.