Aggregation and deposition of colloidal particles: Effect of surface properties of collector beads

The effect of the surface properties of collector beads on the transport of colloidal particles in porous media has been experimentally investigated. Both batch and continuous column experiments were conducted to study the dynamics of deposition and aggregation of colloids (polystyrene latex sulfate, d = 100 nm) in contact with collector particles (soda lime glass beads, d = 212-300 micron). Various rinsing methods were systematically used to wash the surface of soda lime glass beads. Time-resolved dynamic light scattering (TR-DLS) and ultraviolet- visible spectroscopy (UV-vis) were employed to evaluate the concentration of colloidal particles and their aggregation in columns packed with glass beads. Rinsing of glass beads was found to release the surface ions of collectors into the colloidal suspension and subsequently led to the aggregation of colloids. In batch experiments, leaching-induced increase of ion concentration in the suspension triggered the aggregation process, while, the collision frequency governed the aggregation dynamics later on. In column experiments, however, the initiation of aggregation by released ions was dependent on the length of the column. In a long column, a blockingripening mechanism was observed at the lower pH that indicated the concurrent aggregation and deposition of colloidal particles. In a short column, however, the concentration of eluted colloids did not decline over time that revealed incapability of leaching process to initiate aggregation. Furthermore, the solution chemistry was realized to be more effective in determining the fate of colloidal particles inside packed columns than the surface chemistry of collector beads. This study provides valuable insight into the effect of surface properties of collectors on aggregation and deposition of colloidal particles in a packed environment.