Kinetics of capture of colloidal particles in packed beds under attractive double layer interactions

Abstract

The kinetics of capture of suspended colloidal particles in a packed bed of granular material in the presence of attractive double layer interactions have been investigated. Colloid deposition experiments were carried out with positively charged polystyrene latex colloids and negatively charged glass beads packed in a laboratory scale column. A notable increase in colloid deposition rates was observed when the ionic strength of the aqueous solution was reduced from 0.1 M to a value of 10 −6−10 −5 M. The experimental results were generally in good agreement with theoretical deposition rates, which were calculated from a numerical solution of the convective diffusion equation with colloidal and hydrodynamic interactions fully incorporated. The enhancement of the colloid deposition rates is attributed to the increase in the range and magnitude of the attractive double layer interactions as the ionic strength decreases. When attractive double layer interactions extend to large distances from the collector surface, the transport of particles toward the collector increases beyond that of pure convective diffusion, and, as a result, colloid deposition rates also increase.