Prediction of colloid detachment in a model porous media: hydrodynamics

Understanding the mobility of colloids through porous media is important in both engineered and natural applications. This study employed a model system to explore physically based colloid detachment. Polystyrene colloids were attached in the primary minimum to glass beads in a packed column, and a residually attached fraction was subsequently detached via hydrodynamic shear. Colloid fractions released from the surfaces in the porous media were experimentally quantified. A flowrate of 75 ml/min detached 50% of the residual colloid fraction from the surface. The residual colloid fraction released was predicted with a model incorporating an interaction energy distribution and system physics. In this model, detachment is realized when the applied rolling moment from hydrodynamic shear overcomes the resistance associated with rolling. With the exception of one parameter, the hysteresis loss factor, system characteristics were described a priori. Using the hysteresis loss factor and interaction energy distribution developed from extended-DLVO theory, the detachment of the residual colloid fraction from the packed bed was well predicted. This work decomposes colloid detachment into the constitutive mechanisms dependent upon thermodynamics and hydrodynamics. (C) 2000 Elsevier Science Ltd. All rights reserved.