FACTORS CONTROLLING THE HYDRODYNAMIC DETACHMENT OF PARTICLES FROM SURFACES

The detachment of colloidal particles (5 to 40 μm) from surfaces has been studied. The influence of several variables such as flow rate, particle size, particle elasticity, ionic strength, pH, and gravity has been considered. Experiments were conducted to measure the critical hydrodynamic force required to detach particles from a flat glass substrate. It was demonstrated by conducting centrifuge experiments that the mechanism of detachment is rolling rather than sliding or lifting. The influence of particle size and elasticity as well as the surface chemical interactions between the particle and the substrate was included in a model that adequately explains the observed behavior. A consistent method is presented to compute the deformation of the particle and the adhesion and lift forces acting on it at equilibrium. These quantities allow us to compute the critical hydrodynamic force required for particle release. A comparison of the computed and experimentally measured forces shows good agreement, indicating that the essential physics of the problem has been captured in the model. © 1992.