Effect of Surface Hydrophobicity on the Hydrodynamic Detachment of Particles from Surfaces

Experiments were performed to evaluate the hydrodynamic force required to detach colloidal particles from substrates by fluids in simple shear flow. The role of DLVO and acid−base interactions on the process of adhesion and removal of colloidal particles, from model surfaces, in various fluid environments was investigated. Particles and substrates with varying degrees of hydrophobicity were used. The free energy of interaction between these surfaces in a number of fluid media was calculated using the acid−base approach. Good qualitative agreement was obtained between calculated values of free energy of interaction using the acid−base approach and the critical hydrodynamic force required to detach the particles if long range electrostatic repulsion is properly accounted for. Results for a range of particles and substrates of varying hydrophobicity and for a range of solvents can be consistently explained using this approach.