Removal of surface adhered particles by surfactants and fluid motions

Removing or detaching particles from a surface is of interest in filter bed regeneration, cleaning of semiconductor surfaces, migration of fines in underground reservoirs, and detergency. A two-stage removal process proposed involves penetration of the surfactant solution, diffusion and adsorption of surfactant molecules, followed by the particle removal by hydrodynamic force. The particle-substrate system, considered here as a plate-plate system, takes into account the surface roughness of the substrate in the form of asperities. The concept of critical hydrodynamic force required to remove or detach a particle adhering to a substrate in the presence of surfactant solution is discussed, as well as its calculation of typical values. The critical hydrodynamic force depends on the surface roughness, particle size, and other parameters of the system. When asperity size is comparable to the equilibrium distance of separation, the critical hydrodynamic force becomes very large in magnitude, indicating that particle removal is very difficult. Higher critical hydrodynamic force is required for the removal of particles of small size.