Removal of Surface Adhered Particles by Surfactants and Fluid Motions

Abstract

Remo®ing or detaching particles from a surface is of interest in filter bed regeneration, cleaning of semiconductor surfaces, migration of fines in underground reser®oirs, and detergency. A two-stage remo®al process proposed in®ol®es penetration of the surfactant solution, diffusion and adsorption of surfactant molecules, followed by the particle remo ®al 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 remo®e or detach a particle adhering to a substrate in the presence of surfactant solution is discussed, as well as its calculation of typical ®alues. 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 ®ery large in magnitude, indicating that particle remo®al is ®ery difficult. Higher critical hydrodynamic force is required for the remo®al of particles of small size.