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 un derground reservoirs, and detergency. A two-stage removal process proposed involves penetration of the surfactant solution, diffusion and adsorption o f surfactant molecules, followed by the particle removal by hydrodynamic fo rce. 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 o r detach a particle adhering to a substrate in the presence of surfactant s olution is discussed, as well as its calculation of typical values. The cri tical hydrodynamic force depends on the surface roughness, particle size, a nd 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 difficul t. Higher critical hydrodynamic force is required for the removal of partic les of small size.