14 - The Use of Surfactants to Enhance Particle Removal from Surfaces

Abstract

Surfactants can enhance particle removal from surfaces by modifying the particle–surface interaction forces. Adsorbed surfactant molecules can alter the van der Waals attractive force, electrostatic force, hydrophobic force, as well as provide a steric barrier to contact. The effect of surfactant on these forces can result in greatly enhanced particle removal efficiency. Surfactant adsorption density and structure are important factors in determining removal enhancement performance associated with surfactants. Cleaning is generally most effective above the surface aggregation concentration (sac), which for naturally hydrophilic surfaces allows for bilayer or multilayer level surfactant coverage that provides significant charge repulsion as well as a steric barrier. Adsorption below the monolayer level renders naturally hydrophilic substrates hydrophobic, which tends to reduce removal efficiency. In contrast, naturally hydrophobic surfaces are likely to benefit from both sub-monolayer and multilayer coverages of surfactant that occur, respectively, below and above the sac. Existing adsorption theory and available formulas can aid in the prediction of the sac, which is an important parameter in predicting the performance of surfactants in particle removal enhancement. Equations are also available to predict the effectiveness of surfactants in enhancing particle removal.