Aqueous foams and emulsions stabilized by mixtures of silica nanoparticles and surfactants: A state-of-the-art review

Abstract

In the last years, mixtures of silica nanoparticles and surfactants have been widely and successfully used to stabilize a multiplicity of aqueous foams and emulsions with current and potential applications in the engineering processes. The physicochemical properties and large-scale industrial production of silica nanoparticles, as well as the practical and cheap methods offered by surfactants to modify the nanoparticles' wettability, are the main reasons for the silica nanoparticle-surfactant pair to be an effective combination on the stabilization of both aqueous foams and emulsions. This state-of-the-art review aims to offer a well-defined picture of the contemporary research on foams and emulsions (oil-in-water, water-in-oil, and the particular case of the bicontinuous ones) stabilized by mixtures of silica nanoparticles and surfactants (cationic, anionic, nonionic, and zwitterionic) featuring the top results and outlining future research in the area. Attention is paid to the processes and materials where the foams and emulsions discussed are present. The function of silica nanoparticles-surfactants synergy on stabilizing foams and emulsions is also discussed.

Keywords

• Silica nanoparticles (SiO2 NPs)
• Surfactants
• Foams
• Emulsions
• Bicontinuous emulsions