CO-stabilisation mechanisms of nanoparticles and surfactants in Pickering Emulsions produced by membrane emulsification

• Emulsions formed by membrane emulsification are used for an experimental co-stabilisation study.
• Co-stabilisation arising from Interactions of both electrostatic and steric stabilised nanoparticles with different types of surfactant are reported.
• Two distinct co-stabilisation mechanisms of nanoparticles and surfactants are identified.
• Competitive adsorption kinetics or Gibbs Marangoni equilibrium play the key role in the co-stabilisation.

Two different membrane emulsification methods were used to study mechanisms for co-stabilisation of emulsions, by either electrostatic or steric stabilised nanoparticles with anionic, cationic or non-ionic surfactants. The experimental results demonstrated the existence of two distinct co-stabilisation mechanisms that arise from interactions of the nanoparticles and surfactant molecules. When significant interaction is not involved, independent competitive adsorption of nanoparticles and surfactant molecules occurs spontaneously to stabilise droplets in formation. The adsorption/desorption equilibrium between surfactant molecules determines the longevity of the droplet stability. When the surfactant molecule reacts with the nanoparticle surface, the resultant surface modification appears to generate faster wetting kinetics for nanoparticles at the oil/water interface and yields enhanced stabilisation. The paper discusses the implications of controlling these interactions for emulsion production membrane systems.

Competitive Adsorption vs Gibbs Marangoni EquilibriumFigure optionsDownload high-quality image (162 K)Download as PowerPoint slide