Response of Surfactant Stabilized Oil-in-Water Emulsions to the Addition of Particles in an Aqueous Suspension

• Published in: Langmuir Vol. 30; no. 43; pp. 12736 - 12742
• Main Authors: Katepalli, Hari, Bose, Arijit
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 04.11.2014
• DOI: 10.1021/la502291q
• ISSN: 0743-7463

As a model for understanding how surfactant-stabilized emulsions respond to the addition of interacting and noninteracting particles, we investigated the response of dodecane-in-water emulsions stabilized by SDS (anionic), CTAB (cationic), and Triton X-100 (nonionic) surfactants to the addition of an aqueous suspension of negatively charged fumed silica particles. The stability of the emulsion droplets and the concentration of surfactants/particles at the oil–water interfaces are sensitive to surfactant–particle interactions, mixing conditions, and the particle concentration in the bulk. Addition of the particle suspension to the SDS-stabilized emulsions showed no effect on emulsion stability. Coarsening of emulsion droplets is observed when fumed silica particles were added to emulsions stabilized by Triton X-100. Depending on the concentration of silica particles in the suspension, the addition of fumed silica particles to CTAB-stabilized emulsions resulted in droplet coalescence and phase separation of oil and water or formation of particle-coated droplets. Vigorous (vortex) mixing allows the particles to breach the oil–water interfaces and stabilize emulsions. While we have examined a specific particle suspension and a set of three surfactants, these observations can be generalized for other surfactant–particle mixtures.