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Emulsion formation in the presence of particle mixtures

Research Area: Chemistry, colloid and interface science, materials science, soft matter and nanotechnology

Supervisor: Dr Catherine Whitby

Description: Small particles present in colloidal systems such as food emulsions and foams, oil recovery processes and in antifoam formulations added to control foaming in pulp and paper production play a crucial role in controlling the stability and structure of these systems. The particles attach to the fluid interfaces [1] and stabilize the drops against coalescence [2]. The formation of emulsions in the presence of a single type of particle has been extensively characterized. [3] Commercial emulsion and foam formulations rarely, however, contain a single type of particle. The aim of this project is to investigate how mixtures of particles (of different wettability, size or shape) affect emulsion formation.

Approach: The interactions between oil drops and mixtures of particles of different types (wettability, size, shape) will be investigated in concentrated emulsions and dilute systems consisting of single drops. The structure and stability of concentrated emulsions prepared in the presence of particle mixtures will be characterized by a range of techniques including optical and electron microscopy and light scattering. The interactions between particle mixtures and single oil drops will also be investigated.

The questions to be addressed include:

• How do particles of different shapes or sizes organize in the interfacial layer?
• Do the behaviour of emulsions stabilized by particle mixtures reflect the average of the different types of particles?
• Can the interactions between drops and particle mixtures be tuned (using pH, salt, surfactant or polymer) such that one type of particle is selectively attached at the interface?
• Can particles of different types be selectively detached from fluid interfaces?

References
1. J. Ralston, D. Fornasiero and R. Hayes, 'Bubble-Particle Attachment and Detachment in Flotation', International Journal of Mineral Processing, 56 (issues 1-4), 133-164 (1999).
2. S. Arditty, C. P. Whitby, B. P. Binks, V. Schmitt and F. Leal-Calderon, 'Some General Features of Limited Coalescence in Solid-Stabilised emulsions', European Physical Journal E, 11 (issue 3), 273-281 (2003).
3. R. Aveyard, B. P. Binks and J. H. Clint, 'Emulsions Stabilized Solely by Colloidal Particles', Advances in Colloid and Interface Science, 100-102, 503-546 (2003).

Funding
International students should apply for an International Postgraduate Research Scholarship (IPRS) and a UniSA President's Scholarship (UPS). To be eligible for UPS, applicants must have a supervisor willing to nominate them for consideration.

Australian students should apply for an Australian Postgraduate Award (APA) and a UniSA Australian Postgraduate Research Award (USAPRA).

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