(132f) A Process-Based Analysis On the Generation of Pickering Emulsions

The replacement of surfactants by solid particles in emulsification processes offers many advantages and raises new opportunities. Unfortunately, the current state of knowledge does not allow for process design mainly because the lack of information about the stabilization mechanisms which are completely different from surfactant-based systems. At a process level these mechanisms can be divided into four steps: Droplet formation by breakage, the particle/droplet approach and collision, the particle adsorption and the formation of the particles network. Being mainly interested in the development of new emulsification processes, the global aim of this work is to model the generation and the stabilization of the droplets with particles in a system representative of industrial conditions. This work specifically investigated the impact of process parameters on the resulting emulsions.

Emulsification experiments were performed in an unbaffled tank using an off-centred pitched blade turbine. The parameters investigated were time under mixing, particles fraction, impeller speed and oil viscosity. Emulsification efficiency was quantified by means of size distribution measurements (Malvern Mastersizer 3000). Visualization techniques (PVM probe from Mettler Toledo and Optical microscopy) were also used to observe emulsion evolution during processing and evaluate the final droplet coverage by the particles.

Results showed that all the parameters affecting the hydrodynamics interact strongly and optimal conditions should be defined to produce the smallest droplets with the narrowest distribution. This interaction can be attributed to the fact that two different phenomena are involved simultaneously: droplet production and droplet coverage. This is completely different from surfactant-based systems where the stabilization step is much faster than the droplet production in addition to promoting droplet breakage by reducing the interfacial tension. Impeller speed and the emulsification time results highlighted the relevance of the fluid circulation and process time in the stabilization mechanism. The particles fraction results clearly showed the importance of the stabilization rate.