DEPMod – Multiscale continuous double emulsification processes: monitoring and modelling

PhD topic description

Emulsions are widely used in many materials and practical applications. Most of them are fabricated by batch mixing processes using impellers or rotor-stator devices. At the industrial scale, the development of continuous emulsification processes would be beneficial. The challenging issue is that both the process and the formulation (type of ingredients and their concentrations) influence the emulsification efficiency and the final product stability. Double emulsions (DEs), also known as liquid membrane systems, are small droplets immersed within larger ones. They are employed for instance for setting up fat-reduced food products, encapsulating different molecules in a single carrier for the formulation of pharmaceutics or the extraction of solutes during wastewater treatment. DEs represent a much higher complexity than single emulsions, due to their structure with a bigger number of phenomena that may occur, a more complex formulation and a more challenging emulsification process. Modelling the preparation and/or the stability of DEs has been rarely addressed so far, as well as their formulation in continuous mode. The present project aims at exploring innovative continuous double emulsification processes through the use of microfluidic devices and static mixers, and developing predictive models of the manufacture and the stability of these complex systems.

During the preparation step and the shelf-life of DEs, different phenomena may occur, including outer droplet breakage and coalescence, escape of the inner droplets, swelling or shrinkage, over-swelling leading to outer droplet disintegration, creaming and phase separation. These phenomena are governed by physico-chemical parameters as well as the energy dissipated by the emulsification device during preparation. In DEPMod project, the preparation of DEs using continuous processes will be investigated with the help of online/offline monitoring of the important physico-chemical and process parameters. The fundamental differences between the phenomena occurring during the preparation of single and double emulsions necessitate a specific effort of modelling and optimization of DE processes. Beyond the preparation procedure, DE properties evolution during the storage phase will be studied as well. The collected experimental data will be exploited to build dynamic models aiming to predict the behavior of the system during preparation and storage phases. For each phase, two population balances accounting for the inner and outer droplet size distributions variation in time and space will be developed. They will consider the different abovementioned phenomena affecting the droplets size and the encapsulation efficiency, which represent the main two properties determining the quality of the double emulsion. The outcome of modelling is a disclosure of the most relevant parameters pertaining to the formulation, the preparation process and the storage of double emulsions.

PhD duties and environment
Within the frame of this project funded by the French National Research Agency, the PhD student will be located at the LAGEPP (https://lagepp.univ-lyon1.fr/en/home/) in Villeurbanne, France under the supervision of Dr. Noureddine Lebaz (Associate Professor in LAGEPP) and of Dr. Nida Othman (CNRS Research Director in LAGEPP). The student will be surrounded by other members of the project and technical staff.
Concerning the experimental part, the PhD student will have to adapt/modify the existing set-up for double emulsions preparation at different scales and carry out the experiments (preparation, stability) for data acquisition. These experimental data will be used for the development and the validation of phenomenological models based on the population balance equation. Numerical developments would be necessary to consider the different phenomena.