Microfluidic/Liquid-liquid extraction: role of the interface in extraction kinetics

Florent Malloggi, Valérie Geertsen, Fabienne Testard



The liquid-liquid interface where the hydrophobic species can react with the hydrophilic species plays a key role in the processes of extraction or liquid-liquid mass transfer. The special case of transfer of salts is found both in natural processes but also in many industrial applications, although the mechanisms involved at the interface are not well understood. The flexible nature of the interface combined to low concentrations entail difficult in situ experimental measures.

The specific tools micro / nanofluidic developed these last years offer new perspectives in terms of mechanistic study of interfacial reactions and development of new reactions in confined areas. In these systems, the specific surface areas are large and diffusion distances and low fluid management (and therefore reactive) controlled. Many examples have demonstrated the interest of these tools for the study or development of systems based on interfacial reactions. The microfluidic tool allows to control the interface by making the interfacial reactions predominating over bulk ones and providing thus the opportunity to analyze the liquid - liquid extraction kinetics.

This thesis focuses on liquid-liquid extraction of salts by microfluidics. The objective is to determine the structure of the parallel interface and the kinetics of extraction through this very same interface for a rational control of the extraction kinetics. Three major classes of techniques are used in this thesis,

Microfluidic tools (manufacture and management chips ETDE fluids) , analytical techniques to determine speciation in different phases (ICP-MS, UV, fluorescence ..), the techniques of structural analysis and surface (SAXS, SANS, X-reflectivity, neutron, ...).

Besides a fundamental interest, this topic is directly related to salt mining applications for the treatment waste, but also for purification processes.