Liquid-liquid extraction, i.e. control of the reversible transfer of cations between phases, is a core chemical process for metal purification and recycling. The objective of the “REE-CYCLE” project (Rare Earth Element reCYCling with Low harmful Emissions)[1] is to develop the fundamental understanding involved in the process’ complex fluids (both experimental and theoretical) in order to render environmentally friendly processes economically competitive.
Current technology is based on engineering arts, with a strong input of ienaics[2], the science of control of ion circulation in emulsified complex fluids. In order to develop predictive theories, one needs to acquire experimental data on selectivity, chemical potential differences and solvent activities versus temperature, pH and “modifiers”, the engineering trick for process intensification[3].
We describe a microfluidic device enabling for the first time simultaneous fast measurement of the free energy of mass transfer per ion pair between complex fluids as determined by XRF and solvent activity as determined by vapor pressure analysis. Examples will be shown on AOT-HDEHP mixed reverse micelles as model system for which the effect of long-range chemical interactions beyond the first neighbor between metal cations and reverse micelles[4] is important. The four-channel “ionoscope” device described in this talk should be a versatile efficient tool to provide reliable data for meso-scale modeling. Data obtained by XR fluorescence and FTIR spectroscopy will be presented to elucidate the phases.
Microfluidic device with on-line measurement sites.
[1] www.icsm.fr and reecycle-erc.blogspot.fr
[2] C Bauer et al., Thomas Graham medal lecture (25th Sept. 2013) and Colloids and Polymers (2014) In press.
[3] P Bauduin et al., Solubilization in alkanes by alcohols as reverse hydrotropes or "lipotropes". J Phys Chem B (2008)112:12354.
[4] RG French, VA Parsegian et al., Long range interactions in nanoscale science. Rev Mod Phys (2010)82:1887.
johannes.theisen@cea.fr
