Solvent extraction processes are typically governed by thermodynamics, hydrodynamics and mass transfer mechanisms. A deep understanding of these phenomena is essential for optimizing the process flowsheet. While thermodynamic as hydrodynamic data can be readily acquired, determination of the mass transfer constants related to the extraction kinetics remains challenging.
For reactive chemical systems, few experimental techniques ensure to separate effects of diffusion from chemical reaction on the mass transfer kinetics [1, 2].
Thanks to enhancement of mass transfer efficiency in these devices, microfluidic devices recently demonstrated their potential to estimate the intrinsic chemical kinetics of fast reactions. Unlike setup as Nitsch and rotating cells or Single drop technic which are influenced by hydrodynamics, microfluidic experiments at high velocity flows aim to minimize the diffusion boundary layer, allowing for the measurement of kinetic constants that closely approach the intrinsic chemical reaction constant [3, 4].
In this context, uranium(VI) extraction kinetics by a monoamide solvent were studied using high velocities-stratified flows in a Y-Y microfluidic device. The experimental data obtained at short residence times (between 8 and 17 ms) were modelled using a simple approach [4]. The results suggest that mass transfer is operated under a mixed regime, with an apparent chemical kinetic constant around 10-4 m.s-1. When compared to experimental results carried out in same conditions with the Single drop technique, this value is one order of magnitude higher.
This methodology, initially developed for studying the extraction kinetics of uranium(VI) with TBP, confirms its applicability to a different chemical system.