Industrial applications of ionic liquids (ILs)solvents
that can serve as green alternatives to volatile organic compoundsare
often hampered by their high cost. Solvent recycling provides a feasible
pathway to recover IL solvents to reduce lifecycle costs. Herein,
we demonstrate a continuous microfluidic process to purify metal-ion-loaded
IL solvents, wherein Fe(III) ions are extracted from a prototypical
IL, 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide
(BMIM-NTf2), to deionized (DI) water with subsequent membrane
separation of the IL and aqueous phases. Inline analytical tools,
design of experiment statistical optimization, and a self-optimizing,
modified Nelder-Mead simplex algorithm facilitate locating the best
parametric operating conditions to optimize both ion extraction and
physical phase separation. This process was then adapted to a more
challenging purification application: recovery of the IL trihexyl(tetradecyl)phosphonium
bis(2,4,4-trimethyl-pentyl)phosphinate (Cyphos 104) from the rare-earth
metal Nd(III). This application demonstrated that optimized conditions
obtained from a single stage could be applied across a multistage
process. Together, these results demonstrate that statistical and
inline optimization tools can be used to identify working parameters
for different flow systems with a variety of governing fluid properties,
for example, viscosity and interfacial tension.
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