Toward Liquid–Liquid\nExtraction Using Switchable\nHydrophilicity Solvents in Microfluidic Poly(dimethylsiloxane) Chips

One promising solution for the development of greener\nchemical\nprocesses is the utilization of reversible CO<sub>2</sub>-switchable\nhydrophilicity solvents (CO<sub>2</sub>-SHSs) that offer an energy-friendly\nalternative to solvents with fixed solvation properties. The use of\nthese solvents needs efficient interactions between the solvent and\nthe trigger as mass transfer issues can significantly affect efficiency.\nIn this study, a novel approach for fast investigation of SHS performances\nis proposed by employing 2-2-dibutylaminoethanol (DBAE) as a known\nCO<sub>2</sub>-SHS within a continuous microfluidic device made of\npoly(dimethylsiloxane) (PDMS). This method allowed the examination\nof mass transport in the phase change reaction and a considerable\nreduction of the time required for the phenomenon to occur to subminute\ntime scales. A proof of concept is presented for the extraction of\nsoybean oil from a soybean oil/DBAE mixture, which paves the way for\nthe development of continuous microfluidic liquid–liquid extraction\nprocesses. In addition to this study, spectroscopic analyses conducted\non DBAE under a CO<sub>2</sub> atmosphere also revealed that water\nis unnecessary for initiating the switch of DBAE into a hydrophilic\ncompound, implying the existence of an additional reaction pathway.\nThis finding could extend the potential applications of DBAE as an\nSHS to hydrophilic solvents other than water.