Toward Liquid–Liquid Extraction Using Switchable Hydrophilicity Solvents in Microfluidic Poly(dimethylsiloxane) Chips

One promising solution for the development of greener chemical processes is the utilization of reversible CO₂-switchable hydrophilicity solvents (CO₂-SHSs) that offer an energy-friendly alternative to solvents with fixed solvation properties. The use of these solvents needs efficient interactions between the solvent and the trigger as mass transfer issues can significantly affect efficiency. In this study, a novel approach for fast investigation of SHS performances is proposed by employing 2-2-dibutylaminoethanol (DBAE) as a known CO₂-SHS within a continuous microfluidic device made of poly(dimethylsiloxane) (PDMS). This method allowed the examination of mass transport in the phase change reaction and a considerable reduction of the time required for the phenomenon to occur to subminute time scales. A proof of concept is presented for the extraction of soybean oil from a soybean oil/DBAE mixture, which paves the way for the development of continuous microfluidic liquid–liquid extraction processes. In addition to this study, spectroscopic analyses conducted on DBAE under a CO₂ atmosphere also revealed that water is unnecessary for initiating the switch of DBAE into a hydrophilic compound, implying the existence of an additional reaction pathway. This finding could extend the potential applications of DBAE as an SHS to hydrophilic solvents other than water.