(591h) Ionic Liquids in Microdroplet System: Droplet Formation and Interfacial Mass Transfer Study

Ionic liquids (ILs), which are characterized as liquids composed of anions and cations exclusively, are attracting more and more attention due to their superior features and versatile applications in catalysis, electrochemistry, separation and so on. In this work, we proposed to accommodate ILs in microdroplet system to utilize them more efficiently and controllably. Firstly, droplet formation with ILs as one of the two phases were studied experimentally. Flow regime classification and droplet size scaling laws were investigated in detail and compared with those in regular fluid systems thoroughly. The high viscosity of ILs turned out to have significant influence on this process. Further, when water/IL droplets were formed where water served as the dispersed phase and IL ([C₄mim][PF₆]) served as the continuous phase, interfacial mass transfer in this system was studied using micro-LIF (laser-induced fluorescence) technique. Not only were qualitative details analyzed based on the visualization results, but the mass transfer coefficient were also calculated quantitatively. The results showed that the droplet system could enhance the interfacial mass transfer from three aspects: increased driving force, larger interfacial area and higher mass transfer coefficient. This work demonstrated the great potential of combining ILs and droplet-based microfluidics to enhance the mass transfer in IL-involved multiphase systems and promote the whole process efficiency.