Microfluidic liquid-liquid extraction system with a chemically induced three-phase flow

This paper deals with a liquid extraction system of two immiscible liquids, i.e. heptane-dichloromethane-acetonitrile and water-acetonitrile that after confluence form a three-phase system. Each of three chemically induced phases mainly consists of heptane (1st phase), acetonitrile/ dichloromethane (2nd phase) and water (3rd phase). stable interfaces between all of three phases were observed under flow conditions, when two initial phases were injected into a microchannel of 200(W)×100(D) μm. The mass transfer of the model compound (rhodamine 6G) between phases was studied in static conditions and analytical characteristics of the processes were obtained for different compositions of initial phases. For microchannel flow conditions, it was found that equilibrium was almost reached in a 1 second after the confluence of initial phases. This short time constant was attributed to the fast diffusion across the chemically induced phases in the microchannel, large area to volume ratio of the interfacial regions, and to the phase formation mechanism, which is characterized by the transfer of a large extent of acetonitrile from the initial phase to a chemically induced phase with simultaneous transfer of dye molecules.