A segmented flow separation of two immiscible liquids in microprocesses can be achieved by using a membrane microseparator. Driving force of a membrane separation is difference in wetting properties between both liquids. Usually a hydrophobic membrane is used which wets organic phase and retains water phase. In order for the organic phase to pass through membrane pores, a sufficient transmembrane pressure needs to be applied. The transmembrane pressure is function of fluid properties, flow rate and outlet tube dimensions. For a successful separation with the membrane microseparator, transmembrane pressure must be lower than capillary pressure, which is a function of membrane properties and interfacial tension. In comparison to other separators for slug flow separation, membrane microseparators have larger operating window and at the same time, they are easier to manufacture. The most important property of membrane microseparators is ability to completely separate both phases.
There are two key strategies for scaling-up microprocesses: a numbering-up and a scale-out by suitable dimension enlarging, the latter one was used for developing my membrane microseparator. FreeCAD was used to design the new microseparator, which would have allow higher flow rates during separation. Separation experiments were conducted for three different two-phase systems: water-dichloromethane, water-n-butanol and water-heptane with flow rate ratio 1:1. For total flow rates in range 1-4 ml/min separation, efficiency was 100%. A direct comparison of 100% separations of other membrane separators cannot be carried out because they were performed in different two-phase systems. Nevertheless higher flow rates in the manufactured membrane microseparator should be achieved by using a membrane with bigger pores and by an implementation of back pressure regulator.
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