Purification of Ge(IV) in milliflow reactors

Using in-line membrane-based phase separation

 

In millifluidic reactors, membrane separators have become popular for the separation of the phases. Usually the continuous phase is permeated over the membrane while the dispersed phase remains in the retentate. Because of the hydrophobic nature of the tubing used in this type of reactors, the organic phases always form the continuous phase and therefore hydrophobic membranes are selected to allow permeation of the continuous organic phase. The required pressure for permeation over the membrane is dependent on the viscosity and can be expected to be relatively high for ionic liquids which can result in failure of the separation module.

 

One way to lower viscosity is to increase the temperature, however working at elevated temperatures can reduce the life time of the membrane. Another way to lower viscosity is to use diluents. In this work, the aromatic solvent p-cymene was used because it can be considered a greener alternative to toluene as it can be derived from biomass. For the current system, reduction of the viscosity of the organic phase and use of a membrane with a sufficiently small pore size allowed a good separation performance. Fig. 1 shows a schematic representation of the experimental setup used during the single- and multi-stage continuous millifluidic experiments.