L. (Luuk) van der Velden

BSc student

University of Twente

Science and Technology

Meander, ME 312

P.O. Box 217

7500 AE Enschede

The Netherlands

Email l.vandervelden@student.utwente.nl

Research description

Liquid-liquid two phase flows and solvent extraction

The present bachelor assignment is included within a research project currently being conducted, which aims at producing an efficient microfluidic device for liquid-liquid extraction. Basically, the device is to generate an emulsion of two immiscible fluids, one of them organic and the other aqueous; after the emulsion is generated both fluids remain in intimate contact and a dispersed solute originally present in the organic fluid diffuses towards the aqueous fluid through the fluid-fluid interface; once the extraction of the dispersed solute is complete, both fluids are separated by means of a selective membrane or a membrane-like device (See sketch if Fig. 1).

Fig 1. Sketch of the microfluidic device for liquid-liquid extraction

In this context, the bachelor assignment will support the research project with a three-fold task:

First, it will generate a liquid-liquid two-phase flow in a micro T-junction and a subsequent microfluidic channel. The working fluids will be an alkene, presumably pentene, and water. This two phase flow will be characterised, identifying the regions of the different flow regimes. Special focus will be for droplet based regimes and their hydrodynamic conditions. The different regimes of formation of droplets can be also identified, for a further analysis of the mass transfer in the initial stages of the two-phase flow. The study of the two-phase flows will be performed with brightfield microscopic imaging.

Once the two-phase flow conditions have been characterised a dispersed solute, presumably a dye, will be added to the organic fluid to analyse the performance of its extraction to the aqueous phase, at different locations along the microfluidic channel and as a function of different factors such as, initial concentration of solute, slugs length and slugs velocity. The performance parameters include the extraction factor, the distribution coefficient and the mass transfer coefficient. The analysis of the solute extraction during the initial stages of the two-phase flow is also an interesting possibility, that will allow to identify whether the different regimes of droplet formation play an important role in the overall process or not. The comparison of the extraction performance between droplet-based flows and other two-phase flow regimes remains as a possibility as well. For this task, it must be assessed whether or not the added solute interferes in the properties of the fluids, such as the relative viscosities or the interface tensions. The mass transfer data will be obtained both with brightfield microscopic imaging and UV-Vis detection.

Finally, the previous step will be complemented comparing it with the results of a numerical analysis of the mass transfer process in the droplet-based two phase flow. For this analysis the nature of the flow will be previously simplified and a commercial simulation tool, presumably COMSOL Multiphysics, will be used.