Solvent extraction in membrane microcontactors: modeling, spacer structuring and applications
8 January 2015
Campus VUB Etterbeek - Promotiezaal - Pleinlaan 2 - 1040 Etterbeek
5:00 PM - 7:00 PM
Prof. dr. ir. Wim Demalsche / Prof. dr. ing. Tom Breugelmans
PhD defence Jonas Hereijgers - Faculty of Applied Engineering (UAntwerp) - Faculty of Engineering
Microfluidic technology concerns the manipulation of fluids (gas or liquid) in channels with dimensions lower than 1 mm, typically between 10-100 µm and has grown over the past 25 years into a mature field. Because of these small channel dimensions, chemical process operations like mixing, reactions, dosing, analyses, etc. have acquired substantial efficiency gains. However, one aspect remains underdeveloped: general techniques that enable continuous purification, in other words downstream processing. One technique that has been reported to be promising for microfluidics, because of its universal applicability, is solvent extraction.
Solvent extraction is the distribution of one or more chemical species (solutes) between two immiscible liquids due to a difference in solubility and used to separate the solutes from one another. To execute solvent extraction the liquids are first contacted, typically by mixing (i.e. dispersing) to acquire equilibrium, and then again separated. Both steps preferably proceed as fast as possible. The paradox that however exists in solvent extraction is that equilibrium is quickly obtained upon intensive dispersing, but this adversely affects the subsequent phase separation step.
In this work, a membrane microcontactor concept is proposed that can either be employed on the laboratory scale (e.g. parameter screening), but also easily scaled to small-scale production levels. With membrane contactors the two liquids flow along each side of the membrane, preventing dispersion of the two solutions and consequently omitting a phase separation step. However, with current membrane contactors the equilibrium is attained slowly, typically in the range of hours. To speed this up, microfluidic technology was combined with the membrane contactor concept into a membrane microcontactor, enhancing the extraction rate substantially.
In the first part of the thesis, models were developed to describe the extraction rate, investigate interface stability effects, and provide general design guidelines. In the second part, the performance of the membrane microcontactor was examined both in the field of sample preparation for analytical purposes as in the field of hydrometallurgy for metal separation.
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