University of Twente
Faculty of Science and Technology
P.O. Box 217
7500 AE Enschede
The enhancement of mass transfer/extraction efficiency of liquid-liquid (LL) extraction systems using an inert gas phase (GLL) is an interesting phenomena with applicability to a wide number of systems. More recently, work has been done to measure the extraction performance and mechanism by studying the process at smaller length scales in capillaries (mm scale) by performing extractions and measuring the resulting flow patterns by visualization (high-speed camera). At these scales, the interfacial forces cannot be neglected and play an important role in phase stability and the nature of flow through the system; parallel-flows or two- and three-phase slug flows may arise, which have important implications for the mass transfer efficiency in these types of systems. The mechanism behind this enhancement is presently under investigation, requiring detailed measurements at varying flow conditions in order to determine the gas effect on various process parameters. These include interfacial area between liquid phases and the stability of flow regimes for example.
The purpose of the proposed assignment is to investigate the influence of patterned wettability gradients in a capillary on the two- and three-phase flows (LL and GLL) and liquid-liquid extraction in these systems . Switching between hydrophilic and hydrophobic domains in a periodic fashion can lead to phase inversions/mixing patterns which may greatly enhance mass transfer. This will be accomplished through image/video capture using a high-speed camera, with subsequent flow patterns characterized using image analysis. Study of these flow patterns is then highly relevant for quantifying what possible enhancements can be realized through the use of such patterned-capillaries. Corresponding liquid-liquid extractions will be investigated using an established model system (acetic acid-water-octanol) initially, with an emphasis on determining the role of gas and wettability patterning on the resulting extraction efficiencies vs. a two-phase flow system.