Flow patterns of ionic liquid based aqueous biphasic systems in small channels

Ionic liquid based aqueous biphasic systems (IL-ABS) were formed by the addition in water of a hydro-philic ionic liquid (1-Butyl-3-methylimidazolium Chloride, C4mimCl) and a kosmotropic salt (tripotas-sium phosphate, K3PO4). The flow patterns of IL-ABS were studied in capillary channels with 0.2, 0.5 and 0.8 mm internal diameter; this is the first time such two-phase flows have been investigated. Three weight concentrations of the ionic liquid and the salt (18, 20 and 22 wt%) were chosen within the biphasic region. The main flow patterns included plug, dispersed and parallel flow. It was found that both channel diameter and weight concentrations would affect the flow patterns observed. Finally, a gen-eralized flow pattern map was plotted using a combination of capillary and Reynolds numbers, where the transition boundaries of plug flow collapsed for all ionic liquid and salt concentrations studied.& COPY; 2022 The Author(s). Published by Elsevier Ltd. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).

Automated summary

Ionic liquid based aqueous biphasic systems (IL-ABS) were formed by adding a hydrophilic ionic liquid (C4mimCl) and a kosmotropic salt (K3PO4) to water. Flow patterns in capillary channels were investigated for the first time, using three different internal diameters and weight concentrations of the IL and salt. The main flow patterns observed were plug, dispersed, and parallel flow, which were influenced by both channel diameter and weight concentrations. A generalized flow pattern map was plotted based on capillary and Reynolds numbers, showing the collapse of plug flow boundaries.