Flooding characteristics of an aqueous two-phase system in a counter-current Kühni-type column

• Flooding characteristics of an aqueous two-phase system were investigated.
• The extraction device was a continuous agitated Kühni-type column.
• The onset of flooding was well predicted using classical literature correlations.
• Correlations for droplet diameter in the agitated column are valid.
• The maximum column capacity is low, due to small density difference.

The flooding behavior of an aqueous two-phase system was investigated using a laboratory-scale counter-current agitated Kühni-type column. Experimental flooding limits were compared to the literature which has been established for aqueous–organic two-phase systems. Although the density difference and interfacial tension in the aqueous two-phase system studied were beyond the values typically encountered in aqueous-organic systems, comparison to the existing literature allowed for a prediction of the onset of flooding. Thus existing estimation procedures of the mean Sauter droplet diameter and terminal droplet velocity can be applied to aqueous two-phase systems.