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.