Detailed mass transfer studies of a ternary system associated with intermittent jerking of the liquid − liquid interface

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Experiments were carried out to transfer diethylamine (DEA) from water to carbon tetrachloride under static conditions inside a 50 cm3 buret for the fixed initial concentration of 2.5 mol dm−3. Initial concentration was chosen after ruling out lower concentrations to study the long-term instability. The phase volumes (i.e., 5 and 10 cm3) were equal for the separate trials at different extraction times. During extraction, intermittent interfacial jerking occurred up to 1800 s. After this time, the jerking frequency decreased and disappeared by 3600 s. The jerking time interval increased as the extraction progressed. Jerking resulted in profuse streaming into the extract phase, coupled with a throw of liquid from the interfacial region to the bulk of the aqueous phase. The complete concentration profiles of the solute in both phases were developed immediately after the jerking phenomena. In the aqueous phase, the concentration profiles revealed one and two zones of the minimum concentration of DEA in the bulk of the 5- and 10-cm3 phase volumes, respectively. The interfacial mass transfer coefficient during the jerking was high due to the absence of any interfacial barrier. The interfacial mass transfer coefficient in the absence of instability was much less than that in the presence of jerking. Also, it was higher than that for the systems where unidirectional ejections occurred due to the energy instability of the liquid–liquid interface. This work has also estimated the average spreading velocity of the interface, which caused the jerking due to the obstruction from the wall.