Salt Effects on Single Aqueous Drops Falling through an Immiscible Organic Liquid

Abstract

Drop settling (or rising) is crucial to the breaking of liquid-liquid dispersions. Most of the empirical correlations for terminal velocity of drops are formulated based on experimental data for systems of dispersed organic phase and continuous aqueous phase using pure and nearly pure liquids. Because the presence of the various third components in one or both of the phases may affect the settling of the drops, the terminal velocity and the onset of oscillation of aqueous drops containing various concentrations of electrolytes falling through n-dodecane were studied in this work. The applicability of existing empirical correlations to these reversed systems of continuous organic phase and dispersed aqueous phase was also examined.Dissolved electrolytes have the effect of causing the terminal velocities and their peak velocities at the onset of drop oscillation to become faster and the peak diameters to become smaller when their concentrations are high enough to cause sufficient changes of physical properties. Existing correlations for drop terminal velocity in pure systems are shown to be adequate in the presence of electrolytes. For high interfacial tension systems, the Hu-Kinter correlation predicts the terminal velocity of organic drops in water and aqueous drops in organics equally well, independent of the presence of electrolytes.The criteria of Hu-Kintner can be used to estimate the peak velocities and peak diameters at the onset of oscillation within a deviation of 3.7%.

An experimental study on single drop rising in a low interfacial tension liquid–liquid system

“…As a result, increase of density difference becomes the major factor to influence terminal velocity. Therefore, terminal velocity increase obviously at high concentrations, which also accounts for the same trend in literature (Chen et al, 2010). But the difference is that the butanol/water system shows a very small variation at low concentration due to limit interfacial tension change.…”

“…His work revealed that a toluene drop was slowed down because the addition of salt. Also in toluene-water test system, Chen et al (Chen et al, 2010) found that the terminal velocity was increased as the salt concentration increased from 0.01M to 2M. Zameek et al (Zameek et al, 2016) derived the same trend as Chen et al, they studied the single crude oil drop rising in electrolytes with low, moderate and high concentration.…”