Phase inversion of liquid-liquid dispersions under applied electric fields

This paper presents experimental studies on the effects of applied electric fields on aqueous/organic liquid-liquid dispersions, using toluene/water s ystems with certain physical properties modified by various additives. In g eneral, because of polarization and deformation effects, coalescence of aqu eous drops is facilitated by the application of electric fields. As a resul t, with an increase in the applied voltage, the ambivalence regime the rang e of the organic volume fraction plotted versus energy input, in which eith er phase may be continuous or dispersed-is narrowed and shifted toward high er volume fi-action of the organic phase. Effects of physical properties of liquid-liquid dispersions such as aqueous-phase conductivity, organic-phas e viscosity, aqueous-phase pH, and liquid-liquid interfacial surface tensio n are reported here. Variation of these physical properties affected the am bivalence regime differently under the conditions with and without an appli ed electric field. The phase-inversion behavior was studied in the agitatio n range of 450-1000 rpm for an applied-voltage range of 0-1000 V, using a s tirred tank equipped with a Rushton impeller. The effect of electric fields on the drop size distribution was also studied for both organic-phase-disp ersed and aqueous-phase-dispersed. The drop size distribution of aqueous dr ops shifted toward larger size while no significant change in the size of o rganic drops was observed as the field strength increased. The experimental results are qualitatively interpreted based on the electric polarization m echanism and drop-breakage/coalescence arguments.