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 systems with certain physical properties modified by various additives. In general, because of polarization and deformation effects, coalescence of aqueous drops is facilitated by the application of electric fields. As a result, with an increase in the applied voltage, the ambivalence regime-the range of the organic volume fraction plotted versus energy input, in which either phase may be continuous or dispersed-is narrowed and shifted toward higher volume fraction of the organic phase. Effects of physical properties of liquid-liquid dispersions such as aqueous-phase conductivity, organic-phase viscosity; aqueous-phase pH, and liquid-liquid interfacial surface tension are reported here. Variation of these physical properties affected the ambivalence regime differently under the conditions with and without an applied electric field. The phase-inversion behavior was studied in the agitation range of 450-1000 rpm for an applied-voltage range of 0-1000 V, using a stirred tank equipped with a Rushton impeller. The effect of electric fields on the drop size distribution was also studied for both organic-phase-dispersed and aqueous-phase-dispersed. The drop size distribution of aqueous drops shifted toward larger size while no significant change in the size of organic drops was observed as the field strength increased. The experimental results are qualitatively interpreted based on the electric polarization mechanism and drop-breakage/coalescence arguments.