Phase inversion studies in liquid-liquid dispersions

A study of the phase inversion behavior of liquid-liquid dispersions in stirred vessels is performed for liquids of various physical properties at various operating conditions. Physical parameters studied are density (867 to 1180 kg/m³), viscosity (0.00096 to 0.00378 Pa·s), and interfacial tension (0.0089 to 0.0323 N/m). Ambivalence region plots are presented and compared with results reported in the literature. Experiments are performed to examine the effects of impeller type and impeller-to-tank diameter ratio (D/T) on the ambivalence behavior. Also, phase inversion time experiments are performed to investigate the time required for complete phase inversion under various dynamic conditions. The traditional method of plotting the organic phase volume fraction at phase inversion against the agitation speed at that condition is compared with the method of plotting the initially dispersed phase volume fraction at phase inversion against the agitation speed at that condition. A hysteresis phenomenon is shown in phase inversion from O/W to W/O and W/O to O/W dispersions. Also, it is shown that, depending on the physical properties of the dispersed and continuous phases, phase inversion may occur when the agitation speed is increased or decreased.