The effect of an applied electrical field on the interfacial tension at an oil/water interface has been explored. Water droplets were formed at a charged nozzle immersed in a low dielectric constant liquid. The diameters of detaching water droplets were measured by recording the volume of a given number of detaching droplets and interfacial tension was calculated from the drop diameter using the Harkins-Brown formula. The oil phase in our studies was heptane with and without a metal extractant. The metal extractant studied was P50 (5-nonylsalicylaldoxime). In another range of experiments the oil phase was a mixture of heptane and octanol in different proportions. A decrease in drop diameter (corresponding to a decrease in the interfacial tension) with increased applied voltage was observed in all instances. The decrease in interfacial tension, which denotes the accumulation of charge carriers (ions) at the interface, depends upon the transport numbers and concentrations of the ions in the two phases and also upon the current. The behavior of interfacial tension in the presence of an applied electrical field is the same for systems with and without extractant in the organic phase. The purpose of the study was to gain an insight into the phenomenon of mass transfer intensification of a solute across an interface of two immiscible liquids by an electric field applied normal to the interface.
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