It is known that heterogeneous liquid-in-liquid system can exist in two general states: Properties of emulsions, mini- and micro-emulsions This paper might be of interest for people specializing in the following fields: We suggest that ion exchange between the exterior and interior diffuse layers leads to a gradual collapse of the exterior DL and explains all the experimental observations. This fact, combined with conductivity measurements, indicates a strong role for electrostatic factors in emulsion stability and its transition to mini-emulsion state. In the final state the mini-emulsion droplets generate practically no electroacoustic signal and appear uncharged. The measured electroacoustic signal gradually decays with time. The conductivity exhibits a rapid change during the first 10 hours of emulsion coalescence, but the rate becomes much slower as the mini-emulsion fraction begins to grow.Įlectroacoustic measurements shows that the original emulsion droplets carry a substantial surface charge, which we are able to calculate using Shilov’s theory for overlapped DLs. It takes another 24 hours for the emulsion droplets to completely transform into a mini-emulsion state. At this point a mini-emulsion fraction appears with a droplet size of only 25 nm and the droplet size distribution becomes bimodal. After 10 hours the droplet size has increased to about 5 microns. The original droplets, having a size of about 0.4 micron, slowly coalesce into larger droplets. We confirm our measurements with microscopic image analysis.Īcoustic measurements yield information about the droplet size evolution in time. Continuous stirring prevents sedimentation. We continuously monitor this transition in relatively concentrated samples (5% vl water), without dilution, using Acoustic, Electroacoustic and Conductivity measurements. Water-in-kerosene emulsion stabilized with SPAN surfactants exhibit a slow transition (on scale of hours) from an emulsion to a mini-emulsion state. Evolution of water-in-oil emulsion controlled by droplet-bulk ion exchange.Īcoustic, electroacoustic, conductivity and image analysis.ĭispersion Technology Inc., 364 Adams Street, Bedford Hills, NY 10507, U.S.A.
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