Some Stability Criteria for Double Emulsions

Abstract

Double W/O/W emulsions consist in an inverse emulsion which is dispersed within a water continuous phase as direct emulsion droplets. The aim of this paper is to explore the basic rules that govern the stability of double emulsions. By associating both water-and oil-soluble surfactants in various concentrations, we produce W/O/W double emulsions. We identify two types of instabilities that are responsible for the evolution of double emulsions: (i) coalescence of the small inner droplets with the globule interface or (ii) coalescence between the small inner droplets within the oil globule. The first type of instability leads to a complete delivering of the small inner droplets toward the external phase whereas the second one does not. We show that the kinetics associated with the release of the small inner droplets due to this former instability is clearly related to the hydrophilic surfactant concentration in the external phase. Depending on the value of this concentration, multiple emulsions may be destabilized with a time scale ranging from several months to a few minutes. We discuss the basic criteria which are responsible for the suppression or the starting of these instabilities, emphasizing the influence of the composition of the interfacial films.

Removal of Heavy Metal From Aqueous Wastewater by Emulsion Liquid Membrane.

“…Double emulsions may be either of the water-in-oil-in-water type (W/O/W) (with dispersed oil drops containing smaller aqueous droplets) or of the oil-in-water-in-oil type (O/W/O) (with dispersed aqueous globules containing smaller oil dispersed droplets). [8] Liquid membrane extraction processes have certainly some attractive features like simple operation, high efficiency, extraction and stripping in one stage, larger interfacial area and scope of continuous operation. [9,10] In ELM mass transfer surface area to volume ratio is very high up to (1000 -3000m 2 /m 3 ) and internal surface area to volume ratio is also lager (106 m 2 /m 3 ).…”

“…On the other hand, an overly stable emulsion causes problems during its settling and de-emulsification after it extracts the pollutants [12]. There are only a small number of investigations have been made on the stability of (W/O/W) Fig.1 Different Types of Emulsion [8] emulsion system in stirred vessels. [13] Instability of ELM results in their tendency to undergo swelling and internal phase leakage (breakage).…”

A Double Emulsion-Based, Plastic-Glass Hybrid Microfluidic Platform for Protein Crystallization

“…There are several factors that affect the stability of emulsions, such as preparation methods, compound formulation, storage conditions, and so forth [47]. Here, we focused on storing double emulsions under different environments with the results shown in Figure 3a.…”

<b>Formulation and characterization of a multiple emulsion containing 1% L-ascorbic acid</b>

“…Although diffusion is the most important mechanism of transport in the multiple emulsion systems, there is evidence that ionized materials may pass across the oil layer. Kita et al [25] suggested that ionized drug along with water is mixed with micelles of hydrophilic and hydrophobic surfactants and cross the oil layer. Another possible transport mechanism is carrier mediated transport [26].…”

“…For the multiple emulsion, while no liquefaction was observed in the samples kept at 8 o C (in refrigerator) and 25 o C (in oven) during 28 days, slight liquefaction was observed in the samples kept at 40 o C (in oven), 40 o C at 75% RH (in stability cabin) on 21st day. Liquefaction is the sign of instability; it may be attributed to the passage of water from the internal phase to external phase as described by many researchers [23,25].…”