The Role of Added Electrolyte in the Stabilization of Inverse Emulsions

✍ Scribed by Paul Kent; Brian R. Saunders

• Publisher: Elsevier Science
• Year: 2001
• Tongue: English
• Weight: 130 KB
• Volume: 242
• Category: Article
• ISSN: 0021-9797
• DOI: 10.1006/jcis.2001.7792

✦ Synopsis

In this study the effect of added MgSO 4 on the properties of water-in-oil (inverse) emulsions is investigated. Addition of MgSO 4 resulted in improved emulsion stability with respect to coalescence. The average droplet size of the emulsions increased with increasing MgSO 4 concentration. However, the equilibrium oil-water interfacial tension (γ o/w ) was a decreasing function of MgSO 4 concentration. These apparently contradictory results can be attributed to differences in the relative importance of the rates for surfactant adsorption during each type of experiment. It is proposed that MgSO 4 decreases the rate of surfactant adsorption at the oil-water interface, which results in increased nonequilibrium interfacial tension during emulsification and increased droplet size. This contrasts with the interfacial tension measurements, which were made under conditions that favored the attainment of an equilibrium adsorbed surfactant concentrations. When the concentration of MgSO 4 used during the emulsion preparation was greater than or equal to 0.037 M, the tendency to flocculation upon standing increased. This behavior was ascribed to greater sedimentation forces being operative for the emulsions containing a larger average droplet size. The relatively low energetic barrier to flocculation for W/O emulsions (cf. O/W emulsions) appears to make these emulsions more susceptible to differences in sedimentation forces.