Effect of Added Salt on Three-Phase Behavior in a Sucrose Monoalkanoate System

Abstract

Effect of added salt on the three-phase behavior of microemulsion in water/octaethylene glycol dodecyl ether (C12EO8)/hexanol/decane and water/sucrose monododecanoate (SMD)/hexanol/ decane systems was investigated at 25 °C. The three-phase body is shifted to higher hexanol mixing ratio upon addition of KSCN, whereas the opposite tendency is observed upon addition of NaCl in the C12EO8 system. These phenomena can be explained by salting-out and salting-in effects, respectively. On the other hand, the three-phase body is shifted to higher hexanol mixing ratio upon addition of both inorganic salts in the SMD system. In the absence of oil, however, the effect of added salt on the clouding phenomena in the SMD system is similar to that in the C 12EO8 system. The mixing fraction of hexanol in the total surfactant (nonionic surfactant + hexanol) in the interface of micro-oil and water domains inside the middle-phase microemulsion is estimated according to the geometrical relation of a three-phase body in the space of compositions. As a result, the effect of added inorganic salt on the mixing fraction in the interface is opposite to that on the apparent mixing fraction of hexanol in the total surfactant to form the three-phase body in the SMD system. Consequently, this novel phenomenon can be explained by the change in the nature of excess oil phase or micro-oil domain due to the high solubility of hexanol in oil. LA961067W

Sugar-Ester Nonionic Microemulsion: Structural Characterization

“…Consequently, increasing the temperature does not induce a phase inversion in microemulsion systems based on sucrose esters, as was observed in microemulsions based on alkyl ethoxylates. Temperature-insensitive sucrose-ester-based microemulsions are described in the literature (8,11,12). In most cases a paraffinic oil phase was used and the surfactants were mostly mixtures of ethoxylated alcohols and sucrose esters.…”

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“…Another aim of this work is to investigate the effect of added monovalent electrolyte on the microemulsion phase behavior of mixed anionic-cationicoil-water systems. Although a number of researchers have evaluated the effect of added electrolyte on the microemulsion phase behavior of ionic surfactants (36)(37)(38)(39), previous research has not evaluated alcohol-free mixed anionic-cationic surfactant systems. Anton et al (20) studied the effect of added monovalent electrolyte on the cationic surfactant fraction in a mixed anionic-cationic surfactant system for an oil-NaCl-alcohol system.…”

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“…The three-phase body does not shrink very much over the measured range with added NaClO 4 , so it is doubtful there is a tricritical point nearby. The effect of various salts on the phase behavior of microemulsions made with sucrose monoalkanoates is similar (40).…”