Solubility limits of water in systems of aromatic oils and non-ionic surfactants

Abstract

The aim of this study was to formulate an aromatic oil-based concentrate stabilized by a non-ionic surfactant with a high ability to solubilize water, i.e., to produce a single-phase water-in-oil (W/O) microemulsion. The oils used were benzene, methylbenzene, 1,4-dimethylbenzene and 1,3,5-trimethylbenzene. The surfactants used were commercial nonyl phenyl polyoxyethylenes, Berol 02 with six ethoxy groups and Berol 268 with 11 ethoxy groups, and a surfactant mixture, Berol 223 with a mass fraction dipropylene glycol monomethyl ether equal to 0.2. The extension of the W/O-microemulsion phase in the systems was determined visually at 298.2 K. At low surfactant contents the solubility of water in surfactant-aromatic oil solutions is small but increases with increasing surfactant content and reaches a maximum at a given oil to surfactant ratio. At high surfactant contents the water solubility decreases again and a lamellar liquid crystalline phase is formed. As the non-ionic surfactants are mixed with sodium 1,4-bis(2-ethylhexyl) sulfosuccinate (AOT) the water solubility is obviously enhanced at low surfactant contents.