Cloud Point and Microemulsion Phase Behavior of Sodium Linear Alkylbenzene Sulfonate with Tetrabutyl- And Benzyltributyl-Substituted Ammonium Halides

Abstract

We report cloud point phenomenon in binary water-anionic surfactant (sodium linear alkylbenzene sulfonate, NaLAS) after incorporation of organic salts, such as tetrabutyl- and benzyltributyl- ammonium halides. The effect of alkyl/aromatic hydrophobic substituents of such reagents on the cloud point phenomenon was also investigated. It was observed that the aqueous solution clouding behavior is dependent upon surfactant concentration, type of hydrophobic substituent of the salt, and operating temperature. At a given temperature, with increasing surfactant concentration, a higher amount of salt is required for the onset of clouding. Besides, at a given surfactant concentration, the amount of salt required for the cloud point is inversely proportional to the temperature. With addition of an oil phase to the binary water(salt)-surfactant system, a three-phase microemulsion could be generated. Phase diagrams for these ternary systems were determined, and the formation of the microemulsion phase behavior was established from phase visualization and oil—water interfacial tension measurements.