Study of the Cloud Point of Nonionic Surfactant and Nonionic-cationic Surfactant Mixture: Effect of Electrolytes

Clouding phenomenon generally occurs with nonionic surfactants when the temperature of the system is raised to a certain value. This critical temperature is termed the cloud point (CP). The aqueous solutions of nonionic surfactants show complex phase behaviour including liquid-liquid phase separation at this temperature. The cloud point of aqueous surfactant solutions is influenced by the presence of other materials. In this study, we used cetyltrimethylammonium bromide (CTAB) as cationic surfactant and polyoxyethylene (10) lauryl ether (C12EO10) as nonionic surfactant. We report the effect of electrolytes (NaCl, KCl, CaCl2 and MgCl2) on the CP of nonionic surfactant and nonionic with cationic surfactant mixture. All the electrolytes have a large amount of effect on CP. INTRODUCTION Surfactants contain both hydrophobic and hydrophilic regions, which make possible molecular aggregate disolution in water. This amphiphilic molecules form dynamic aggregates namely micelles, which makes the solubilization of waterinsoluble molecules in an aqueous matrix possible [1, 2]. Clouding is a phenomenon familiar in nonionic surfactants; upon raising the temperature, the system becomes cloudy and phase-separates at a well-defined temperature. The phase separation in nonionic micellar solutions is due to the van der Waals attractive forces between the micelles, and there exists a temperature at which the degree of hydration of the hydrophilic portion is just insufficient to solubilize the remaining hydrocarbon portion. At this temperature, surfactant is no longer soluble in water and solution becomes hazy and cloudy. Nonionic surfactants are widely used as solubilizers, emulsifiers and detergents in many industrial processes. Furthaermore, they are used as auxiliaries improving dye adsorbtion and levelling or dispersing agents [3, 4, 5]. Therefore, the cloud point (CP) data are of considerable practical