Effect of Water on the Dispersion of Colloidal Alumina in Cyclohexane Solutions of Aerosol OT

Colloidal dispersions in nonpolar media are used in a variety of technological applications, and in most of these applications, water is present and plays a major role in determining the dispersion behavior. The effect of water on the stability of colloidal suspensions of alumina in cyclohexane in the presence of a surfactant, Aerosol OT, is discussed here. A succession of flocculated, dispersed, and again flocculated states are observed as the amount of water added to the suspension is increased. Adsorption studies show colloidal stability to be controlled by the activity of water in solution which is best described by the ratio Wo (H~)/(AOT]. Tests using electron spin resonance (&9R) spectroscopy detected an increase in lateral diffusion of the surfactant molecules at the interface as more water was added to the system. A fingering mechanism in which the water phase forms bridges between particles is proposed for the waterinduced flocculation in nonpolar media.