The Effect of the zeta Potential on the Stability of a Non-Polar Oil-in-Water Emulsion

The aim of this work was to investigate the electrophoretic properties of emulsion droplets of aliphatic hydrocarbons containing C6 to C16 carbon atoms in hydrocarbon chains. As it was observed experimentally, the emulsion droplets of hydrocarbons C9 to C16 revealed a completely different course of changes of the zeta potential due to pH than the n-alkanes of shorter hydrocarbon chains (C6 to C8). They revealed a negative value of the zeta potential, lower by almost twice. The zeta potentials of emulsion droplets of the n-alkanes, from n-nonane to n-hexadecane, do not practically depend on the length of the hydrocarbon chain but, first of all, on the pH of aqueous solutions. The cause of the origin of the negative zeta potential of n-alkane droplets lies in the selective adsorption of -OH ions, causing the gathering of the excessive negative charge at the oil-water interface. As it was assumed, the stability of oil-in-water emulsion droplets in the solution, i.e., the time of collection of liquid hydrocarbons C6H28 on the surface of aqueous solutions, is the criterion of the life of emulsion droplets of n-alkanes. The observations indicate a close correlation between the emulsion droplets stability of the tested aliphatic hydrocarbons in water and the value changes of the zeta potential.