Influence of valence and concentration of electrolytes on the ?-potential of polyacrylic lattices

The zeta-Potential of Silicone Oil Droplets Dispersed in Aqueous Solutions

An experimental method to measure the zeta-potential of small liquid droplets dispersed in another immiscible liquid was presented in this paper. Basically, a liquid droplet was held stationary in a test cell by applying a proper static electric field. An existing theory shows that the electrical force experienced by the droplet can be related to the zeta-potential of the liquid droplet. Thus the zeta-potential can be determined from the force balance among the electrical force, the gravitational force, and the buoyancy force being exerted on the stationary droplet. This electrical suspension method was applied to study the effects of pH values, ionic features, and concentrations of three electrolytes and two ionic surfactants on the zeta-potential of the silicone oil (No. 1) droplets. Copyright 1998 Academic Press.

An Electrical Suspension Method for Measuring the Electric Charge on Small Silicone Oil Droplets Dispersed in Aqueous Solutions

The electric charge on small liquid droplets dispersed in another immiscible liquid is of fundamental interest in various colloidal and interfacial phenomena and industrial processes. In this paper, the authors present a new experimental method to measure the charge on small silicone oil droplets in aqueous solutions. Basically, an oil droplet was kept stationary inside a test cell between two electrode plates by application of an electric field of an appropriate polarity and strength. Thus, the electric charge on the oil droplet was determined from the force balance among the electrical force, the gravitational force, and the buoyancy force exerted on it. By using the electrical suspension method, the effects of two different silicone oils, pH values, valences, and concentrations of three different electrolytes on the measured electric charge were investigated. One of the two silicone oils is heavier (rho1 = 1050 kg m-3) and the other is lighter (rho2 = 963 kg m-3) than the aqueous solutions. There was an appreciable difference between the measured electric charges for the two silicone oils. The point of zero charge (pzc) for the heavier oil droplets was found to be pH approximately 5.0, which is essentially the same as the value for the mineral oil droplets in the oil-in-water (O/W) emulsions reported by other researchers. It was also observed that the electric charge depends strongly on not only the concentrations but also the ionic valences of electrolytes added to the solutions. More specifically, divalent and trivalent cations, such as Ca2+ and Al3+, were more readily adsorbed on the oil-water interface. Therefore, their effects were more pronounced than that of monovalent cations, Na+, on reducing the negative charge or even reversing the charge polarity as their ionic concentrations increase, in accordance with the valence difference. Copyright 1997 Academic Press. Copyright 1997Academic Press