Study of the properties of oil, particles, and water on particle adsorption dynamics at an oil/water interface using the colloidal probe technique

The replacement of traditional molecular surfactants by nano- or micrometer-sized solid particles in emulsification processes offers many advantages and new opportunities for process industries. The solid-stabilization of emulsions occurs in three steps: (1) the particles first approach and contact.the fluid/fluid interface, (2) the particles adsorb to and are trapped at the interface, and (3) the adsorbed particles form a network that stabilizes the emulsion. The current state of knowledge makes process design impossible or impracticable, mainly because of the lack of information on the overall stabilization mechanism. A colloidal probe technique (atomic force microscopy) was used to measure the adsorption force and time of model glass and polyethylene microspheres to a planar silicone oil/water interface. Particle approach, contact, adsorption, and detachment as well as adsorption time were studied. Force curves revealed that a repulsive force is involved during approach and contact and an attractive force is involved during adsorption. Particle properties governed the approach, contact, adsorption, and detachment steps, and oil viscosity had a significant impact on the contact force and adsorption time. Aqueous phase pH and salinity had no significant effect on the adsorption and detachment time but were involved during the approach step through their effect the electrostatic double layer force. (c) 2016 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.