Solids-Stabilized Emulsions: A Review

Introduction An emulsion is a system of dispersed droplets of one immiscible liquid in another. Simple emulsions are either oil-in-water (o/w) or water-in-oil (w/o). Emulsions can be defined as colloidal systems, although emulsion droplets are usually larger than the range specified for a colloidal system, i.e. diameter > 1 μm. Emulsions are encountered in many industries and scientific disciplines. Multidisciplinary study is required for a better understanding of emulsion behaviour and better control over industrial emulsions. In this review, solids-stabilized emulsions are reviewed and they are defined as an emulsion that is stabilized by fine solid particles. Some finely divided solids assist in the emulsion formation, and/or improve its stability. These types of emulsions have widespread applications in industrial settings and have a history of being studied, dating back to 1903. Objective of review Over the last decade, solids-stabilized emulsion experimentations are becoming increasingly more sophisticated and focused on microscopic level understanding. Some recent work has been performed to study the structure of particles at the droplet interfaces. In this review we will summarize important experimental and theoretical studies related to solids-stabilized emulsions. Considering the vast literature on solids-stabilized emulsions, this review aims at a selective, not comprehensive, overview of the progress in the field, with emphasis on key factors affecting the stability of solids-stabilized emulsions and the structure of emulsion drop interfaces.