The mechanism of emulsion stabilization by small silica (Ludox) particles

Abstract

Small silica particles of the Ludox type, when combined with a costabilizer, can be used to stabilize fine droplet sized oil-in-water emulsions, having an excellent stability towards coalescence. The stabilization mechanism involves two steps; (i) agglomeration of the silica particles and (ii) adsorption of agglomerates of silica particles at the oil/water interface. The high emulsion stability is due to the presence of multiple silica particle layers around the droplets. The role of the costabilizer is to induce silica particle agglomeration. Silica particle aggregates seem to adsorb spontaneously at the oil/water interface irrespective of their charge density or structure. The important role of agglomeration in emulsion stabilization by small particles is discussed with reference to the practice and theory of fine particle flotation.