Ostwald ripening and solubilization in alkane in water emulsions stabilized by different surfactants

Abstract

The Ostwald ripening (OR) and the solubilization of alkanes in water emulsions stabilized by the anionic surfactant sodium dodecyl benzene sulfonate (SDBS) and the non-ionic surfactants hexaoxyethylene glycol n-dodecyl ether (C₁₂E₆) and polyoxyethylene (20) sorbitan monolaurate (Tween20) were investigated. For the emulsions stabilized by the anionic SDBS the mass transport in both OR and solubilization is molecular diffusion of the oil through the continuous phase and no contribution of a micellar mediated transport is observed. For the emulsions stabilized by the non-ionic surfactants three different situations occur. For emulsions prepared in one single step under the high shear conditions of a microfluidizer, the mass transport is also mainly molecular diffusion. For already prepared emulsions to which extra surfactant is added, there is, besides molecular diffusion, a small contribution by a micellar mediated mechanism. Finally, in the solubilization studies the mass transport is a fusion–fission mechanism rather than molecular diffusion.