INFLUENCE OF MOLECULAR-STRUCTURE OF HYDROCARBON EMULSION DROPLETS ON THEIR SOLUBILIZATION IN NONIONIC SURFACTANT MICELLES

Light scattering was used to study the mass transport of hydrocarbon m olecules from emulsion droplets to nonionic surfactant micelles. The h ydrocarbons used as the dispersed phase of the emulsions were: 1-tetra decene, n-tetradecane, 1-hexadecene, n-hexadecane, 1-octadecene and n- octadecane. Oil-in-water emulsions were prepared which had the same in itial droplet diameter (0.3 mu m), but different droplet concentration s (0 to 0.05 wt.%). The emulsion droplets were then suspended in eithe r pure water or an aqueous micellar nonionic surfactant solution (2 wt .% polyoxyethylene sorbitan monolaurate) and the time-dependence of th e droplet concentration and size distribution monitored at 30 degrees C using static light scattering. In the absence of surfactant micelles the size and concentration of the hydrocarbon droplets remained const ant, but in their presence the droplet concentration decreased with ti me, and the mean droplet diameter increased, indicating that solubiliz ation occurred. The growth in droplet size with time is attributed to enhanced Ostwald ripening in the presence of surfactant micelles. The mass-transport rate of oil molecules from droplets to micelles, the gr owth in droplet size with time and the maximum amount of oil solubiliz ed per unit amount of surfactant, increased in the following order: n- octadecane < 1-octadecene < n-hexadecane< 1-hexadecene <. n-tetradecan e < 1-tetradecene.