(175a) Synergistic Stabilization of Emulsions and Foams With Particles and Surfactants

The combination of zwitterionic surfactants and silica or clay nanoparticles and microparticles provides synergism in formation and stabilization of dodecane droplets in synthetic seawater. These combined amphiphiles are of interest for mitigation of oil leaks at the ocean floor. The surfactant lowers the oil/water interfacial tension and allows the formation of oil/water emulsions composed of small oil drops (<100 micron diameter), while the presence of nanoparticles at the oil/water interface enhances emulsion stability by providing a larger steric barrier to droplet coalescence than surfactants alone.  

Droplet sizes were analyzed with optical microscopy and static light scattering, and the dispersion mechanisms for various formation pathways were explored via scanning electron microscopy. Droplet size and emulsion stability were characterized for a range of temperatures down to 4°C, to simulate deep-sea conditions, and over time-scales up to one month. The effect of particle hydrophilicity was also explored by using cation-exchange to tune surfactant adsorption on clay surface sites, which decreases hydrophilicity.

Similar synergistic benefits of combined surfactant/particle dispersant mixtures have been observed for emulsions and foams of carbon dioxide and water, which is of interest in enhanced oil recovery.  Thus, the phenomena of particle/surfactant synergy may be of interest in many fields where stable emulsions or foams are desired.