Phase studies of microemulsions with alcohol ethoxylates: effects of temperature and salinity

Abstract

The phase behavior of microemulsions of motor oil with alcohol ethoxylates was studied. The addition of n-butanol as a cosurfactant was found to facilitate microemulsion formation. For the alcohol ethoxylate (E03)-n-butanol-motor oil- water system, temperature had a significant effect on the microemulsion phase transformation and the lowest value of critical microemulsion concentration (CµC) was achieved at 40 °C, the solubilization capacity increased with increasing in temperature. For the mixed surfactants of methyl ester sulfonate (MES) and alcohol ethoxylate (E03) at a weight fraction of MES = 0.02, an increase in NaCl concentration increased the CµC and the solubilization capacity. From the solubilization parameter (SP) results, temperature and salinity facilitated the solubilization of oil and the formation of the middle (Winsor type III) microemulsion phase. In addition, the lowest IFT increased with increasing temperature. For salinity effect, the IFT reached ultra-low value at the salinity range from 3.9 to 4.7 %wt/vol. The CMC of the alcohol ethoxylate(E03)/MES mixed surfactants was 0.01 %wt/vol which was close to those of both single alcohol ethoxylate(E03) and single MES surfactant systems.