THE FORMATION OF WATER-IN-OIL MICROEMULSIONS USING A CONCENTRATED SALINE AQUEOUS-PHASE

The formation of a water-in-oil (W/O) microemulsion with a water phase containing up to 30% w/w NaNO2 and diesel oil as the oil phase, with the cationic surfactant cetyltrimethylammonium bromide (CTAB) and an a lcoholic cosurfactant has been examined. The cosurfactant chain length , alcohol isomerism, solution salinity, temperature, CTAB:alcohol rati o and the effect of combining various alcohols were studied. The best set of conditions for the formation of a microemulsion with a maximum salt concentration whilst utilising a minimal amount of surfactant hav e been determined. The use of short chain unbranched alcohols (C3-C5), especially 1-butanol, or a combination of short alcohols (1-butanol a nd 2-propanol), and a CTAB:alcohol ratio between 60:40 and 70:30, with 68:32 are seen to be of primary importance for microemulsion formatio n. In addition, the extent of the W/O region on the phase diagram is s hown to be temperature dependent, with higher temperatures increasing the extent of the one phase region. (C) 1998 Elsevier Science B.V.