FORMATION AND PHASE-BEHAVIOR OF WATER-IN-DIESEL OIL MICROEMULSION WITH SODIUM OLEATE AND CETYLTRIMETHYLAMMONIUM BROMIDE

The phase behavior and solubilization of multiphase microemulsions in mixed anionic-cationic surfactant systems ware studied for fixed ratio s of water to diesel oil and surfactant to alcohol. In the mixed surfa ctants (sodium oleate + cctyltrimethylammonium bromide) /diesel oil/ a lcohol/water systems, microemulsion and birefringent phases are formed by adjusting the surfactant ratio epsilon and the cationic weight fra ction delta. The bicontinuous-->birefringent-->o/w microemulsion trans ition takes place with dilution for i-pentanol-containing systems. The birefringent region shrinks rapidly with increasing alcohol and/or CT AB weight fractions in total surfactant concentration. The normal solu tion-->w/o microemulsion transition for n-hexanol systems and only win microemulsion for n-octanol systems were observed along the dilution with diesel oil and water. And microemulsion domain enlarges with incr easing epsilon for three alcohol systems. The optimum surfactant conce ntration gamma increases and the corresponding optimum delta decreases with increasing epsilon and the optimum gamma decreases with increasi ng the alcohol chain length from i-pentanol to n-octanol and the optim um delta decreases in the order of i-pentanol > n-octanol > n-hexanol. Conductivity measurements have been performed in the single phase reg ion of the system containing mixed-surfactants and alcohols at 25 degr ees C. The conductivity results indicate where a transition takes plac e and which these different types of phase structure may be in the sin gle-phase of the system containing anionic-cationic mixed-surfactants.