Phase Behavior of Sodium Dodecyl Sulfate-n-Butanol-Kerosene-Water Microemulsion System

Experiments were carried out to investigate the influences of cation from electrolytes and acidity/alkalinity on the phase behavior of sodium dodecyl sulfate-n-butanol-organics-water (with electrolytes) microemulsion system. The organics used is commercial kerosene. The volume ratio of water to organics is 1:1. The results show that the type and valence of electrolyte cations are important factors influencing the microemulsion behavior. Bivalent Ca²⁺ is more effective than monovalent K⁺ and Na⁺ for the formation of Winsor type III and II microemulsion. For electrolytes with the same monovalent cation Na⁺, #em/em#.e. NaCl and Na₂CO₃, anions in the electrolyte have some effect. Bivalent anion leads to a lower activity of cation Na⁺ than monovalent anion Cl^-. NaOH (or KOH) behaves similar with NaCl (or KCl). When HCl is used as electrolyte, its acidity plays an important role. Phase inversion of microemulsion from type III (or II) to type I is observed through precipitation of Ca²⁺ using Na₂CO₃, neutralization of HCl by NaOH, and addition of water to the system, which releases the oil from the microemulsion.