Turbidimetric evaluation of the solubilization rate: dissolution of dodecane nanodrops in 7.5 mM sodium dodecylsulfate solutions at selected sodium chloride concentrations

Rodriguez, Jose Daniel; Espinoza, Maurice; Rahn-Chique, Kareem; Urbina-Villalba, German

The rate of micelle solubilization (SR) can be appraised following the decrease of the radius of a macroscopic drop of oil in contact with a surfactant solution [Todorov, 2002]. Alternatively, the time required for the dissolution of a liquid dispersion can be used for this purpose. Here, the decrease of the turbidity of a dodecane-in-water (d/w) nanoemulsion in 7.5 mM sodium dodecylsulfate (SDS) is studied at sodium chloride concentrations of 100, 300, 500, 700, 900, and 1000 mM NaCl. These salinities correspond to non-aggregating (<300), aggregation-promoted (500) and surfactant precipitation regimes (>700). It is found that SR is equal to 2.3 x 10^-11, half the value observed in the absence of salt for a neat aqueous surfactant solution above its critical micelle concentration (7.0