Surface properties, micellar molecular interaction, and physical properties for binary systems of sodium oleate with three anionic surfactants

Abstract

The mixed micellization of the anionic surfactant sodium oleate (NaOL) and three anionic surfactants (NaDC, AOT, SDS) of different structures in 0.01 mol/L NaCl solution were investigated by surface tension measurement at different temperatures. All the investigated mixtures exhibited nonideal behaviors as the experimental CMC values are less than the CMC ideal 12 values calculated by using of Clint's equation. Negative β m values calculated by using of Rubingh's equation and |ln(CMC 1 /CMC 2 )| < |β m | proved synergism in the three systems of higher α NaOL or lower α NaOL . An interesting phenomenon of double inflection points were observed for pure NaOL and mixtures of high α NaOL . The negative ΔG 0 m values for the mixed systems imply that the micelle formations are spontaneous process. The NaOL/NaDC system was also studied in buffer solution (pH 8, 12) at 30 ºC which also exhibited nonideal behavior. Synergism existed at pH 12 but not at pH 8 for NaOL/NaDC system. It is noteworthy that there were not Downloaded by [University of Nebraska, Lincoln] at 12:16 04 June 2016 2 double inflection points for NaOL/NaDC system in buffer solution (pH 8, 12). K. P. and calcium stability data show that these three anionic surfactants can improve the water solubility and hard-water resistance of soap. GRAPHICAL ABSTRACT

Effect of Monovalent and Divalent Salts on the Interfacial Tension of n-Heptane against Aqueous Anionic Surfactant Solutions

“…Table summarizes salts and anionic surfactants concentration used in aqueous solutions. The Krafft point of SDS and AOT is 280.65 and 304.15 K, respectively . So, all IFT measurements in this work were carried out at 313.15 ± 0.1 K.…”

“…The Krafft point of SDS and AOT is 280.65 and 304.15 K, respectively. 36 So, all IFT measurements in this work were carried out at 313.15 ± 0.1 K.…”

“…Importantly, this IFT effect was not reported earlier for such low salinity–surfactant formulations. It is widely accepted that the minimum IFT is found at the vicinity of the critical micellar concentration (CMC). ,, Evidence also suggests that a middle phase microemulsion may form when cosurfactants are used, which reduces IFT to a very low value. , The surface pressure at this point is the suitable measure of the effectiveness of a surfactant in terms of reducing IFT. If the solubility of a surfactant is below the CMC at a specific, constant temperature, then the minimum IFT is achieved at the point of maximum solubility.…”

“…It is widely accepted that the minimum IFT is found at the vicinity of the critical micellar concentration (CMC). 8,27,36 Evidence also suggests that a middle phase microemulsion may form when cosurfactants are used, which reduces IFT to a very low value. 23,24 The surface pressure at this point is the suitable measure of the effectiveness of a surfactant in terms of reducing IFT.…”