Conductometric study of the mixing behaviour of sodium benzoate and salicylate with an anionic surfactant sodium lauroylsarcosinate

ABSTRACT

Effects of two anionic hydrotropes – sodium benzoate (NaBz) and sodium salicylate (NaSal) – on the mixed-micelle formation with an amino-acid-based surfactant – sodium lauroylsarcosinate (SLS) – in water were investigated by the conductometric method. Specific conductivity was measured for SLS/NaBz/water and SLS/NaSal/water systems to determine the critical micelle concentration (cmc). Using the regular solution theory for non-ideal mixing, the pairwise interaction parameter, β₁₂, and micellar composition, χ, were estimated in the mixed micelle. The cmc values of the surfactant–hydrotropes mixtures were generally lower than those predicted from the ideal mixing theory. The β₁₂ values are generally negative for the two systems at all mole fractions with an average value of −2.83 for the SLS/NaBz and −3.31 for SLS/NaSal systems, respectively, indicative of a strong attractive interaction between the SLS/NaBz and SLS/NaSal mixed micelle. The calculated thermodynamic parameters of micellisation all indicated spontaneity in mixed-micelle formation for the systems studied.

KEYWORDS:

• Surfactants
• hydrotropes
• mixed-micelle
• synergistic interaction
• interaction parameter
• spontaneity

Acknowledgement

The authors acknowledge the Department of Chemistry, Obafemi Awolowo University, Ile Ife, Nigeria for provision of facilities used for this work.

Disclosure statement

No potential conflict of interest was reported by the authors.