Effect of Additional Alkyl Substituents on the Adsorption Properties of Sodium Branched-alkylbenzenesulfonates

Abstract

Four sodium branched-alkylbenzenesulfonates with or without additional alkyl substituents were synthesized and their adsorption properties were investigated in aqueous solution and in 0.17 M NaCl solution. The critical micelle concentration (cmc), surface excess concentration at interface saturation (Γ_max), surface pressure at the cmc (π _cmc ), p C ₂₀ and standard free energy of adsorption () were calculated from the surface/interfacial tension measurements. It was found that the length of additional alkyl substituents had key effect on adsorptions of branched-alkylbenzenesulfonates. With increasing the carbon number of additional alkyl substituents from 1 to 3, Γ_max decreased constantly, while π _cmc changed a little with the decrease of Γ_max at aqueous solution/air interface and NaCl solution/air interface. It was interested that one of the synthesized sodium branched-alkylbenzenesulfonates can arrive ultra-low interface tension (10⁻³ mN/m) at NaCl solution/nonane interface.

Keywords:

• Critical micelle concentration
• interfacial tension
• sodium branched-alkybenzenesulfonates
• surface excess
• surface tension