Equilibrium and Dynamic Surface Properties of Sulfosuccinate Surfactants

The equilibrium and dynamic surface tension of three sulfosuccinate surfactants at the air/aqueous solution interface were investigated. Wilhelmy plate method was used to determine critical micelle concentration (CMC) and the equilibrium surface tension (gamma (eq)). The dynamic surface tensions in the range 10-100 s were measured by maximum bubble pressure method. The well-known Ward-Tordai equation was employed to analyze the adsorption of the sulfosuccinate surfactants. The parameters and effective diffusion coefficients (D (eff)) of dynamic surface tension have been calculated and analyzed. The equilibrium surface tension results showed that disodium laureth (3) sulfosuccinate (AEO(3)-SS), disodium laureth (6) sulfosuccinate (AEO(6)-SS) and disodium alkyl ethoxy glucoside sulfosuccinate (AEG-SS) are surfactants possessing strong surface activity, adsorbing to the interface rapidly and their gamma (eq) values were in the range 25-32 mN/m. CMC of the three surfactants increases with the number of hydrophilic groups and AEO(3)-SS has the lowest CMC. According to the values of some dynamic surface tension parameters, AEG-SS is the most hydrophilic surfactant of them and AEO(3)-SS is energetically more favorable to adsorb to the interface than the others. According to Ward-Tordai equation, the D (eff) values were calculated, the adsorption mechanism was diffusion controlled at short times and toward the end good evidence was found for an activated-diffusion mechanism with an energy barrier.