Micellization and interfacial behavior of sodium fatty alcohol polyoxyethylene ether carboxylate surfactants in low-concentration aqueous hydrogen peroxide

Abstract

The micellar properties of sodium fatty alcohol polyoxyethylene ether carboxylate surfactants in H2O2-free and H2O2-containing solutions, as well as their adsorption behavior at the gas–liquid interface, were investigated. The surface tension in water and a 6 wt% aqueous H2O2 solution was measured as a function of the logarithm of surfactant concentration, using glass plates rather than platinum plates, at temperatures of 283 K, 293 K, 303 K, 313 K, and 323 K. The data were used to calculate the critical micelle concentration (CMC), the surface tension at the CMC (γCMC), the maximum surface excess concentration (Γmax), and the minimum area occupied (Amin). The effects of the polyoxyethylene chain length, temperature, and H2O2 on the physical properties of surfactants were analyzed. The results indicated that the CMC values in water initially decreased with increasing polyoxyethylene chain length before rising due to competing effects of enhanced hydrophilicity and reduced electrostatic repulsion. Notably, the CMC decreased in the presence of H2O2, and the magnitude of the decrease was correlated with the hydrophilicity of the surfactant. Temperature variations further influenced CMC trends in different media (water and H2O2 solutions). Additionally, the presence of H2O2 altered the interfacial properties, leading to an increase in both γCMC and Amin.