Surface tensions, densities, and speeds of sound for aqueous solutions of lauryl ether ethoxylates

Abstract Surface tensions for aqueous solutions of lauryl ether ethoxylates at the temperature 298.15 K were measured using a Lauda drop volume tensiometer. The non-ionic surfactants analyzed in this work were polyoxyethylene 9 lauryl ether (polidocanol) and polyoxyethylene 4 lauryl ether (brij 30). The surface tension values were used to determine the critical micelle concentrations (CMC) of the surfactant aqueous solutions as well as to calculate the infinite dilution activity coefficient of the surfactant following two different models: the first one combines the Volmer surface equation of state and the Gibbs adsorption equation, and the second one is a group contribution model that takes into account the mass spectra of the surfactants. Density and sound velocity measurements at surfactant concentrations above the CMC and in a wide range of temperature were also determined with the aim to analyze the aggregate structure of these lauryl ether ethoxylates. The Van der Waals equation was used to analyze the sound velocity behavior of these solutions.