MEASUREMENT OF THE DYNAMIC INTERFACIAL-TE NSION IN THE SYSTEM AQUEOUSSURFACTANT SOLUTION ORGANIC-SOLVENT

Dynamic interfacial tensions provide insight into the mechanism of sur factant adsorption at and transport across an interface. As an example , the adsorption kinetics and the distribution of a surfactant (alkyl dimethyl phosphine oxide with an alkyl chain length of 13) was studied at the water/hexane interface. The drop shape method used yields dyna mic interfacial tensions that pass through a minimum under certain con ditions. Model calculations show that depth, width and location of the minimum and the equilibrium adsorption state depend on several parame ters: the diffusion coefficients of the surfactant in the two liquids, the distribution coefficient between the phases, the liquids volume r atio, and the total surfactant concentration in the system. One can co nclude that surfactants are often soluble in both liquid phases, and t ransfer across the interface between them has to be considered. If a s urfactant is to be optimized in a liquid-liquid system to achieve maxi mum efficiency of a technological process, the surfactant distribution coefficient plays a significant role.