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Adsorption behavior of nonionic surfactants studied by drop volume technique

: Teipel, U.


Chemical Engineering and Technology 24 (2001), Nr.4, S.393-400
ISSN: 0930-7516
ISSN: 1521-4125
Fraunhofer ICT ()

This study shows that the drop volume technique can be used to determine the adsorption behavior and interfacial adsorption kinetics of surfactants at fluid interfaces. Using this tensiometric method, one can determine not only the interfacial tension of the pure phases but also the critical concentration for the formation of micelles (CMC) in a surfactant system, the quasi-static (equilibrium) interfacial tension, the diffusion coefficient as a function of surfactant concentration, and the maximum adsorption density at the interface. The determination of the dynamic interfacial tension allows to indirectly characterize the kinetics of surfactant adsorption. The time dependence of the interfacial coverage resulting from this adsorption process is well described by two approximation solutions (for short and long adsorption times), with the result that the diffusion coefficients calculated as a function of surfactant concentration using these two methods show good agreement. The droplet formation and dripping process of a surfactant solution in a capillary was found to be quite different depending on whether the process occurred in gaseous or fluid surroundings. In particular, the formation of satellite droplets was different for the two different media, in terms of both the volume and shape of the satellite droplets.