  We review the free energy approach to the kinetics of surfactant adsorption
at fluid/fluid interfaces. The formalism is applied to several systems. For
non-ionic surfactant solutions the results coincide with previous models while
indicating their limits of validity. We study the case of surfactant mixtures,
focusing on the relation between the mixture kinetics and the properties of its
individual constituents. Strong electrostatic interactions in salt-free ionic
surfactant solutions drastically modify the adsorption kinetics. In this case
the theory accounts for experimental results which could not be previously
understood. The effect of screening by added salt is studied as well. Our
theoretical predictions are compared with available experiments.
