On the Adsorption Kinetics of Surface-Chemically Pure n-Dodecanoic Acid at the Air/Water Interface

摘要

The dynamic surface tension data for n-dodecanoic acid in 0.005 M hydrochloric acid,for as-received as well as for surface-chemically pure solutions,show the presence of a prolonged induction period,clearly indicating that the adsorption of this nonionic surfactant is not simply diffusion-controlled.A kinetic model for the reversible formation of monolayer islands,long known in the field of electrochemistry,is shown to also apply to the adsorption of n-dodecanoic acid at the air/water interface.The rate constant increases linearly with increasing bulk concentration,while the induction time decreases exponentially.The phenomenon of nucleation at the air/water interface is consistent with the direct experimental observation of the formation of solid-like patches as the interfacial region is drastically compressed.