On the reversibility of asphaltene adsorption at oil-water interfaces

The irreversibility of asphaltene adsorption at oil-water interfaces is still debated in the literature. We have used a Tracker instrument (Teclis) in which both liquid drops and bridges can be analyzed and interfacial tensions measured. Rinsing in the liquid bridge configuration is possible, making possible the study of opaque fluids. We confirmed that asphaltene adsorption is irreversible, for bulk concentrations below and above the CNAC, even at short times, when the interfacial layers are not yet consolidated. Despite working with a highly purified sample and avoiding part of the problems linked to the competition of different species for the interface, we did not observe significant differences in adsorption times and in the behavior upon compression with respect to asphaltenes with wider mass distribution.