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The sorption and rheological properties of an acidic polyaromatic compound (C5PeC11), which can be used to further our understanding in the behavior of asphaltenes, are determined experimentally. The results show that C5PeC11 exhibits the type of pH-dependent surface activity and interfacial shear rheology observed in C6-asphaltenes with a decrease in the interfacial tension concomitant to the elastic modulus when the pH increases. Surface pressure-area (Π-A) isotherms show evidence of aggregation behavior and π-π stacking at both the air/water and oil/water interfaces. Similarly, interactions between adsorbed C5PeC11 compounds are evidenced through desorption experiments at the oil/water interface. Contrary to indigenous asphaltenes, adsorption is reversible, but desorption is slower than for noninteracting species. The reversibility enables us to create layers reproducibly, whereas the presence of interactions between the compounds enables us to mimic the key aspects of interfacial activity in asphaltenes. Shear and dilatational rheology show that C5PeC11 forms a predominantly elastic film both at the liquid/air and the liquid/liquid interface. Furthermore, a soft glassy rheology model (SGR) fits the data obtained at the liquid/liquid interface. Yet, it is shown that the effective noise temperature determined from the SGR model for C5PeC11 is higher than for indigenous asphaltenes measured under similar conditions. Finally, from a colloidal and rheological standpoint, the results highlight the importance of adequately addressing the distinction between the material functions and true elasticity extracted from a shear measurement and the apparent elasticity measured in dilatational-pendant drop set-ups.

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This article is the continuation of a preceding paper (Part I) in which the adsorption and desorption of asphaltenes from the oil/water interface by pure solvent and model demulsifiers was studied. In this second part, the composition of mixed interfaces of asphaltenes and two demulsifiers (Brij®-93 and Pluronic® PE8100) was studied. Desorption of asphaltenes by demulsifiers, and vice versa, was determined. First, the composition of a mixed interface (asphaltenes and demulsifiers) through the use of the Langmuir equation of state (EoS) was determined. Second, an experimental set-up that mimics, to some extent, the chemical demulsification of water-in-crude oil emulsions during the production stages was used.Desorption of already adsorbed asphaltenes at the liquid-liquid interface by the action of two demulsifiers was assessed. It was found that desorption is always initiated by interactions between demulsifiers and asphaltenes. It is followed by the plausible formation of complexlike structures to finally end in the replacement, by displacement from the interface, of asphaltenes by demulsifiers. Third, the assessment of Brij®-93 and PE8100 desorption from the oil/water interface by the action of asphaltenes was also carried out. It was found that asphaltenes can desorb PE8100 at low surface coverage.

Adsorption of an acidic polyaromatic asphaltene model compound (C5PeC11) and indigenous C 6 -asphaltenes onto the liquid-solid surface is studied. The model compound C5PeC11 exhibits a similar type of adsorption with a plateau adsorbed amount as C 6 -asphaltenes onto three surfaces (silica, calcite and stainless steel). The model compound