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    A Quartz Crystal Microbalance Study of the Adsorption of Asphaltenes and Resins onto a Hydrophilic Surface

    Year: 2002

    Journal: Journal of Colloid and Interface Science Vol. 247, No. 2, March 15, 2002, 20100827

    Authors: Ekholm P., Blomberg E., Claesson P., Auflem I.H., Sjöblom J., Kornfeldt A.

    Last authors: Anna Kornfeldt

    Organizations: Department of Chemistry, Surface Chemistry, Royal Institute of Technology, Drottning Kristinas väg 51, Stockholm, SE-100 44, Sweden Institute for Surface Chemistry, Box 5607, Stockholm, SE-114 86, Sweden Department of Chemical Engineering, The Norwegian University of Science and Technology (NTNU), Trondheim, N-7491, Norway Statoil R&D, Trondheim, N-7005, Norway ABB Corporate Research, Västerås, SE-721 78, Sweden

    Country: Sweden

    The adsorption of extracted and purified samples of asphaltenes and resins onto gold surfaces has been studied as a function of bulk concentration using a quarts crystal microbalance with dissipation measurements (QCM-D). With this device, which works equally well in transparent, opaque, and nontransparent samples, the adsorbed amount is measured through a change in resonant frequency of the quartz oscillator. The measured change in dissipation reports on changes in layer viscoelasticity and slip of the solvent at the surface. The results show that the adsorbed amount for resins from heptane corresponds to a rigidly attached monolayer. The adsorbed amount decreases with increasing amount of toluene in the solvent and is virtually zero in pure toluene. Asphaltenes, on the other hand, adsorb in large quantities and the mass and dissipation data demonstrate the presence of aggregates on the surface. The aggregates are firmly attached and cannot be removed by addition of resins. On the other hand, resins and asphaltenes associate in bulk liquid and the adsorption from mixtures containing both resins and asphaltenes is markedly different from that obtained from the pure components. Hence, we conclude that preformed resin aggregates adsorb to the surface. These results are compared and discussed in relation to adsorption from crude oil diluted in heptane/toluene mixtures.