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    Probing Mechanical Properties of Water-Crude Oil Interfaces and Colloidal Interactions of Petroleum Emulsions Using Atomic Force Microscopy

    Year: 2017

    Journal: Energy Fuels, Volume 31, APR, page 3445–3453

    Authors: Kuznicki, Natalie P.; Harbottle, David; Masliyah, Jacob H.; Xu, Zhenghe

    Organizations: Natural Sciences and Engineering Research Council of Canada (NSERC) Industrial Research Chair Program in Oil Sands Engineering; Alberta Innovates Energy and Environmental Solutions (AI-EES)

    Atomic force microscopy (AFM) is frequently used to elucidate complex interactions in emulsion, systems. However, comparing results :obtained with "model" planar surfaces to curved emulsion interfaces often proves unreliable, because droplet curvature can affect adsorption and arrangement of surface-active species, while droplet deformation affects the net interaction three. In the current study, AFM was used to study the interactions between a colloidal probe and water droplet. Force magnitude and water droplet deformation were measured in toluene solutions of asphaltene or bitumen at different concentrations and varying droplet aging time. Interfacial stiffening and an,increase in particle droplet; adhesion force were observed upon droplet aging in bitumen solution. As reported in our previous study (Kuznicki, N. P.; Harbottle, D.; Masliyah, J.; Xu, Z. Dynamic Interactions between a Silica Sphere and Deformable Interfaces in Organic Solvents Studied by Atomic Force Microscopy. Langmuir 2016, 32 (38); 9797-9806), a viscoelasticity parameter should be included in the high-force Stokes -Reynolds-Young-Laplace (SRYL) equations to account for the interfacial stiffening and non-Laplacian response of the water droplet at longer aging times. However, following the addition of a biodegradable demulsifier, ethyl cellulose (BC), an immediate:, reduction in both the particle droplet adhesion force and the rigidity of the water droplet occurred. Following EC addition, the interface reverted back to a Laplacian response and droplet deformation was once again accurately predicted by the classical SRYL model. These Changes in both droplet deformation and particle-droplet adhesion; tracked by AFM, imply a rapid asphaltene/bitumen film displacement by EC molecules, The colloidal probe technique provides a convenient way to quantify forces at deformable oil/water interfaces and:characterize the in situ effectiveness of competing surface-active species.
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