Microstructure and flow behavior of cellulose nanocrystal stabilized emulsions with repulsive and attractive interactions
Date
2018-12-17
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Abstract
Surface properties of nanoparticles have a direct effect on the microstructure and rheological properties of the emulsions. In this thesis, I have utilized oscillatory shear rheology in conjunction with confocal microscopy and Cryo-SEM to understand the role of surface charge of Cellulose nanocrystal (CNCs) on the microstructure and rheology of dodecane in water emulsions. These fundamental understandings were applied to demonstrate the applicability of CNC stabilized emulsions as a conformance control agent through sandpack experiments. CNCs are a promising class of renewable nanomaterial with a rod-shaped morphology and negatively charged sulfate ester groups on the surface. Two different desulfation approaches were employed to modulate the surface charge of the CNCs. CNCs desulfated with hydrochloric acid (a-CNCs) were highly aggregated in water and shown to adsorb faster to the oil-water interface, yielding emulsions with smaller droplets sizes and a thicker CNC interfacial layer. CNCs desulfated using sodium hydroxide (b-CNCs) stabilized larger emulsion droplets and had a higher amount of non-adsorbed CNCs in the water phase. Rheological measurements showed that emulsions stabilized by a-CNCs formed a stronger network than for b-CNC stabilized emulsions due to increased van der Waals and H-bonding interactions that were not impeded by electrostatic repulsion. Based on these observations the conformance control performance and plugging efficiency of a-CNC stabilized emulsions through sandpack flow experiments was tested. The injected emulsions were aged inside the porous media for one day to develop a strong droplet network. The aged emulsions showed a promising selective phase blocking behavior with a very large pressure gradient required for water to flow as compared to dodecane. This selective phase blocking behavior can be specifically useful for near wellbore water shut-off treatment. The results of this investigation demonstrate the unique interactions between nanoparticles surface charge and the resulting emulsion properties which showed an interesting selective phase blocking behavior in porous media.
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Pickering Emulsions, Cellulose Nanocrystal, Conformance control, Rheology
Citation
Pandey, A. (2018). Microstructure and flow behavior of cellulose nanocrystal stabilized emulsions with repulsive and attractive interactions (Master's thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca.