A Quartz Crystal Microbalance study of Adsorption Phenomena at Oil/Water Interfaces: Implications for Stability of Water in Oil Emulsions(Abstract)

摘要

Adsorption of bituminous components from heptane/toluene mixtures at oil/water and oil/gold interfaces was measured in situ by a Quartz Crystal Microbalance. The adsorption kinetics follows two distinct regimes depending on bitumen concentration. At low concentration (<1.5wt percent), an unsteady irreversible adsorption at oil/water interface manifests in the form of a slow and continuous build-up of asphaltenes with minor resins into multilayers. At high concentration, a steady adsorption with limited reversibility is measured where saturation is reached after formation of a monolayer composed of asphaltenes with major resins. The concentration regimes are determined by the resin to asphaltene ratio in the bulk phase. The rigidity of oil-water interface at low bitumen concentration is related to the rigid network formed by sterically non-stabilized asphaltenes. In this regime, formation of asphaltene bridges between water drops destabilize the emulsions against flocculation, thus dewatering of bitumen froth is easy. However at high bitumen concentration, in the steady regime, water-in-oil emulsions are kinetically stabilized against flocculation by sterically stabilized asphaltene layers, and dewatering of bitumen froth becomes difficult.