Studying bitumen–bubble interactions using atomic force microscopy

Processing of oil sands using water-based extraction processes requires selective aeration of liberated bitumen droplets to facilitate transport of aerated bitumen to the top of the slurry where it is recovered. Colloidal forces between bubble and bitumen or silica control the selective attachment of bitumen to air bubbles as desired. In this study, interaction forces between bubble and bitumen or silica were measured in various aqueous solutions using atomic force microscopy (AFM). The wettability of the silica particles was found to play a significant role in controlling bubble–silica interactions. There exists a long-range repulsive force and zero adhesion between air bubbles and hydrophilic silica spheres, in contrast to strong attractive force and large adhesion force between the air bubble and hydrophobic silica spheres. The results suggest the potential of unwanted aeration of hydrophobic solids, leading to a poor froth quality. Study on bitumen–bubble interaction shows that the types of surfactants have a great effect on the long-range interaction due to their adsorption on the bubble surface, which could cause the bubble surface either positively or negatively charged, leading to different electrostatic forces. In the plant process water or in the anionic surfactant solution, the bitumen-coated silica sphere could penetrate into the bubble to form a three-phase contact (TPC) line when the external loading force exceeds a threshold value.