Studies of bitumen-silica and oil-silica interactions in ionic liquids

Previous work in this laboratory has shown that bitumen and oil can be readily separated from sand, using ionic liquids at ambient temperatures. To probe the mechanism underlying the relative ease of separation, atomic force microscopy (AFM) has been used to study interaction forces and adhesion between bitumen surfaces and a silica probe in the presence of liquid media. The energy of adhesion between bitumen samples obtained from both Canadian and U.S. oil sands are approximately an order of magnitude smaller in an ionic liquid medium than in aqueous solution. This behavior was traced to the ability of ionic liquids to form layered charge structures on surfaces. Although interactions between the silica probe and an aged crude oil sample could not be determined, because the probe adhesion to the oil film exceeded the force capacity of the AFM, thermodynamic considerations indicate that the energy of separation of silica from aged oil is also significantly smaller in an ionic liquid medium than in aqueous solution.