The objective of this project was to gain a molecular-level understanding of the surface chemistry on mineral materials in the presence of solvent, water, bitumen and surfactants. We use IR-visible sum frequency generation (SFG) vibrational spectroscopy to obtain information about molecules adsorbed directly to surfaces. This research allowed us to understand and control the chemistry of mineral surfaces, and provide new information for the design of new non-aqueous oil sands extraction processes.
Experiments were carried out on well characterized quartz surfaces to study the interfacial water structures, the competitive adsorption of solvents and bitumen components, and the factors determining the wettability of the surface. This project provided both qualitative and quantitative information on species liquid/silica interfaces. A thin layer of water ( ~ 100 µm) prevented the adsorption of toluene and heptane onto silica, but thin layers of toluene or heptane did not prevent water adsorption onto silica. As expected, some residual water always exists at solvent/silica interfaces under ambient conditions. Unexpectedly, the water molecules form a highly H-bonded structure at heptane/silica interfaces, preventing further adsorption of water molecules onto the heptane/water interfaces.
Finally, we found that the competitive adsorption between heptane and toluene on silica depended on the treatment history of silica – the surface ratio of adsorbate was different than bulk ratio from mixture. This adsorption competition of heptane and toluene on silica is reversible. This adsorption behavior is important for understanding the forces between the clay particles, which will be strongly affected by such adsorbed surface species.
Principal Investigator(s): Keng Chang Chou & Murray Gray
Research Team: Zheng Yang & Qifeng Li
Project Number: COSI 2007-02
Close Date: March 31, 2009