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The effect of weathering on the surface chemical composition and wettability of the oil sand solids and bitumen was studied by contact angle measurement, film flotation technique, XPS analysis, and ellipsometry thickness measurement. It was found that mild bitumen oxidation occurred during ore weathering. However, it has negligible effect on the bitumen surface wettability. In contrast, weathering forced more organic matters to adsorb onto the mineral solid surfaces, which made the solids more hydrophobic. A mechanism on how the organic matters adsorb on the solid surface due to weathering was put forward. The loss of the formation water due to weathering resulted in an intimate contact of bitumen with the mineral solids and thus offered the opportunity for the organic matters to adsorb, which was responsible for the enrichment of organic matters on the mineral solid surface. It was further observed that hot water washing partially removed the organic matters from the solids surface and hence decreased the solids hydrophobicity.

The wettability of mineral solids and bitumen isolated from nine different Athabasca oil sands ores was determined to establish its role in water-based extraction of bitumen from oil sands. The processability of oil sands ores was determined using Denver flotation tests. The contact angle of a water drop on a bitumencoated silica wafer was measured using the sessile drop method. For fine solids (<45 µm), the water drop penetration time was measured on a surface of a compressed disk of fine solids. For coarse solids (106-250 µm), the wettability of solids was evaluated by determining the partitioning of the solids between an oil and a water phase. It was found that the processability of different oil sands ores varies significantly in term of bitumen recovery, bitumen froth quality, and bitumen froth morphology. The wettability of bitumen, on the other hand, does not significantly depend on the source of oil sands ores. However, the wettability of the fine and coarse mineral solids is ore-dependent, which affects both bitumen recovery and bitumen froth quality. The presence of hydrophobic solids in oil sands ores depresses bitumen recovery.

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