In our previous study, ethylcellulose (EC), an effective, nontoxic, and biodegradable natural polymer, was found effective in dewatering water-in-diluted bitumen emulsions. In this study, the demulsification mechanism of water-in-diluted bitumen emulsions by EC is investigated. In situ experiments using a micropipet apparatus provided direct evidence on both flocculation and coalescence of water droplets in diluted bitumen by EC. The addition of EC was found to decrease naphtha-diluted bitumen-water interfacial tension significantly. At the molecular level, AFM imaging revealed disruption of the continuous interfacial films formed from surface-active components of bitumen by EC. Our study clearly indicates that the demulsification by EC is through both flocculation and coalescence of water droplets, attained by competitive adsorption of EC at the oil-water interface and disruption of the original protective interfacial films formed from the surface-active components of bitumen.

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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.

We report patterning of AFM cantilevers by inverted dip-pen nanolithography, thereby markedly enhancing the development of combinatorial AFM as a high-throughput force-measuring instrument capable of determining interactions between opposing libraries of biomolecules.