This paper presents a preliminary study on the synergetic effect of a polymer flocculant, derived from hydrolyzed polyacrylamide (HPAM), on both bitumen extraction and tailings treatment as applied to oil sands. Bitumen extraction experiments and tailings settling tests were carried out with the addition of HPAM directly in the bitumen extraction process. To understand how the polymer affects bitumen recovery and tailings treatment, the long-range interaction and adhesion forces between bitumen and solids (clay and silica) and between clay and silica were measured using an atomic force microscope (AFM). Our study clearly demonstrated a synergetic role of HPAM in processing poor oil sand ores, which are characterized by high clay fines content. The addition of HPAM at an appropriate dosage not only improved bitumen liberation and recovery but also increased the tailings settling rate. Such improvements were attributed to the selective flocculation of clay fines by HPAM, which was supported by the AFM data. On the basis of the results of the present study, it is suggested to directly add HPAM into the bitumen extraction process, rather than to tailings, to facilitate both bitumen recovery and tailings treatment in production operations.

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Process aids are generally required to improve bitumen recovery from poor-processing oil sand ores containing a relatively high amount of divalent metal ions and fine solids/clays. In this paper, the role of acidified sodium silicates as a dispersant/depressant of clay fines in bitumen extraction was evaluated using a laboratory hydrotransport extraction system (LHES) at low temperature (35 °C). Bitumen recovery experiments showed that adding acidified silicates during the bitumen extraction process resulted in a higher degree of bitumen liberation from sand grains, a faster bitumen flotation rate, and a better bitumen froth quality than adding caustic. Solution chemistry analysis demonstrated that acidified sodium silicate is a better process aid than caustic because it has three functions: to precipitate calcium and magnesium in the process water, which minimizes the synergistic effect of divalent cations in inducing a clay coating on the bitumen surface and clay gelation; to maintain an adequate pulp slurry pH for better bitumenair bubble attachment; and to disperse/depress clay fines from flotation by its specific species.

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