Clay minerals in nonaqueous extraction of bitumen from Alberta oil sands: Part 2. Characterization of clay minerals

Although not used commercially, a nonaqueous extraction process is of great interest to extract bitumen from the Alberta oil sands due to its potential advantages, such as high bitumen recovery even from low grade oil sands ores and the elimination of slow settling, sludge tailings ponds with stable suspensions. While clay minerals have been characterized in water-based bitumen extraction from the oil sands to some extent, the gap of knowledge in the characterization of clay minerals in a nonaqueous bitumen extraction process has led to the current research. Two Syncrude oil sands ores, a high grade, low fines, good processing ore and a mid grade, high fines, poor processing ore, were used in the nonaqueous bitumen extraction. The raw oil sands ores, products of the extraction (supernatant) and the tailings generated from the extraction were investigated by low-pressure scanning electron microscopy (SEM). These observations showed some important differences between the two ore samples in terms of the settling behavior of the solids after nonaqueous extraction. In addition, the clay size fractions (< 2 μm) of the oil sands ores and supernatants were analyzed by transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM) and X-ray diffraction (XRD) after removing the organic matter. Kaolinite and illite were found to be the dominant clay minerals based on XRD analysis. Quantitative XRD analysis revealed an enrichment of kaolinite in the supernatant when compared with the ore. HRTEM studies showed the presence of monolayer smectitic clay minerals in clay fraction of ore and supernatant while these Monolayers were not detectable by XRD.