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Artificial mixtures of bitumen with three natural clay standards, dominated by illite, kaolinite, and chlorite, were reacted for several days and washed three times each with cyclohexane to remove bitumen from the clays. The main goal was to determine and better understand the effect of nonswelling clay minerals (illite, kaolinite, and chlorite) on nonaqueous solvent bitumen extraction. The experimental results showed that the total amount of residual cyclohexane insoluble organic carbon (CIOC) measured for clay−bitumen mixtures after nonaqueous solvent bitumen removal is a function of intrinsic resistance of high molecular weight (MW) organic compounds to cyclohexane extraction and the nature of nonswelling clays. The intrinsic resistance of high MW organic compounds to cyclohexane extraction accounted for 42−80% of the total CIOC content. The nonswelling clays retained from 20 to 58% of CIOC of the total CIOC content primarily on the external surfaces (basal planes and edges) of clay mineral particles in the form of patches rather than continuous coatings. Cation exchange capacity (CEC) and specific surface area (SSA) were reduced by the reaction with bitumen due to organic coatings on the clay mineral surfaces and/ or due to bridging of clay particles to aggregates. The results indicate that the SSA is the primary controlling parameter affecting the amount of CIOC retained on the nonswelling clays within the studied experimental conditions. Higher amounts of CIOC resist on clays which have larger SSAs. CEC and layer charge density (LCD) are contributing parameters possibly affecting the extractability of bitumen from studied clays. It seems that, with increasing CEC and LCD, the CIOC was bonded more strongly to the clay mineral surface; consequently, more CIOC resisted nonaqueous solvent bitumen removal. ■ INTRODUCTIONThe Alberta oil sands deposits represent the third largest resource of bitumen on the planet after Venezuela and Saudi Arabia. 1 Commercial recovery of bitumen from the Alberta oil sands is achieved by water-based extraction processes. Alternative nonaqueous solvent extraction processes have been investigated since the mid-1960s due to their potential advantages such as high bitumen recovery, elimination of sludge tailings ponds, and decrease in water consumption. 2 The Alberta oil sands are a mixture of coarse sand, fine clays, bitumen, and water. Quartz is the principal mineral of Alberta oil sands along with a small amount of clay minerals, carbonates, feldspars, and traces of TiO 2 minerals and pyrite. 3 Kaolinite, illite, chlorite, and interstratified illite−smectite have been reported as the main clay minerals of Alberta oil sands. 3 Variability in ore composition is known to affect bitumen recovery from the oil sands. It has been recognized that the presence of clay minerals may have negative consequences on bitumen extraction. 4,5 However, different types of clay minerals may have differing effects on the processability of oil sands ore during the extraction process, likely due to their d...

Two natural clay standards, dominated by montmorillonite (SWy-2) and Illite-smectite (ISCz-1), were mixed with bitumen and reacted for 8 days. The clay-bitumen mixtures were then washed three times each with cyclohexane to extract bitumen from the clays. The aim was to better understand the role of swelling clay minerals on nonaqueous solvent bitumen extraction. The experimental results showed that montmorillonite and Illite-smectite contained 4.6 to 8.2 wt % and 7.1 to 8.2 wt % of carbon after cyclohexane bitumen extraction, respectively. The residual organic material after cyclohexane bitumen extraction was retained on the outer and inner (interlayer space) surfaces of the swelling clay mineral particles in the form of patchy rather than continuous coating. Cation exchange capacity (CEC), specific surface area (SSA), and layer charge density (LCD) were all reduced by the reaction with bitumen due to organic coatings on the clay mineral surfaces and/or due to gluing of clay particles to aggregates. Comparison of the present study with our recent paper revealed that swelling and nonswelling clay minerals reacted differently with bitumen. These differences are reported and discussed in the present study. Overall, the results indicate that clays with larger SSAs retain more residual organic matter after nonaqueous solvent bitumen extraction within the studied experimental conditions. In the case of montmorillonite SWy-2, the amount of carbon after nonaqueous solvent bitumen extraction was heavily affected by different relative humidity (RH) conditions. The pretreatment of SWy-2 at higher RH conditions dramatically increased the amount of residual organic matter. This is likely related to the opening of the interlayer space (i.e., swelling) of montmorillonite upon exposure to higher RH and subsequent retention of a larger amount of organic material.

The aim of this study was to perform mineral and chemical characterisation of the four petrologic end members of Alberta oil sands in order to better understand the mineralogical and geochemical factors affecting bitumen extraction. X‐ray diffraction (XRD) results revealed that the petrologic end members contain a variable amount of quartz, clay minerals, carbonates, K‐feldspar, TiO2 minerals and pyrite and the Fe‐containing phases were also observed in Mössbauer spectra. Scanning electron microscopy‐energy dispersive X‐ray (SEM‐EDX) analysis also showed the presence of Fe–Ti oxide minerals. Mössbauer results also indicated the presence of lepidocrocite in the fine fractions in amounts below the detection limit of XRD. Interstratified illite–smectite was found only in clay‐rich petrologic end members. Calcite and dolomite were primarily concentrated in the fine fractions of marine petrologic end members. Conversely, siderite was found mainly in the coarse fraction of estuarine petrologic end members. The relative amount of toluene insoluble organics was higher in the fine fractions of marine petrologic end members.

The current research was performed on four petrologic end members samples from Syncrude's North Mine collected in 2012 (NM12), i.e. marine clay (MC), marine sand (MS), estuarine clay (EC), and estuarine sand (ES). The mineralogical compositions of the four petrological end members were determined using X-ray diffraction (XRD), quantitative XRD (QXRD), elemental analysis, and particle size distribution (PSD) measurements.Bulk samples from the four petrologic end members, after bitumen removal, were mainly composed of clay minerals (kaolinite, illite, chlorite, and mixed-layer expandable clays) and non-clay minerals such as quartz, carbonates, feldspars, and traces of TiO 2 minerals, gypsum, and pyrite. Bulk samples of the clay end members were composed of significantly higher amounts of clay minerals and lower amounts of quartz compared with the bulk samples of the sand end members. XRD analysis of oriented preparations (air dried-54 % RH and ethylene glycolated) of the < 0.2 mm fractions of the four end members showed that interstratified illite-smectite of high ($30 %) and low ($10 %) expandability were observed only in clay-rich end members, i.e. NM12-EC and MC, respectively. Kaolinite-smectite was only found in the < 0.2 mm fraction of the NM12-MC with an expandability between 5 and 10 %. Interstratification of illite-smectite was observed in the < 0.2 mm fraction of NM09-MC and EC samples but the expandability was only 10 % for both fractions. However, kaolinite-smectite was not found in the same fraction for NM09-MC and EC. ES and EC had the highest and lowest bitumen contents, respectively, for the NM12, NM09, and AM10 samples.

Clays cause problems in all crucial stages of bitumen extraction, and they affect bitumen recovery and waste management. It is thus of great importance to understand the mineralogy, chemistry, and surface properties of clays to improve both bitumen recovery and tailings treatment. Four petrologically different types of Alberta oil sands orescalled "endmembers"were examined in this study by cation exchange capacity (CEC), specific surface area (SSA), total specific surface area (TSSA), and negative layer charge density (LCD) measurements in order to better understand the effects of clay surface properties on bitumen nonaqueous extraction and solvent recovery from the extraction tailings. The surface properties are primarily controlled by the mineralogy of the petrologic end-members, mainly by the type and quantity of clay minerals. CEC, SSA, TSSA, and LCD increased as the amount of 2:1 clays (illite and illite−smectite), in particular expandable interstratified illite−smectite, increased. CEC values increased with increasing SSA and TSSA. The number of H-aggregates increased and the number of monomers decreased in the second derivative spectra of Rhodamine 6G and Methylene Blue as the 2:1 clays content in the petrologic end-members increased. This indicated a greater negative layer charge density with an increasing amount of 2:1 clays. The molecular aggregation of the organic dyes (Rhodamine 6G and Methylene Blue) was observed in the second derivative spectra for petrologic end-members bearing >25 wt % of 2:1 clays. Overall, the results indicate that interstratified illite−smectite may be largely responsible for high CEC, SSA, TSSA, and LCD in the fine size fractions of petrologic end-members from Alberta oil sands.

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The wettability of fine solids in Alberta oil sands is one of the most important factors affecting nonaqueous bitumen extraction and subsequent solvent recovery from the extraction gangue. However, there is some controversy as to which method is most suitable for wettability determination of fine solids isolated from the oil sands. In this paper, four different methodsi.e., particle partition, static sessile drop contact angle coupled with penetration time, Washburn capillary rise, and film flotationwere investigated and compared in order to determine suitable methods to examine the wettability of these fine solids. Two model samples, high-purity kaolinite (hydrophilic) and bitumen-treated kaolinite (hydrophobic), were used to investigate the suitability of the above four methods. These methods were then used to measure the surface wettability of fine solids isolated from the oil sands (marine clay) after toluene extraction, either untreated or heated at 400 °C for 2 h. The results showed that the Washburn capillary rise method was not applicable. In addition, the particle partition and static sessile drop contact angle coupled with penetration time methods had some deficiencies and were not very suitable to determine the wettability of fine solids isolated from the oil sands. The film flotation method was determined to be the most appropriate method, because (i) it was sufficiently sensitive to distinguish solid surface hydrophilicity and hydrophobicity; (ii) it could quantify the hydrophilicity and hydrophobicity, based on the measured “mean critical surface tension”; and (iii) it could be used to determine the surface heterogeneity of the solids, based on the standard deviation of the measurements. By using the film flotation method, the mean critical surface tensions of fine solids was >68.1 mN/m, while that of the heat-treated solids was >72.0 mN/m, and the standard deviation of the critical surface tensions of the floating particles (0–25.9 wt %) for fine solids was 40.5 mN/m, which indicated that heat treatment caused the fine solids to become more hydrophilic and the hydrophobicity of the fine solids was heterogeneous. In addition to direct application of the four standard methods, we have further developed the methods and gained some new insights into them.