Effect of Swelling Clay Minerals (Montmorillonite and Illite-Smectite) on Nonaqueous Bitumen Extraction from Alberta Oil Sands

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.