Influence of Nonswelling Clay Minerals (Illite, Kaolinite, and Chlorite) on Nonaqueous Solvent Extraction of Bitumen

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.