Article pubs.acs.org/EF
Surface Properties of Petrologic End-Members from Alberta Oil Sands and Their Relationship with Mineralogical and Chemical Composition Marek Osacky,*,†,‡ Mirjavad Geramian,† Qi Liu,† Douglas G. Ivey,† and Thomas H. Etsell† †
Department of Chemical and Materials Engineering, University of Alberta, Edmonton, Alberta T6G 2V4, Canada Department of Geology of Mineral Deposits, Comenius University, Mlynska Dolina, Bratislava 84215, Slovakia
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ABSTRACT: 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 orescalled “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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INTRODUCTION The oil sands of Northern Alberta, Canada represent a significant resource of bituminous hydrocarbons. The generation of vast amounts of tailings is one of the major difficulties of the current commercial water-based processes used to recover bitumen from the oil sands. Alternative, nonaqueous solvent bitumen extraction processes have been investigated for several decades,1−5 because of their potential advantages, such as high bitumen recovery and the elimination of slow settling, sludge tailing ponds. Settling and consolidation of the tailings are affected by the particle size distribution, mineral composition, residual organics, water chemistry and ultimately by the permeability and compressibility of the system.6,7 Although the oil sands deposit in Alberta displays a wide variety of mineral compositions, the mineral and textural variability can be described in terms of a mixture of four petrologic “endmembers”, i.e., estuarine sand, estuarine clay, marine sand, and marine clay. Mined Alberta oil sands ores are a combination of these four petrologically different types of rocks, deposited in marine and estuarine sedimentary environments. Oil sands composition is one of the most important factors affecting water-based and nonaqueous solvent bitumen extraction processes. The amount of solids in the fine size fraction (45 μm) then was separated from the solids by wet sieving in a Sepor sieve shaker, using distilled water. The subsieve fraction (
