Adsorption of Indole on Kaolinite in Nonaqueous Media: Organoclay Preparation and Characterization, and 3D-RISM-KH Molecular Theory of Solvation Investigation Jonathan Fafard, †,‡ Olga Lyubimova, §,∥ Stanislav R. Stoyanov, §,⊥ Gustave Kenne Dedzo, †,‡ Sergey Gusarov, § Andriy Kovalenko,* ,§,∥ and Christian Detellier* ,†,‡ † Department of Chemistry, University of Ottawa, 10 Marie Curie, Ottawa, Ontario, K1N 6N5, Canada ‡ Centre for Catalysis Research and Innovation, University of Ottawa, Ottawa, Ontario, Canada § National Institute for Nanotechnology, National Research Council of Canada, 11421 Saskatchewan Drive, Edmonton, Alberta, T6G 2M9, Canada ∥ Department of Mechanical Engineering and ⊥ Department of Chemical and Materials Engineering, University of Alberta, Edmonton, Alberta, Canada * S Supporting Information ABSTRACT: Current oil sand mining operations in the Athabasca basin are predominantly aqueous-based. Extracts containing large amounts of fines lead to the formation of stable organoclay suspensions in froths giving lower yields and greater tailing wastes and making the development of more efficient extraction methods desirable from both economical and environmental perspectives. We examine an indole- kaolinite system as a model for these oil fines and their resistance to washing in nonaqueous solvents. The prepared organoclays show indole loading exclusively on the external surface of the clay. Micron-scaled vermicular structures, similar to natural kaolinite, are observed. Their formation is believed to be driven by strong adsorbate− adsorbate interactions. Indole is the primary adsorbate, as solvent adsorption is shown to be minimal based on both experimental and computational results. Isotherms are constructed and parameters calculated from linear regression analysis fitted to the Brunauer−Emmett−Teller equation. Monolayer quantities calculated match well to the theoretical amount calculated from surface areas measurements. Washing the organoclays with both toluene and isopropanol results in a 50% decrease of loaded organic material, leaving a monolayer equivalent of organic matter. The statistical-mechanical 3D-RISM-KH molecular theory of solvation is employed to perform full sampling of solvent orientations around a kaolinite platelet and gain insights into the preferred orientation and adsorption thermodynamics of indole on kaolinite in toluene and heptane solvents. In its preferred orientation, indole is hydrogen-bonded to one or two O atoms at the aluminum hydroxide surface of kaolinite. The calculated solvation free energy and potential of mean force for adsorption of indole and solvents on kaolinite in solution yield the increasing adsorption strength order of heptane < toluene < indole on the aluminum hydroxide surface. Multilayer adsorption profiles are predicted based on the integrated three-dimensional distribution functions of indole, toluene, and heptane. ■ INTRODUCTION The last three decades have brought a sharp increase in energy demand, mostly arising from the emerging economies of newly industrialized countries. 1 The discovery of conventional sources is projected to decline 2 and oil production is expected to shift toward nonconventional sources in the coming decades. Oil sands, a mixture of sand, clays, water, and bitumen, are a very important unconventional source of oil. Canada’s oil sands hold the second largest hydrocarbon deposit after Saudi Arabia. 3 Substantial research effort has been made to develop oil sands extraction methods based on aqueous extraction methods 4 and centered mainly in the Athabasca Basin 5,6 in Western Canada. Aqueous extraction requiring approximately 12 barrels of water are required to produce 1 barrel of oil. Large amounts of water are incorporated into excessive, environmentally harmful tailing wastes. 7 The ecological and land management consequences of these tailing wastes pose a great challenge for oil sands mining operations and require the development of alternative extraction and treatment methods. Fine organoclay particles are an important constituent of tailing wastes. The Athabasca Basin organoclays, predominantly kaolinite and Illite, 8 are hydrophobic in nature due to adsorbed organic matter, 9,10 such as bitumen fixated during extraction, and form stable aqueous emulsions. 11 Despite its inertness compared to smectitic clays, kaolinite features a modicum of reactivity due to the presence of the aluminum hydroxide layer. This property has been used extensively to prepare a variety of Received: June 28, 2013 Published: August 9, 2013 Article pubs.acs.org/JPCC © 2013 American Chemical Society 18556 dx.doi.org/10.1021/jp4064142 | J. Phys. Chem. C 2013, 117, 18556−18566