Preparation of these workshop lectures on the broad topic of ‘clay in oil sands’ was motivated by two observations. The first was the growing interest in the effects of clay on oil-sands operations, in particular bitumen flotation and fine-tailings management. The second was the lack of a common basis of understanding, or even common vocabulary, among the various disciplines involved in investigating and managing those effects. The hope is that the contributions herein will summarize current knowledge about the effects of clay on oil-sands operations, while gently introducing basic theory, terminology, and methods that the authors and editors believe will facilitate further advances.

Depending on the context and discipline, the terms ‘clays’ or ‘clay’ may be used in three different ways: as a particle-size term, as a mineral term, and as a rock term ( Moore, 1996 ). The field of oil-sands research makes no exception and various uses can be encountered in the literature, including terms such as ‘clay-sized minerals,’ ‘fine clays,’ ‘ultrafine clays’ (or ‘ultrafines’), ‘estuarine clay,’ ‘marine clay,’ etc. In this chapter, an overview is given of: (1) the nomenclature associated with clays and clay minerals; (2) the structure and crystal chemistry of phyllosilicates; and (3) the geology and clay mineralogy of oil sands.

The oil-sand ores of northern Alberta provide a significant proportion of the overall energy portfolio for North America. Surprisingly, the presence of nano-sized clay minerals plays a defining role both in the extraction of bitumen and in tailings management. Although seemingly insignificant in size, naturally occurring clay minerals present in the oil sand ores of northern Alberta create significant challenges in all aspects of bitumen extraction and recovery, processing of oil sand ores, and management of tailings. Although a significant body of knowledge exists in relation to the characterization of ‘oil-sands clay minerals,’ much of this work has focused on the identification of the clay minerals present and not on their respective surface chemistries. This chapter focuses on some of the unique structural features of the clay minerals found in the oil sands and their respective surface chemistries.

Slurry colloidal and particle interaction theory is described and applied to clay mineral suspensions. Mechanisms which affect the colloidal properties of the dewatering behaviour of clay mineral suspensions are described, after which the processes of coagulation and flocculation are discussed. Finally, sedimentation and self-weight consolidation are discussed as the mechanisms by which a low-density slurry transitions to a high-density slurry or soil.

With the myriad of measurement techniques and definitions of clays, the first question generally asked is “how much clay is there” in a sample? This often refers to the magnitude of a clay attribute in the sample and the answer to this question may vary depending on the measurement method. Does the method measure the clay-mineral type, the size distribution or mean size, the surface area, cation exchange capacity (CEC), rheology, or plasticity? Clay mineral type, particle size, and surface area are commonly used in mining operations to optimize oil-sand ore blending. In bitumen extraction and tailings management, where slurry behavior contributes to the process performance, propertiess uch as rheology and plasticity are also used. The previous chapters in the volume have introduced the various properties of clay particles and clay minerals. The present chapter describes the common methods of measuring clays and clay minerals in oil sands.

The clay fundamentals explained in the preceding chapters affect the macroscale oil-sands processes discussed in the following chapters of this volume through a series of mesoscale phenomena. Each mesoscale phenomenon is itself the subject of a field of science, and applications to different fields of engineering have led to a confusion of terminology. Understanding the underlying physical processes helps to elucidate the positive and negative effects of clay in oil-sands processes.

The clay minerals present in the oil-sands ore are responsible for some of the most challenging (and intriguing) processing behavior experienced on a routine basis in oil-sands surface mining. In previous chapters, significant details have been provided on how specific clay properties can give rise to changes in slurry rheology and interface phenomena. Because the bitumen extraction process relies heavily on manipulation of interfacial effects to enhance separation, changes in clay content in the ore, not surprisingly, can have a dramatic impact on the ability to process the material. This chapter provides an overview of the extraction process, the influence of clay minerals on bitumen recovery, and the challenges in reacting to changes in the ore clay content in a typical operation. The chapters that follow focus on the larger issue of tailings treatment to create a reclaimed landscape at the end of mine life.

The particle-size distribution of oil-sands tailings has always figured prominently in the mine planning and overall operations and closure strategy in surface-mined oil sands. In oil-sands applications, the convention is to define the sand as the mineral components >44 μm in size and the fines as the mineral component which is <44 μm. The water-based extraction process uses 2 m 3 of water to extract the bitumen from 1 m 3 of oil sand, and as the bulk of this water is recycled, large containment areas are required to maintain a supply of extraction water. A significant proportion of water that is not recycled is retained in both the sand and fines components of the resulting tailings streams and the essence of tailings management comes down to separating and managing the water that can be recovered from the tailings. As the mining operations have become larger, and ore properties vary over wider ranges, the designation of sand and fines was simply inadequate in explaining the behavior of many of the tailings and a thorough understanding of the entire particle-size distribution became more important. Due in part to the upgrading and refinery operations often associated with bitumen production, the oil sands industry is relatively sophisticated in its approach to tailings characterization and tailings management. As a result, any discussion of clays can, and often does, include both a size and mineralogy component. In any case, there is no doubt about the importance of understanding and quantifying the clay component of any tailings stream when defining a dewatering or management strategy. Historically, it might have been argued that the strong correlation between clay content and fines content would be an adequate characterization and tailings-planning parameter. Although this is still largely true, the clay to fines correlations can sometimes be measurably different from operation to operation, resulting in varying tailings performance. In addition, some tailings-management options such as thickeners and centrifuges can separate the fines fraction and even the clay fraction in a fluid fine tailings stream. These upset operational modes can create what are known colloquially as Franken-Fines, a stream with a very disproportionately high clay content that can create an equally disproportionate tailings problem. The tailings strategies that will be discussed include composite/consolidated/non-segregating tailings, thickening, freeze-thaw processes, rim ditching, thin lift dewatering, and centrifugation. The present chapter outlines the evolution of many of these tailings-management strategies that have been tested extensively or are currently in use in the surface-mined oil-sands industry, with a particular emphasis on the importance of understanding the clay size and clay mineralogy in the evaluation and understanding of tailings dewatering performance.

The effects of clay on the geotechnical properties of oil-sands tailings deposits are discussed. The sources of fluid fine tailings are reviewed, and types of tailings deposits are described. The effects of clay on geotechnical index properties, hydraulic conductivity, compressibility, and shear strength are discussed, with example predictions for consolidation and strength gain in fines-enriched sand tailings and deep fines-dominated tailings deposits.

Abstract Montmorillonite is an extraordinary, naturally occurring plate-like material ~1 nm thick with dimensions of at least 150-200 nm with robust mechanical properties (the modulus is ~ 180 GPa). It is non-toxic (the FDA classification of montmorillonite is GRAS (‘generally regarded as safe’ for most applications)). The surface area of the particle is enormous (>750m 2 /g). The capacity of montmorillonite to have a negative charge allows for the modification of the montmorillonite with quaternary ammonium ions (which have a positive charge) to displace the inorganic counter ions associated with the mineral. This displacement provides a wide range of hydrophilic-hydrophobic balance on the surface of montmorillonite which is key to the utilization of organomontmorillonites in a wide range of different markets (rheology control for coatings, inks, oil-well drilling fluids, grease, etc. and polymer nanocomposites). The utility of organomontmorillonite is not discussed here. The significant independent variables that relate to successful preparation of organo-montmorillonites are described below and listed in the conclusions.

Abstract Smectite clays have been modified with organic onium ions for more than 60 y and are important in a diverse range of industries including oil-well drilling, paint, grease, ink, cosmetics, environmental clean-up, polymer nanocomposites, and pharmaceuticals. The number of commercially available onium ions limits the variety of surface modifications that can be made. A substantial amount of research has been conducted on other methods of organic modification of smectite clays in order to remedy this situation. One method that has seen increased attention is the use of ion-dipole-bonding of organic molecules, oligomers, or polymers to the exchangeable cation on the clay surface. Utilizing this method, a unique class of surface-modified clays can be produced. In some cases self-assembly of certain organic molecules has been discovered in which the molecules form rigid posts around each cation on the surface. The intercalation/exfoliation behavior of smectite clays modified via ion-dipole bonding utilizing various small organic molecules and selected polar polymers is discussed here. The types of organic molecules that can be utilized to surface modify smectites is discussed in detail as are the characteristics of the complexes that are formed.

Abstract The kaolin-group minerals with 1:1 layered structure can be used for the synthesis of new hybrid organo-inorganic nanomaterials. An appropriate selection of the reacting molecules introduced via intercalation and/or grafting reactions and synthesis conditions may induce interesting properties, e.g. luminescence, catalytic activity, and affinity to sorb ions and molecules. To date, several new materials have been synthesized using the 1:1 layered structure as a building block. The most interesting materials could be obtained via grafting reaction involving the inner-surface OH groups of the octahedral sheet. Such materials show increased thermal stability as well as stability in aqueous solutions, unlike intercalation compounds. Note the susceptibility of the octahedral sheet of kaolinite to interact with selected organic molecules and the subsequent formation of Al–O–C bonds in the interlayer. Four different types of materials which could be obtained using kaolin-group minerals and their possible applications are discussed here: (1) kaolinite nanotubes in the synthesis of polylactide-based nanocomposites; (2) methoxy-kaolinite and intercalates with ammonium salts; (3) interlayer quaternized kaolinites and their anion-exchange properties; and (4) interlayer grafted kaolinites for heavy-metal sorption.

Abstract The present chapter is devoted to recent developments in the area of surface modifications of commercially available synthetic clays by post treatments (i.e. intercalation or grafting) and by one-pot synthesis through a sol-gel process. Special attention is paid to the modifications aimed at forming pillared clays, organoclays, and organic-inorganic hybrids with a 2:1 layered structure. The different approaches are described and debated. The properties of the materials obtained are also discussed.

Abstract In this work, we explored to The grafting of thiol group- terminated chains onto single- layer α-zirconium phosphate (ZrP) nanosheets, which were subsequently oxidized to sulfonic- acid groups, was examined here. The sulfuric acid- functionalized ZrP nanosheets were thoroughly characterized extensively and the results proved that sulfonic acid group- terminated chains were successfully grafted successfully onto the ZrP nanosheets surfaces with a high significant loading density. Such Such a strong a solid acid, based on inorganic nanosheets, can be well dispersed in polar solvents, leading to high good access to the acid functional groups. The acid Meanwhile, it can also be easily separated easily from the dispersion system by centrifugation or filtration. The sulfonic acid- functionalized ZrP nanosheets can serve as an effective heterogeneous catalyst for various reactions (such as the Baeyer-Villiger oxidation). The nanosheets y were also incorporated into proton- exchange membranes to form composite membranes, which exhibited excellent performance in single- cell evaluation, showing promiseing for fuel-cell applications.

Abstract Three relatively unusual techniques that might deliver interesting information about the surface modifications performed on clay minerals are described here. The instruments used and the techniques were: (1) a streaming current detector (more commonly known as particle-charge detector) to monitor changes in the colloidal charge of the surfaces of modified particles; (2) a dispersion analyzer to monitor sedimentation/ dispersion behavior as a function of the modification, and in several cases even to yield a very good estimate of size of the particles (as long as they are between 10 nm and 10 mm); and (3) nuclear magnetic resonance-based specific surface area measurements, that yield information on the area and in some cases even on changes in the hydrophobic-hydrophillic surfaces formed due to the modification. As with all analytical techniques, these methods have advantages accompanied by problems, interesting research opportunities coupled with severe limitations that might lead to misinterpretation of the results. A few examples for each technique are presented here.

Abstract Fibrous clay minerals (sepiolite and palygorskite) have large specific surface areas which offer interesting opportunities for the assembly of diverse types of nanoparticles (NPs) which, in certain cases, remain bonded through the silanol groups located at the external surfaces of these clays. Various methodologies used in the preparation of new nanoarchitectures, based on the attachment of NPs to fibrous clays, with special emphasis on the use of the sol-gel approach combined with organosepiolites to build nanostructured porous functional materials for different applications ( e.g. photocatalysis), are introduced here. Other examples refer to the in situ formation of NPs, e.g. zeolites, which become attached to the clay fiber during the synthesis process via covalent bonds. The use of ferrofluids allows the development of nanoarchitectures in which iron-oxide NPs decorate sepiolite fibers and add superparamagnetic properties to the resulting materials. Examples of various multifunctional materials based on magnetite-sepiolite nanoarchitectures are also introduced and discussed critically here.