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.

Abstract Clay minerals have interlayer surfaces and edge surfaces, the former being the most important, especially in the case of swelling clays or smectites. Water is by far the most important adsorbed molecule in the interlayer space, where it interacts with the exchangeable cations and with the siloxane surface. Transition metal ion complexes are selectively ion-exchanged in the interlayer space of smectites. Polyamine complexes easily lose their axial ligands to adopt a square planar configuration. The more stable and bulky tris(bipyridyl) and tris(phenanthroline) complexes in the interlayer space give chiral clay mineral composites that can be used in columns for chiral chromatography, in asymmetric catalysis and in non-linear optics. The formation of clay mineral-dye complexes is a two-step process: instantaneous adsorption of the dye molecules, mainly as aggregates, followed by a slower redistribution process over the clay-mineral surface. With careful choice of dye molecules, non-linear optical materials can be prepared which exhibit properties such as second harmonic generation and two-photon absorption. Ion exchange of cationic proteins is a three-step process: (1) instantaneous adsorption at the edges; (2) adsorption in the interlayer space, followed by; (3) weak adsorption in excess of the cation exchange capacity. The extent to which these three processes occur depends on (1) the kind of exchangeable cation in the interlayer; and (2) the molecular weight, shape and charge of the protein molecules.

Abstract Solid-water interfaces are ubiquitous in the soil and near-subsurface regions of the earth. These interfaces are important because they control chemical and biological transformations, water quality, Theological properties, and the distribution and availability of plant nutrients (Hochella and White, 1990a). In addition, the fate and transport of organic chemicals in soil and subsurface environments are strongly influenced by interactions at the soil solution-colloid interface. This is illustrated in Figure 1 showing the potential interactions an organic solute may have with solution and solid phase components. Organic solutes in the aqueous phase may interact with clay mineral surfaces as well as other crystalline and amorphous solid phases and humic substances. Depending on the nature of the solute-surface interaction, the organic solute may undergo abiotic transformation, be strongly or weakly bound to the clay surface, or excluded from the colloid-solution. In addition, dissolved organic matter, surfactants, or non-aqueous phase liquids in solution may compete with the solid phase components for the organic solute thereby increasing its solution-phase activity. For organic solutes in soils and sediments, microbial degradation is controlled by the activity of the solute in solution. If the compound is retained strongly by solid phase components then it will not be accessible to soil microorganisms and will have reduced bioavailability. Furthermore, these reactions determine the potential for abiotic transformation of the organic solute as well as transport to ground and surface waters.

Abstract Fate and transport of organic chemicals used in agricultural and industrial operations are largely controlled by their sorption and desorption by mineral and organic constituents of soils and sediments. These processes are also important in developing and evaluating contaminant remediation technologies. Consequently, there has been a great deal of interest in investigating these processes in recent years. Because most organic compounds of interest as environmental pollutants are small nonionic molecules, their sorption involves weak interactions such as van der Waals-London, hydrogen bonding, dipole-dipole and other electrostatic forces or entropy-driven hydrophobic bonding (see reviews by Hamaker and Thompson, 1972; Mortland, 1986). However, wide ranges in compositions of the natural sorbents under varying moisture conditions and reaction time periods result in complex sorption reactions. As both the vapor and liquid phases of pollutants are involved in these reactions, the two are discussed here separately.

Abstract Benzene, toluene and xylenes (BTX) are found in most petrochemical spills (for example in crude oil, gasoline, diesel and jet fuel spills). These single-ring aromatic compounds are toxic to humans and aquatic ecosystems. The need to solve these environmental problems demands development of novel technologies that are both effective and economical for the removal of these pollutants. The availability and low cost of natural zeolites makes these materials excellent candidates for environmental remediation cases. However, these minerals are not very efficient to remove neutral organics from aqueous solutions in their natural form. A simple modification of zeolitic tuffs, using organic cations, greatly improves the sorptive capacity of these minerals for single-ring aromatics. Zeolites are tectosilicate minerals. They comprise a large family of naturally-occurring, crystalline, hydrated aluminosilicate minerals of alkali and alkaline-earth cations. Since their discovery in 1756 by F. A. F. Cronstedt (Boles et al., 1986), 39 naturally-occurring zeolite species have been characterized and 100 synthetic species have been reported in the literature (Dyer, 1988). Cronstedt took the name from two Greek words that mean “boiling stones” due to the intumescence exhibited when heated. For 200 years after their discovery, zeolites were almost totally ignored. Museums and collectors were the most interested in them (Boles et al., 1986). Since the first use of zeolites as catalysts by oil companies in 1960, extensive natural zeolite deposits have been discovered (Dyer, 1988). Zeolites are now recognized as one of the most abundant minerals on earth. There are important deposits in the USA,

Abstract Chemical waste discharges to landfills and hazardous waste disposal sites must be contained with a high degree of integrity to minimize their potential effects on human health and the environment. Containment practice generally focuses on preventing the escape of leachates, i.e., mobile, soluble portions of the waste. Regulatory requirements typically specify a maximum hydraulic conductivity (typically 10 −7 cm/sec) and minimum thickness for landfill barriers, based on the assumption that control of water movement through the barrier will eliminate migration of pollutants. Design criteria are thus generally dominated by considerations of hydraulic conductivity, and typically do not address potential diffusive transport of contaminants (e.g., EPA, 1984). Under sufficiently low permeability conditions in barriers, molecular diffusion may become a dominant transport mechanism. One practical method for minimizing organic contaminant migration by this means is to add sorbent materials, an aspect of barrier design that should be given more attention. This paper focuses on factors controlling organic contaminant transport through earthen clay barriers, in particular clay liners and soil-bentonite slurry walls. It further addresses the potentially important aspect of diffusive transport through such barriers, and means for preventing or retarding such migration.

Abstract In recent years, large-scale research and commercial activities have occurred in soil bioremediation. While in many cases these activities have been successful in reaching treatment criteria, sometimes bioremediation has not performed as expected, either in terms of rates of pollutant removal or pollutant endpoint concentrations. As shown in Figure 1, behavior often has an initial rapid removal stage with attainment of an intermediate endpoint where subsequent removal is slow. Issues related to limited bioavailability for the microorganisms and its relationship to sorption-desorption processes in contaminated soil have increasingly been of interest to practitioners in this field. While many of these issues have been reviewed separately in detail, the purpose of this review is to provide for the bioremediation specialist an overview of recent work relating biodegradation, sorption and desorption in soils as well as a discussion of some of the leading questions now being investigated.

Abstract Direct physical methods such as, optical spectroscopy, can provide a wealth of information on the chemical interactions of organic adsorbates with mineral surfaces. Probing an organic sorbate-clay complex with electromagnetic radiation can elucidate the information on surface speciation, conformation of the sorbate and the nature of the local chemical environment at the mineral/water interface. The typical spectroscopic study is depicted in Figure 1. A sample is placed in the path of an impinging source of electromagnetic radiation. Reaction of the sample with the incident radiation results in excitation of the analyte from its ground state, S 0 , to an excited state S 1 concomitant with absorption of some fraction of the electromagnetic radiation. The analyst monitors the quantity of radiation transmitted through the sample as it is excited to S,, or emitted by the sample when it relaxes back to S 0 , across a range of frequency and time domains (see Figure 2).

Abstract Contamination of soils and sediments with organic chemicals and the potential movement of these chemicals to ground water are of increasing public concern. Because of their large surface area and charge, clays comprise the most important inorganic component in controlling the fate and transport of organic chemicals entering soils and sediments. It is essential, therefore, to understand interactions of organic pollutants with clays. The chapters in this volume consider the roles of clays in sorption, transport, attenuation, and bioremediation of organic pollutants in contaminated systems.