Interface mineral-water

G. A. Parks, Surface energy and adsorption at mineral/water interfaces an introduction, in M. F. Hochella and A. F. White, eds., Mineral-Water Interface Geochemistry, The Mineralogical Society of America, Washington, D. C (1990). 

The force needed to break the mineral-air interface is called the work of adhesion, WA, and is equal to the work needed to separate the mineral-air interface and produce in place air-water and mineral-water interfaces. This, in other words, may be represented with interfacial tensions in place as ... 

Stumm, W. Process at the Mineral-Water Interface and Particle-Water Interface in Natural Systems. Wiley New York, 1992. 

Manning BA, Goldberg S (1997a) Adsorption and stability of arsenic (III) at the clay mineral-water interface. Environ Sci Technol 31 2005-2011 Manning BA, Goldberg S (1997b) Arsenic(III) and arsenic(V) adsorption on three California soils. Soil Sci 162 886-895... 

Kulik, D. A., 2002, Gibbs energy minimization approach to model sorption equilibria at the mineral-water interface Thermodynamic relations for multi-site-surface complexation. American Journal of Science 302,227-279. ... 

Of major interest in geochemistry and in natural water systems are semiconducting minerals for which the absorption of light occurs in the near UV or visible spectral region and as a result of which redox processes at the mineral-water interface are induced or enhanced. Table 10.1 gives band gap energies of a variety of semiconductors. 

Comans, R. N. J. (1990), "Adsorption, Desorption and Isotopic Exchange of Cadmium on lllite Evidence for Complete Reversibility", in Sorption of Cadmium and Cesium at Mineral/Water Interfaces, Ph. D. Thesis, Rijksuniversiteit Utrecht, Netherlands. 

Hering, J., and W. Stumm (1991), "Fluorescence Spectroscopic Evidence for Surface Complex Formation at the Mineral-Water Interface Elucidation of the Mechanism of Ligand-Promoted Dissolution," Langmuir7, 1567-1570. 

This book deals only with the chemistry of the mineral-water interface, and so at first glance, the book might appear to have a relatively narrow focus. However, the range of chemical and physical processes considered is actually quite broad, and the general and comprehensive nature of the topics makes this volume unique. The technical papers are organized into physical properties of the mineral-water interface adsorption ion exchange surface spectroscopy dissolution, precipitation, and solid solution formation and transformation reactions at the mineral-water interface. The introductory chapter presents an overview of recent research advances in each of these six areas and discusses important features of each technical paper. Several papers address the complex ways in which some processes are interrelated, for example, the effect of adsorption reactions on the catalysis of electron transfer reactions by mineral surfaces. 

In this overview we discuss recent advances in the study of chemical reactions at the mineral-water interface as we introduce the... 

Surface spectroscopy offers the best opportunity to elucidate the structures of chemical species at the mineral-water interface (see Sposito, Chapter 11). The application of spectroscopic methods to probe the molecular environment of the interface is still a relatively new field. Chapters 16-19 present reviews and some recent advances in investigations of molecular structure at the mineral-water interface. A recent review of spectroscopic methods applied to soil and clay mineral systems is given in Stucki and Banwart (72). 

Additional Transformation Reactions. Other reactions that can be catalyzed by mineral surfaces are substitution, elimination, and addition reactions of organic molecules. Substitution and elimination are two general types of reactions that occur at saturated carbon atoms of organic molecules. Both types are initiated by nucleophilic attack however, in elimination reactions it is the basicity of the nucleophile that determine its reactivity rather than its nucleophilicity. Since mineral surfaces are expected to have both nucleophilic and basic properties, these types of reactions should also occur at mineral-water interfaces (see Chapter 22). It remains to be shown whether or not these reactions are catalyzed under environmental conditions. 

Experimental studies of the thermodynamic, spectroscopic and transport properties of mineral/water interfaces have been extensive, albeit conflicting at times (4-10). Ambiguous terms such as "hydration forces", "hydrophobic interactions", and "structured water" have arisen to describe interfacial properties which have been difficult to quantify and explain. A detailed statistical-mechanical description of the forces, energies and properties of water at mineral surfaces is clearly desirable. 

To a certain extent a similar statement could be made about research on the chemistry of mineral-water interfaces. Some theoretical models (2,3) developed to date have focused primarily on their ability to fit data collected from one experimental technique, namely potentiometric titration. While these models have done much to improve our understanding of the oxide-water interface, we do not have a complete picture of the interfacial region at present. Although potentiometric titrations can still provide new insights, failure to utilize other techniques may result in the problem mentioned in Forni s statement above. 

To put things into perspective, we. can broadly classify these analytical methods into bulk, dry surface, and in situ interfacial techniques. This chapter focuses on the last category, illustrating two in situ techniques used to study anion binding at the goethite (a-FeOOH)-water interface titration calorimetry and cylindrical internal reflection-Fourier transform infrared (CIR-FTIR) spectroscopy. In fact, CIR-FTIR could prove to be extremely powerful, since it allows direct spectroscopic observation of ions adsorbed at the mineral-water interface. 

It is for this reason that spectroscopy offers the only experimental method for characterizing the interfacial region that is not automatically destined to run into basic conceptual difficulties. This is not to say that difficulties of a technical nature will not arise (40-48), nor that the conceptual difficulty of differing time scales among spectroscopic techniques will cause no problems (50). Nonetheless, it is to be hoped that future investigations of sorption reactions will focus more on probing the molecular structure of the mineral/water interface than on attempting simply to divine what the structure may be. 

Chemical relaxation methods can be used to determine mechanisms of reactions of ions at the mineral/water interface. In this paper, a review of chemical relaxation studies of adsorption/desorption kinetics of inorganic ions at the metal oxide/aqueous interface is presented. Plausible mechanisms based on the triple layer surface complexation model are discussed. Relaxation kinetic studies of the intercalation/ deintercalation of organic and inorganic ions in layered, cage-structured, and channel-structured minerals are also reviewed. In the intercalation studies, plausible mechanisms based on ion-exchange and adsorption/desorption reactions are presented steric and chemical properties of the solute and interlayered compounds are shown to influence the reaction rates. We also discuss the elementary reaction steps which are important in the stereoselective and reactive properties of interlayered compounds. 

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