Oxide minerals, aqueous surface

Parks, G. A. (1967), "Aqueous Surface Chemistry of Oxides and Complex Oxide Minerals Isoelectric Point and Zero Point of Charge," in Equilibrium Concepts in Natural Water Systems, Advances in Chemistry Series, No. 67, American Chemical Society, Washington, DC. 

Even though the vacuum-oriented surface techniques yield much useful information about the chemistry of a surface, their use is not totally without problems. Hydrated surfaces, for example, are susceptible to dehydration due to the vacuum and localized sample heating induced by x-ray and electron beams. Still, successful studies have been conducted on aquated inorganic salts (3), water on metals (3), and hydrated iron oxide minerals (4). Even aqueous solutions themselves have been studied by x-ray photoelectron spectroscopy (j>). The reader should also remember that even dry samples can sometimes undergo deterioration under the proper circumstances. In most cases, however, alterations in the sample surface can be detected by monitoring the spectra as a function of time of x-ray or electron beam exposure and by a careful, visual inspection of the sample. 

Table 16.2 Characteristics of common iron(hydr)oxide minerals. Reprinted with permission from Pecher K, Haderline SB, Schwarzenbach RP (2002) Reduction of polyhalogenated methanes by surface-bound Fe(II) in aqueous suspensions of iron oxides. Environ Sd Technol 36 1734-1741. Copyright 2002 American Chemical Society...

Aqueous Surface Chemistry of Oxides and Complex Oxide Minerals... 

Phillips BL, Casey WH, Karlsson M (2000) Bonding and reactivity at oxide mineral surfaces from model aqueous complexes. Nature 404 379-382... 

Parks, G.A. 1967. Aqueous surface chemistry of oxides and complex oxide minerals Isoelectric point and zero point of charge, p. 121-160. In R.F. Gould (ed.) Equilibrium concepts in natural water systems. Vol. 67. Advances in Chemistry Series, ACS, Washington, DC. 

Molecular-level studies of chemistry in solution and at interfaces, including mineral interfaces (e.g., the behavior of metal ions in aqueous solution and on metal oxide or clay surfaces for vadose zone, tank, and groundwater remediation and catalysis)—a detailed understanding of redox (electron transfer chemistry) is broadly needed studies of the interactions of biological molecules with surfaces for bioremediation are also needed and being pursued. 

The fate of organic contaminants in soils and sediments is of primary concern in environmental science. The capacity to which soil constituents can potentially react with organic contaminants may profoundly impact assessments of risks associated with specific contaminants and their degradation products. In particular, clay mineral surfaces are known to facilitate oxidation/reduction, acid/base, polymerization, and hydrolysis reactions at the mineral-aqueous interface (1, 2). Since these reactions are occurring on or at a hydrated mineral surface, non-invasive spectroscopic analytical methods are the preferred choice to accurately ascertain the reactant products and to monitor reactions in real time, in order to determine the role of the mineral surface in the reaction. Additionally, the in situ methods employed allow us to monitor the ultimate changes in the physico-chemical properties of the minerals. 

The preceding results were conducted under laboratory conditions using freshly prepared natural mineral surfaces that were reacted for relatively short time periods. In order to assess the effectiveness of natural Fe(II) oxides in reducing and immobilizing transition metal under natural aquifer conditions, several important parameters need to be assessed. These include the reductive capacity of the oxide minerals, the impact of surface passivation and the effects of competition and poisoning by of other aqueous species. 

As a first step, the simulation of a mineral-aqueous interface requires treatment of the issue of surface hydroxylation, which is fundamentally tied to the dissociation of water and the energetics of acid-base reactions on mineral surfaces (Blesa et al. 2000). Even just setting the problem up requires some knowledge of the protonation states of the oxide ions at the surface are they aquo, hydroxo, or oxo functional groups If one cannot describe the processes behind Figure 1, it is not possible to go further. This description is... 

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