Mineralogy, oxide, effect

RAT grinding operations. This surface layer was removed except for a remnant in a second grind. Spectra - both 14.4 keV and 6.4 keV - were obtained on the undisturbed surface, on the bmshed surface and after grinding. The sequence of spectra shows that nanophase Oxide (npOx) is eiu-iched in the surface layer, while olivine is depleted. This is also apparent from a comparison of 14.4 keV spectra and 6.4 keV spectra [332, 346, 347]. The thickness of this surface layer was determined by Monte-Carlo (MC)-Simulation to about 10 pm. Our Monte Carlo simulation program [346, 347] takes into account all kinds of absorption processes in the sample as well as secondary effects of radiation scattering. For the MC-simulation, a simple model of the mineralogical sample composition was used, based on normative calculations by McSween [355]. 

In this case, the mineralogical studies on the mechanism of sulfide alteration and on the genesis and evolution of secondary oxidation products are of paramount environmental relevance because they allow a better understanding of the source and the mechanisms of release of the ecotoxic elements and the effective... 

Effect of Oxide Mineralogy on Reductive Dissolution. Oxide/hydrox-ide surface structures and the coordinative environment of metal centers may change substantially throughout the course of a reductive dissolution reaction. Nonstoichiometric and mixed oxidation state surfaces produced during surface redox reactions may exhibit dissolution behavior that is quite different from that observed with more uniform oxide and hydroxide minerals. 

The geochemical classification using major oxides shows that the samples used in this study plot in the litharenite field, and, implies that they are mineralogically submature. Major-element concentrations point to significant weathering effect in the source area of the sample set. Provenance analyses, based on major-and trace-element compositions suggest... 

Borggaard, O.K. (1983) Effect of surface area and mineralogy of iron oxides on their surface charge and anion-adsorption properties. Clays Clay Min. 31 230-232 Borggaard, O.K. (1983 a) The influence of iron oxides on phosphate adsorption by soil. J. 

Sorensen, M.A. Bender Koch, C. Stackpoole, M.M. Bordia, R.K. Benjamin, M.M. Christensen, T.H. (2000) Effects of thermal treatment on mineralogy and heavy metal behavior in iron oxide stabilized air pollution control residues. Environ. Sci. Techn. 34 4620-4627... 

An actual contribution of humic substances to metal oxide reduction in natural systems has not been demonstrated, and there are processes such as adsorption or decomposition that could limit their effectiveness. Kostka et al. (2002a) observed that AQDS additions elicited a larger increase in Fe(III) reduction by S. oneidensis growing on ferrihydrite than smectite clay minerals. This suggests that the influence of humic substances may depend on soil or sediment mineralogy. Nevertheless, there is ample evidence to suggest that a portion of the anaerobic metabolism that was previously attributed to direct enzymatic Fe(III) and Mn(IV) reduction was actually none-nzymatic reduction by microbially reduced humic substances. 

The susceptibility of metal oxides to reduction and dissolution depends on mineralogy, crystallinity, surface area, the effectiveness of reducing and chelating agents, and microbial activity. Early culture studies with Ee(Hl)-respiring bacteria demonstrated that Ee(lll) reduction rates vary with mineral form or crystallinity... 

Burdige D. J., Dhakar S. P., and Nealson K. H. (1992) Effects of manganese oxide mineralogy on microbial and chemical manganese reduction. Geomicrobiol. J. 10, 27-48. 

Nyashanu R., Monhemius A., and Buchanan D. (1999) The effect of ore mineralogy on the speciation of arsenic in bacterial oxidation of refractory arsenical gold ores. In International Biohydrometallurgy of Symposium IBS 99, Madrid (eds. R. Amils and A. Ballester). Elsevier, Oxford, pp. 431-441. 

The most common use of the Mossbauer effect in mineralogy and geology has been the determination of the oxidation states of iron in various minerals (2). The study of the Mossbauer spectral area also gives valuable information on the concentration of the different minerals in rocks (2). Recently the Mossbauer effect was applied to the study of iron-bearing minerals in coal to determine the amount of pyritic sulfur (3, 4, 5). 

The effects of the mineral matter depend on the chemical and mineralogical composition. Many standard analytical techniques are available to quantify the elements present in the mineral species. These include silicon, aluminum, iron, calcium, magnesium, sodium, potassium, titanium and others. The elements are usually reported as oxides, because the oxide anion is the predominant one in fly ash. However, the mineral species are not usually simple oxides, but very frequently are tied up in the different mineral forms as more complex aluminosilicates or other species as indicated above. A variety of techniques is used to identify the mineral matter. 

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