By ferric oxyhydroxide

Kent et al. (1986) have tabulated reported TL intrinsic constants and , values for a variety of metal oxyhydroxides of Al, Si, Fe, and Ti. More recently. Smith and Jenne (1988,1991) reevaluated published TL modeling of adsorption by ferric oxyhydroxide solids and by 5-Mn02. Their analysis led to a set of intrinsic constants based on measurement and estimation that have been reproduced in Tables 10.12 and 10.13. The intrinsic constants in the tables were derived independent of values for C[ chosen by others. Few studies have applied TL modeling to adsorption by clays, although James and Parks (1982) and Mahoney and Langmuir (1991) TL-modeled alkali metal and alkaline earth adsorption by clays, including beidellite, illite, kaolinite, and montmorillonite. 

The relative percent adsorption of Cu, Zn, Ni, and Ca by ferric oxyhydroxide, shown in Fig. 10.17(b), obeys the Irving-Williams order. The plot suggests an overall adsorption affinity of... 

From MW17, the ground water flows initially SE beneath the NATA but due to rock outcrops veers N to combine with surface water in the RA. The sediment in this area has been contaminated with As from the surficial runoff from the ARS as well as earlier mining operations. The As in the surface water is then attenuated by ferric (Fe(lll)) oxyhydroxides (HFO) so that by the time it reaches Snow Lake level of As are significantly reduced to <0.005 mg/L. 

As we pointed out earlier, the H subunit catalyses the ferroxidase reaction, which occurs at all levels of iron loading, but decreases with increasing amounts of iron added (48-800 Fe/ protein). Reaction (19.8) catalysed by both FI- and L-chain ferritins, occurs largely at intermediate iron loadings of 100-500 Fe/protein. Once nucleation has taken place, the role of the protein is to maintain the growing ferrihydrite core within the confines of the protein shell, thus maintaining the insoluble ferric oxyhydroxide in a water-soluble form. 

An end-member case would be precipitation of ferric oxyhydroxide by photosynthetic Fe(II)-oxidizing bacteria through simple Rayleigh fractionation, with no external Fe(II) flux or return of Fe(II) to the pool from Fe(III)-reducing bacterial activity, which will produce extreme Fe isotope compositions, but only in the latest fluids and precipitates (Fig. 17). In... 

Harrison, P.M. Fischbach, F.A. Hoy, T.G. Haggis, G.H. (1967) Ferric oxyhydroxide core of ferritin. Nature 216 1188-1190 Harvey, D.T. Linton, R.W (1981) Chemical characterization of hydrous ferric oxides by X-ray photoelectron spectroscopy. Anal. 

All physical evidence points to a compact structure for the pol5mier. Its shape is spherical and its density, 3.0, is fairly high. Nevertheless, the tetrahedral coordination of the iron significantly lowers the coordination requirements for the oxygen from what they are in the ferric oxyhydroxides, which are similar in composition. In these materials, each oxygen is surrounded by four iron atoms on the average 43). Given the stoichiometry of the polymer, and the assumption that the waters are at the surface occup)dng one iron coordination site, then a coordi-... 

Iron dextran is a stable complex of ferric oxyhydroxide and dextran polymers containing 50 mg of elemental iron per milliliter of solution. It can be given by deep intramuscular injection or by intravenous infusion, although the intravenous route is used most commonly. Intravenous administration eliminates the local pain and tissue staining that often occur... 

Wetlands have the potential to remove metals from AD by metal adsorption on ferric oxyhydroxides, metal uptake by plant and algae, metal complexation by organic materials, and metal precipitation as oxides, oxyhydroxides, or sulfides. However, only metal precipitation as either oxides or sulfides has long-term metal-removal potential (Evangelou, 1995b). 

XPS study by Buckley and Woods (1984b) showed that freshly fractured chalcopyrite surfaces exposed to air formed a ferric oxyhydroxide overlayer with an iron-deficient region composed of CuSi. Acid-treated surfaces of fractured chalcopyrite showed an increase in the thickness of the CuS2 layer and the presence of elemental sulfur. Hackl et al. (1995) suggested that dissolution of chalcopyrite is passivated by a thin (< 1 pm) copper-rich surface layer that forms as a result of solid-state changes. The passivating surface layer consists of copper polysulhde, CuS , where n > 2. Hackl et al. (1995) described the dissolution kinetics as a mixed diffusion and chemical reaction whose rate is controlled by the rate at which the copper polysulhde is leached. The oxidation of chalcopyrite in the presence of ferric ions under acidic conditions can be expressed as... 

The exposure of sulfide minerals contained in mine wastes to atmospheric oxygen results in the oxidation of these minerals. The oxidation reactions are accelerated by the catalytic effects of iron hydrolysis and sulfide-oxidizing bacteria. The oxidation of sulfide minerals results in the depletion of minerals in the mine waste, and the release of H, SO4, Fe(II), and other metals to the water flowing through the wastes. The most abundant solid-phase products of the reactions are typically ferric oxyhydroxide or hydroxysulfate minerals. Other secondary metal sulfate, hydroxide, hydroxy sulfate, carbonate, arsenate, and phosphate precipitates also form. These secondary phases limit the concentrations of dissolved metals released from mine wastes. 

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