Iron mineralization

Iron Mat Iron matte Iron minerals Iron-mischmetal... 

Starch is a polysaccharide found in many plant species. Com and potatoes are two common sources of industrial starch. The composition of starch varies somewhat in terms of the amount of branching of the polymer chains (11). Its principal use as a flocculant is in the Bayer process for extracting aluminum from bauxite ore. The digestion of bauxite in sodium hydroxide solution produces a suspension of finely divided iron minerals and siUcates, called red mud, in a highly alkaline Hquor. Starch is used to settle the red mud so that relatively pure alumina can be produced from the clarified Hquor. It has been largely replaced by acryHc acid and acrylamide-based (11,12) polymers, although a number of plants stiH add some starch in addition to synthetic polymers to reduce the level of residual suspended soHds in the Hquor. Starch [9005-25-8] can be modified with various reagents to produce semisynthetic polymers. The principal one of these is cationic starch, which is used as a retention aid in paper production as a component of a dual system (13,14) or a microparticle system (15). 

Minerals. Iron-bearing minerals are numerous and are present in most soils and rocks. However only a few minerals are important sources of iron and thus called ores. Table 2 shows the principle iron-bearing minerals. Hematite is the most plentiful iron mineral mined, followed by magnetite, goethite, siderite, ilmenite, and pyrite. Siderite is unimportant in the United States, but is an important source of iron in Europe. Tlmenite is normally mined for titania with iron as a by-product. Pyrite is roasted to recover sulfur in the form of sulfur dioxide, leaving iron oxide as a by-product. 

Sodium sihcate (41°Bh, 1 3.22 ratio Na20 Si02) is added in the milling operation to disperse the slime, mosdy kaolin. Dispersion also aids the grinding process. The rod mill serves to grind the ore to 0.833 mm (—20 mesh) or to the point where mica, quart2, feldspar, and iron minerals are Hberated. Cyclones, or rake, hydrauhc, or other types of classifiers, are used after grinding to produce coarse and fine mica fractions that are treated separately. 

Flake mica is also produced from mica schist which normally contains from 30—60% recrysta11i2ed muscovite mica along with quart2 and iron minerals. The quart2 is usually not suitable for glass sand or high purity material, however. 

Typically, ore bodies are relatively low in iron content. Iron minerals are finely divided in a gangue matrix. Wet grinding is usually required to Hberate the iron minerals, although some beach sands may have Hberated iron mineral values. Wet dmm separators are limited to the treatment of material <10 mm. The magnetic dmm separators appHed are usually related to the grinding circuit required to Hberate the iron mineral, and are typically designated by appHcation as cobbers, roughers, or finishers. 

Cobbers. Magnetic dmms used in cobbing services are designated to obtain maximum rejection of a nonmagnetic product and maximum recovery of the iron mineral. Typically, cobbers are appHed on a rod mill discharge product. Because the objective is to obtain maximum capacity, these dmms are 914 or 1219 mm in diameter and incorporate wear covers on the dmm shells to take the wear introduced by the relatively coarse feed size. 

Magnetite is common in Pb-Zn-Mn and Cu deposits but has not been reported in Au-Ag deposits. It commonly coexists with other iron minerals such as hematite, pyrite, pyrrhotite, siderite, and chlorite and also occurs in both the main stage of sulfide mineralization and in the late stage of mineralization. 

The /co2 values could be estimated based on FeCOa content of carbonates coexisting with iron minerals (pyrite, hematite, magnetite, pyrrhotite) and minerals containing... 

It is difficult to give an exact limit because the impact of thickness broadening depends on the intrinsic width of experimental lines [31], which often exceeds the natural width 2r at by 0.05—0.1 mm s for Fe as studied in inorganic chemistry. This inhomogeneous broadening, which is due to heterogeneity and strain in the sample, causes a reduction of the effective thickness. Rancourt et ai. have treated this feature in detail for iron minerals [32]. 

Osmond JK, Ivanovich M (1992) Uraninm series mobilization and surface hydrology. In Uranium-series disequihbrium. Ivanovich M, Harmon RS (eds) Clarendon Press, Oxford, p 259-289 Payne XE, Davis JA, Waite XD (1994) Uranium retention by weathered schists—the role of iron minerals. Radiochim Acta 66/67 297-303... 

The alkali process uses sodium hydroxide and is well known as Bayer s process. It involves relatively simple inorganic and physical chemistry and the entire flowsheet can be divided into caustic digestion, clarification, precipitation and calcination. Although mineral assemblage in bauxites is extensive, processing conditions are primarily influenced by the relative proportions of alumina minerals (gibbsite and boehmite), the iron minerals (goethite and hematite), and the silica minerals (quartz and clays-usually as kaolinite). 

The migration of iron mineral fines, primarily hematite and magnetite, is a common occurrence in portions of the Appalachian Basin. The phenomenon often occurs after well stimulation and can result in the continuing production of iron mineral fines which pose a significant disposal problem. The migration of iron mineral fines through propped fractures can substantially reduce the fracture flow capacity. Many of these are mineral fines are native to the formation and are not formed by precipitation of acid-soluble iron salts present in injection waters during or after acidi-... 

Radford,E.P., and K.G. St.Clair Renard, Lung Cancer in Swedish Iron Miners Exposed to Low Doses of Radon Daughters, The New England Journal of Medicine, 310 1485 (1984). 

Radford, E. P. and K. G. St. Clair Renard, Lung cancer in Swedish iron miners exposed to low doses of radon daughters, New Engl. J. Med. 310 1485-1494 (1984). 

Fig. 12.2. Redox-pH diagram for the Fe-S-H20 system at 100 °C, showing speciation of sulfur (dashed line) and the stability fields of iron minerals (solid lines). Diagram is drawn assuming sulfur and iron species activities, respectively, of 10-3 and 10-4. Broken line at bottom of diagram is the water stability limit at 100 atm total pressure. At pH 4, there are two oxidation states (points A and B) in equilibrium with pyrite under these conditions.

Nordstrom, D. K., 1982, Aqueous pyritc oxidation and the consequent formation of secondary iron minerals. In Acid Sulfate Weathering. Soil Science Society of America Special Publication 10, 37-56. 

Lewin, A., Moore, G.R. and Le Bran, N.E. (2005) Formation of protein-coated iron minerals, Dalton Trans., 22, 3579-3610. 

Canfield DE, Raiswell R, Bottrell S (1992) The reactivity of sedimentary iron minerals toward sulfide. Am J... 

Fredrickson JK, Zachara JM, Kennedy DW, Dong H, Onstott TC, Hinman NW, Li S (1998) Biogenic iron mineralization accompanying the dissimilatory reduction of hydrous ferric oxide by a groundwater bacterium. Geochim Cosmochim Acta 62 3239-3257... 

Glasauer S, Langley S, Beveridge TJ (2002) Intracellular iron minerals in a dissimilatory iron-reducing bacterium. Science 295 117-119... 

The Chemical Speciation of Iron Mineral Precipitation and Dissolution... 

Acid leaching is usually carried out using sulfuric acid under pressure to dissolve the majority of the iron minerals and to release the cobalt and nickel. If this is carried out at 150-250°C, then the iron(III) is precipitated as haematite or jarosite, reducing the amount of iron in the leachate. The... 

No one person is given credit for the discovery or identification of irons minerals/ores or the technologies involved in the sophisticated metallurgical processes used today. Many people have contributed to the understanding of the chemistry and how to make practical use of this important element. Modern civilization, with its many skyscrapers, large ships, trains, cars, and so forth, would not be possible without the knowledge and uses of the many iron and steel products manufactured today. 

Klupinski et al. (2004) conclude that the reduction of nitroaromatic compounds is a surface-mediated process and suggest that, with lack of an iron mineral, reductive transformation induced only by Fe(II) does not occur. However, when C Cl NO degradation was investigated in reaction media containing Fe(II) with no mineral phase added, a slow reductive transformation of the contaminant was observed. Because the loss of C Cl NO in this case was not described by a first-order kinetic model, as in the case of high concentration of Fe(II), but better by a zero-order kinetic description, Klupinski et al. (2004) suggest that degradation in these systems in fact is a surface-mediated reaction. They note that, in the reaction system, trace amounts of oxidize Fe(II), which form in situ suspended iron oxide... 

Reduction by Fe(ll) results in an increase in the amount of iron oxides, which favor further reaction. Such autocatalytic behavior characterizes the oxidation of Fe(II) by and explains C Cl NO reduction by Fe(ll) in the absence of an iron mineral phase. Generalizing this behavior, it can be assumed that Fe(III) colloids derived from Fe(ll) oxidation in subsurface anoxic systems, together with other colloids, affect the environmental persistence of nitroaromatic contaminants. Colon et al. (2006), for example, elucidate factors controlling the transformation of nitrosobenzenes and N-hydroxylanilines, which are the two intermediate... 

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