Iron in ores

The metal content of iron in ores can be determined by a redox procedure in which the sample is first oxidized with Br2 to convert all the iron to Fe3+ and then titrated with Sn2+ to reduce the Fe3+ to Fe2+. The balanced equation is... 

Tailings for ground or underground disposal should contain fewer sulphides and thus be less reactive. Most of the iron in ore, as pyrite, will be disposed of as iron silicate slag that is relatively unreactive. Sulphur may be di >osed of into surface dumps as unreactive sulfates at some disposal cost but using practices that are well established already. 

Quantitative gas chromatographic schemes now exist for the determination of beryllium in blood, urine, and tissue,chromium in serum," aluminum in uranium, aluminum, gallium, and indium, in aqueous solu-tions," iron in ore, chromium in steel, titanium in bauxite, aluminum, iron, and copper in alloys,uranium, tungsten and molybdenum in alloys and ores, " and the list continues to grow rapidly. In the ultratrace analysis of beryllium the lower limit of detectability is ca. 10 g. The gas... 

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. 

The Utah deposit is located in southwestern Utah near Cedar City. The iron ore deposits are of contact metamorphic origin. The cmde ore contains 35 to 65% iron, primarily in the form of magnetite and goethite. Mining is done by the open pit method. The cmde ore is cmshed, screened at —75 mm (—200 mesh size) and shipped as lump ore containing 54% iron. The ore is rescreened at the steel mill to produce lump ore (10—64 mm) for the blast furnace and sinter feed (0—10 mm) for the sinter plant. 

In most ores, sufficient Fe is already present. For some ores, it is necessary to add metallic iron. In practice, the oxidation potential of the solution can be monitored and controlled using the Fe /Fe ratio. Very high leaching efficiencies with H2SO ate common, eg, 95—98% dissolution yield of uranium (39). If acid consumption exceeds 68 kg/1 of ore treated, alkaline leaching is preferred. The comparative costs of acid, sodium hydroxide, and sodium carbonate differ widely in different areas and are the determining factor. 

An alternative commercial form of a metallic mixed lanthanide-containing material is rare-earth siUcide [68476-89-1/, produced in a submerged electric-arc furnace by the direct reduction of ore concentrate, bastnasite, iron ore, and quart2. The resulting alloy is approximately 1/3 mischmetal, 1/3 sihcon, and 1/3 iron. In addition there are some ferro-alloys, such as magnesium—ferrosilicons, derived from cerium concentrate, that contain a few percent of cerium. The consumption of metallic cerium is overwhelmingly in the mixed lanthanide form in ferrous metallurgy. 

Eor example, beryUium occurs at the bottom of a displacement series with NTA allowing this metal to be recovered as the hydroxide by pH adjustment of an ore processing solution all of the interfering metals remain sequestered by chelation (14). Additionally, because other metals present caimot displace iron in an iron—EHPG chelate, the chelate can be used in highly calcareous soils to supply iron as a trace nutrient in agriculture (15). 

The most important indusuial reaction of this kind occurs in die ironmaking blast furnace in which iron oxide ore is reduced by carbon in the form of coke. The mixture is heated by the combustion of part of the coke input in air to produce temperatures as high as 2000 K. The reduction reaction is caiTied out via the gas phase by the reaction... 

Table 7-10. Comparison of Results of Chemical and X-ray Determinations of Iron and Manganese in Ores...

The stoichiometric point is reached when all the Fe2+ has reacted and is detected when the purple color of the permanganate ion persists. A sample of ore of mass 0.202 g was dissolved in hydrochloric acid, and the resulting solution needed 16.7 mL of 0.0108 M KMn04(aq) to reach the stoichiometric point, (a) What mass of iron(ll) ions is present (b) What is the mass percentage of iron in the ore sample ... 

Although this chemistry is complex, the basic process is reduction of iron oxide by carbon in an atmosphere depleted of oxygen. Archaeologists have found ancient smelters in Africa (in what is now Tanzania) that exploited this chemistry to produce iron in prehistoric times. Early African peoples lined a hole with a fuel of termite residues and added iron ore. Chamed reeds and charcoal provided the reducing substance. Finally, a chimney of mud was added. When this furnace was fired, a pool of iron collected in the bottom. 

Leblanc wrestled with the problem for five years between 1784 and 1789. Then finally, somehow, someway, he stumbled on the solution. Ancient ironmakers had used carbon in the form of charcoal when hot, the carbon is highly reactive and wrests the oxygen from iron oxide ores. As Leblanc heated his sodium sulfate with charcoal, he added a key new ingredient—common limestone (chalk)—as his source of C03. Almost miraculously, the transformation took place ... 

Iron does not occur in nature as a native metal. Lumps of meteoritic iron, which fell to the surface of the earth from outer space, are often found, however. It has been argued whether the earliest iron used by humans was of meteoritic origin or smelted from ores (Piaskowsky 1988). Combined with other elements, iron occurs in a varied range of ferruginous (iron-containing) ores that are widely dispersed on the upper crust of the earth some common iron ores often used for smelting are listed in Table 37. 

First, determine the mass of Fe, then the percentage of iron in the ore. 

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