Iron hematitic

Some simple oxides are brighdy or strongly colored, and have been used as pigments. This includes the common oxides of iron, hematite, which is red and black, and goethite (syn. limonite), which is yellow or brown. These compounds have also been called ocher, yellow ocher, or brown ocher. Minium and massicot... 

Iron Hematite [Fe203], goethite [FeOOH], magnetite [Fe Fei+04] Iron and steel... 

The catalysts often used in commercial processes consist in hematite (a-Fe203) and promoters such as potassium oxide and chromium oxide, among others [92]. It is well-known [92-97] that potassium acts as electronic promoter increasing the iron activity and also contributes to decrease the coke formation. On the other hand, chromium acts as textural promoter increasing the specific surface area of hematite [92, 93]. These catalysts are cheap and very active and selective, but have some drawbacks such as the low specific smface area and the instability of the active oxidation state of iron hematite (a-Fe203) is preferred for... 

Heavy water, see Hydrogen[ H] oxide Heazlewoodite, see rn-Nickel disulfide Hematite, see Iron(III) oxide Hermannite, see Manganese silicate Hessite, see Silver telluride Hieratite, see Potassium hexafluorosilicate Hydroazoic acid, see Hydrogen azide Hydrophilite, see Calcium chloride Hydrosulfite, see Sodium dithionate(III)... 

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. 

High intensity magnetic separators are used to upgrade iron ores containing hematite or ilmenite. Dry separators require ore that is finely sized and bone dry. They are dusty, expensive, and have a low capacity. Wet separators have larger capacity, are less dusty and can handle ore sizes up to 1 mm. 

Assuming that the initial iron oxide is hematite, Fe202, and this ore is completely converted to FeO, ie, no metallic iron is formed, the reduction would be 33.33%. Thus the relationship between metallization and reduction is... 

The reduction of iron ore is accompHshed by a series of reactions that are the same as those occurring in the blast furnace stack. These include reduction by CO, H2, and, in some cases soHd carbon, through successive oxidation states to metallic iron, ie, hematite [1309-37-17, Fe202, is reduced to magnetite [1309-38-2], Fe O, which is in turn reduced to wustite [17125-56-3], FeO, and then to metallic iron, Fe. The typical reactions foUow. 

Iron compounds (qv) in limestone are seldom injurious to a lime product unless a very pure lime is required. Normally, the iron compounds are in the form of limonite [1317-63-1] (ferric hydroxide) and pyrite [1309-36-0] EeS2. Occasionally, hematite, magnetite, marcasite, and other forms of iron are found in limestone. 

Iron Oxide Reds. From a chemical point of view, red iron oxides are based on the stmcture of hematite, a-Fe202, and can be prepared in various shades, from orange through pure red to violet. Different shades are controlled primarily by the oxide s particle si2e, shape, and surface properties. Production. Four methods are commercially used in the preparation of iron oxide reds two-stage calcination of FeS047H2 O precipitation from an aqueous solution thermal dehydration of yellow goethite, a-FeO(OH) and oxidation of synthetic black oxide, Fe O. ... 

Wet preparation of red iron oxides can involve either a hydrothermal process (see Hydrothermal processing) or a direct precipitation and growth of iron oxide particles on specially prepared nucleating seeds of Fe202- In the hydrothermal process, iron(II) salt is chemically oxidized to iron(III) salt, which is further treated by alkahes to precipitate a hydrated iron(III) oxide gel. The gel can be dehydrated to anhydrous hematite under pressure at a temperature around 150°C. 

Transparent red iron oxide is composed mainly of hematite, a-Ee202, having primary particles about 10 nm. It is prepared by a precipitation reaction from a dilute solution of an iron salt at a temperature around 30°C, foUowed by a complete oxidation in the presence of some seeding additives,... 

In a modification the conversion process, the jarosite residue is hydrothermaHy decomposed to hematite by autoclaving at 220—250°C. This solubilizes zinc and other metal values and the hematite has a potential for iron recovery. Hematite stockpiles are less of a problem than jarosite because hematite is denser and holds up less of the soluble metals. 

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