Oxide Ores

A very important but rather complex application of surface chemistry is to the separation of various types of solid particles from each other by what is known as flotation. The general method is of enormous importance to the mining industry it permits large-scale and economic processing of crushed ores whereby the desired mineral is separated from the gangue or non-mineral-containing material. Originally applied only to certain sulfide and oxide ores. 

Chlorination. In some instances, the extraction of a pure metal is more easily achieved from the chloride than from the oxide. Oxide ores and concentrates react at high temperature with chlorine gas to produce volatile chlorides of the metal. This reaction can be used for common nonferrous metals, but it is particularly useful for refractory metals like titanium (see Titanium and titanium alloys) and 2irconium (see Zirconium and zirconium compounds), and for reactive metals like aluminum. 

A.cidSolutions. DHute sulfuric acid is the most important solvent for oxide ore and for dead roasted sulfide concentrates. For instance, the leaching of zinc oxide, described by the foHowing equation, can be written as foHows ... 

Pyrometa.llurgica.1 Processes. Nickel oxide ores are processed by pyrometaHurgical or hydrometaHurgical methods. In the former, oxide ores are smelted with a sulfiding material, eg, gypsum, to produce an iron—nickel matte that can be treated similarly to the matte obtained from sulfide ores. The iron—nickel matte may be processed in a converter to eliminate iron. The nickel matte then can be cast into anodes and refined electrolyticaHy. 

HydrometaHurgical Processes. The hydrometaHurgical treatments of oxide ores involve leaching with ammonia or with sulfuric acid. In the ammoniacal leaching process, the nickel oxide component of the ore first is reduced selectively. Then the ore is leached with ammonia which removes the nickel into solution, from which it is precipitated as nickel carbonate by heating. A nickel oxide product used in making steel is produced by roasting the carbonate. 

In the acid-leaching process, the oxide ore is leached with sulfuric acid at elevated temperature and pressure, which causes nickel, but not iron, to enter into solution. The leach solution is purified, foHowed by reaction with hydrogen sulfide and subsequent precipitation of nickel and cobalt sulfides. 

The direct American process is basically a metallurgical operation. Ziac oxide ores are reduced usiag coal (qv) ia a rotary kiln at temperatures of 1000—1200°C to 2iac metal. At these temperatures the produced 2iac metal evaporates and is oxidi2ed with air to ZnO ia the upper part of the kiln. 

Because of the limited availabiUty of high quaUty 2iac oxide ores and the consequent lower quaUty of produced 2iac oxide which can contain oxides of Pb, Cd, etc, the America production process has limited appHcations. 

Polymers containing 8-hydroxyquinoline appear to be selective adsorbents for tungsten in alkaline brines (95). In the presence of tartrate and citrate, quinaldic acid [93-10-7] allows the separation of zinc from gallium and indium (96). Either of these compounds can selectively separate lead and zinc from oxide ores as complexes (97). It is also possible to separate by extraction micro quantities of rhenium(VII), using quinoline in basic solution (98). The... 

Chloride Process. In the chloride process (Fig. 3), a high grade titanium oxide ore is chlorinated in a fluidized-bed reactor in the presence of coke at 925-1010°C ... 

Zinc ores are generally floated at the mine (18). In the case of simple zinc sulfide ores, flotation is carried out by treatment with copper sulfate to activate the sphalerite causing it to be wet by the organic collector (eg, xanthate). The now-hydrophobic zinc ore particles attach themselves to the rising bubbles. Oxidized ore particles present must be sulftdized with sodium sulfide to be floated (19). Flotation produces concentrates which are ca 50—60% zinc. In mixed ore, the lead and copper are usually floated after depressing the sphalerite with cyanide or zinc sulfate. The sphalerite is then activated and floated. 

HydrometaHurgical processes for copper can be categorized as (/) acid extraction of copper from oxide ore (2) oxidation and solution of sulfides in waste rock from mining, concentrator tailings, or in situ ore bodies (J) dissolution of copper in concentrates to avoid conventional smelting and (4) extraction of copper from deep-sea manganese nodules. 

Xinc. Oxidized ores are calcined to drive off water of hydration and carbon dioxide. The sulfide ore is always roasted before smelting. 

Manganese. Manganese ore, rhodochrosite, or manganese carbonate (MnCOg) is calcined at about 1525 K to produce the oxide (Mn,304). When the oxide ore is available but is in a finely divided state, the rotaiy kiln is used only for nodulizing. 

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... 

Viable methods of producing the metals from oxide ores have to siumount two problems. In the first place, reduction with carbon is not possible because of the formation of intractable carbides (p. 299), and even reduction with Na, Ca or Mg is unlikely to remove all the oxygen. In addition, the metals are extremely reactive at high temperatures and, unless prepared in the absence of air, will certainly be contaminated with oxygen and nitrogen. 

Production methods for all three elements are complicated and dependent on the particular ore involved they will therefore only be sketched in outline. In the case of nickel the oxide ores are not generally amenable to concentration by normal physical separations and so the whole ore has to be treated. By contrast the sulfide ores... 

A few of the oxide ores of copper can be reduced directly to the metal by heating with coke, but the bulk of production is from sulfide ores containing iron, and they require more complicated treatment. These ores are comparatively lean (often 0.5% Cu) and their exploitation requires economies of scale. They are therefore obtained in huge, open-pit operations employing shovels... 

In 1789 M. H. Klaproth examined pitchblende, thought at the time to be a mixed oxide ore of zinc, iron and tungsten, and showed that it contained a new element which he named uranium after the recendy discovered planet, Uranus. Then in 1828 J. J. Berzelius obtained an oxide, from a Norwegian ore now known as thorite he named this thoria after the Scandinavian god of war and, by reduction of its tetrachloride with potassium, isolated the metal thorium. The same method was subsequendy used in 1841 by B. Peligot to effect the first preparation of metallic uranium. 

If the metallic compound in the ore can be selectively leached by acid or base without dissolving much of the remaining ore, then the energy requirement is only about 10 J/kg. Examples are leaching of oxide ores of copper, zinc, or uranium with sulfuric acid. 

Hematite. This additive can be used to increase the specific weight of a cement slurry to as high as 19 Ib/gal. This is an iron oxide ore with a specific gravity of about 5.02. Hematite requires the addition of some water when it is used as an additive. Hematite has minimal effect on thickening time and compressive strength of the cement. 

Oxide Ores Al from Al203l Fe from Fe203... 

Write balanced equations for the reduction of each of the following oxide ores by carbon monoxide ... 

Ni is found in many ores in combination with S, As Sb, the chief sources being the minerals chalcopyrite, pyrrhotite and pentlandite. Ni ores are of two types, sulfide and oxide, the former accounting for two-thirds of the world s consumption. Sulfide ores are refined by flotation and roasting to sintered Ni oxide, and either sold as such or reduced to metal, which is cast into anodes and refined electrolytically or by the carbonyl (Mond) process. Oxide ores are treated by hydrometallurgjcal refining, eg, leaching with ammonia. Much secondary Ni is recovered from scrap (Refs 6 7) 1... 

Titanium dioxide (E171, Cl white 6) is a white, opaque mineral occurring naturally in three main forms rutile, anatase, and brookite. More than 4 million tons of titanium dioxide are produced per year and it is widely used for industrial applications (paints, inks, plastics, textiles) and in small amounts as a food colorant. ° "° Production and properties — Titanium oxide is mainly produced from ilmenite, a titaniferous ore (FeTiOj). Rutile and anatase are relatively pure titanium dioxide (Ti02) forms. Titanium oxide pigment is produced via chloride or sulfate processes via the treatment of the titanium oxide ore with chlorine gas or sulfuric acid, followed by a series of purification steps. High-purity anatase is preferred for utilization in the food industry. It may be coated with small amounts of alumina or silica to improve technological properties. 

Oxides and hydroxides Bauxite laterites copper oxide ores uranium ores zinc ores and calcines manganese ores and nodules... 

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