Production of Metals

Because metals in their combined forms always have positive oxidation numbers, the production of a free metal is a reduction process. Preliminary operations may be necessary to convert the ore to a chemical state more suitable for reduction. For example, an ore may be wasted to drive off volatile impurities and at the same time to convert the carbonates and sulfides to the corresponding oxides, which can be reduced more conveniently to yield the pure metals  

This last equation demonstrates that the conversion of sulfides to oxides is a major source of sulfur dioxide, a notorious air pollutant. 

How a pure metal is obtained by reduction from its combined form depends on the standard reduction potential of the metal. Table 23.2 outlines the reduction processes for several metals. Most major metallurgical processes now in use involve pyrometallurgy, procedures carried out at 

TABLE 23.2 I Reduclioii Proces.Ne fof Some Orairum Metals 

Chromium, manganese, titanium, vanadium, iron, zinc 

Electrolytic reduction of anhydrous oxide (in molten ciyolite) 

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Traditionally, production of metallic glasses requites rapid heat removal from the material (Fig. 2) which normally involves a combination of a cooling process that has a high heat-transfer coefficient at the interface of the Hquid and quenching medium, and a thin cross section in at least one-dimension. Besides rapid cooling, a variety of techniques are available to produce metallic glasses. Processes not dependent on rapid solidification include plastic deformation (38), mechanical alloying (7,8), and diffusional transformations (10). 

A. T2cM y,A.tomicyation The Production of Metal Powder, Metal Powder Industries Federation, Princeton, N.J., 1992. 

Metals Handbook, 9th ed. Vol. 7, Powder Metallurgy-. Production of Metal Powders, American Society of Metals, Metals Park, Ohio, 1984. 

Others. Oxahc acid is used for the production of cobalt, as a raw material of various agrochemicals and pharmaceuticals, for the manufacture of electronic materials (76—83), for the extraction of tungsten from ore (84), for the production of metal catalysts (85,86), as a polymerization initiator (87—89), and for the manufacture of zirconium (90) and beryhium oxide (91). 

Fig. 1. Simplified flow chart for the production of metallic chromium and chromium compounds from chromite.

Fig. 6. Flash smelting-flash converting process for continuous production of metallic copper. Courtesy of Keimecott Corp.

Table 6. Production of Metals by Electrolysis of Aqueous Solutions ...

In die production of metallic objects for technological applications, an important way to produce drese is via die compacting of metal powders. One... 

The production of metals which form very stable oxides by tire aluminothermic process, such as manganese, clrromium and vanadium is carried out with reactants at room temperature which react to provide enough heat to raise the temperature of the products to high temperatures at which the whole system is liquid. The metal phase which is produced can therefore separate from the liquid slag which is formed. The production of clrromium serves as a useful... 

In the production of metallic uranium the fluoride UF4 is used for magnesium reduction since die reduction of UCI4 does not produce sufficient heat. The chloride can be reduced with calcium, when a signihcantly greater amount of heat is generated to reach die desired temperature. 

A complication of tire extension of tire electrolysis route for metal production, is tlrat in the case of the alkali metals, there is a significant solubility of the metal which would be produced by electrolysis in tire molten chloride. The dissolved metal provides very mobile electrons to tire melt, thus reducing the salt resistance, and dissipating the increased cuiTent, at a given applied potential, without the production of metal. To describe this phenomenon in... 

The purity ot the scrap mainly determines the fraction of energy needed to produce metal from it, and the value of recycling. Clean copper scrap need only be remelted and cast to form recycled copper if the copper is contaminated with organic materials and other metals, more complex separation processes are needed that are similar to production from ores. It is easier to remelt the steel of a car driven in Arizona compared to one rusted by the road salt in snowy areas. Scrap that is produced as a by-product of metal processing can be easily recycled, and it can be collected from relatively few locations. There has been a strong effort to educate both householders and industrial users to separate scrap and return it to waste collectors, leading to a supply of reasonably separated scrap. 

The production of metal vapor upon arc interruption necessary to control current chopping and permit voltage recovery and... 

Wood is particularly valuable for many conditions which are corrosive to common metals (e.g. acids and external exposure), and for contact with foodstuffs and beverages. It is not subject to corrosion in the electrochemical sense of the term applied to metals, but in saline conditions it can be attacked by the products of metal corrosion (alkali and iron salts) where poor technology or unsuitable wood species are used. Although wood is attacked by both extremely alkaline and acid conditions, particularly those which are oxidising, it can be employed over a wider pH range than most other materials. 

Nail sickness Nail sickness is chemical decay associated with corroded metals in marine situations. Chemical degradation of wood by the products of metal corrosion is brought about by bad workmanship or maintenance, or unsuitable (permeable) timber species, all of which permit electrolyte and oxygen access which promotes corrosion. Chemical decay of wood by alkali occurs in cathodic areas (metal exposed oxygen present). Softening and embrittlement of wood occurs in anodic areas (metal embedded oxygen absent) caused by mineral acid from hydrolysis of soluble iron corrosion products. 

In the first cell the net reaction is the production of metallic mercury and gaseous oxygen through electrolysis of aqueous mercuric nitrate ... 

With the aid of a table of solubility products of metallic sulphides, we can calculate whether certain sulphides will precipitate under any given conditions of acidity and also the concentration of the metallic ions remaining in solution. Precipitation of a metallic sulphide MS will occur when [M2 + ] x [S2 ] exceeds the solubility product, and the concentration of metallic ions remaining in the solution may be calculated from the equation ... 

Values for the solubility products of metallic hydroxides are, however, not very precise, so that it is not always possible to make exact theoretical calculations. The approximate pH values at which various hydroxides begin to precipitate from dilute solution are collected in Table 11.2. 

The processes for the production of metallic Na, Na-Ha or Na-Pb alloy have been reviewed. ... 

Production of Metallic Nanoparticles Inside Langmuir-Blodgett Films... 

Jensen WB (1997) A note on the term Chalcogen . J Chem Educ 74 1063-1064 Fischer W (2001) A second note on the term Chalcogen . J Chem Educ 78 1333 Fthenakis V, Wang W, Kim HC (2009) Life cycle inventory analysis of the production of metals used in photovoltaics. Renewable Sustainable Energy Rev 13 493-517 Waitkins GR, Bearse AE, Shutt R (1942) Industrial utilization of selenium and tellurium. Ind Eng Chem 34 899-910... 

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