Metallic aluminum

Industrial aluminum manufacture currently almost exclusively by the Hall-Heroult process 

The industrial manufacture of aluminum is ba.sed on the Hall-Heroult process developed in 1886. In this process aluminum oxide (see Section 3.2.4.2 for the production of aluminum oxide from bauxite) is dissolved in a cryolite (Na3AlF5) melt and electrolyzed at 940 to 980°C with direct current. Molten metallic aluminum is deposited at the carbon electrode (cladding of the bottom) and taken off as a liquid. Oxygen is formed at the anode, also of carbon (presintered or Soederberg-electrode), with which it reacts forming carbon dioxide and carbon monoxide. 

The electrolyte essentially consists of sodium hexafluoroaluminate (synthetic cryolite) with added aluminum fluoride and lithium fluoride. The latter is formed in situ from lithium carbonate. These additives make up 2 to 5% of the bath content and result in a reduced melt temperature, an increase in the melt conductivity, an 

Aluminum oxide is added in an amount of 7 to 12%, dependent upon the bath composition. The eutectic mixture, sodium aluminum hexafluoride/aluminum oxide with 10.5% aluminum oxide, melts at 960°C. The yield with respect to current consumed is 85 to 95%, the cell voltage is 4,5 to 5%, the anode consumption is ca. 0.5 kg/kg aluminum, the power rating of a plant - consisting of many (100 to 200) individual cells connected in series - is in the range 50 to 300 kA. 

Aluminum production is very energy intensive, ca. 18 kWh is on average consumed per kg aluminum (in modern plants 14 kWh/kg). 

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Producing lead—calcium—aluminum alloys is difficult. Calcium and aluminum can be added simultaneously to lead using a calcium (73 wt %)—aluminum (27 wt %) master alloy (11) (see Aluminumand aluminum alloys). Using this method, the calcium and aluminum contents can be precisely controlled. Pressed pellets of metallic aluminum andmetaUic calcium are also used. 

Organoaluminum Compounds. Apphcation of aluminum compounds in organic chemistry came of age in the 1950s when the direct synthesis of trialkylalurninum compounds, particularly triethylalurninum and triisobutylalurninum from metallic aluminum, hydrogen, and the olefins ethylene and isobutylene, made available economic organoalurninum raw materials for a wide variety of chemical reactions (see a-BONDED alkyls and aryls). 

Metals do not generally react with vitreous siUca below 1000°C or their melting point, whichever is lower. Exceptions are alurninum, magnesium, and alkah metals. Aluminum readily reduces siUca at 700—800°C. Alkali metal vapors attack at temperatures as low as 200°C. Sodium vapor attack involves a diffusion of sodium into the glass, followed by a reduction of the siUca. 

WeU-cleaned aluminum filings react at room temperature in the presence of mercuric chloride (20,21). In an autoclave, metallic aluminum and ethyl alcohol react without a catalyst at 120°C (22). The reaction can also be promoted by the addition of sodium ethoxide (23). Aluminum should be avoided as a material of constmction for ethanol service. 

Hydrogen fluoride Catalyst in some petroleum refining, etching glass, silicate extraction by-product in electrolytic production of aluminum Petroleum, primary metals, aluminum Strong irritant and corrosive action on all body tissue damage to citrus plants, effect on teeth and bones of cattle from eating plants... 

FIG. 28-2 Effect of pH on the corrosion rate, a) Iron, (h) Amphoteric metals (aluminum, zinc), (c) Noble metals. 

Clean metallic aluminum is extremely reactive. Even exposure to air at ordinary temperatures is sufficient to promote immediate oxidation. This reactivity is self-inhibiting, however, which determines the general corrosion behavior of aluminum and its alloys due to the formation of a thin, inert, adherent oxide film. In view of the great importance of the surface film, it can be thickened by anodizing in a bath of 15% sulfuric acid (H2SO4) solution or by cladding with a thin layer of an aluminum alloy containing 1 % zinc. 

The fluorine industry is intimately related to aluminum production. Aluminum oxide, (AljOj) is electrolyzed to metallic aluminum with a flux of sodium fuoroaluminate (Na AlF,), called cryolite - a rare mineral found in commercial quantities only in Greenland with other uses glass, enamels, and as a filler for resin-bonded grinding wheels. 

The thermite reaction is spectacular and highly exothermic. It involves the reaction between Fe203, ferric oxide, and metallic aluminum. The reaction produces white-hot, molten iron in a few seconds. Given ... 

It is important to recognize that all materials will have problems in certain environments, whether they are plastics, metals, aluminum, or something else. For example, the chemical effect and/or corrosion of metal surfaces has a damaging effect on both the static and dynamic strength properties of metals because it ultimately creates a reduced cross-section that can lead to eventual failure. The combined effect of corrosion and stress on strength characteristics is called stress corrosion. When the load is variable, the com-... 

Keywords Group 13 metals (aluminum, gallium, indium, thalhum), Ambidentate ligands. Phosphorus-nitrogen bidentate ligands, Pyridyl phosphanes, Aminoiminophosphoranes, Lewis acid catalysis... 

Part I General Aspects. By E. B. Sandell and Hiroshi Onishi Part IIA Individual Metals, Aluminum to Lithium. By Hiroshi Onishi... 

B. Bogdanovic, M. Felderhoff, S. Kaskel, A. Pommerin, K. Schlichte, F. Schiith, Reversible Storage of Hydrogen using Doped Alkali Metal Aluminum Hydrides, 2001, WO 03/053848 Al. 

The elements in the lower left portion of the p-block of the periodic table are the main group metals. Although the most important metals of technological society are transition metals from the d block, three main group metals, aluminum, lead, and tin, have considerable technological importance. 

The surface-phase layers will difier in character depending on the stractures of metal and oxide. On certain metals (zinc, cadmium, magnesium, etc.), loose, highly porous layers are formed which can attain appreciable thicknesses. On other metals (aluminum, bismuth, titanium, etc.), compact layers with low or zero porosity are formed which are no thicker than 1 pm. In a number of cases (e.g., on iron), compact films are formed wfiicfi fiave a distorted lattice, owing to the influence of substrate metal stracture and of the effect of chemical surface forces. The physicochemical and thermodynamic parameters of such films differ from tfiose of ordinary bulk oxides. Because of the internal stresses in the distorted lattice, such films are stable only when their thickness is insignificant (e.g., up to 3 to 5 nm). 

The extraction of metals fundamentally relies on their availability in nature. Three terms are important while one refers to availability. One is the crustal abundance and the other two are the terms resources and reserves. The average crustal abundance of the most abundant metals, aluminum, iron and magnesium, are 8.1%, 5.0% and 2.1% respectively. Among the rare metals titanium is the most abundant, constituting 0.53% of the Earth s crust No metal can be economically extracted from a source in which its concentration is the same... 

The aluminum reduction of a refractory metal oxide invariably yields a metal product containing significant amounts of residual aluminum and oxygen, represented usually as a metal-aluminum-oxygen alloy. When the metal contains aluminum in addition to oxygen, a number of reactions can occur during pyrovacuum treatments. These are ... 

Mediated by Tin. In 1983, Nokami et al. observed an acceleration of the reaction rate during the allylation of carbonyl compounds with diallyltin dibromide in ether through the addition of water to the reaction mixture.74 In one case, by the use of a 1 1 mixture of ether/water as solvent, benzaldehyde was allylated in 75% yield in 1.5 h, while the same reaction gave only less than 50% yield in a variety of other organic solvents such as ether, benzene, or ethyl acetate, even after a reaction time of 10 h. The reaction was equally successful with a combination of allyl bromide, tin metal, and a catalytic amount of hydrobromic acid. In the latter case, the addition of metallic aluminum powder or foil to the reaction mixture dramatically improved the yield of the product. The use of allyl chloride for such a reaction,... 

Co. In the presence of cobalt(II) chloride and metallic aluminum, allylic halides react with aldehydes at room temperature in tetrahydro-furan-water to afford the corresponding alcohols in high yields.174... 

There are an estimated 800 plants in the U.S. involved in the primary or secondary recovery of nonferrous metals. These plants represent 61 subcategories. However, many of these subcategories are small, represented by only one or two plants, or do not discharge any wastewater. This chapter focuses on 296 facilities that produce the major nonferrous metals [aluminum, columbium (niobium), tantalum, copper, lead, silver, tungsten, and zinc]. The volume of wastewater discharged in this industry varies from 0 to 540 m3/T (0 to 160,000 gal/t) of metal produced.13 The global size of the industry is reflected in Table 3.1 (reported in 1000 USD) for the top 20 export countries for nonferrous base metal waste and scrap.4 Here T = metric ton = 1000 kg = 2204.6 lb, t = 2000 lb. 

The primary and secondary aluminum industry produces ingots of pure (greater than 99%) aluminum that serve as feedstock for other materials and processes. Within the U.S., the leading end-users of aluminum come from three industries containers and packaging, transportation, and building and construction. Examples of materials produced with aluminum are sheet metal aluminum plate and foil rod, bar, and wire beverage cans automobiles aircraft components and window/door frames. 

Tables 3.41 and 3.42 illustrate the TRI releases and transfers for the secondary nonferrous metals smelting and refining industry. For the industry as a whole, the largest releases were the various metals aluminum (fume or dust), zinc compounds, lead compounds, copper, and zinc (fume or dust).

Vol. 3 Photometric Determination of Traces of Metals. Fourth Edition Part I General Aspects. By E. B. Sandell and Hiroshi Onishi Part IIA Individual Metals, Aluminum to Lithium. By Hiroshi Onishi Part IIB Individual Metals, Magnesium to Zirconium. By Hiroshi Onishi Vol. 4 Organic Reagents Used in Gravimetric and Volumetric Analysis. By John F. Flagg (out ofprint)... 

Electrodeposition of Transition Metal-Aluminum Alloys from Chloroaluminate Molten Salts... 

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