Aluminum abundance

In contrast, aluminum (abundance = 7.5%), despite its usefulness, was little more than a chemical curiosity until about a century ago. It occurs in combined form in clays and rocks, from which it cannot be extracted. In 1886 two young chemists, Charles Hall in the United States and Paul Herroult in France, independently worked out a process for extracting aluminum from a relatively rare ore, bauxite. That process is still used today to produce the element. By an odd coincidence, Hall and Herroult were born in the same year (1863) and died in the same year (1914). 

Aluminum can now be produced from clay, but the process is not economically feasible at present. Aluminum is the most abundant metal to be found in the earth s crust (8.1%), but is never found free in nature. In addition to the minerals mentioned above, it is found in granite and in many other common minerals. 

Iron [7439-89-6J, Fe, from the Latin ferrum, atomic number 26, is the fourth most abundant element in the earth s cmst, outranked only by aluminum, sihcon, and oxygen. It is the world s least expensive and most useful metal. Although gold, silver, copper, brass, and bron2e were in common use before iron, it was not until humans discovered how to extract iron from its ores that civilization developed rapidly (see Mineral processing and recovery). 

The concentration of most metals in the earth s cmst is very low, and even for abundant elements such as aluminum and iron, extraction from common rock is not economically feasible. An ore is a metallic deposit from which the metal can be economically extracted. The amount of valuable metal in the ore is the tenor, or ore grade, usually given as the wt % of metal or oxide. Eor precious metals, the tenor is given in grams per metric ton or troy ounces per avoirdupois short ton (2000 pounds). The tenor and the type of metallic compounds are the main characteristics of an ore. The economic feasibihty of ore processing, however, depends also on the nature, location, and size of the deposit the availabihty and cost of a suitable extraction process and the market price of the metal. 

Aluminum [7429-90-5] Al, atomic number 13, atomic weight 26.981, is, at 8.8 wt %, the third most abundant element in the earth s cmst. It is usually found in siUcate minerals such as feldspar [68476-25-5] clays, and mica [12001 -26-2]. Aluminum also occurs in hydroxide, oxide—hydroxide, fluoride, sulfate, or phosphate compounds in a large variety of minerals and ores. 

There is much discussion on the nature of the aluminum species present in slightly acidic and basic solutions. There is general agreement that in solutions below pH 4, the mononuclear Al " exists coordinated by six water molecules, ie, [ ( 20) ". The strong positive charge of the Al " ion polarizes each water molecule and as the pH is increased, a proton is eventually released, forming the monomeric complex ion [A1(0H)(H20) ]. At about pH 5, this complex ion and the hexahydrated Al " are in equal abundance. The pentahydrate complex ion may dimerize by losing two water molecules... 

Aluminum chlorite, (Al,Fe)4(Si,Al)402Q(0H)g, in which a gibbsitelike interlayer proxies in part for the bmcitelike interlayer, is being discovered in increasing occurrences and abundance (11,141). Chloritelike stmctures have been synthesi2ed by precipitation of Mg and Al between montmorillonite sheets (143). Cookite [1302-92-7], an aluminous chlorite containing lithium, has been found in high alumina refractory clays and bauxite [1318-16-7] (139). 

The demand for aviation gasoline during World War II was so great that isobutanc from alkylation feedstock was insufficient. This deficiency was remedied by isomerization of abundant normal butane into isobutane using the isomerization catalyst aluminum chloride on alumina promoted by hydrogen chloride gas. 

Where considerable quantities of energy are used in the process, relatively cheap and abundant sources of energy need to be available (for example, alumina and aluminum smelting, steel making). 

Except for argon, the third-row elements make up an important fraction (about 30%) of the earth s crust. Silicon and aluminum are the second and third most abundant elements (oxygen is the most abundant). Both the occurrence and the mode of preparation of each element can be understood in terms of trends in chemistry discussed earlier in this chapter. 

Aluminum (third most abundant element) is found as the Al+ ion in oxides and as the complex ion AlFImportant minerals are bauxite, which is best described as a hydrated aluminum oxide, Al203-.xH20, and cryolite, NaaAlFs. The element is readily oxidized and is not found in an uncombined state in nature. 

Aluminum, though the third most abundant element, was quite expensive until about 1886, when a practical commercial electrolysis process was developed by a young American chemist, C. M. Hall. Bauxite, A1203-jcH20, is dissolved at about 1000°C in molten cryolite, Na3AlF6, and electrolyzed. 

Oxygen and silicon are the most abundant elements in the earth s crust. Table 25-111 shows that 60% of the atoms are oxygen atoms and 20% are silicon atoms. If our sample included the oceans, hydrogen would move into the third place ahead of aluminum (remember that water contains two hydrogen atoms for every oxygen atom). If the sample included the central core... 

Many of the metals used by ancient man— coppei (cuprum, Cu), silver (argentum, Ag), gold (aurum, Au), tin (stannum, Sn), and lead (plumbum, Pb)—are in relatively short supply. Ancient man found deposits of the first three occurring as the elementary metals. These three may also be separated from their ores by relatively simple chemical processes. On the othei hand, aluminum and titanium, though abundant, are much more difficult to prepare from their ores. Fluorine is more abundant in the earth than chlorine but chlorine and its compounds are much more common—they are easier to prepare and easier to handle. However, as the best sources of the elements now common to us become depleted, we will have to turn to the elements that are now little used. 

Aluminum is the most abundant metallic element in the Earth s crust and, after oxygen and silicon, the third most abundant element (see Fig. 14.1). However, the aluminum content in most minerals is low, and the commercial source of aluminum, bauxite, is a hydrated, impure oxide, Al203-xH20, where x can range from 1 to 3. Bauxite ore, which is red from the iron oxides that it contains (Fig. 14.23), is processed to obtain alumina, A1203, in the Bayer process. In this process, the ore is first treated with aqueous sodium hydroxide, which dissolves the amphoteric alumina as the aluminate ion, Al(OH)4 (aq). Carbon dioxide is then bubbled through the solution to remove OH ions as HCO and to convert some of the aluminate ions into aluminum hydroxide, which precipitates. The aluminum hydroxide is removed and dehydrated to the oxide by heating to 1200°C. 

The feldspars are aluminosilicates in which as much as half the silicon(IV) has been replaced by aluminum(III). They are the most abundant silicate materials on Earth and are a major component of granite, a compressed mixture of... 

Iron, Fe, the most widely used of all the d-metals, is the most abundant element on Earth and the second most abundant metal in the Earth s crust (after aluminum). Its principal ores are the oxides hematite, Fe203, and magnetite, Fc C)4. The sulfide mineral pyrite, FeS2 (see Fig. 15.11), is widely available, but it is not used in steelmaking because the sulfur is difficult to remove. 

The nuclei of some elements are stable, but others decay the moment they are formed. Is there a pattern to the stabilities and instabilities of nuclei The existence of a pattern would allow us to make predictions about the modes of nuclear decay. One clue is that elements with even atomic numbers are consistently more abundant than neighboring elements with odd atomic numbers. We can see this difference in Fig. 17.11, which is a plot of the cosmic abundance of the elements against atomic number. The same pattern occurs on Earth. Of the eight elements present as 1% or more of the mass of the Earth, only one, aluminum, has an odd atomic number. 

Aluminum is the third most abundant element in the Earth s cmst and the most abundant metal. Nevertheless, aluminum was not discovered until 1825 and was still a precious rarity 60 years later. The reason for this elusiveness is the high stability of Al. The reduction of aluminum compounds to the free... 

Aluminum trichloride, a cheap, abundant waste product of the chemical industry, forms a gel under certain conditions with carbonates and on mixing with alkalies. Laboratory and field tests showed that aluminum trichloride can be used as a gel-forming agent for reducing the permeability of waterconducting channels [673]. 

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... 

Zinc is the fourth most widely used metal after iron, aluminum, and copper (lead is fifth). In abundant supply world-wide, zinc is mined and produced mainly in Canada, the former Soviet Union, Australia, Peru, Mexico, and the U.S. Historically, in the U.S. recoverable zinc has been mined in... 

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