Aluminum

Aluminum is a metal element, the element symbol is Al, which is a silver-white light metal. There is malleability. Commodities are often made into rods, flakes, foils, powders, ribbons and filaments. It can form an oxide film to prevent metal corrosion in humid air. Aluminum powder can burn violently when heated in the air and emit a dazzling white flame. It is easily soluble in dilute sulfuric acid, nitric acid, hydrochloric acid, sodium hydroxide and potassium hydroxide solution, but hardly soluble in water. The relative density is 2.70. Melting point is 660°C. The boiling point is 2327°C. The content of aluminum in the earth’s crust is second only to oxygen and silicon, ranking third, and it is the most abundant metal element in the earth’s crust. The development of the three important industries of aviation, construction, and automobiles requires the characteristics of materials to have the unique properties of aluminum and its alloys, which greatly facilitates the production and application of this new metal aluminum. The application is extremely wide.

On October 27, 2017, the list of carcinogens published by the International Agency for Research on Cancer of the World Health Organization was preliminarily compiled for reference, and aluminum products were included in the list of carcinogens in the first category.

The Preparation Of Aluminum

In 1854, French chemist Deville mixed bauxite, charcoal, and table salt, and then heated it with chlorine gas to obtain NaCl, AlCl₃ double salt, and then melted this double salt with excess sodium to obtain metal aluminum. In 1886, Howe of the United States and Hylandt of France independently electrolyzed a mixture of molten bauxite and cryolite (Na3AlF6) to produce metallic aluminum, laying the foundation for large-scale aluminum production in the future.

Aluminum exists in various rocks or ores in the form of a chemical state, such as feldspar, mica, kaolinite, bauxite, alunite and so on. Aluminum can be produced by eutectic electrolysis of aluminum oxide and cryolite (Na3AlF6). The main reaction process is as follows:

The reaction process of extracting aluminum from bauxite

• Dissolution: Dissolve bauxite in NaOH(aq): Al2O3+ 2NaOH+3H2O= 2NaAl(OH)4 (sodium tetrahydroxy aluminate)
• Filtration: Removal of residual ferrous oxide (FeO), sodium aluminosilicate, etc.
• Acidification: pass excess CO₂ into the filtrate: NaAl(OH)4+ CO₂ = Al(OH)3↓+ NaHCO3
• Filtering and burning Al(OH)₃: 2Al(OH)₃ = high temperature = Al₂O₃+ 3H₂O
• Electrolysis: In order to lower the melting temperature of alumina during electrolysis, cryolite (Na₃AlF6) is added to Al₂O₃. Do not melt AlCl3 electrolytically to make Al; Reason: AlCl3 is a covalent compound, and its molten state has very poor conductivity.

The Development History Of Aluminum

The English name of aluminum comes from alum (alum), which is the double salt of sulfate KAl(SO4)2·12H2O. In prehistoric times, humans have used clay containing aluminum compounds (Al2O3·2SiO2·2H2O) to make pottery. The content of aluminum in the earth’s crust is second only to oxygen and silicon, ranking third. However, due to the weak oxidation of aluminum compounds, aluminum is not easily reduced from its compounds, so metallic aluminum cannot be separated for a long time. After the Italian physicist Volta invented the battery, David tried to use electric current to separate the metal aluminum from the alumina, but it was unsuccessful, but he suggested that it be named “alumium” and later changed to “aluminum”, which will soon be modified to aluminium. This word form is common throughout the world, except in North America, where the American Chemical Society (ACS) decided in 1925 to use “aluminum” in publications.

The chemical symbol Al, belongs to group IIIA in the periodic table of elements, atomic number 13, atomic weight 26.98154, face-centered cubic crystal, common valence is +3. Aluminum is the most important light metal.

The word aluminium is derived from the ancient Roman word alumen (alum). In 1746, German J.H. Pott made an oxide from alum, namely alumina. In the 18th century, French Lavoisier (A.L. Lavoisier) believed that this was an oxide of an unknown metal. Its affinity with oxygen was so great that it was impossible to reduce it with carbon and other reducing agents known at the time. In 1807, the British H. Davy tried to electrolyze molten alumina to obtain metal, but failed. In 1809, he named this imaginary metal alumium, which was later changed to aluminum. In 1825, the Danish H.C. Oersted used potassium amalgam to reduce anhydrous aluminum chloride and obtained several milligrams of metallic aluminum for the first time, pointing out that it has the same color and luster as tin. In 1827, F.Whler, Germany, used potassium to reduce anhydrous aluminum chloride to obtain a small amount of metal powder. In 1845, he used aluminum chloride gas to pass through the surface of molten metal potassium, and obtained some aluminum beads, each weighing about 10-15 mg, thus making a preliminary determination of the density and ductility of aluminum, and pointed out that the melting point of aluminum is not high. In 1854, S.C. Deville, France, used sodium instead of potassium to reduce NaAlCl4 complex salt to produce metal aluminum. The factory was built in the same year, and some aluminum helmets, tableware and toys were produced. At that time, the price of aluminum was close to that of gold. In 1886, American Hall (C.M.Hall) and France (P.L.T.Héroult) almost simultaneously obtained patents for producing metal aluminum by cryolite-alumina molten salt electrolysis. In 1888, the first electrolytic aluminum plant was established in Pittsburgh, USA, and aluminum production has entered a new stage. In 1956, the world’s aluminum output began to surpass that of copper and ranked first among non-ferrous metals. The price of aluminum is relatively cheap in terms of volume among commonly used non-ferrous metals.

In the later period, aluminum was a treasure enjoyed by the emperors and nobles. The French Emperor Napoleon III used aluminum forks at banquets; the King of Thailand used aluminum bracelets. At the Paris Exposition in 1855, it was exhibited with the jewel on the crown, and the label stated “silver from clay”. In 1889, Mendeleev also received vases and cups made of aluminum alloy as a gift from the Chemical Society of London. By the end of the 19th century, the price of aluminum had fallen thousands of times. First, it was because Siemens improved the generators in the 1870s to have cheap electricity; secondly, because Heroult of France and CM Hall of the United States developed the electrolysis of alumina in cryolite (Na3AlF6) in 1886, respectively. method. They were both 22 years old at the time. This pioneering work enabled large-scale production of aluminum and laid the foundation for today’s industrial method of electrolytic aluminum in the world. So far, various aluminum products have been widely used in thousands of households.

On October 27, 2017, the list of carcinogens published by the International Agency for Research on Cancer of the World Health Organization was preliminarily compiled for reference, and aluminum products were included in the list of carcinogens in the first category.

On July 30, 2018, an international research team said that they had clearly detected a radioactive molecule (aluminum fluoride, the radioactive isotope of aluminum “aluminum-26”) in the universe for the first time, and this molecule may be due to two reasons. Stars collided and “splashed” into interstellar space.

The Content Distribution Of Aluminum

The most abundant metal element in the earth’s crust, with a content of 8.3%. It mainly exists as aluminosilicate ore, as well as bauxite and cryolite. Alumina is a white amorphous powder with many variants, among which the most familiar ones are α-Al₂O₃ and β-Al₂O₃. The corundum that exists in nature belongs to α-Al₂O₃. Its hardness is second only to diamond, and it has a high melting point and is resistant to acids and alkalis. It is often used to make bearings, abrasives, and refractory materials. Such as corundum crucible, can withstand high temperature of 1800℃. Al₂O₃ has many colors due to different impurities. For example, those containing a small amount of Cr(III) are red, called rubies; those containing Fe(II), Fe(III) or Ti(IV) are called sapphires.

Aluminum is a light metal, chemical symbol is Al, atomic number: 13. The content of aluminum in the earth’s crust is second only to oxygen and silicon, ranking third. It is the most abundant metal element in the earth’s crust, and its reserves rank second among metals. Among metal varieties, it is second only to steel and is the second largest category of metals.

The Physical Properties Of Aluminum

Aluminum is silver-white light metal. There is malleability. Commodities are often made into columns, rods, sheets, foils, powders, ribbons and filaments. It can form an oxide film to prevent metal corrosion in humid air. The acid-treated aluminum powder can burn violently when heated in the air and emit a dazzling white flame. Easily soluble in dilute sulfuric acid, dilute nitric acid, hydrochloric acid, sodium hydroxide and potassium hydroxide solution, insoluble in water, but can slowly react with hot water to form aluminum hydroxide, relative density 2.70, elastic modulus 70Gpa, Poisson’s ratio 0.33 . Melting point is 660°C. The boiling point is 2327°C. It is widely used for its light weight, good electrical and thermal conductivity, high reflectivity and oxidation resistance. The aluminum used for daily-use utensils is usually called “steel steel” or “steel grade”. Thermal expansion coefficient of Al at (room temperature) 25°C 0.0000236mm/°C or 23.6ppm*k-1

The Isotope Of Aluminum

There are 24 isotopes of aluminum, of which only one is stable. The isotope list is as follows:

Symbol	Proton	Neutron	Quality	Half Life	Spin	Relative abundance
19 Al	13	6	19.0(218)#
20 Al	13	7	(20.0194)#
21 Al	13	8	21.02804(32)#		1/2+#
22 Al	13	9	22.01952(10)#	59(3) ms	(3)+
23 Al	13	10	23.007267(20)	470(30) ms	5/2+#
24 Al	13	11	23.9999389(30)	2.053(4) s	4+
25 Al	13	12	24.9904281(5)	7.183(12) s	5/2+
26 Al	13	13	25.98689169(6)	7.17(24)E+5 a	5+
27 Al	13	14	26.98153863(12)	stable	5/2+	1.0000
28 Al	13	15	27.98191031(14)	2.2414(12) min	3+
29 Al	13	16	28.9804450(13)	6.56(6) min	5/2+
30 Al	13	17	29.982960(15)	3.60(6) s	3+
31 Al	13	18	30.983947(22)	644(25) ms	(3/2,5/2)+
32 Al	13	19	31.98812(9)	31.7(8) ms	1+
33 Al	13	20	32.99084(8)	41.7(2) ms	(5/2+)#
34 Al	13	21	33.99685(12)	56.3(5) ms	4-#
35 Al	13	22	34.99986(19)	38.6(4) ms	5/2+#
36 Al	13	23	36.00621(23)	90(40) ms
37 Al	13	24	37.01068(36)	10.7(13) ms
38 Al	13	25	38.01723(78)	7.6(6) ms
39 Al	13	26	39.02297(158)	7.6(16) ms	3/2+#
40 Al	13	27	40.03145(75)#	10# ms [>260 ns]
41 Al	13	28	41.03833(86)#	2# ms [>260 ns]	3/2+#
42 Al	13	29	42.04689(97)#	1# ms

The Main Purpose Of Aluminum

The use of a substance largely depends on the nature of the substance. Because aluminum has a variety of excellent properties, aluminum has a very wide range of uses.

Aluminum and aluminum alloys are currently one of the most economical and suitable materials that are widely used. Since 1956, the world’s aluminum output has surpassed the copper output and has always ranked first in non-ferrous metals. The current production and consumption of aluminum (calculated in ton) is second only to steel, becoming the second largest metal used by mankind; and aluminum resources are very abundant. According to preliminary calculations, aluminum reserves account for more than 8% of the earth’s crust. .

Aluminum’s light weight and corrosion resistance are two outstanding features of its performance.

• The density of aluminum is very small, only 2.7 g/cm³. Although it is relatively soft, it can be made into various aluminum alloys, such as hard aluminum, super-hard aluminum, rust-proof aluminum, cast aluminum, etc. These aluminum alloys are widely used in manufacturing industries such as airplanes, automobiles, trains, and ships. In addition, space rockets, space shuttles, and satellites also use large amounts of aluminum and its aluminum alloys. For example, a supersonic aircraft is composed of approximately 70% aluminum and its aluminum alloys. Aluminum is also used in large quantities in ship construction, and the amount of aluminum used in a large passenger ship often reaches several thousand tons.
• The conductivity of aluminum is second only to silver, copper and gold. Although its conductivity is only 2/3 of copper, its density is only 1/3 of copper. Therefore, the quality of aluminum wire is only half that of copper wire for the same amount of electricity. . The oxide film on the surface of aluminum not only has the ability to resist corrosion, but also has a certain degree of insulation, so aluminum has a wide range of uses in the electrical manufacturing industry, wire and cable industry, and radio industry.
  Aluminum is a good conductor of heat, and its thermal conductivity is three times greater than that of iron. Aluminum can be used to manufacture various heat exchangers, heat dissipation materials and cooking utensils in the industry.
• Aluminum has good ductility (its ductility is second only to gold and silver), and can be made into aluminum foil thinner than 0.01 mm at 100 ℃ to 150 ℃. These aluminum foils are widely used for packaging cigarettes, candy, etc., and can also be made into aluminum wire, aluminum strips, and rolled various aluminum products.
  Due to the dense oxide protective film on the surface of aluminum, it is not susceptible to corrosion. It is often used to manufacture chemical reactors, medical equipment, refrigeration equipment, petroleum refining equipment, oil and natural gas pipelines, etc.
• Aluminum powder has a silver-white luster (generally the color of metal in powder form is mostly black). It is commonly used as paint, commonly known as silver powder and silver paint, to protect iron products from corrosion and be beautiful.
• Aluminium can emit a lot of heat and dazzling light when burned in oxygen. It is often used to make explosive mixtures, such as ammonium-aluminum explosives (mixed with ammonium nitrate, charcoal powder, aluminum powder, soot and other combustible organic matter), combustion mixtures (For example, bombs and shells made of thermite can be used to attack hard-to-fire targets or tanks, artillery, etc.) and lighting mixtures (such as 68% barium nitrate, 28% aluminum powder, 4% shellac).
• Thermite is often used to smelt refractory metals and weld steel rails. Aluminum is also used as a deoxidizer in the steelmaking process. Aluminum powder, graphite, titanium dioxide (or oxides of other high melting point metals) are uniformly mixed in a certain ratio, then coated on the metal and calcined at high temperature to make high temperature resistant cermet. It has important applications in rocket and missile technology. .
• Aluminum plate also has good reflection performance to light. It reflects ultraviolet rays stronger than silver. The purer the aluminum, the better its reflection ability. Therefore, it is often used to manufacture high-quality mirrors, such as solar cooker mirrors.
• Aluminum has sound-absorbing properties and good acoustics, so aluminum is also used in the ceilings of broadcast rooms and modern large-scale buildings. Low temperature resistance. When the temperature is low, aluminum will increase its strength without brittleness. Therefore, it is an ideal material for low-temperature equipment, such as cold storage, freezer, and Antarctic snowmobile production equipment.

The Toxicological Properties Of Aluminum

Studies have found that aluminum can damage human brain cells. According to the evaluation of the World Health Organization, the daily intake of aluminum is specified as 0-0.6mg/kg, where kg refers to the weight of a person, that is, the allowable intake for a 60kg person is 36mg. my country’s “Food Additives Use Standard GB2760-2011” stipulates that the residual amount of aluminum should be less than or equal to 100mg/kg. Based on this calculation, if a person weighing 60kg eats no more than 360g of fried dough sticks a day, there is no need to worry.

Aluminum accumulates slowly in the human body, and the toxicity caused by it is slow and difficult to detect. However, once the toxic reaction of metabolic disorders occurs, the consequences are very serious. Therefore, we must pay our attention to prevent the absorption of aluminum and reduce the use of aluminum products in daily life. The harm of aluminum and its compounds to mankind is incomparable with its contribution. As long as people pay attention to it and maximize its strengths and avoid weaknesses, it will play a more important role in human society.

Avoid method:

• Avoid using cookware made of aluminum.
• Eat less fried dough sticks, aluminum-wrapped candies and other foods, and drink less soft drinks in cans.
• Some medicines are made of aluminum-containing substances, so the consumption of aluminum-containing medicines should be reduced, such as: Al(OH)3 that can neutralize gastric acid.

According to relevant data, under my country’s special resource and energy situation, the process of technological innovation has been spawned. After the large-scale application of special-shaped cathode structure electrolyzers, new-type flow guide cells and high-efficiency energy-saving electrolyzers, the magnetic fluid optimization design technology for large-capacity electrolyzers was developed to further optimize the magnetic field balance of the electrolyzers. In the new production capacity in the western region, a large number of enterprises have adopted various new variable cross-section cathode steel bar technologies to better improve the relationship between the aluminum level and the vertical magnetic fluid ratio, reduce the amplitude of the aluminum liquid, and provide space for reducing the pole pitch. At the same time, improved current density, enhanced heat preservation, and energy saving and consumption reduction tests such as trenching and perforating on the anode have achieved good results.

Since the reform and opening up, China’s aluminum industry has made great progress and has become a major country in the world’s aluminum industry, forming a relatively complete industrial system integrating bauxite, alumina, electrolytic aluminum, aluminum processing, and research and development.

In 2006, Aluminum Corporation of China quickly turned from industry-wide losses in 2005 to industry-wide profits of 32.4 billion yuan and profits and taxes of more than 50 billion yuan. The backward self-baking tank production capacity of electrolytic aluminum was eliminated. In 2006, the capacity of 160kA and above accounted for 83% of the 12 million tons of electrolytic aluminum production capacity. The backward self-baking tank production capacity has been completely eliminated, and the production capacity of some small pre-baked tanks has been transformed. .