Aluminum Element | what is Aluminum Toxicity | What Aluminum is Used For

Aluminum Element, Silver-white light metal. It is malleable. Products are often made in the shape of rods, flakes, foils, powders, ribbons and filaments. It can form an oxide film to prevent metal corrosion in the humid air. 

Aluminum powder burns violently when heated in the air and emits a dazzling white flame. Soluble in dilute sulfuric acid, nitric acid, hydrochloric acid, sodium hydroxide and potassium hydroxide solution, hardly soluble in water. The relative density is 2.70. The 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 is the most abundant metal element in the earth’s crust. 

The development of the three major industries of aeronautics, construction, and automobiles requires that the material properties have the unique properties of aluminum and its alloys, which greatly benefits the production and application of this new metal, aluminum.

Classification of Aluminum

According to the composition of aluminum, it can be divided into three categories:

name Aluminum content (%)
Premium pure aluminum 99.93 ~ 99.999
Industrial high purity aluminum 99.85 ~ 99.9
Industrial pure aluminum 98 ~ 99.7

Aluminum Preparation

Aluminum exists in various rocks or ores in a compound state, such as feldspar, mica, kaolinite, bauxite, alum, and so on. Aluminum can be prepared from aluminum oxide and cryolite (Na 3 AlF 6 ) by co-melting and electrolysis. The main reaction process is as follows:

Reaction process of extracting aluminum from bauxite

  1. Dissolution: Dissolving bauxite in NaOH (aq): Al₂O₃ + 2NaOH + 3H₂O = 2NaAl (OH) 4 (sodium tetrahydroxyaluminate)
  2. Filtration: remove residues of ferrous oxide (FeO), sodium aluminosilicate, etc.
  3. Acidification: Pass excess CO₂ into the filtrate: NaAl (OH) 4+ CO₂ = Al (OH)₃↓ + NaHCO₃
  4. Filtration and burning Al (OH)₃: 2Al (OH) ₃ = high temperature = Al₂O₃ + 3H₂O
  5. Electrolysis: 2Al₂O₃ (l) = energized = 4Al + 3O₂↑

Note: To reduce the melting temperature of alumina during electrolysis, add cryolite (Na₃AlF₆) to Al₂O₃. AlCl is not electrolytically melted to make Al, Reason: AlCl is a covalent compound, and its conductivity in the molten state is extremely poor.

Chemical properties

Aluminum is a lively metal. A dense oxide film with a thickness of about 50 Angstroms (1 Angstrom = 0.1 nm) is immediately formed on the surface of aluminum in dry air so that aluminum does not further oxidize and is resistant to water.

However, mixing the aluminum powder with air is extremely easy combustion, molten aluminum can violently with water, the corresponding metal, aluminum is amphoteric, easily soluble in the strong base, can be dissolved in acid.

React with acid

2Al + 6HCl ==== 2AlCl₃ + 3H₂ ↑
2Al + 3H₂SO₄ (Rare) ==== Al₂ (SO₄) ₃
+ 3H₂ ↑ Al + 6HNO₃ (Concentrated) == Δ == Al (NO₃) ₃ + 3NO₂ ↑ + 3H₂O
Al + 4HNO₃ (Rare) ==== Al (NO₃) ₃ + NO ↑ + 2H₂O
8Al + 30HNO₃ (Rarely Diluted) ==== 8Al (NO₃) ₃ + 3N₂O ↑ + 15H₂O
8Al + 30HNO₃ (Very Dilute) == == 8Al (NO₃) ₃ + 3NH₄NO₃ + 9H₂O

6CH₃COOH + 2Al = 2Al (CH₃COO) ₃ + 3H₂ ↑

React with alkali

2Al + 2NaOH + 6H2O = 2NaAl (OH) 4 + 3H2 ↑

(There are also documents written as 2Al + 2NaOH + 2H2O = 2NaAlO2 + 3H2 ↑)

Reacts with non-metals

4Al + 3O₂ ==== 2Al₂O₃ (ignited)

2Al + 3Cl₂ ==== 2AlCl₃ (ignited)

2Al + 3S ==== Al₂S₃ (Heating)

Aluminothermic reaction

2Al + Fe₂O₃ == Ignite == Al₂O₃ + 2Fe (aluminum thermal reaction)

8Al + 3Fe₃O4 == high temperature == 4Al₂O₃ + 9Fe

React with water

Based on the reducibility of aluminum, it can be inferred that aluminum can react with water, but experiments have found that there is almost no reaction between aluminum and boiling water, but aluminum can react significantly with water vapor under heating conditions, but the reaction begins with the generation of oxygen in the water A dense oxide film prevents the reaction from proceeding further.

Physical properties

Basic physical properties

Aluminum is a silver-white light metal. It is malleable. Commodities are often made in the shape of columns, rods, flakes, foils, powders, ribbons and filaments. It can form an oxide film to prevent metal corrosion in the humid air. Heated in the air, the acid-treated aluminum powder can burn violently and emit a dizzying white flame. 

Aluminium

Easily soluble in dilute sulfuric acid, dilute nitric acid, hydrochloric acid, sodium hydroxide and potassium hydroxide solution, insoluble in water, but can react slowly with hot water to produce aluminum hydroxide, relative density 2.70, elastic modulus 70Gpa, poise Loose ratio 0.33. 

The melting point is 660°C. The boiling point is 2327°C. Its light, good electrical and thermal conductivity performance, high reflectivity and resistance to oxidation is widely used. The aluminum used for household utensils is usually called ” steel ” or ” steel grade “. The thermal expansion coefficient of Al at room temperature (25 ° C) is 0.0000236mm / ° C or 23.6ppm * k -1.

Aluminum Uses

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

Aluminum and aluminum alloys are currently one of the most widely used and most economically applicable materials. The world’s aluminum output has surpassed the copper output since 1956 and has always been the first in non-ferrous metals. 

The current production and consumption of aluminum (calculated in ton) is second only to steel and has become the second-largest metal used by humans. Moreover, aluminum is very rich in resources. According to preliminary calculations, the mineral reserves of aluminum account for more than 8% of the crustal constituents.

Aluminum’s lightweight and corrosion resistance are two outstanding characteristics of its performance.

  1. 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 aircraft, automobile, train, ship, and other manufacturing industries. In addition, space rockets, space shuttles, and satellites also use a large amount of aluminum and aluminum alloys. For example, a supersonic aircraft consists of about 70% aluminum and its aluminum alloy. Ships also use a large amount of aluminum, and a large passenger ship often uses thousands of tons of aluminum.
  2. 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, so the same amount of electricity is transmitted. The quality of the aluminum wire is only half that of copper wire. . The oxide film on the aluminum surface 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 appliance manufacturing industry, wire and cable industry and radio industry.
  3. Aluminum is a good conductor of heat, and its thermal conductivity is three times greater than that of iron. Industrially, aluminum can be used to make various heat exchangers, heat dissipation materials and cookers.
  4. Aluminum has good ductility (its ductility is second only to gold and silver), and it can be made into aluminum foil thinner than 0.01 mm at 100 ℃ ~ 150 ℃. These aluminum foils are widely used for packaging cigarettes, candies, etc. They can also be made into aluminum wires and bars and can be rolled into various aluminum products.
  5. Due to the dense oxide protective film on the surface of aluminum, aluminum is not easy to be corroded. It is often used to make chemical reactors, medical equipment, refrigeration equipment, petroleum refining equipment, and oil and gas pipelines.
  6. Aluminum powder has a silvery-white luster (generally, the color of the metal in powder is mostly black). It is commonly used as a coating, commonly known as silver powder and silver paint, to protect iron products from corrosion and to be beautiful.
  7. The combustion of aluminum in oxygen can release a lot of heat and dazzling light. It is often used to make explosive mixtures, such as ammonium-aluminum explosives ( combined with ammonium nitrate, charcoal powder, aluminum powder, smoke black and other combustible organic substances), combustion mixture (For example, bombs and shells made of aluminizing agents can be used to attack targets or tanks, artillery, etc. that are difficult to catch fire) and lighting mixtures (such as containing barium nitrate 68%, aluminum powder 28%, shellac 4%).
  8. Aluminizing agents are commonly used to smelt refractory metals and weld rails. Aluminum is also used as a deoxidizer in steelmaking. Aluminum powder, graphite, titanium dioxide (or other high melting point metal oxides) are uniformly mixed at a certain ratio, coated on the metal, and calcined at high temperature to make high-temperature resistant cermet. It has important applications in rocket and missile technology. .
  9. The aluminum plate also has a good light reflection performance. It reflects ultraviolet light more strongly than silver. The purer the aluminum, the better its reflection ability. Therefore, it is often used to make high-quality mirrors, such as solar stove mirrors.
  10. Aluminum has sound absorption performance and sound effect is also good, so the ceiling of the broadcasting room, modern large-scale building, etc. also uses aluminum.

Low-temperature resistance. When the temperature is low, aluminum will increase its strength without brittleness. Therefore, it is ideal for low-temperature device materials, such as refrigerators, freezers, snow vehicles in Antarctica, and hydrogen oxide production devices.

Test Methods

Method Name: Sucralfate-Determination of Aluminum-Complex Titration

Application Range: Determination of aluminum content in sucralfate by complex titration, suitable for the determination of aluminum content in sucralfate.

Principle of the method: Take an appropriate amount of the test product, after dissolving and diluting and neutralizing it, add acetic acid -ammonium acetate buffer solution, add ethylenediaminetetraacetic acid disodium titration solution (0.05mol / L), and boil for 3 ~ 5 minutes Cool to room temperature. Each 1mL of ethylenediaminetetraacetic acid sodium titration solution (0.05mol / L) is equivalent to 1.349mg of aluminum, which is calculated.

Assay reagent:

  1. Water (newly boiled to room temperature)
  2. Acetic acid-ammonium acetate buffer (pH6.0)
  3. Xylenol orange indicator liquid
  4. Zinc titration solution (0.05mol / L)
  5. Ethylenediamine tetraacetic acid disodium titration solution (0.05mol / L)
  6. Reference zinc oxide
  7. Dilute hydrochloric acid
  8. Methyl red in ethanol (0.025%)
  9. Ammonia test solution
  10. Chrome black T indicator
  11. Ammonia- ammonium chloride buffer (pH 10.0)

Steps:

Take about 1.0g of this product, accurately weigh it, place it in a 200mL volumetric flask, add 10mL of dilute hydrochloric acid to dissolve it, add water to dilute to the mark, shake well, take 20mL with precision measurement, neutralize with ammonia test solution to just precipitate, and then drip Add dilute hydrochloric acid until the precipitate just dissolves, add 20 mL of acetic acid-ammonium acetate buffer (pH 6.0), and then add 25 mL of ethylenediaminetetraacetic acid disodium titration solution (0.05mol / L), and boil for 3 to 5 minutes.

 Cool to room temperature, add 1 mL of xylenol orange indicator solution, titrate with zinc titration solution (0.05 mol / L) until the solution changes from yellow to red, and correct the titration result with a blank test.

Note 1: “Precise weighing” means that the weighed weight should be accurate to one-thousandth of the weighed weight. “Precision weighing” means that the accuracy of the measured volume should conform to the national standard for the volume of the pipette. Precision requirements.

Note 2: “Determination of moisture” uses the drying method, taking 2 to 5 g of the test sample, and spreading it in a flat weighing bottle that is dry to constant weight, the thickness is not more than 5 mm, and the loose test sample is not more than 10 mm.

Open the bottle cap and dry it at 100 ~ 105 ℃ for 5 hours. Place the cap on the dryer, cool it for 30 minutes, and weigh it precisely. Then dry it at the above temperature for 1 hour, cool it, and weigh it twice. The difference in weighing does not exceed 5 mg. Calculate the moisture content (%) in the test product based on weight loss.

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