Preparation of aluminum

Aluminum is a metal element, the element symbol is al, is a silver white light metal. It's malleable. Commodities are often made into rod, sheet, foil, powder, ribbon and silk. In humid air, a layer of oxide film can be formed to prevent metal corrosion. When aluminum powder is heated in the air, it can burn violently and emit dazzling white flame. It is easy to dissolve in dilute sulfuric acid, nitric acid, hydrochloric acid, sodium hydroxide and potassium hydroxide solution, but difficult to dissolve in water. The relative density is 2.70. The melting point is 660 ℃. The boiling point is 2327 ℃. Aluminum is the most abundant metal element in the earth's crust. With the development of aviation, construction and automobile industries, the unique properties of aluminum and its alloys are required, which is greatly conducive to the production and application of this new metal aluminum. It is widely used.

On October 27, 2017, the list of carcinogens published by the international agency for research on cancer of the World Health Organization (who) was preliminarily sorted out for reference, and aluminum products were included in the list of class I carcinogens.

In 1854, the French chemist de vill mixed bauxite, charcoal and salt, added chlorine and heated to obtain NaCl, ALCL ₃ double salt, and then fused the double salt with excess sodium to obtain aluminum. In 1886, hall of the United States and helante of France independently electrolyzed the mixture of fused bauxite and cryolite (Na3AlF6) to produce metallic aluminum, which laid the foundation for large-scale production of aluminum in the future.

Aluminum exists in various rocks or ores in the form of compound, such as feldspar, mica, kaolinite, bauxite, alum, etc. Aluminum can be prepared by eutectic electrolysis of aluminum oxide and cryolite (Na3AlF6)

Reaction process of extracting aluminum from bauxite

Dissolution: bauxite is dissolved in NaOH (AQ): Al2O3 + 2naoh + 3H2O = 2naal (OH) 4 (sodium tetrahydroxyaluminate)

Filtration: remove residual ferrous oxide (FeO), sodium aluminosilicate, etc

Acidification: the filtrate is filled with excess Co Ψ: NaAl (OH) 4 + CO Ψ = Al (OH) 3 ↓ + NaHCO3

Filtration and burning Al (OH) ₃: 2Al (OH) ₃ = high temperature = Al к o ₃ + 3H к o

electrolysis:

Note: in order to reduce the melting temperature of alumina, cryolite (Na ₃ alf6) is added to Al Ψ o ₃. The reason is that AlCl3 is a covalent compound and its conductivity in molten state is very poor.