Chemistry is the foundation of our life. All household items consist of compounds of the elements of the periodic table. Every minute in the human body there are complex transformations in which chemicals are involved. This article will talk about such a metal as molybdenum: where it is used, its properties and role in the human body.
Deep into history
Minerals containing molybdenum were known in ancient Greece. These natural compounds had a structure similar to graphite. Therefore, they were often used along with it to create leads. Molybdenite MoS₂ had a gray-green tint when written on paper. For its characteristic brilliance, it was given the name molybdaena - "like lead."
Karl Wilhelm Scheele conducted research, thanks to which he synthesized MoO₃ trioxide, but due to the lack of an appropriate furnace, he could not isolate the metal in its pure form. Jöns Jakob Berzelius succeeded in obtaining molybdenum in 1817 byoxide reduction not with carbon, but with hydrogen. The synthesized chemical element was carefully studied and described in the works of the scientist.
Physical properties
What is molybdenum? It is a light gray metal that, in its pure form, is resistant to oxidation (under normal conditions). With an increase in temperature to 400-600 degrees, this ability decreases, and MoO₃ trioxide is formed.
Molybdenum is ductile and malleable, easily stamped. Metal density 10.2 g/cm3, melting point 2620 ⁰С, boiling point - 4800 ⁰С. From these indicators, it can be seen that it is quite refractory. The presence of carbon, nitrogen or sulfur contaminants affects the physical properties, in particular, the substance becomes brittle and brittle. Molybdenum is paramagnetic. With increasing temperature, its strength increases significantly.
Natural molybdenum compounds, obtaining
You should know that in its pure form, molybdenum does not occur, it is present in nature only in compounds with other elements. The approximate content of metal in the earth's crust is 3∙10-4%. There are about 15 minerals, of which the most common are:
- disulfide MoS2 – molybdenite;
- CaMoO4 – powellite;
- PbMoO4 – wulfenite.
The main deposits of these compounds are closely related to the processes of precipitation in hydrothermal vents.
Molybdenum disulphide is mined for industrial purposes. Its use to obtain pure metal is veryimportant. This happens with the help of ore beneficiation by flotation. This is how a concentrate is obtained, which is subsequently fired.
2MoS2+7O2=2MoO3+4SO 2
The isolated oxide is purified and reduced by a dry current of hydrogen at a temperature of 700 degrees. The reaction product is molybdenum powder. In the future, it can be used in its pure form or as a material for the creation of rolled and stamped products.
Production of alloy steels
Ferrous metallurgy uses molybdenum powder. Where is it applied? For alloying steels and cast irons. The addition of this element to the composition of alloys significantly improves their quality. Elasticity, wear resistance, impact resistance increase. About 0.5% molybdenum is added to structural steels, because of this their structure becomes fine-grained and more uniform, and the brittleness of final products decreases.
The addition of other substances makes it possible to obtain special compositions widely used in various industries. Alloys, which include cob alt and nickel (50-60%), as well as chromium (about 20-28%), are alloyed by adding molybdenum. Where is this material used? The answer lies in its special properties - high heat resistance. It is used in the manufacture of aircraft and missile skin parts.
Application of molybdenum alloys
When niobium, titanium and other heavy-duty metals are added to molybdenum, heat resistance increasesalloys. Such a composition can be used to create parts for gas turbines and combustion chambers in rocket science.
In alloys with a high content of molybdenum (17-28%), corrosion resistance increases. They are not afraid even of interaction with any acid (except hydrofluoric acid).
The refractory properties of molybdenum and its use in the creation of special pipes are of great importance in nuclear energy. Such products are able to withstand exposure to molten lithium. It acts as a coolant in uranium reactors. In addition, molybdenum itself, in the form of the Mo-99 isotope, has found use as an indicator in the nuclear industry.
Due to the infusibility of molybdenum, molybdenum is used to create molds for casting parts from copper, aluminum and zinc. The high strength of the metal allows for processes under high pressure.
Rolling and stamping, application
From blanks obtained by smelting powder, rolled products are created - rods and wire. They are made up of a pure metal called molybdenum. Where is this product used? It is most often used in the manufacture of thermocouples, which are used to measure temperatures above 2000 ⁰C. Hooks and cores for winding a tungsten filament in an incandescent lamp are also made from molybdenum wire. Cathode leads and focusing electrodes in X-ray tubes and generator lamps must be reliable and meet the requirements of high metal refractoriness. Rolled molybdenum is excellent for these purposes.
Rods and platesare used instead of electrodes in high temperature melting furnaces. They must be in a special environment consisting of argon, hydrogen or vacuum. Due to the fact that molybdenum does not enter into chemical reactions with glass, it is used to make parts of a melting furnace.
Application in other industries
Molybdenum has found application in the oil industry. There it is used as a catalyst capable of cleaning products from sulfur impurities. Lubricants are made on the basis of aluminum disulfide. They stabilize the operation of various devices and protect surfaces from mechanical stress at high temperatures. It has such a lubricant and anti-corrosion properties.
In the manufacture of paints and varnishes, where molybdenum and its oxides are used, persistent pigments of yellow-orange tones are obtained. The synthesis of artificial fibers also does not work without this substance. To increase the nitrogen content in the soil, microfertilizers are used, which include molybdenum.
The role of molybdenum in the body
Molybdenum plays a significant role in the human body. It is involved in the synthesis of hemoglobin, nitrogen and purine metabolism. Responsible for the absorption of iron and vitamin C, is a powerful antioxidant. The trace element has an oncoprotective, rejuvenating effect.
Foods rich in molybdenum are legumes and cereals, leafy vegetables. The required amount of micronutrient dailyenters the body if you eat right. Its lack can be replenished using mineral complexes.
