The formula of manganese is structural chemical. Manganese: main characteristics, production and use of the substance

DEFINITION

Manganese is the twenty-fifth element of the Periodic Table. Designation - Mn from the Latin "manganum". Located in the fourth period, group VIB. Refers to metals. The core charge is 25.

Manganese belongs to fairly common elements, making up 0.1% (mass.) of the earth's crust. Of the compounds containing manganese, the most common mineral is pyrolusite, which is manganese dioxide MnO 2 . The minerals hausmanite Mn 3 O 4 and brownite Mn 2 O 3 are also of great importance.

In the form of a simple substance, manganese is a silvery-white (Fig. 1) hard brittle metal. Its density is 7.44 g / cm 3, melting point 1245 o C.

Rice. 1. Manganese. Appearance.

Atomic and molecular weight of manganese

Relative molecular weight of a substance(M r) is a number showing how many times the mass of a given molecule is greater than 1/12 of the mass of a carbon atom, and relative atomic mass of an element(A r) - how many times the average mass of atoms of a chemical element is greater than 1/12 of the mass of a carbon atom.

Since in the free state manganese exists in the form of monatomic Mn molecules, the values of its atomic and molecular masses coincide. They are equal to 54.9380.

Allotropy and allotropic modifications of manganese

Four crystalline modifications of manganese are known, each of which is thermodynamically stable in a certain temperature range. Below 707 o C, α-manganese is stable, having a complex structure - its unit cell includes 58 atoms. The complexity of the structure of manganese at temperatures below 707 o With cause its fragility.

Isotopes of manganese

It is known that manganese can occur in nature in the form of the only stable isotope 55 Mn. The mass number is 55, the nucleus of an atom contains twenty-five protons and thirty neutrons.

There are artificial isotopes of manganese with mass numbers from 44 to 69, as well as seven isomeric states of nuclei. The longest-lived isotope among the above is 53 Mn with a half-life of 3.74 million years.

manganese ions

On the outer energy level of the manganese atom, there are seven electrons that are valence:

1s 2 2s 2 2p 6 3s 2 3p 6 3d 5 4s 2 .

As a result of chemical interaction, manganese gives up its valence electrons, i.e. is their donor, and turns into a positively charged ion:

Mn 0 -2e → Mn 2+;

Mn 0 -3e → Mn 3+;

Mn 0 -4e → Mn 4+;

Mn 0 -6e → Mn 6+;

Mn 0 -7e → Mn 7+.

Molecule and atom of manganese

In the free state, manganese exists in the form of monatomic Mn molecules. Here are some properties that characterize the atom and molecule of manganese:

manganese alloys

Manganese is mainly used in the production of alloy steels. Manganese steel containing up to 15% Mn has high hardness and strength. Working parts of crushing machines, ball mills, railway rails are made from it. In addition, manganese is a constituent of magnesium-based alloys; it increases their resistance to corrosion. An alloy of copper with manganese and nickel - manganin has a low temperature coefficient of electrical resistance. Manganese is found in small amounts in many aluminum alloys.

Examples of problem solving

EXAMPLE 1

Exercise

Manganese is produced by the reduction of manganese (III) oxide with silicon. Technical oxide weighing 20 g (mass fraction of impurities is equal to 5.2%) was reduced to metal. Calculate the mass of the obtained manganese.

Solution

We write the equation for the reduction of manganese (III) oxide with silicon to manganese:

2Mn 2 O 3 + 3Si = 3SiO 2 + 4Mn.

Calculate the mass of manganese (III) oxide without impurities:

ω pure (Mn 2 O 3) \u003d 100% - ω impurity;

ω pure (Mn 2 O 3) \u003d 100% - 5.2 \u003d 94.8% \u003d 0.984.

m pure (Mn 2 O 3) = m impurity (Mn 2 O 3) × ω pure (Mn 2 O 3) / 100%;

m pure (Mn 2 O 3) \u003d 20 × 0.984 \u003d 19.68 g.

Let's determine the amount of manganese (III) oxide substance (molar mass - 158 g / mol):

n (Mn 2 O 3) \u003d m (Mn 2 O 3) / M (Mn 2 O 3);

n (Mn 2 O 3) \u003d 19.68 / 158 \u003d 0.12 mol.

According to the reaction equation n (Mn 2 O 3) : n (Si) \u003d 2: 3, which means that

n(Si) \u003d 3/2 × n (Mn 2 O 3) \u003d 3/2 × 0.12 \u003d 0.2 mol.

Then the mass of silicon will be equal to (molar mass - 28 g / mol):

m (Si) = n (Si) × M (Si);

m(Si) = 0.2 × 28 = 5.6 g.

Answer

Mass of silicon 5.6 g

EXAMPLE 2

Exercise

Calculate the mass of potassium permanganate required to oxidize 7.9 g of potassium sulfite in a neutral medium.

Solution

We write the equation for the oxidation of potassium sulfite with potassium permanganate in a neutral medium:

2KMnO 4 + 3K 2 SO 3 + H 2 O \u003d 2MnO 2 + 3K 2 SO 4 + 2KOH.

Calculate the number of moles of potassium sulfite (molar mass - 158 g / mol):

n (K 2 SO 3) \u003d m (K 2 SO 3) / M (K 2 SO 3);

n (K 2 SO 3) \u003d 7.9 / 158 \u003d 0.05 mol.

According to the reaction equation n (K 2 SO 3): n (KMnO 4) \u003d 3: 2, which means that

n (KMnO 4) \u003d 2/3 × n (K 2 SO 3) \u003d 2/3 × 0.05 \u003d 0.03 mol.

The mass of potassium permanganate necessary for the oxidation of potassium sulfite in a neutral medium is (molar mass - 158g / mol):

m (KMnO 4) \u003d n (KMnO 4) × M (KMnO 4);

m (KMnO 4) \u003d 0.03 × 158 \u003d 4.74 g.

Answer

The mass of potassium permanganate is 4.74 g

Fulfilled : first year student

Faculty of Engineering

15 b group

Koshmanov V.V.

Checked by: Kharchenko N.T.

Velikie Luki 1998

History reference. 3

distribution in nature. 3

Physical and chemical properties. 3

Compounds of divalent manganese. four

Compounds of tetravalent manganese. four

Compounds of hexavalent manganese. 5

Compounds of heptavalent manganese. 5

Receipt. 6

The use of manganese and its compounds. 6

Literature. 7

History reference.

Manganese minerals have been known for a long time. The ancient Roman naturalist Pliny mentions a black stone, which was used to decolorize a liquid glass mass; about the mineral pyrolusite MnO2 . In Georgia, pyrolusite has served as a filler material in the production of iron since ancient times. For a long time, pyrolusite was called black magnesia and was considered a type of magnetic iron ore. In 1774, K. Schelle proved that this was a compound of an unknown metal, and another Swedish scientist, J. Gai, by strongly heating a mixture of pyrolusite with coal, obtained carbon-contaminated manganese. The name Manganese is traditionally derived from the German Marganerz- manganese ore.

distribution in nature.

The average content of manganese in the earth's crust is 0.1%, in most igneous rocks 0.06-0.2% by mass, where it is in a dispersed state in the form Mn2+ (analogue Fe2+). On the earth's surface Mn2+ easily oxidized, minerals are also known here Mn3+ and Mn4+. In the biosphere, manganese migrates vigorously under reducing conditions and is inactive under oxidizing conditions. Manganese is most mobile in the acidic waters of the tundra and forest landscapes, where it is in the form Mn2+ . The content of manganese here is often elevated and cultivated plants in places suffer from an excess of manganese; in soils, lakes, swamps, iron-manganese competitions, lake and swamp ores are formed. In dry steppes and deserts, in an alkaline oxidizing environment, manganese is inactive. Organisms are poor in manganese, cultivated plants often need manganese micro-fertilizers. River waters are poor in manganese (10 -6 -10 -5 g/l), but the total removal of this element is huge, and most of it is deposited in the coastal zone.

Physical and chemical properties.

In its pure form, manganese is obtained either by electrolysis of a solution of manganese sulfate ( II) , or recovery from oxides of silicon in electric stoves. Elemental manganese is a silvery-white hard but brittle metal. Its brittleness is explained by the fact that at normal temperatures per unit cell Mn includes 58 atoms in a complex openwork structure that is not among the close-packed. Density of manganese is 7.44 g/cm 3 , melting point is 1244 o C, boiling point is 2150 o C. In reactions it exhibits valency from 2 to 7, the most stable oxidation states are +2,+4,+7.

Compounds of divalent manganese.

Divalent manganese salts can be obtained by dissolving in dilute acids: Mn+2HCl MnCl 2 +H2 When dissolved in water, hydroxide is formed. Mn(II): Mn + 2HOH Mn (OH) 2 + H 2 Manganese hydroxide can be obtained in the form of a white precipitate by treating solutions of divalent manganese salts with alkali: MnSO4 +2NaOH Mn(OH)2 +NaSO4

Mn(II) compounds unstable in air, and Mn(OH)2 in air it quickly turns brown, turning into tetravalent manganese oxide-hydroxide.

2 Mn(OH) 2 +O 2 MnO(OH) 2

Manganese hydroxide exhibits only basic properties and does not react with alkalis, and when interacting with acids gives the corresponding salts.

Mn(OH) 2 +2HCl MnCl 2 + 2H2O

Manganese oxide can be obtained by decomposition of manganese carbonate:

MnCO3 MnO+CO2

Or when reducing manganese dioxide with hydrogen:

MnO 2 + H 2 MnO + H 2 O

Compounds of tetravalent manganese.

Of the compounds of tetravalent manganese, manganese dioxide is the most well-known. MnO2 - pyrolusite. Since valence IV is intermediate, connections Mn (VI) are formed as in the oxidation of divalent manganese. Mn(NO 3) 2 MnO 2 +2NO 2

So in the reduction of manganese compounds in an alkaline medium:

3K 2 MnO 4 +2H 2 O 2KMnO 4 +MnO 2 +4KOH The last reaction is an example of a self-oxidation reaction - self-healing, which is characterized by the fact that some of the atoms of the same element are oxidized, simultaneously restoring the remaining atoms of the same element:

Mn 6+ +2e=Mn 4+ 1

Mn 6+ -e=Mn 7+ 2

In its turn Mn O 2 can oxidize halides and halogen hydrogens, for example HCl :

MnO 2 +4HCl MnCl 2 +Cl 2 +2H 2 O

Manganese dioxide is a solid powdery substance. It exhibits both basic and acidic properties.

Compounds of hexavalent manganese.

When fused MNO 2 with alkalis in the presence of oxygen, air or oxidizing agents, hexavalent salts are obtained manganese called manganates.

MNO 2 +2KOH+KNO 3 K 2 MNO 2 +KNO 2 +H 2 O

Few compounds of hexavalent manganese are known, and of these, manganese salts are the most important.

Permanganic acid itself, as well as its corresponding manganese trioxide MNO 3 , does not exist in free form due to instability to oxidation-reduction processes. Replacing a proton in an acid with a metal cation leads to the stability of manganates, but their ability to undergo oxidation-reduction processes is preserved. Solutions of manganates are colored green. When they are acidified, permanganic acid is formed, decomposes to compounds manganese tetravalent and heptavalent.

Strong oxidizing agents convert hexavalent manganese to heptavalent manganese.

2K2MnO 4 +Cl2 2 2KMnO 4 +2KCl

Compounds of heptavalent manganese.

In the heptavalent state, manganese exhibits only oxidizing properties. Potassium permanganate is widely used among the oxidizing agents used in laboratory practice and in industry. KMnO 2 , in everyday life called potassium permanganate. Potassium permanganate is a black-purple crystals. Aqueous solutions are colored purple, characteristic of the ion MnO4- .

Permanganates are salts of manganese acid, which is stable only in dilute solutions (up to 20%). These solutions can be obtained by the action of strong oxidizing agents on divalent manganese compounds:

2Mn(NO 3 ) 2 +PbO 2 +6HNO 3 2HMnO 4 +5Pb(NO 3 ) 2 + 2H 2 O

Manganese is an element of a side subgroup of the seventh group of the fourth period of the periodic system of chemical elements of D. I. Mendeleev, with atomic number 25. It is denoted by the symbol Mn (lat. manganum).

The history of the discovery of manganese

The famous naturalist and writer of ancient Rome, Pliny the Elder, pointed to the miraculous ability of black powder to lighten glass. For a long time this substance, which gives a black powder when crushed, has been called pyrolusite, or manganese dioxide. Vanocchio Biringuccio also wrote about the ability of pyrolusite to clean glass in 1540. Pyrolusite is the most important ore for producing manganese, a metal used mainly in metallurgy.

From the word "magnesia" got their names manganese and magnesium. The origin of the name of two chemical elements from the same word is explained by the fact that for a long time pyrolusite was opposed to white magnesia and was called black magnesia. After obtaining the metal in its pure form, manganese was renamed. The name was based on the Greek word "manganese", which meant to purify (a hint of its use in antiquity as a "cleaner" of glass). Some researchers believe that the name of the element comes from the Latin word "magnes" - a magnet, since pyrolusite, from which manganese is extracted, was considered in antiquity to be a kind of substance that is now called magnetic iron ore.

Manganese was discovered in 1774 by the Swedish chemist Carl Wilhelm Scheele. True, neither manganese, nor molybdenum, nor tungsten was isolated by Scheele in its pure form; he only pointed out that the minerals he studied contained these new elements. Element No. 25 was discovered in the mineral pyrolusite MnO 2 · H 2 O, known to Pliny the Elder. Pliny considered it a kind of magnetic ironstone, although pyrolusite is not attracted by a magnet. Pliny explained this contradiction.

In the manuscripts of the famous alchemist Albert the Great (XIII century), this mineral is called "magnesia". In the XVI century. the name "manganese" is already found, which, perhaps, was given by glassmakers and comes from the word "manganidzein" - to clean.

When Scheele was investigating pyrolusite in 1774, he sent samples of this mineral to his friend Johan Gottlieb Hahn. Gan, later a professor, an outstanding chemist of his time, rolled pyrolusite into balls, adding oil to the ore, and heated the pyrolusite strongly in a crucible lined with charcoal. Metal balls were obtained, weighing three times less than ore balls. It was manganese. The new metal was first called "magnesia", but since white magnesia, magnesium oxide, was already known at that time, the metal was renamed "magnesium"; this name was adopted by the French Commission on Nomenclature in 1787. But in 1808 Humphry Davy discovered magnesium and also called it "magnesium"; then, in order to avoid confusion, manganese began to be called “manganum. »

In Russia, pyrolusite was called manganese for a long time, until in 1807 A.I. Scherer did not propose to call the metal obtained from pyrolusite manganese, and the mineral itself was called black manganese in those years.

The prevalence of manganese in nature

Manganese is the 14th most abundant element on Earth, and after iron, it is the second heavy metal contained in the earth's crust (0.03% of the total number of atoms in the earth's crust). In the biosphere, manganese migrates vigorously under reducing conditions and is inactive in an oxidizing environment. Manganese is most mobile in the acidic waters of the tundra and forest landscapes, where it is in the form of Mn 2+ . The content of manganese is often increased here, and cultivated plants in places suffer from an excess of manganese. The weight content of manganese increases from acid (600 g/t) to basic rocks (2.2 kg/t). It accompanies iron in many of its ores, but there are also independent deposits of manganese. Up to 40% of manganese ores are concentrated in the Chiatura deposit (Kutaisi region). Manganese scattered in rocks is washed out by water and carried away to the World Ocean. At the same time, its content in sea water is insignificant (10 -7 -10 -6%), and in deep places of the ocean its concentration increases to 0.3% due to oxidation by oxygen dissolved in water with the formation of water-insoluble manganese oxide, which in hydrated form (MnO 2 x H 2 O) and sinks into the lower layers of the ocean, forming the so-called iron-manganese nodules at the bottom, in which the amount of manganese can reach 45% (they also contain impurities of copper, nickel, cobalt). Such concretions may become a source of manganese for industry in the future.

This metal is distributed about the same as sulfur or phosphorus. Rich deposits of manganese ores are found in India, Brazil, West and South Africa.

In Russia, it is an acutely scarce raw material, the following deposits are known: Usinskoye in the Kemerovo region, Polunochnoye in the Sverdlovsk region, Porozhinskoye in the Krasnoyarsk Territory, Yuzhno-Khinganskoye in the Jewish Autonomous Region, Rogachevo-Taininskaya area and Severo-Taininskoye » field on Novaya Zemlya.

Obtaining manganese

The first metallic manganese was obtained by reducing pyrolusite with charcoal: МnО 2 + C → Mn + 2CO. But it was not elemental manganese. Like its neighbors on the periodic table - chromium and iron, manganese reacts with carbon and always contains an admixture of carbide. This means that pure manganese cannot be obtained using carbon. Now three methods are used to obtain metallic manganese: silicothermic (reduction by silicon), aluminothermic (reduction by aluminum) and electrolytic.

The aluminothermic method, developed at the end of the 19th century, found the widest distribution. In this case, it is better to use not pyrolusite, but manganese oxide Mn 3 O 4 as a manganese raw material. Pyrolusite reacts with aluminum with the release of such a large amount of heat that the reaction can easily become uncontrollable. Therefore, before restoring pyrolusite, it is fired, and the already obtained oxide is mixed with aluminum powder and set on fire in a special container. The reaction 3Mn 3 O 4 + 8Al → 9Mn + 4Al 2 O 3 begins - quite fast and does not require additional energy costs. The resulting melt is cooled, brittle slag is chipped off, and the manganese ingot is crushed and sent for further processing.

However, the aluminothermic method, like the silicothermic method, does not produce high purity manganese. It is possible to purify aluminothermic manganese by sublimation, but this method is inefficient and expensive. Therefore, metallurgists have long been looking for new ways to obtain pure metallic manganese and, of course, primarily hoped for electrolytic refining. But unlike copper, nickel, and other metals, the manganese deposited on the electrodes was not pure: it was contaminated with oxide impurities. Moreover, the result was a porous, fragile, inconvenient metal for processing.

Many well-known scientists tried to find the optimal mode of electrolysis of manganese compounds, but to no avail. This problem was also solved in 1919 by the Soviet scientist R.I. Agladze (now a full member of the Academy of Sciences of the Georgian SSR). According to the electrolysis technology he developed, from chloride and sulfate salts, a rather dense metal is obtained, containing up to 99.98% of element No. 25. This method formed the basis for the industrial production of metallic manganese.

Outwardly, this metal is similar to iron, only harder than it. It oxidizes in air, but, like aluminum, the oxide film quickly covers the entire surface of the metal and prevents further oxidation. Manganese reacts rapidly with acids, forms nitrides with nitrogen, and carbides with carbon. In general, a typical metal.

Physical properties of manganese

The density of Manganese is 7.2-7.4 g/cm 3 ; t pl 1245 °C; t bale 2150 °C. Manganese has 4 polymorphs: α-Mn (body-centered cubic lattice with 58 atoms per unit cell), β-Mn (body-centered cubic lattice with 20 atoms per cell), γ-Mn (tetragonal with 4 atoms per cell) and δ-Mn ( cubic body-centered). Transformation temperature: α=β 705 °С; β=γ 1090 °С and γ=δ 1133 °С; α-modification is fragile; γ (and partly β) is plastic, which is important when creating alloys.

The atomic radius of Manganese is 1.30 Å. ionic radii (in Å): Mn 2+ 0.91, Mn 4+ 0.52; Mn7+ 0.46. Other physical properties of α-Mn: specific heat (at 25°C) 0.478 kJ/(kg K) [t. e. 0.114 kcal/(g °C)]; temperature coefficient of linear expansion (at 20°C) 22.3·10 -6 deg -1; thermal conductivity (at 25 °C) 66.57 W/(m K) [t. e. 0.159 cal/(cm sec °C)]; specific volumetric electrical resistance 1.5-2.6 μm·m (i.e. 150-260 μΩ·cm): temperature coefficient of electrical resistance (2-3)·10 -4 deg -1. Manganese is paramagnetic.

Chemical properties of manganese

Manganese is quite active, when heated, it interacts vigorously with non-metals - oxygen (a mixture of manganese oxides of different valence is formed), nitrogen, sulfur, carbon, phosphorus and others. At room temperature, manganese does not change in air: it reacts very slowly with water. It dissolves easily in acids (hydrochloric, dilute sulfuric), forming salts of divalent manganese. When heated in a vacuum, manganese easily evaporates even from alloys.

When oxidized in air, it is passivated. Powdered manganese burns in oxygen (Mn + O 2 → MnO 2). When heated, manganese decomposes water, displacing hydrogen (Mn + 2H 2 O → (t) Mn (OH) 2 + H 2), the resulting manganese hydroxide slows down the reaction.

Manganese absorbs hydrogen, with increasing temperature its solubility in manganese increases. At temperatures above 1200 °C, it interacts with nitrogen, forming nitrides of various composition.

Carbon reacts with molten manganese to form Mn 3 C carbides and others. It also forms silicides, borides, phosphides.

It reacts with hydrochloric and sulfuric acids according to the equation:

Mn + 2H + → Mn 2+ + H 2

With concentrated sulfuric acid, the reaction proceeds according to the equation:

Mn + 2H 2 SO 4 (conc.) → MnSO 4 + SO 2 + 2H 2 O

Manganese is stable in alkaline solution.

Manganese forms the following oxides: MnO, Mn 2 O 3 , MnO 2 , MnO 3 (not isolated in the free state) and manganese anhydride Mn 2 O 7 .

Mn 2 O 7 under normal conditions, dark green liquid oily substance, very unstable; in a mixture with concentrated sulfuric acid ignites organic substances. At 90 °C Mn 2 O 7 decomposes with an explosion. The most stable oxides are Mn 2 O 3 and MnO 2 , as well as the combined oxide Mn 3 O 4 (2MnO·MnO 2 , or Mn 2 MnO 4 salt).

When manganese (IV) oxide (pyrolusite) is fused with alkalis in the presence of oxygen, manganates are formed:

2MnO 2 + 4KOH + O 2 → 2K 2 MnO 4 + 2H 2 O

Manganate solution has a dark green color. When acidified, the reaction proceeds:

3K 2 MnO 4 + 3H 2 SO 4 → 3K 2 SO 4 + 2HMnO 4 + MnO(OH) 2 ↓ + H 2 O

The solution turns crimson due to the appearance of the anion MnO 4 - and a brown precipitate of manganese hydroxide (IV) precipitates from it.

Permanganic acid is very strong, but unstable, it cannot be concentrated to more than 20%. The acid itself and its salts (permanganates) are strong oxidizing agents. For example, potassium permanganate, depending on the pH of the solution, oxidizes various substances, being reduced to manganese compounds of different oxidation states. In an acidic environment - to manganese (II) compounds, in a neutral one - to manganese (IV) compounds, in a strongly alkaline environment - to manganese (VI) compounds.

When calcined, permanganates decompose with the release of oxygen (one of the laboratory methods for obtaining pure oxygen). The reaction proceeds according to the equation (for example, potassium permanganate):

2KMnO 4 →(t) K 2 MnO 4 + MnO 2 + O 2

Under the action of strong oxidizing agents, the Mn 2+ ion passes into the MnO 4 − ion:

2MnSO 4 + 5PbO 2 + 6HNO 3 → 2HMnO 4 + 2PbSO 4 + 3Pb(NO 3) 2 + 2H 2 O

This reaction is used for the qualitative determination of Mn 2+

When alkalinizing solutions of Mn (II) salts, a precipitate of manganese (II) hydroxide precipitates from them, which quickly turns brown in air as a result of oxidation.

The use of manganese in industry

Manganese is found in all types of steel and cast iron. The ability of manganese to produce alloys with most known metals is used to obtain not only various grades of manganese steel, but also a large number of non-ferrous alloys (manganines). Of these, alloys of manganese with copper (manganese bronze) are especially remarkable. It, like steel, can be hardened and at the same time magnetized, although neither manganese nor copper show noticeable magnetic properties.

The biological role of manganese and its content in living organisms

Manganese actively affects the metabolism of proteins, carbohydrates and fats. The ability of manganese to enhance the action of insulin and maintain a certain level of cholesterol in the blood is also considered important. In the presence of manganese, the body uses fats more fully. Cereals (primarily oatmeal and buckwheat), beans, peas, beef liver and many bakery products are relatively rich in this trace element, which practically replenish the daily human need for manganese - 5.0-10.0 mg.

Do not forget that manganese compounds can have a toxic effect on the human body. The maximum permissible concentration of manganese in the air is 0.3 mg/m 3 . With severe poisoning, damage to the nervous system is observed with a characteristic syndrome of manganese parkinsonism.

Production volumes of manganese ore in Russia

Marganetsky GOK - 29%

The deposit of manganese ores was discovered in 1883. In 1985, the Pokrovsky mine began mining ore on the basis of this deposit. With the development of the mine and the emergence of new quarries and mines, the Marganetsky GOK was formed.
The production structure of the plant includes: two open pit mines for manganese ore, five mines for underground mining, three processing plants, as well as the necessary auxiliary shops and services, incl. repair and mechanical, transport, etc.

Ordzhonikidzevsky GOK - 71%

The main type of manufactured products is manganese concentrate of various grades with pure manganese content from 26% to 43% (depending on grade). By-products - expanded clay and sludge.

The enterprise extracts manganese ore from the ore fields assigned to it. The ore reserves will last for more than 30 years. Reserves of manganese ore in Ukraine in total for Ordzhonikidzevsky and Manganese mining and processing plants make up one third of all world reserves.

Manganese is a chemical element located in the periodic system of Mendeleev at atomic number 25. Its neighbors are chromium and iron, which determines the similarity of the physical and chemical properties of these three metals. Its nucleus contains 25 protons and 30 neutrons. The element's atomic mass is 54.938.

properties of manganese

Manganese is a transition metal from the d-family. Its electronic formula is as follows: 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 5 . The hardness of manganese on the Mohs scale is estimated at 4. The metal is quite hard, but, at the same time, brittle. Its thermal conductivity is 0.0782 W / cm * K. The element is characterized by a silvery-white color.

There are four modifications of metal known to man. Each of them is characterized by thermodynamic stability under certain temperature conditions. So, a-manganese has a rather complex structure and shows its stability at temperatures below 707 0 C, which determines its fragility. This modification of the metal in its elementary cell contains 58 atoms.

Manganese can have completely different oxidation states - from 0 to +7, while +1 and +5 are extremely rare. When the metal interacts with air, it is passivated. Powdered manganese burns in oxygen:

Mn+O2=MnO2

If the metal is exposed to elevated temperature, i.e. heated, then it will decompose into water with the displacement of hydrogen:

Mn+2H0O=Mn(OH)2+H2

It should be noted that manganese hydroxide, the layer of which is formed as a result of the reaction, slows down the reaction process.

Hydrogen is absorbed by the metal. The higher the temperature rises, the higher becomes its solubility in manganese. If the temperature is exceeded by 12000C, then manganese reacts with nitrogen, as a result of which nitrites are formed, which have a different composition.

The metal also interacts with carbon. The result of this reaction is the formation of carbides, as well as silicides, borides, phosphides.

The metal is resistant to alkaline solutions.

It is able to form the following oxides: MnO, Mn 2 O 3, MnO 2, MnO 3, the last of which has not been isolated in the free state, as well as manganese anhydride Mn 2 O 7. Under normal conditions of existence, manganese anhydride is a liquid oily substance of a dark green color, which does not have much stability. If the temperature is raised to 90 0 C, then the anhydride decomposition is accompanied by an explosion. Among the oxides that show the greatest stability, Mn 2 O 3 and MnO 2 are distinguished, as well as the combined oxide Mn 3 O 4 (2MnO·MnO 2, or salt Mn 2 MnO 4).

Manganese oxides:

During the fusion of pyrolusite and alkalis with the presence of oxygen, a reaction occurs with the formation of manganates:

2MnO 2 + 2KOH + O 2 \u003d 2K 2 MnO 4 + 2H 2 O

The manganate solution is characterized by a dark green color. If it is acidified, then the reaction proceeds with tinting the solution in a crimson color. This is due to the formation of the MnO 4 − anion, from which a precipitate of manganese oxide-hydroxide precipitates, which has a brown color.

Permanganic acid is strong, but does not show particular stability, and therefore, its maximum permissible concentration is no more than 20%. The acid itself, like its salts, acts as a strong oxidizing agent.

Salts of manganese do not show stability. Its hydroxides have a characteristic basic character. Manganese chloride decomposes when exposed to high temperatures. It is this scheme that is used to obtain chlorine.

Application of manganese

This metal is not in short supply - it belongs to common elements: its content in the earth's crust is 0.03% of the total number of atoms. He belongs to the third place in the ranking among heavy metals, which include all elements of the transition series, skipping ahead of iron and titanium. Heavy metals are those whose atomic weight exceeds 40.

Manganese can be found in small amounts in some rocks. Basically, localization of its oxygen compounds in the form of pyrolusite mineral - MnO 2 occurs.

Manganese has many uses. It is essential for the production of many alloys and chemicals. Without manganese, the existence of living organisms is impossible, as it acts as an active trace element, and is also present in almost all living and plant organisms. Manganese has a positive effect on the processes of hematopoiesis in living organisms. It is also found in many foods.

Metal is an indispensable element in metallurgy. It is manganese that is used to remove sulfur and oxygen from steel during its production. This process requires large volumes of metal. But it is worth saying that not pure manganese is added to the melt, but its alloy with iron, called ferromanganese. It is obtained in the process of the reduction reaction of pyrolusite with coal. Manganese also acts as an alloying element for steels. Thanks to the addition of manganese to steels, their wear resistance increases significantly, and they also become less susceptible to mechanical stress. The presence of manganese in the composition of non-ferrous metals significantly increases their strength and resistance to corrosion.

Metal dioxide has found its application in the oxidation of ammonia, and it is also a participant in organic reactions and decomposition reactions of inorganic salts. In this case, manganese dioxide acts as a catalyst.

The ceramic industry also does not do without the use of manganese, where MnO 2 is used as a black and dark brown dye for enamels and glazes. Manganese oxide is highly dispersed. It has a good adsorbing capacity, due to which it becomes possible to remove harmful impurities from the air.

Manganese is introduced into bronze and brass. Some metal compounds are used in fine organic synthesis and industrial organic synthesis. Manganese arsenide is characterized by a gigantic magnetocaloric effect, which becomes much stronger when subjected to high pressure. Manganese telluride acts as a promising thermoelectric material.

In medicine, it is also appropriate to use manganese, or rather its salts. So, an aqueous solution of potassium permanganate is used as an antiseptic, and they can also wash wounds, gargle, lubricate ulcers and burns. In some poisonings with alkaloids and cyanides, its solution is even indicated for oral administration.

Important: Despite the huge number of positive aspects of the use of manganese, in some cases, its compounds can adversely affect the human body and even have a toxic effect. Thus, the maximum allowable concentration of manganese in the air is 0.3 mg/m 3 . In the case of pronounced poisoning with a substance, the human nervous system is affected, for which the syndrome of manganese parkinsonism is characteristic.

Obtaining manganese

Metal can be obtained in several ways. Among the most popular methods are the following:

aluminothermic. Manganese is obtained from its oxide Mn 2 O 3 by a reduction reaction. The oxide, in turn, is formed during pyrolusite calcination:

4MnO 2 \u003d 2Mn 2 O 3 + O 2

Mn 2 O 3 + 2Al \u003d 2Mn + Al 2 O 3

restorative. Manganese is obtained by reducing the metal with coke from manganese ores, resulting in the formation of ferromanganese (an alloy of manganese and iron). This method is the most common, since the bulk of the total metal production is used during the production of various alloys, the main component of which is iron, in connection with this, manganese is extracted from ores not in pure form, but in an alloy with it;
electrolysis. The metal in its pure form is obtained using this method from its salts.

True, empirical, or gross formula: Mn

Molecular weight: 54.938

Manganese- an element of a side subgroup of the seventh group of the fourth period of the periodic system of chemical elements of D. I. Mendeleev with atomic number 25. It is designated by the symbol Mn (lat. Manganum, manganum, in Russian formulas it is read as manganese, for example, KMnO 4 - potassium manganese o four). The simple substance manganese (CAS number: 7439-96-5) is a silver-white metal. Along with iron and its alloys, it belongs to ferrous metals. Five allotropic modifications of manganese are known - four with a cubic and one with a tetragonal crystal lattice.

Discovery history

One of the main minerals of manganese - pyrolusite - was known in antiquity as black magnesia and was used in glass melting to clarify it. It was considered a kind of magnetic iron ore, and the fact that it is not attracted by a magnet, Pliny the Elder explained by the female sex of black magnesia, to which the magnet is “indifferent”. In 1774, the Swedish chemist K. Scheele showed that the ore contained an unknown metal. He sent samples of the ore to his friend, the chemist Yu. Gan, who, by heating pyrolusite with coal in an oven, obtained metallic manganese. At the beginning of the 19th century, the name "manganum" was adopted for it (from the German Manganerz - manganese ore).

Distribution in nature

Manganese is the 14th most abundant element on Earth, and after iron, it is the second heavy metal contained in the earth's crust (0.03% of the total number of atoms in the earth's crust). The weight content of manganese increases from acid (600 g/t) to basic rocks (2.2 kg/t). It accompanies iron in many of its ores, but there are also independent deposits of manganese. Up to 40% of manganese ores are concentrated in the Chiatura deposit (Kutaisi region). Manganese, dispersed in rocks, is washed out by water and carried away to the oceans. At the same time, its content in sea water is insignificant (10−7-10−6%), and in deep places of the ocean its concentration increases to 0.3% due to oxidation by oxygen dissolved in water with the formation of water-insoluble manganese oxide, which in hydrated form (MnO2 xH2O) and sinks into the lower layers of the ocean, forming the so-called iron-manganese nodules at the bottom, in which the amount of manganese can reach 45% (they also contain impurities of copper, nickel, cobalt). Such concretions may become a source of manganese for industry in the future.
In Russia, it is an acutely scarce raw material, the following deposits are known: Usinskoye in the Kemerovo region, Polunochnoye in the Sverdlovsk region, Porozhinskoye in the Krasnoyarsk Territory, Yuzhno-Khinganskoye in the Jewish Autonomous Region, Rogachevo-Taininskaya area and Severo-Taininskoye » field on Novaya Zemlya.

manganese minerals

pyrolusite MnO 2 xH 2 O, the most common mineral (contains 63.2% manganese);
manganite (brown manganese ore) MnO(OH) (62.5% manganese);
brownite 3Mn 2 O 3 MnSiO3 (69.5% manganese);
hausmanite (MnIIMn2III)O 4 ;
rhodochrosite (manganese spar, raspberry spar) MnCO 3 (47.8% manganese);
psilomelan mMnO MnO 2 nH 2 O (45-60% manganese);
purpurite Mn 3 +, (36.65% manganese).

Receipt

Aluminothermic method, reducing oxide Mn 2 O 3 formed during pyrolusite calcination.
Recovery of iron-containing manganese oxide ores with coke. Ferromanganese (~80% Mn) is usually obtained in this way in metallurgy.
Pure metallic manganese is produced by electrolysis.

Physical Properties

Some properties are shown in the table. Other properties of manganese:

Electron work function: 4.1 eV
Coefficient of linear thermal expansion: 0.000022 cm/cm/°C (at 0°C)
Electrical conductivity: 0.00695 106 ohm -1 cm -1
Thermal conductivity: 0.0782 W/cm K
Enthalpy of atomization: 280.3 kJ/mol at 25°C
Enthalpy of fusion: 14.64 kJ/mol
Enthalpy of vaporization: 219.7 kJ/mol
Hardness

Brinell scale: MN/m²
Mohs scale: 4

Vapor pressure: 121 Pa at 1244 °C
Molar volume: 7.35 cm³/mol

Chemical properties

Typical oxidation states of manganese: 0, +2, +3, +4, +6, +7 (oxidation states +1, +5 are uncharacteristic). When oxidized in air, it is passivated. Powdered manganese burns in oxygen.
Manganese, when heated, decomposes water, displacing hydrogen. In this case, the layer of manganese hydroxide formed slows down the reaction. Manganese absorbs hydrogen, with increasing temperature its solubility in manganese increases. At temperatures above 1200 °C, it interacts with nitrogen, forming nitrides of various composition.
Carbon reacts with molten manganese to form Mn 3 C carbides and others. It also forms silicides, borides, phosphides. Manganese is stable in alkaline solution.
Manganese forms the following oxides: MnO, Mn 2 O 3 , MnO 2 , MnO 3 (not isolated in the free state) and manganese anhydride Mn 2 O 7 .
Mn 2 O 7 under normal conditions, a liquid oily substance of a dark green color, very unstable; in a mixture with concentrated sulfuric acid ignites organic substances. At 90 °C Mn2O7 decomposes with an explosion. The most stable oxides are Mn 2 O 3 and MnO 2 , as well as the combined oxide Mn 3 O 4 (2MnO·MnO 2 , or Mn 2 MnO 4 salt). When manganese (IV) oxide (pyrolusite) is fused with alkalis in the presence of oxygen, manganates are formed. Manganate solution has a dark green color. The solution turns crimson due to the appearance of the MnO 4 − anion, and a brown precipitate of manganese (IV) oxide-hydroxide precipitates from it.
Permanganic acid is very strong, but unstable, it cannot be concentrated to more than 20%. The acid itself and its salts (permanganates) are strong oxidizing agents. For example, potassium permanganate, depending on the pH of the solution, oxidizes various substances, being reduced to manganese compounds of different oxidation states. In an acidic environment - to manganese (II) compounds, in a neutral one - to manganese (IV) compounds, in a strongly alkaline environment - to manganese (VI) compounds.
When calcined, permanganates decompose with the release of oxygen (one of the laboratory methods for obtaining pure oxygen). Under the action of strong oxidizing agents, the Mn 2+ ion passes into the MnO 4 - ion. This reaction is used for the qualitative determination of Mn 2+ (see section "Determination by chemical analysis methods").
When solutions of Mn (II) salts are alkalized, a precipitate of manganese (II) hydroxide precipitates out of them, which quickly turns brown in air as a result of oxidation. For a detailed description of the reaction, see the section "Determination by chemical analysis methods".
Salts MnCl 3 , Mn 2 (SO 4) 3 are unstable. Hydroxides Mn (OH) 2 and Mn (OH) 3 are basic, MnO (OH) 2 - amphoteric. Manganese (IV) chloride MnCl 4 is very unstable, decomposes when heated, which is used to obtain chlorine. The zero oxidation state of manganese manifests itself in compounds with σ-donor and π-acceptor ligands. So, for manganese, a carbonyl of the composition Mn 2 (CO) 10 is known.
Other manganese compounds with σ-donor and π-acceptor ligands are also known (PF 3 , NO, N 2 , P(C 5 H 5) 3).

Application in industry

Application in metallurgy

Manganese in the form of ferromanganese is used to "deoxidize" steel during its melting, that is, to remove oxygen from it. In addition, it binds sulfur, which also improves the properties of steels. The introduction of up to 12-13% Mn into steel (the so-called Hadfield Steel), sometimes in combination with other alloying metals, strongly strengthens the steel, makes it hard and resistant to wear and impact (this steel is sharply hardened and becomes harder on impact). Such steel is used for the manufacture of ball mills, earth-moving and stone-crushing machines, armor elements, etc. Up to 20% Mn is introduced into "mirror cast iron". In the 1920s-40s, the use of manganese made it possible to smelt armored steel. In the early 1950s, a discussion arose in the journal Stal on the possibility of reducing the manganese content in cast iron, and thereby refusing to support a certain manganese content in the process of open-hearth melting, in which, together with V.I. Yavoisky and V.I. Baptizmansky was attended by E.I. Zarvin, who, on the basis of production experiments, showed the inexpediency of the existing technology. Later, he showed the possibility of conducting an open-hearth process on low-manganese cast iron. With the launch of ZSMK, the development of the conversion of low-manganese cast iron in converters began. An alloy of 83% Cu, 13% Mn, and 4% Ni (manganin) has a high electrical resistance that changes little with temperature. Therefore, it is used for the manufacture of rheostats, etc. Manganese is introduced into bronze and brass.

Application in chemistry

A significant amount of manganese dioxide is consumed in the production of manganese-zinc galvanic cells, MnO 2 is used in such cells as an oxidizing agent-depolarizer. Manganese compounds are also widely used both in fine organic synthesis (MnO 2 and KMnO 4 as oxidizing agents) and industrial organic synthesis (components of hydrocarbon oxidation catalysts, for example, in the production of terephthalic acid by oxidation of p-xylene, oxidation of paraffins to higher fatty acids) . Manganese arsenide has a gigantic magnetocaloric effect that increases under pressure. Manganese telluride is a promising thermoelectric material (thermoelectric power with 500 μV/K).

Biological role and content in living organisms

Manganese is found in the organisms of all plants and animals, although its content is usually very low, on the order of thousandths of a percent, it has a significant impact on vital activity, that is, it is a trace element. Manganese affects growth, blood formation, and gonadal function. Beet leaves are especially rich in manganese - up to 0.03%, and large amounts of it are found in the organisms of red ants - up to 0.05%. Some bacteria contain up to several percent manganese. Excessive accumulation of manganese in the body affects, first of all, the functioning of the central nervous system. This is manifested in fatigue, drowsiness, deterioration of memory functions. Manganese is a polytropic poison that also affects the lungs, cardiovascular and hepatobiliary systems, causes an allergic and mutagenic effect.

Toxicity

The toxic dose for humans is 40 mg of manganese per day. The lethal dose for humans has not been determined. When taken orally, manganese is one of the least toxic trace elements. The main signs of manganese poisoning in animals are growth inhibition, loss of appetite, impaired iron metabolism, and altered brain function. There are no reports of manganese poisoning in humans caused by eating foods high in manganese. Basically, poisoning of people is observed in cases of chronic inhalation of large amounts of manganese at work. It manifests itself in the form of severe mental disorders, including hyperirritability, hypermotility and hallucinations - "manganese madness". In the future, changes in the extrapyramidal system develop, similar to Parkinson's disease. It usually takes several years for the clinical picture of chronic manganese poisoning to develop. It is characterized by a rather slow increase in pathological changes in the body caused by an increased content of manganese in the environment (in particular, the spread of endemic goiter, not associated with iodine deficiency).

Field

Usinsk manganese deposit