What is manganese? Properties of manganese. Applications of manganese

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FEDERAL STATE

BUDGET EDUCATIONAL INSTITUTION

HIGHER PROFESSIONAL EDUCATION

(FSBEI HPE named after N. P. OGAREV)

Institute of Physics and Chemistry

Department of General and Inorganic Chemistry

Course work

Manganese oxides

Olkhovskaya V.E.

Head of work: KHN, professor

Zyuzina L.F.

Saransk - 2014

Introduction

This work is devoted to the study of manganese oxides: their physical and chemical properties, the production of manganese dioxide. The solution to this problem is of great theoretical and practical importance.

The purpose of the course work is to identify the most promising and economically feasible method for producing manganese dioxide.

In accordance with the set goal, the following tasks were solved:

· Conduct an analysis of the literature on the physical and chemical properties, production methods, methods of using manganese and manganese oxides,

· Reveal the technologies for producing manganese doxide and identify the most effective;

· Carry out calculations.

The information base for the study was library collection materials, professional websites, and teacher consultations.

During the research, I used the general scientific method of analysis.

The work consists of an introduction, the main part, a conclusion, an appendix, and a list of references.

Analytical review

MANGANESE OXIDES

The oxygen compounds of manganese are so numerous and varied in properties as for no other element; the following are known: MnO, Mn3O4, Mn2O3, MnO2, MnO3, Mn2O7. The composition of the higher oxide determines the position of Manganese in the 7th group of the periodic table. The lowest oxide is a base; salts corresponding to MnO, nitrous oxide, are obtained by the action of acids on metallic Manganese and all its oxides, and excess oxygen is released from the higher ones

MnnОm + 2nHX = nМnХ2 + nН2O + (m?n)O;

When you consume hydrochloric acid, chlorine is released:

MnnОm + 2mHCl = nMnCl2 + mH2O + (m?n)Cl2.

At room temperature, all oxides can exist; when heated, only one is constant - Mn3O4; when heated on a blowtorch in a crucible with access to air, MnO absorbs oxygen, and MnO2 loses it, as well as Mn2O3 - in both cases, Mn3O4 is formed, and therefore, in quantitative analysis, weighing in the form of this oxide is used; higher oxides MnO3 and Mn2O7 in free form are very unstable, even at ordinary conditions. pace. The basic properties of MnO are very significant; as oxygen accumulates, the basic properties weaken, but they can be noticed even for Mn2O7; on the other hand, MnO2, being an extremely weak base, already exhibits the properties of a weak acidic oxide; the anhydride properties of MnO3 and especially Mn2O7 are quite pronounced.

Manganese oxide is most conveniently obtained by heating higher oxides or manganese carbonate in the form of a greenish powder in a stream of hydrogen; it turns into transparent, green, shiny octahedra if the hydrogen in which it is heated contains some hydrogen chloride; These crystals, without changing shape, transform into Mn3O4 when heated in air. Nitrous hydrate Mn(OH)2 is precipitated by alkalis from solutions of nitrous salts in the form of a white precipitate that quickly turns brown in air due to oxidation. The chemical properties of MnO are very similar to MgO; the basic properties of MnO are sharper; MnX2 salts are similar either to MgX2 salts or to FeX2, NiX2, CuX2 salts.

Table 1. Manganese oxides.

Name	Melting temperature	Boiling temperature
Manganese(II) oxide
Manganese(II,III) oxide			brown
Manganese(II,IV) oxide
Manganese(III) oxide	940 °C (dec.)		dark brown
Manganese(IV) oxide
Manganese(VI) oxide
Manganese(VII) oxide			dark green

Manganese(II) oxide

Table 2. Manganese(II) oxide.

Manganese(II) oxide


Systematic name	Manganese(II) oxide
Chem. formula
Physical properties
State	green cubic or hexagonal crystals
Molar mass	70.94 g/mol
Density
Thermal properties
Melting temperature
Boiling temperature

Maarganese(II) oxide -- MnO -- lower manganese oxide, monoxide.

Physical properties

Melting point 1569 °C. Boiling point 3127 °C* (*-sublimes with dissociation) Two systems of manganese(II) oxide crystals are known:

· cubic (a = 0.4448 nm);

· hexagonal modification (stable up to 155.3 °C);

Antiferromagnet with Néel point 122 K, semiconductor. Molar mass 70.94 g/mol. The color of the crystals is green or gray-green. The cubic system has a density of 5.18 g/cm3.

Chemical properties

Insoluble in water. Easily oxidizes to form a brittle MnO2 shell. Reduced to manganese when heated with hydrogen or active metals.

Exhibits predominantly basic properties. It does not interact with water and alkali solutions; it dissolves in acids, forming manganese (II) salts and water:

When fused with alkalis in excess oxygen, it forms hypomanganates:

Shows restorative properties.

Geological properties

Rarely found in nature. Included in manganosite.

Receipt

Manganese(II) oxide can be obtained by calcination at a temperature of 300°C of oxygen-containing manganese(II) salts in an inert gas atmosphere. From common MnO2 it is obtained through partial reduction at temperatures of 700-900 °C with hydrogen or carbon monoxide.

Formed during the thermal decomposition of manganese (II) hydroxide and salts in an inert atmosphere:

or reduction of MnO2:

Application

Used as a catalyst for dehydrogenation of piperidine.

Used for desulfurization of metals.

Component of many ceramic materials.

Manganese(II) salts are widely used as catalysts for oxidation processes. For example, adding flaxseed oil salts accelerates the oxidation of the latter by atmospheric oxygen, thus speeding up the drying of paint. Flaxseed oil containing manganese(II) salts

Manganese(II,III) oxide

Table 3. Manganese(II,III) oxide.

Manganese(II,III) oxide

Systematic name	Manganese(II,III) oxide
Chem. formula
Physical properties
State	brown-black crystals
Molar mass	228.81 g/mol
Density	4.70; 4.856 g/cm
Thermal properties
Temperature. float	1560; 1564; 1705 °C
Molar. heat capacity	139.3 J/(mol K)
Enthalpy of formation	1387.6 kJ/mol

Manganese(II,III) oxide is an inorganic compound, manganese metal oxide with the formula Mn3O4, brown-black crystals, insoluble in water.

Receipt

· The mineral occurs in nature hausmannite -- Mn3O4 with impurities.

Physical properties

Manganese(II,III) oxide forms brown-black crystals of tetragonal system, space group I 41/amd, cell parameters a = 0.575 nm, c = 0.942 nm, b = 103.9°, Z = 4.

At 1160°C there is a transition to the cubic phase.

Paramagnetic.

Manganese(II,IV) oxide

Table 4. Manganese(II,IV) oxide.

Manganese(II,IV) oxide is an inorganic compound, manganese metal oxide with the formula Mn5O8, can be considered as manganese orthomanganite Mn3(MnO4)2, a solid, insoluble in water.

Receipt

· Oxidation manganese(II) oxide or manganese(II,III) oxide:

Physical properties

Manganese(II,IV) oxide-- a solid substance that is insoluble in water.

Chemical properties

When heated, it decomposes:

Manganese(III) oxide

Table 5. Manganese(III) oxide.

Manganese(III) oxide

Systematic name	Manganese(III) oxide
Chem. formula
Physical properties
State	brown-black crystals
Molar mass	157.87 g/mol
Density	4.50; 4.57-4.60 g/cm³
Thermal properties
Temperature. float	decomposition 1080 °C
Mol. heat capacity	107.5 J/(mol K)
Enthalpy of formation	957.7 kJ/mol

Manganese(III) oxide is an inorganic compound, oxide of the manganese metal with the formula Mn2O3, brown-black crystals, insoluble in water.

Receipt

· Minerals found in nature braunite, kurnakite and bixbyite - manganese oxide with various impurities.

· Oxidation of manganese(II) oxide:

Reduction of manganese(IV) oxide:

Physical properties

Manganese(III) oxide forms brown-black crystals of several modifications:

· b-Mn2O3, rhombic system, kurnakite mineral;

· β-Mn2O3, cubic system, space group I a3, cell parameters a = 0.941 nm, Z = 16, mineral bixbyite;

· g-Mn2O3, tetragonal system, cell parameters a = 0.57 nm, c = 0.94 nm.

Does not dissolve in water.

Paramagnetic.

Chemical properties

Decomposes when heated:

Reduced by hydrogen:

· When dissolved in acids, it disproportionates:

· When fused with metal oxides, it forms manganite salts:

Manganese(IV) oxide

Table 6. Manganese(IV) oxide.

Manganese(IV) oxide


Systematic name	Manganese dioxide
Chem. formula
Physical properties
State	black tetragonal crystals
Molar mass	86.9368 g/mol
Density
Thermal properties
Temperature. decomposition
Enthalpy of formation	521.5 kJ/mol

Chemical properties

Under normal conditions it behaves quite inertly. When heated with acids, it exhibits oxidizing properties, for example, it oxidizes concentrated hydrochloric acid to chlorine:

With sulfuric and nitric acids, MnO2 decomposes with the release of oxygen:

When interacting with strong oxidizing agents, manganese dioxide is oxidized to Mn7+ and Mn6+ compounds:

Manganese dioxide exhibits amphoteric properties. Thus, when a sulfuric acid solution of the salt MnSO4 is oxidized with potassium permanganate in the presence of sulfuric acid, a black precipitate of the salt Mn(SO4)2 is formed.

When fused with alkalis and basic oxides, MnO2 acts as an acidic oxide, forming manganite salts:

Is a catalyst for the decomposition of hydrogen peroxide:

Receipt

In laboratory conditions it is obtained by thermal decomposition potassium permanganate:

It can also be prepared by reacting potassium permanganate with hydrogen peroxide. In practice, the resulting MnO2 catalytically decomposes hydrogen peroxide, as a result of which the reaction does not proceed to completion.

At temperatures above 100 °C, reduction of potassium permanganate with hydrogen:

Manganese(VII) oxide

· Manganese(VII) oxide Mn2O7 - greenish-brown oily liquid (tmelt=5.9 °C), unstable at room temperature; a strong oxidizer, upon contact with flammable substances it ignites them, possibly with an explosion. Explodes from a push, from a bright flash of light, when interacting with organic substances. Manganese(VII) oxide Mn2O7 can be obtained by the action of concentrated sulfuric acid on potassium permanganate:

· The resulting manganese(VII) oxide is unstable and decomposes into manganese(IV) oxide and oxygen:

At the same time, ozone is released:

Manganese(VII) oxide reacts with water to form permanganic acid:

Manganese(VI) oxide

Table 7. Manganese(VI) oxide.

Manganese(VI) oxide is an inorganic compound, oxide of the manganese metal with the formula MnO3, a dark red amorphous substance that reacts with water.

manganese dioxide production chemical

Receipt

· Formed by condensation of violet vapors released when the solution is heated potassium permanganate in sulfuric acid:

Physical properties

Manganese(VI) oxide forms a dark red amorphous substance.

Chemical properties

· Decomposes when heated:

Reacts with water:

With alkalis it forms salts - manganates:

Patterns of changes in the properties of manganese oxides

The most stable are MnO2, Mn2O3 and Mn3O4 (mixed oxide - trimanganese tetroxide).

The properties of manganese oxides depend on the degree of oxidation of the metal: with increasing degree of oxidation, the acidic properties increase:

MnO > Мn2О3 > MnO2 > Мn2О7

Manganese oxides exhibit oxidizing or reducing properties depending on the degree of oxidation of the metal: higher oxides are oxidizing agents and are reduced to MnO2, lower oxides are reducing agents, and when oxidized, form MnO2. Thus, MnO2 is the most stable oxide.

methods for producing manganese dioxide

The invention relates to the field of metallurgy, more specifically, to the production of high-quality manganese oxides, which can be widely used in the chemical and metallurgical industries. The method for producing manganese dioxide involves dissolving manganese-containing raw materials in nitric acid to obtain a solution of manganese nitrates and nitrates of calcium, potassium, magnesium, and sodium impurities present in the ore. Then thermal decomposition of nitrates is carried out in an autoclave. Thermal decomposition is carried out with a constant decrease in pressure in the autoclave, starting from a pressure of 0.6 MPa and reducing it to 0.15 MPa at the end of the process. In this case, the pulp during thermal decomposition is continuously stirred with a stirrer rotating at a speed of 1-15 rpm and vibration is applied to it with a frequency of 20-50 hertz. The method can be implemented at chemical enterprises that have autoclaves operating under pressure. The technical result of the invention is the production of manganese dioxide of improved quality. 2 tab., 2 pr.

The invention relates to the field of ferrous metallurgy, more specifically, to the production of high-quality manganese dioxide, which can be widely used in the chemical and metallurgical industries, in particular in the production of electrolytic and electrothermal manganese, medium-carbon ferromanganese, and low-phosphorus alloys based on it.

From the technical literature, several methods are known for producing pure manganese dioxide: chemical, hydrometallurgical, pyrohydrometallurgical and pyrometallurgical.

The main requirements for chemical methods for producing manganese dioxide are:

Phosphorus and gangue removal efficiency;

Simplicity of hardware design;

High performance;

Availability and low cost of reagents.

There is a known method for producing pure manganese dioxide using the sulfuric acid method. The essence of the method is as follows: sulfur dioxide containing sulfur dioxide (SO2) and sulfuric anhydride (SO3) is passed through a suspension (S:L = 1:4) prepared from ore and a solution of calcium dithionate. The dissolution of these gases in water leads to the formation of sulfurous and sulfuric acids. Manganese oxides intensively dissolve in sulfurous acid to form manganese salt of dithionate acid and manganese sulfate according to the reactions: MnO2+2SO2 = MnS2O6; MnO2+SO2 = MnSO4.

In the presence of excess calcium dithionate, calcium sulfate precipitates and manganese dithionate forms: MnSO4+CaS2O6=MnS2O6+CaSO4

The leached pulp is neutralized with lime milk to a pH of 4-5, then it is aerated to oxidize ferrous oxide and remove sulfur dioxide. The following precipitates: ferric iron, phosphorus, aluminum, silica. The precipitate is filtered off, washed with hot water and sent to a dump. From the purified solution, by adding quicklime, manganese is precipitated in the form of hydroxide, and calcium dithionate is again obtained, which is returned to the process:

MnS2O6+Ca(OH)2=Mn(OH) 2+CaS2O6.

The precipitate of manganese hydroxide is filtered off, washed, dried and calcined. The calcined concentrate contains, %: 92 - MnO2, 1.5 - SiO2, 4.0 - CaO, 0.02 - P2O5 and 0.5-3 - SO 2 (M.I. Gasik. Metallurgy of manganese. Kyiv: Technology, 1979, pp.55-56).

The disadvantages of the known method for producing manganese dioxide are:

Complexity of hardware design;

The product is contaminated with waste rock (SiO2, CaO, etc.);

High concentration of sulfur in the final product (from 0.5 to 3%).

The closest to the proposed one in terms of technical essence and achieved effect is the method of producing manganese dioxide by thermal decomposition of manganese nitrate in the presence of calcium, magnesium, potassium and sodium nitrates, according to which the decomposition is carried out at a pressure of 0.15-1.0 MPa (Author’s certificate No. 1102819, class C22B 47/00; C01G 45/02, priority dated 05/20/83, published 07/15/84, bulletin No. 26).

According to the prototype method, manganese dioxide is produced in the presence of calcium, magnesium, potassium and sodium nitrates, decomposition is carried out at a pressure of 0.15-1.0 MPa.

Technological parameters and properties of the prototype method:

Decomposition temperature, °C - 170-190;

The rate of formation of manganese dioxide, kg/m3h - 500-700;

Degree of decomposition of Mn(NO3)2,% of the original amount - 78-87;

Conditions for unloading pulp from the reactor - by gravity;

Energy consumption, MJ/kg - 1.7-2.2;

The disadvantages of this known method are the low rate of decomposition of manganese nitrate, high energy consumption, and the high amount of water in the resulting nitrogen oxides.

The objective of the present invention is to simplify the technology for producing manganese dioxide, increasing the rate of decomposition and product yield.

The goal is achieved by the fact that the process of thermal decomposition is carried out with a gradual decrease in pressure in the autoclave, starting from a pressure of 0.6 MPa and reducing it to 0.15 MPa at the end of the process, while the pulp is continuously processed with a stirrer rotating at a speed of 1-15 rpm /min; in this case, during the process of thermal decomposition, vibration with a frequency of 20-50 hertz is applied to the rotating stirrer.

The upper pressure value for the thermal decomposition of nitrates is determined by the conditions for processing nitrogen oxides into acid (it is carried out at a pressure not exceeding 0.6 MPa), and the lower limit is determined by practical expediency. A gradual decrease in pressure to 0.15 MPa ensures more complete thermal decomposition of manganese nitrates.

Reducing the mixer rotation speed below 1 rpm does not provide a homogeneous pulp solution. Increasing the rotation speed above 15 rpm leads to pulp separation and the appearance of areas with a higher water concentration (due to differences in densities).

Lower vibration frequencies - below 20 hertz, imposed on the mixer, have virtually no effect on the thermal decomposition of manganese nitrate. Increasing the vibration frequency above 50 hertz is not economically justified.

If these conditions are met, not only the rate of decomposition of manganese nitrate increases, but the process itself as a whole becomes more technologically advanced. It has been established that in the proposed process, the pulp yield does not greatly depend on its physical properties, which greatly simplifies the process of unloading it from the reactor, while nitrogen oxides contain lower concentrations of water and can be easily processed back into acid. Table 1 presents comparative data on the technological parameters for producing manganese dioxide using the known and proposed methods. The indicators (averaged) for the proposed method for producing manganese dioxide, presented in Table 8, are taken based on the results of the experiments (example 1).

Table 8

Technological parameters and properties
Famous	Proposed
Decomposition temperature, °C
Pressure, MPa		Gradual decrease in pressure from 0.6 to 0.15
Rate of formation of manganese dioxide, kg/m3h
Time required to form 200 kg of manganese dioxide, h
Degree of decomposition of Mn(NO3)2, % of the original amount
Conditions for unloading pulp from the reactor	By gravity	By gravity

Energy consumption, MJ/kg MnO2

Mixer rotation speed, rpm.

During thermal decomposition, vibration with a frequency of 30 hertz was applied to the rotating stirrer - the degree of decomposition of Mn(NO3)2 increases by 2-3.5%.

Physico-chemical properties of the powder:

Density - 5.10 g/cm3;

H 2O - no more than 3H10-2 wt.%.

Below are examples, not exclusive of others, within the scope of the claims.

Example 1

1.5 kg of nitrate solution of the following composition, wt.%: 40.15 Mn(NO3)2; 25.7 Ca(NO3) 2; 7.3 Mg(NO3)2; 9.2 KNO3; 5.7 NaNO3; 15.0 H2O.

The weight of water removed during thermal decomposition was determined by the difference in its weight in the initial solution and in the liquid phase of the pulp. The amount of released nitrogen oxides was determined by the stoichiometry of the reaction of thermal decomposition of manganese nitrate in accordance with the amount of MnO2 obtained. The main results of the experiments are presented in Table 9.

Table 9

Options	Examples of concrete implementation
Known method	Suggested method

Decomposition temperature, C°
Pressure, MPa*
Mixer rotation speed, rpm
Vibration frequency, Hz
Decomposition time, min
MnO2 formation rate, kg/m3h

Volume of released gases, m3 per 1 kg MnO2
Yield of dry manganese dioxide, %
The upper pressure limit for the thermal decomposition of nitrates is determined by the conditions for processing nitrogen oxides into acid

Manganese dioxide was obtained with the following composition, wt.%: MnO2 - 99.6; R<0,005; S<0,05; SiO2<0,1; (К, Mg, Na, Ca)<0,1.

Thus, the proposed method provides not only faster decomposition of manganese nitrate, but also significantly simplifies the MnO2 production technology, both at the unloading stage and at the stage of regeneration of nitrogen oxides; at the same time, redistribution costs are significantly reduced. The yield of the resulting dry manganese dioxide is 84-92% versus 78% (according to the known method) of the theoretically possible.

Example 2

The resulting manganese dioxide is used for the smelting of metallic manganese by an extra-furnace process.

The charge had the following composition, kg:

Only 15.5 kg.

The mixture was mixed, loaded into the smelting shaft and set on fire using a fuse. The melting time was 2.4 minutes. We obtained 5.25 kg of manganese metal composition. % Mn 98.9; Al 0.96; P - traces (less than 0.005%) and 9.3 kg of slag composition, wt.%: MnO 14.6; Al2O3 68.3; CaO 18.0.

The extraction of manganese into the alloy was 85.0%.

Slag from the smelting of manganese metal can be used as a feedstock (instead of bauxite) in the production of aluminum.

The application of the proposed invention will solve the problem of using significant reserves of low-grade manganese ores, in particular carbonate ores of the Usinsk deposit or ferromanganese nodules, the enrichment of which by any other means is currently unprofitable.

The resulting manganese alloys are distinguished by a high concentration of the leading element (manganese) and a low content of harmful impurities (phosphorus and carbon).

The use of manganese ferroalloys in the smelting of high-quality steel grades leads to a reduction in the metal consumption of structures, simplifies the alloying process and provides a significant economic effect.

The production of manganese concentrates by chemical methods will significantly reduce the country's shortage of manganese ferroalloys, and its production can be organized at chemical plants.

The proposed method for producing manganese dioxide can be organized at enterprises that have the ability to utilize nitrogen oxides.

CLAIM

A method for producing manganese dioxide by thermal decomposition, including dissolving manganese-containing raw materials in nitric acid to obtain a solution of manganese nitrates and nitrates, calcium, potassium, magnesium, sodium impurities present in the ore, and subsequent thermal decomposition of nitrates in an autoclave, characterized in that thermal decomposition is carried out at a constant decrease in pressure in the autoclave, starting from a pressure of 0.6 MPa and reducing it by the end of the process to 0.15 MPa, while the pulp is continuously processed with a mixer rotating at a speed of 1-15 rpm and vibrating it at a frequency of 20 -50 Hz.

experimental part

The above experiences are applied in large enterprises.

I want to consider a laboratory method for obtaining manganese dioxide in tin dioxide.

Accessories:

1. Porcelain crucible:

2.Glass filter.

The essence of the method: Preparation of solid oxides by thermal decomposition of a mixture of SnC2O4*H2O and MnSO4*5H2O, calcination in air.

Preliminary synthesis of SnC2O4*H2O.

To obtain tin oxalate, we took 10 g of tin sulfate and 4.975 g of ammonium oxalate. Solutions of both substances were prepared; for this purpose, tin sulfate was dissolved in 100 ml of water, and ammonium oxalate was dissolved in 50 ml of water. Then, a solution of ammonium oxalate was added to the tin sulfate solution. Active precipitation of white fine sediment (SnC2O4*H2O) was observed. The resulting suspension was filtered on a thick glass filter.

Reaction equation:

SnSO4* H2O +(NH4)2C2O4*H2O>SnC2O4*H2Ov+(NH4)2SO4 + H2O

The result was 7.934 g of tin oxalate, with an estimated mass of 9.675. The reaction yield was 82.0%.

According to the reaction equations

MnSO4*5H2O >MnO + SO3 (g)+ 5 H2O(g) >MnO2.

SnC2O4*H2O >SnO + CO2 + H2O >SnO2

A) 7.5% MnO2 / 92.5% SnO2.

To obtain it, we took: 0.75 g. SnC2O4 * H2O, 0.07 g. MnSO4 * 5H2O. (Since the amount of manganese sulfate was significantly less than the amount of ammonium oxalate, to achieve greater homogeneity of the mixture, after placing it in a porcelain crucible, a few drops of water were added. Then the mixture was calcined on a burner.). The calcination mode at 900 °C for 2 hours did not give any result (the grayish-cream color of the mixture remained). As a result of calcination at 1200 °C for 2 hours, the sample acquired a bright red color. Sample weight 0.5 g.

B) 15% MnO2 / 85% SnO2. (0.761 g SnC2O4*H2O, 0.088 g MnSO4*5H2O) Sample weight 0.53 g.

B) 22% MnO2 / 78% SnO2. (0.67 g SnC2O4*H2O, 0.204 g MnSO4*5H2O). Sample weight 0.52 g.

D) 28% MnO2 / 72% SnO2 (0.67 g. SnC2O4 * H2O, 0.2911 g. MnSO4 * 5H2O). Sample weight 0.56 g.

Conclusion

Before starting the research, I set myself the following tasks:

· Conduct an analysis of the literature on the physical and chemical properties, production methods, methods of use of manganese and manganese oxides;

· Study the properties of manganese oxides;

· Reveal the technologies for producing manganese dioxide and identify the most effective;

· Carry out calculations.

During my work:

1. An analysis of the literature on the physical and chemical properties, production methods, and methods of use of manganese and manganese oxides was carried out;

2. The properties of manganese oxides have been studied;

3. Technologies for producing manganese dioxide are disclosed and the most effective one is identified;

4. Calculations have been carried out.

Many ways to obtain manganese dioxide from different sources were considered, but I decided to focus on the method of obtaining manganese dioxide in tin dioxide. It showed a high degree of crystallinity of the sample and a high yield. It makes sense to use it (for high concentrations of manganese dioxide).

Application

Manganese

Prevalence in nature

Manganese is the 14th most abundant element on Earth, and after iron, it is the second heavy metal found in the earth's crust (0.03% of the total number of atoms in the earth's crust). The weight amount of manganese increases from acidic (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 into 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 is in hydrated form (MnO2 xH2O) and sinks into the lower layers of the ocean, forming so-called iron-manganese nodules on the bottom, in which the amount of manganese can reach 45% (they also contain impurities of copper, nickel, cobalt). Such nodules may become a source of manganese for industry in the future.

World reserves of manganese ores are represented by 90% oxide (38%) and oxide-carbonate (52%) ores.

In South Africa, about 95% of reserves are concentrated in the unique Kuruman manganese-iron ore zone. The largest deposits are Mamatvan (average manganese content 38%), Wessels (47%) Middelplaatz (36%)

In China, manganese reserves are represented by small but numerous deposits of oxide ores. The average content in ores is 20-40%. The country is constantly searching for and exploring new manganese deposits in order to reduce the country's dependence on the import of high-quality ores.

In Kazakhstan, more than 90% is located in the Central Kazakhstan region, in the Karazhal and Ushkatyn fields. Reserves are about 85 million tons (average manganese content 22%).

The Ukrainian deposits are located in the South Ukrainian manganese ore basin. These are the Nikopol group and Bolshetokmakskoye fields, containing 33 and 67% of Ukraine’s proven reserves. Ukraine also has one of the most powerful complexes in Europe for ore processing and production of manganese ferroalloys, including the Nikopol, Zaporozhye and Stakhanov plants.

In Georgia, the main raw material base is the Chiatura deposit. Oxide ores make up 28% (average manganese content 26%) of confirmed reserves, carbonate ores (average manganese content 18%-72%).

In Russia, manganese is an acutely scarce raw material of strategic importance. In addition to the indicated Usinsky and Polunochny deposits, the South Khingan deposits of the Lesser Khingan in the Jewish region, Porozhnenskoye on the Yenisei Ridge, the Rogachevo-Taininskaya area (260 million tons of carbonate ores, with a content of 8-15%) and the underexplored North Taininsky ore field (5 million tons of oxide ores, with a content of 16-24%) on Novaya Zemlya.

Physical and chemical properties

Manganese is a hard, brittle metal. Four cubic modifications of metallic manganese are known. At temperatures from room temperature to 710°C, a-Mn is stable, lattice parameter a = 0.89125 nm, density 7.44 kg/dm3. In the temperature range 710-1090°C there is b-Mn, lattice parameter a = 0.6300 nm; at temperatures 1090-1137°C - g-Mn, lattice parameter a = 0.38550 nm. Finally, at temperatures from 1137°C to the melting point (1244°C), d-Mn with a lattice parameter a = 0.30750 nm is stable. Modifications a, b, and d are brittle, g-Mn is ductile. The boiling point of manganese is about 2080°C.

In air, manganese oxidizes, as a result of which its surface is covered with a dense oxide film, which protects the metal from further oxidation. When calcined in air above 800°C, manganese becomes covered with scale, consisting of an outer layer of Mn3O4 and an inner layer of MnO composition.

Manganese forms several oxides: MnO, Mn3O4, Mn2O3, MnO2 and Mn2O7. All of them, except Mn2O7, which is an oily green liquid at room temperature with a melting point of 5.9°C, are crystalline solids.

Manganese monoxide MnO is formed during the decomposition of divalent manganese salts (carbonate and others) at a temperature of about 300°C in an inert atmosphere:

MnCO3 = MnO + CO2

This oxide has semiconducting properties. The decomposition of MnOOH can produce Mn2O3. The same manganese oxide is formed when MnO2 is heated in air at a temperature of approximately 600°C:

4MnO2 = 2Mn2O3 + O2

Mn2O3 oxide is reduced by hydrogen to MnO, and under the action of dilute sulfuric and nitric acids it turns into manganese dioxide MnO2.

If MnO2 is calcined at a temperature of about 950°C, then the elimination of oxygen and the formation of manganese oxide of the composition Mn3O4 is observed:

3MnO2 = Mn3O4 + O2

This oxide can be represented as MnO·Mn2O3, and in terms of properties Mn3O4 corresponds to a mixture of these oxides.

Manganese dioxide MnO2 is the most common natural manganese compound in nature, existing in several polymorphic forms. The so-called b-modification of MnO2 is the already mentioned mineral pyrolusite. The orthorhombic modification of manganese dioxide, g-MnO2, also occurs in nature. This is the mineral ramsdelite (another name is polyanite).

Manganese dioxide is nonstoichiometric; there is always a deficiency of oxygen in its lattice. If manganese oxides corresponding to lower oxidation states than +4 are basic, then manganese dioxide has amphoteric properties. At 170°C MnO2 can be reduced with hydrogen to MnO.

If concentrated sulfuric acid is added to potassium permanganate KMnO4, the acid oxide Mn2O7 is formed, which has strong oxidizing properties:

2KMnO4 + 2H2SO4 = 2KHSO4 + Mn2O7 + H2O.

Mn2O7 is an acidic oxide; it is represented by the strong permanganic acid НMnO4, which does not exist in a free state.

When manganese interacts with halogens, dihalides MnHal2 are formed. In the case of fluorine, the formation of fluorides of the composition MnF3 and MnF4 is also possible, and in the case of chlorine, also trichloride MnCl3. Reactions of manganese with sulfur lead to the formation of sulfides of the compositions MnS (exists in three polymorphic forms) and MnS2. A whole group of manganese nitrides is known: MnN6, Mn5N2, Mn4N, MnN, Mn6N5, Mn3N2.

With phosphorus, manganese forms phosphides of the compositions MnP, MnP3, Mn2P, Mn3P, Mn3P2 and Mn4P. Several manganese carbides and silicides are known.

Manganese reacts very slowly with cold water, but when heated, the reaction rate increases significantly, Mn(OH)2 is formed and hydrogen is released. When manganese interacts with acids, manganese (II) salts are formed:

Mn + 2HCl = MnCl2 + H2.

From solutions of Mn2+ salts, it is possible to precipitate a base Mn(OH)2, which is poorly soluble in water:

Mn(NO3)2 + 2NaOH = Mn(OH)2 + 2NaNO3

Several acids correspond to manganese, of which the most important are the strong unstable permanganate acid H2MnO4 and manganese acid HMnO4, the salts of which are, respectively, manganates (for example, sodium manganate Na2MnO4) and permanganates (for example, potassium permanganate KMnO4).

Manganates (only alkali metal and barium manganates are known) can exhibit properties as oxidizing agents (more often)

2NaI + Na2MnO4 + 2H2O = MnO2 + I2 + 4NaOH,

and reducing agents

2K2MnO4 + Cl2 = 2KMnO4 + 2KCl.

In aqueous solutions, manganates are disproportionately divided into compounds of manganese (+4) and manganese (+7):

3K2MnO4 + 3H2O = 2KMnO4 + MnO2·H2O + 4KOH.

In this case, the color of the solution changes from green to blue, then to violet and crimson. For its ability to change the color of its solutions, K. Scheele called potassium manganate a mineral chameleon.

Permanganates are strong oxidizing agents. For example, potassium permanganate KMnO4 in an acidic environment oxidizes sulfur dioxide SO2 to sulfate:

2KMnO4 + 5SO2 +2H2O = K2SO4 + 2MnSO4 + 2H2SO4.

At a pressure of about 10 MPa, anhydrous MnCl2, in the presence of organometallic compounds, reacts with carbon monoxide (II) CO to form binuclear carbonyl Mn2(CO)10.

Literature

1. Internet resources.

2. Workshop on inorganic chemistry: Proc. A manual for students. Higher Textbook Establishments/V.A. Aleshin, A.I. Dunaev, A. I. Zhirov; edited by Yu.D. Tretyakov - M.: Publishing house. Center "Academy", 2004.

3. Glinka N.L. General chemistry//M.: Integral-press, 2002.

4. Akhmetov N.S. general and inorganic chemistry. Textbook For universities - 4th ed., revised // M.: Higher. School, Publishing center "Academy", 2001.

5. Inorganic chemistry. Chemistry of elements: Textbook in 2 volumes. T.2/Yu.D. Tretyakov, L.I. Martynenko, A.N. Grigoriev, A. Yu. Tsivadze. - 2nd ed., revised. and additional - M.: Moscow State University Publishing House; ICC "Akademkniga", 2007.

6. Chemical Encyclopedia / Editorial Board: Knunyants I.L. and others // M.: Soviet Encyclopedia, 1992.

7. Ugai Y.A. General chemistry: Textbook for chemistry students. specialist. un-tov//M.: Higher. school, -1984.

8. General and inorganic chemistry. Lecture course. Part II. main classes of inorganic compounds/ Korneev Yu.M., Ovcharenko V.P., Egorov E.N.//M.: School named after A.N. Kolmogorov, Moscow University Publishing House, 2000.

9. Chemist’s Handbook / Editorial Board: Nikolsky B.P. and others. - 2nd ed., revised//M.-L.: Chemistry, 1966. - T.1.

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Properties

Fine or finely crystalline powder of dark brown or black color. Does not dissolve in water. Decomposes when heated above +105 °C. Toxic.

Chemically, the reagent is very stable and is considered the most stable oxygen-containing manganese compound. Under normal conditions, it reacts weakly. Exhibits amphoteric properties, i.e. forms both acids and alkalis. It can act as a reducing agent, but more often as a strong oxidizing agent. Reacts with strong inorganic and organic acids, such as sulfuric, hydrochloric, nitric, oxalic to form salts: sulfates, chlorides, nitrates, oxalates. When reacting with hydrochloric acid, chlorine is released. With nitric and sulfuric acids - oxygen. Interacts with strong oxidizing agents. In reactions with alkalis it forms salts of manganese (H2MnO3) acid - manganites.


		Manganese dioxide 91% EDM

This is interesting

Humanity has been using the substance almost since its inception. Archaeologists have found that the cave paintings from the Lascaux cave (France) were made precisely with manganese dioxide. These drawings, according to radiocarbon dating, are from 17 to 19 thousand years old.
There is even more ancient evidence. Pieces of black stone, which is manganese dioxide, were found in the Pech-de-Laze cave (France). These stones appear to have been used by Neanderthals to start or maintain fires about half a million years ago.

Precautionary measures

Refers to class 2 hazard to human health. May be ingested by inhalation of dust aerosol. Causes irritation upon contact with skin. If swallowed or inhaled, accumulates in the body. A high dose of the reagent entering the body has a negative effect on the respiratory system, central nervous and cardiovascular systems. According to the safety rules established by GOST, when working with manganese dioxide, you should use special clothing, rubber gloves and “Petal” type respirators with a dust filter, and safety glasses. The concentration of the reagent in the air of the work area should be regularly checked. The room itself must be equipped with forced ventilation.

Manganese dioxide is stored and transported in moisture-resistant bags, impregnated paper or plastic, as well as in steel containers and cardboard-wound drums. Stored in covered warehouses.

Application

general review

Manganese is an element VIIB of the IV period subgroup. The electronic structure of the atom is 1s 2 2s 2 2p 6 3s 2 3p 6 3d 5 4s 2, the most characteristic oxidation states in compounds are from +2 to +7.

Manganese is a fairly common element, making up 0.1% (mass fraction) of the earth's crust. Found in nature only in the form of compounds, the main minerals are pyrolusite (manganese dioxide MnO2.), gauskanite Mn3O4 and brownite Mn2O3.

Physical properties

Manganese is a silvery-white, hard, brittle metal. Its density is 7.44 g/cm 3, melting point is 1245 o C. Four crystalline modifications of manganese are known.

Chemical properties

Manganese is an active metal; in a number of voltages it is between aluminum and zinc. In air, manganese is covered with a thin oxide film, which protects it from further oxidation even when heated. In a finely crushed state, manganese oxidizes easily.

3Mn + 2O 2 = Mn 3 O 4– when calcined in air

Water at room temperature acts on manganese very slowly, but when heated it acts faster:

Mn + H 2 O = Mn(OH) 2 + H 2

It dissolves in dilute hydrochloric and nitric acids, as well as in hot sulfuric acid (in cold H2SO4 it is practically insoluble):

Mn + 2HCl = MnCl 2 + H 2 Mn + H 2 SO 4 = MnSO 4 + H 2

Receipt

Manganese is obtained from:

1. electrolysis of solution MnSO 4. In the electrolytic method, the ore is reduced and then dissolved in a mixture of sulfuric acid and ammonium sulfate. The resulting solution is subjected to electrolysis.

2. reduction from its oxides with silicon in electric furnaces.

Application

Manganese is used:

1. in the production of alloy steels. Manganese steel, containing up to 15% manganese, has high hardness and strength.

2. manganese is part of a number of magnesium-based alloys; it increases their resistance to corrosion.

Magrane oxides

Manganese forms four simple oxides - MnO, Mn2O3, MnO2 And Mn2O7 and mixed oxide Mn3O4. The first two oxides have basic properties, manganese dioxide MnO2 is amphoteric, and the higher oxide Mn2O7 is permanganic acid anhydride HMnO4. Manganese(IV) derivatives are also known, but the corresponding oxide MnO3 not received.

Manganese(II) compounds

Oxidation state +2 corresponds to manganese (II) oxide MnO, manganese hydroxide Mn(OH) 2 and manganese(II) salts.

Manganese(II) oxide is obtained in the form of a green powder by reducing other manganese oxides with hydrogen:

MnO 2 + H 2 = MnO + H 2 O

or during thermal decomposition of manganese oxalate or carbonate without air access:

MnC 2 O 4 = MnO + CO + CO 2 MnCO 3 = MnO + CO 2

When alkalis act on solutions of manganese (II) salts, a white precipitate of manganese hydroxide Mn(OH)2 precipitates:

MnCl 2 + NaOH = Mn(OH) 2 + 2NaCl

In air it quickly darkens, oxidizing into brown manganese(IV) hydroxide Mn(OH)4:

2Mn(OH) 2 + O 2 + 2H 2 O =2 Mn(OH) 4

Manganese (II) oxide and hydroxide exhibit basic properties and are easily soluble in acids:

Mn(OH)2 + 2HCl = MnCl 2 + 2H 2 O

Manganese (II) salts are formed when manganese is dissolved in dilute acids:

Mn + H 2 SO 4 = MnSO 4 + H 2- when heated

or by the action of acids on various natural manganese compounds, for example:

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

In solid form, manganese (II) salts are pink in color; solutions of these salts are almost colorless.

When interacting with oxidizing agents, all manganese (II) compounds exhibit reducing properties.

Manganese(IV) compounds

The most stable manganese(IV) compound is dark brown manganese dioxide. MnO2. It is easily formed both during the oxidation of lower and during the reduction of higher manganese compounds.

MnO2- an amphoteric oxide, but both acidic and basic properties are very weakly expressed.

In an acidic environment, manganese dioxide is a strong oxidizing agent. When heated with concentrated acids, the following reactions occur:

2MnO 2 + 2H 2 SO 4 = 2MnSO 4 + O 2 + 2H 2 O MnO 2 + 4HCl = MnCl 2 + Cl 2 + 2H 2 O

Moreover, in the first stage in the second reaction, unstable manganese (IV) chloride is first formed, which then decomposes:

MnCl 4 = MnCl 2 + Cl 2

When fusion MnO2 Manganites are obtained with alkalis or basic oxides, for example:

MnO 2 +2KOH = K 2 MnO 3 + H 2 O

When interacting MnO2 with concentrated sulfuric acid manganese sulfate is formed MnSO4 and oxygen is released:

2Mn(OH) 4 + 2H2SO 4 = 2MnSO 4 + O 2 + 6H 2 O

Interaction MnO2 with stronger oxidizing agents leads to the formation of manganese (VI) and (VII) compounds, for example, when fused with potassium chlorate, potassium manganate is formed:

3MnO 2 + KClO 3 + 6KOH = 3K2MnO 4 + KCl + 3H 2 O

and when exposed to polonium dioxide in the presence of nitric acid - manganese acid:

2MnO 2 + 3PoO 2 + 6HNO 3 = 2HMnO 4 + 3Po(NO 3) 2 + 2H 2 O

Applications of MnO 2

As an oxidizing agent MnO2 used in the production of chlorine from hydrochloric acid and in dry galvanic cells.

Manganese(VI) and (VII) compounds

When manganese dioxide is fused with potassium carbonate and nitrate, a green alloy is obtained, from which dark green crystals of potassium manganate can be isolated K2MnO4- salts of very unstable permanganic acid H2MnO4:

MnO 2 + KNO 3 + K 2 CO 3 = K 2 MnO 4 + KNO 2 + CO 2

in an aqueous solution, manganates spontaneously transform into salts of manganese acid HMnO4 (permanganates) with the simultaneous formation of manganese dioxide:

3K 2 MnO 4 + H 2 O = 2KMnO 4 + MnO 2 + 4KOH

in this case, the color of the solution changes from green to crimson and a dark brown precipitate is formed. In the presence of alkali, manganates are stable; in an acidic environment, the transition of manganate to permanganate occurs very quickly.

When strong oxidizing agents (for example, chlorine) act on a manganate solution, the latter is completely converted into permanganate:

2K 2 MnO 4 + Cl 2 = 2KMnO 4 + 2KCl

Potassium permanganate KMnO4- the most famous salt of permanganic acid. It appears as dark purple crystals, moderately soluble in water. Like all manganese (VII) compounds, potassium permanganate is a strong oxidizing agent. It easily oxidizes many organic substances, converts iron(II) salts into iron(III) salts, oxidizes sulfurous acid into sulfuric acid, releases chlorine from hydrochloric acid, etc.

In redox reactions KMnO4(and he MnO4-)can be restored to varying degrees. Depending on the pH of the medium, the reduction product may be an ion Mn 2+(in an acidic environment), MnO2(in a neutral or slightly alkaline environment) or ion MnO4 2-(in a highly alkaline environment), for example:

KMnO4 + KNO 2 + KOH = K 2 MnO 4 + KNO 3 + H 2 O- in a highly alkaline environment 2KMnO 4 + 3KNO 2 + H 2 O = 2MnO 2 + 3KNO 3 + 2KOH– in neutral or slightly alkaline 2KMnO 4 + 5KNO 2 + 3H 2 SO 4 = 2MnSO 4 + K 2 SO 4 + 5KNO 3 + 3H 2 O– in an acidic environment

When heated in dry form, potassium permanganate already at a temperature of about 200 o C decomposes according to the equation:

2KMnO 4 = K 2 MnO 4 + MnO 2 + O 2

Free permanganate acid corresponding to permanganates HMnO4 has not been obtained in the anhydrous state and is known only in solution. The concentration of its solution can be increased to 20%. HMnO4- a very strong acid, completely dissociated into ions in an aqueous solution.

Manganese (VII) oxide, or manganese anhydride, Mn2O7 can be prepared by the action of concentrated sulfuric acid on potassium permanganate: 2KMnO 4 + H 2 SO 4 = Mn 2 O 7 + K 2 SO 4 + H 2 O

Manganese anhydride is a greenish-brown oily liquid. It is very unstable: when heated or in contact with flammable substances, it explodes into manganese dioxide and oxygen.

As an energetic oxidizing agent, potassium permanganate is widely used in chemical laboratories and industries; it also serves as a disinfectant. The thermal decomposition reaction of potassium permanganate is used in the laboratory to produce oxygen.

Manganese(II) oxide- MnO - lower manganese oxide, monoxide.

Basic oxide. Insoluble in water. Easily oxidizes to form a brittle MnO 2 shell. Reduced to manganese when heated with hydrogen or active metals.

Manganese(II) oxide can be obtained by calcination of oxygen-containing manganese(II) salts at a temperature of 300 °C in an inert gas atmosphere. From the common MnO 2 it is obtained through partial reduction at temperatures of 700-900 ° C with hydrogen or carbon monoxide.

Manganese(II) hydroxide- inorganic compound, manganese metal hydroxide with the formula Mn(OH) 2, light pink crystals, insoluble in water. Shows weak basic properties. Oxidizes in air.

Manganese (II) hydroxide is formed by the interaction of its salts with alkalis:

Chemical properties.

· Manganese (II) hydroxide is easily oxidized in air to brown manganese oxohydroxide, which further decomposes into manganese (IV) oxide:

· Manganese (II) hydroxide has basic properties. It reacts with acids and acid oxides:

· Manganese (II) hydroxide has reducing properties. In the presence of strong oxidizing agents, it can oxidize to permanganate:

Manganese(III) oxide- an inorganic compound, manganese metal oxide with the formula Mn 2 O 3, brown-black crystals, insoluble in water.

Receipt.

· The minerals braunite, kurnakite and bixbyite are found in nature - manganese oxide with various impurities.

· Oxidation of manganese(II) oxide:

Reduction of manganese(IV) oxide:

Chemical properties.

· Decomposes when heated:

· When dissolved in acids, it disproportionates:

· When fused with metal oxides, it forms manganite salts:

Does not dissolve in water.

Manganese(III) hydroxide –Mn2O3ּ H 2 O or MnО(OH) occurs naturally as a mineral manganita(brown manganese ore). Artificially produced manganese (III) hydroxide is used as a black-brown paint.

When interacting with acidic oxidizing agents, it forms manganese salts.

Manganese (II) salts, as a rule, are highly soluble in water, except for Mn 3 (PO 4) 2, MnS, MnCO 3.

Manganese sulfate(II) MnSO 4 is a white salt, one of the most stable compounds of manganese (II). It occurs in nature in the form of crystalline hydrate MnSO 4 7H 2 O. It is used in dyeing fabrics, and also, along with manganese (II) chloride MnCl 2, to produce other manganese compounds.

Manganese carbonate(II) MnCO 3 occurs in nature in the form of manganese pshat and is used in metallurgy.

Manganese nitrate(II) Mn(NO 3) 2 is obtained only artificially and is used for the separation of rare earth metals.

Manganese salts are catalysts for oxidative processes involving oxygen. They are used in driers. Flaxseed oil with the addition of such a drying agent is called drying oil.

Manganese(IV) oxide (manganese dioxide) MnO 2 is a dark brown powder, insoluble in water. The most stable compound of manganese, widespread in the earth's crust (mineral pyrolusite).

Chemical properties.

Under normal conditions it behaves quite inertly. When heated with acids, it exhibits oxidizing properties, for example, it oxidizes concentrated hydrochloric acid to chlorine:

With sulfuric and nitric acids, MnO 2 decomposes with the release of oxygen:

When interacting with strong oxidizing agents, manganese dioxide is oxidized to Mn 7+ and Mn 6+ compounds:

Manganese dioxide exhibits amphoteric properties. Thus, when a sulfuric acid solution of MnSO 4 salt is oxidized with potassium permanganate in the presence of sulfuric acid, a black precipitate of Mn(SO 4) 2 salt is formed.

And when fused with alkalis and basic oxides, MnO 2 acts as an acidic oxide, forming salts - manganites:

Is a catalyst for the decomposition of hydrogen peroxide:

Receipt.

In laboratory conditions it is obtained by thermal decomposition of potassium permanganate:

It can also be prepared by reacting potassium permanganate with hydrogen peroxide. In practice, the resulting MnO 2 catalytically decomposes hydrogen peroxide, as a result of which the reaction does not proceed to completion.

At temperatures above 100 °C, reduction of potassium permanganate with hydrogen:

64. Manganese (VI) compounds, methods of preparation and properties. Manganese (VII) oxide, permanganic acid and permanganates - preparation, properties, application.

Manganese(VI) oxide- an inorganic compound, manganese metal oxide with the formula MnO 3, a dark red amorphous substance, reacts with water.

Formed by the condensation of violet vapors released when heating a solution of potassium permanganate in sulfuric acid:

Chemical properties.

· Decomposes when heated:

Reacts with water:

With alkalis it forms salts - manganates:

Manganese(VI) hydroxide exhibits an acidic character. Free manganese (VI) acid is unstable and disproportionates in an aqueous solution according to the following scheme:

3H 2 MnO 4 (c) → 2HMnO 4 (c) + MnO 2 (s) + 2H 2 O (l).

Manganates (VI) are formed by the fusion of manganese dioxide with alkali in the presence of oxidizing agents and have an emerald green color. In a strongly alkaline environment, manganates (VI) are quite stable. When diluting alkaline solutions, hydrolysis occurs, accompanied by disproportionation:

3K 2 MnO 4 (c) + 2H 2 O (l) → 2KMnO 4 (c) + MnO 2 (s) + 4KOH (c).

Manganates (VI) are strong oxidizing agents that are reduced in an acidic environment to Mn(II), and in neutral and alkaline environments – up to MnO2. Under the influence of strong oxidizing agents, manganates (VI) can be oxidized to Mn(VII):

2K 2 MnO 4 (c) + Cl 2 (g) → 2KMnO 4 (c) + 2KCl (c).

When heated above 500 o C, manganate (VI) decomposes into products:

manganate (IV) and oxygen:

2K 2 MnO 4(t) → K 2 MnO 3(t) + O 2(g).

Manganese(VII) oxide Mn 2 O 7- greenish-brown oily liquid (t pl =5.9 °C), unstable at room temperature; a strong oxidizer, upon contact with flammable substances it ignites them, possibly with an explosion. Explodes from a push, from a bright flash of light, when interacting with organic substances. Manganese(VII) oxide Mn 2 O 7 can be obtained by the action of concentrated sulfuric acid on potassium permanganate:

The resulting manganese(VII) oxide is unstable and decomposes into manganese(IV) oxide and oxygen:

At the same time, ozone is released:

Manganese(VII) oxide reacts with water to form permanganic acid, which has a violet-red color:

It was not possible to obtain anhydrous permanganic acid; in solution it is stable up to a concentration of 20%. This very strong acid, the apparent degree of dissociation in a solution with a concentration of 0.1 mol/dm 3 is 93%.

Permanganic acid – strong oxidizing agent . Interacts even more energetically Mn2O7, flammable substances ignite upon contact with it.

Salts of permanganic acid are called permanganates . The most important of these is potassium permanganate, which is a very strong oxidizing agent. Its oxidizing properties towards organic and inorganic substances are often encountered in chemical practice.

The degree of reduction of permanganate ion depends on the nature of the medium:

1) acidic environment Mn(II) (Mn2+ salts)

MnO 4 - +8H + +5ē = Mn 2+ +4H 2 O, E 0 = +1.51 B

2) neutral environment Mn(IV) (manganese(IV) oxide)

MnO 4 - +2H 2 O+3ē=MnO 2 +4OH - ,E 0 = +1.23 B

3) alkaline environment Mn(VI) (manganates M 2 MnO 4)

MnO 4 - +ē =MnO 4 2-, E 0 = +0.56B

As can be seen, permanganates exhibit the strongest oxidizing properties in an acidic environment.

The formation of manganates occurs in a strongly alkaline solution, which suppresses hydrolysis K2MnO4. Since the reaction usually takes place in fairly dilute solutions, the final product of the reduction of permanganate in an alkaline environment, as in a neutral environment, is MnO 2 (see disproportionation).

At a temperature of about 250 o C, potassium permanganate decomposes according to the following scheme:

2KMnO 4(t) K 2 MnO 4(t) + MnO 2(t) + O 2(g)

Potassium permanganate is used as an antiseptic. Aqueous solutions of varying concentrations from 0.01 to 0.5% are used to disinfect wounds, gargle and other anti-inflammatory procedures. Successfully 2 - 5% solutions of potassium permanganate are used for skin burns (the skin dries out and a bubble does not form). For living organisms, permanganates are poisons (they cause protein coagulation). Their neutralization is carried out with a 3% solution H 2 O 2, acidified with acetic acid:

2KMnO 4 +5H 2 O 2 +6CH 3 COOH→2Mn(CH 3 COO) 2 +2CH 3 COOK +8H 2 O+ 5O 2

65. Rhenium compounds (II), (III), (VI). Rhenium (VII) compounds: oxide, rhenium acid, perrhenates.

Rhenium(II) oxide- an inorganic compound, rhenium metal oxide with the formula ReO, black crystals, insoluble in water, forms hydrates.

Rhenium oxide hydrate ReO H 2 O is formed when rhenium acid is reduced by cadmium in an acidic environment:

Rhenium(III) oxide- an inorganic compound, rhenium metal oxide with the formula Re 2 O 3, black powder, insoluble in water, forms hydrates.

Obtained by hydrolysis of rhenium(III) chloride in an alkaline medium:

Easily oxidizes in water:

Rhenium(VI) oxide- inorganic compound, rhenium metal oxide with the formula ReO 3, dark red crystals, insoluble in water.

Receipt.

· Rhenium(VII) oxide proportionation:

Reduction of rhenium(VII) oxide with carbon monoxide:

Chemical properties.

· Decomposes when heated:

· Oxidized with concentrated nitric acid:

Forms rhenites and perrhenates with alkali metal hydroxides:

· Oxidized by air oxygen:

Reduced by hydrogen:

Rhenium(VII) oxide- inorganic compound, rhenium metal oxide with the formula Re 2 O 7, light yellow hygroscopic crystals, dissolves in cold water, reacts with hot water.

Receipt.

Oxidation of rhenium metal:

· Decomposition when heating rhenium(IV) oxide:

Oxidation of rhenium(IV) oxide:

· Decomposition when heating rhenium acid:

Chemical properties.

· Decomposes when heated:

· Reacts with hot water:

Reacts with alkalis to form perrhenates:

· Is an oxidizing agent:

Reduced by hydrogen:

· Comportizes with rhenium:

Reacts with carbon monoxide:

Rhenic acid- inorganic compound, oxygen-containing acid with the formula HReO 4, exists only in aqueous solutions, forms salts perrhenates.

The transfer of rhenium from poorly soluble compounds, such as ReO and ReS2, into solution is carried out by acid decomposition or alkaline fusion with the formation of soluble perrhenates or rhenium acid. Conversely, the extraction of rhenium from solutions is carried out by precipitation in the form of poorly soluble perrhenates of potassium, cesium, thallium, etc. Ammonium perrhenate is of great industrial importance, from which metallic rhenium is obtained through reduction with hydrogen.

Rhenic acid is obtained by dissolving Re2O7 in water:

Re2O7 + H2O = 2HReO4.

Solutions of rhenium acid are also obtained by dissolving rhenium metal in hydrogen peroxide, bromine water and nitric acid. Excess peroxide is removed by boiling. Rhenic acid is obtained by the oxidation of lower oxides and sulfides from perrhenates using ion exchange and electrodialysis. For convenience, Table 2 shows the densities of rhenium acid solutions.

Rhenic acid is stable. Unlike perchloric and manganese acids, it has very weak oxidizing properties. Its recovery is usually slow. Metal amalgams and chemical agents are used as reducing agents.

Perrhenates are less soluble and thermally more stable than the corresponding perchlorates and permanganates.

Thallium, cesium, rubidium and potassium perrhenates have the lowest solubility.

Perrhenates Tl, Rb, Cs, K, Ag are poorly soluble substances, perrhenates, Ba, Pb (II) have average solubility, perrhenates Mg, Ca, Cu, Zn, Cd, etc. very soluble in water. As part of potassium and ammonium perrhenates, rhenium is isolated from industrial solutions.

Potassium perrhenate KReO4 – small colorless hexagonal crystals. It melts without decomposition at 555°; at higher temperatures it evaporates, partially dissociating. The solubility of the salt in an aqueous solution of rhenium acid is higher than in water, while in the presence of H2SO4 it remains virtually unchanged.

Ammonium perrhenate NH4ReO4 is obtained by neutralizing rhenium acid with ammonia. Relatively well soluble in water. When crystallizing from solutions, it forms continuous solid solutions with KReO4. When heated in air, it decomposes starting at 200°, giving a sublimate containing Re2O7 and a black residue of ReO2. When decomposed in an inert atmosphere, only rhenium (IV) oxide is formed according to the reaction:

2NH4ReO4 = 2ReO2 + N2 + 4H2O.

When a salt is reduced with hydrogen, a metal is obtained.

Among the salts of rhenium acid with organic bases, we note nitrone perrhenate C20H17N4ReO4, which has very low solubility in acetate solutions, especially in the presence of an excess of nitrone acetate. The formation of this salt is used to quantify rhenium.

Author: Chemical Encyclopedia I.L. Knunyants

MANGANESE OXIDES: MnO, Mn 2 O 3, MnO 2, Mn 3 O 4, Mn 2 O 7, Mn 5 O 8. Except for Mn 2 O 7, all oxides are crystals and are insoluble in water. When higher oxides are heated, O2 is split off and lower oxides are formed:

When exposed to air or in an O2 atmosphere above 300 °C, MnO and Mn2O3 are oxidized to MnO2.

Anhydrous and hydrated. Mn oxides are included in the composition of manganese and ferromanganese ores in the form of the minerals pyrolusite b -MnO 2, psilomelane mMO* nMnO 2 * xH 2 O [M = Ba, Ca, K, Mn(H)], manganite b -MnOOH (Mn 2 O 3 * H 2 O), groutite g-MnOOH, braunite 3Mn 2 O 3 * MnSiO 3, etc. with a MnO 2 content of 60-70%. Processing of manganese ores includes wet enrichment and subsequent chemical separation of oxides MnO 2 or Mn 2 O 3 by methods of sulfitization and sulfatization, carbonization, and reduction. roasting, etc.

Monoxide MnO (mineral manganosite). Hexagon is stable up to - 155.3 °C. modification, above - cubic (see table). Semiconductor. Antiferromagnet with Néel point 122 K; mag. susceptibility + 4.85* 10 - 3 (293 K). Has weakly basic properties; is reduced to Mn by hydrogen and active metals when heated. When MnO interacts with acids, Mn(II) salts are formed, with a melt of NaOH at 700-800°C and excess O 2 - Na 3 MnO 4, when exposed to (NH 4) 2 S - MnS sulfide. Obtained by the decomposition of Mn(OH) 2, Mn(C 2 O 4), Mn(NO 3) 2 or MnCO 3 in an inert atmosphere at 300 ° C, controlled by the reduction of MnO 2 or Mn 2 O 3 with hydrogen or CO at 700-900 ° WITH. Component of ferrites and other ceramics. materials, slag for metal desulfurization, microfertilizers, piperidine dehydrogenation catalyst, antiferromagnetic. material.

Sesquioxide Mn 2 O 3 exists in two modifications - rhombic. a (mineral kurnakite) and cubic. b (bixbyite mineral), transition temperature a : b 670 °C; paramagnetic, magnetic susceptibility +1.41 10 - 5 (293 K); is reduced by H 2 at 300°C to MnO, and by aluminum when heated to Mn.

Under the influence of dilute H 2 SO 4 and HNO 3, it turns into MnO 2 and Mn(II) salt. Mn 2 O 3 is obtained thermodynamically by the decomposition of MnOOH.

Manganese (II, III) oxide Mn 3 O 4 (hausmannite mineral); a -Mn 3 O 4 at 1160°C transforms into b -Mn 3 O 4 with cubic crystalline. grate; D H 0 transition a : b 20.9 kJ/mol; paramagnetic, magnetic susceptibility + 1.24* 10 - 5 (298 K). Exhibits chemical properties inherent in MnO and Mn 2 O 3 .

MnO 2 dioxide is the most common Mn compound in nature; The b-modification (mineral pyrolusite) is the most stable. Known rhombus. g -MnO 2 (mineral ramsdelite, or polyanite), as well as a, d and e, considered as solid solutions of various forms of MnO 2. Paramagnetic, magnetic susceptibility + 2.28* 10 - 3 (293 K). Mn dioxide - non-stoichiometric. compound, there is always a lack of oxygen in its lattice. Amphoteric. H2 is reduced to MnO at 170°C. When interacting with NH 3, H 2 O, N 2 and Mn 2 O 3 are formed. Under the influence of O 2 in the melt, NaOH gives Na 2 MnO 4, in a conc. acids - the corresponding salts of Mn(IV), H 2 O and O 2 (or Cl 2 in the case of hydrochloric acid). MnO 2 is obtained by the decomposition of Mn(NO 3) 2 or Mn(OH) 2 at 200°C in air, the reduction of KMnO 4 in a neutral environment, and the electrolysis of Mn(II) salts. Used for the production of Mn and its compounds, driers, as a depolarizer in dry elements, a component of brown pigment (umber) for paints, for glass brightening, as a reagent for the detection of Cl -, an oxidizing agent in hydrometallurgy of Zn, Cu, U, a catalyst component in hopcalite cartridges etc. Active MnO 2, obtained by the interaction of aqueous solutions of MnSO 4 and KMnO 4, is an oxidizing agent in organic chemistry.

Manganese (VII) oxide Mn 2 O 7 (dimanganese heptaoxide, manganese anhydride) - oily green liquid; melting point 5.9 °C; density 2.40 g/cm 3 ; D H 0 sample -726.3 kJ/mol. Above 50 °C, with slow heating, it begins to decompose with the release of O 2 and the formation of lower oxides, and at higher temperatures or high heating rates it explodes; extremely sensitive to mechanical and thermal influences. Strong oxidizing agent; upon contact with Mn 2 O 7, flammable substances ignite. MANGANESE OXIDESb. obtained by reacting KMnO 4 with H Z SO 4 in the cold.

Mn 5 O 8 oxide, or Mn 2 II (Mn IV O 4) 3, is a solid; insoluble in water; can be obtained by oxidation of MnO or Mn 3 O 4 ; easily decomposes into MnO 2 and O 2.

Of the Mn hydroxides, stoichiometric. compounds are only Mn(OH) 2 , MnO(OH) and HMnO 4 , others are hydrate. oxides of variable composition, similar in chemical properties to the corresponding oxides. The acidic properties of hydroxides increase with increasing degree of oxidation of Mn: Mn(OH) 2< MnО(ОН) (или Mn 2 O 3 * xH 2 O) < MnO 2 * xН 2 О < Mn 3 О 4 * xН 2 О < Н 2 MnО 4 < НMnО 4 . Гидроксид Мn(II) практически не растворим в воде (0,0002 г в 100 г при 18 °С); основание средней силы; растворим в растворах солей NH 4 ; на воздухе постепенно буреет в результате окисления до MnО 2 * xН 2 О.

Mn(III) hydroxide MnO(OH) is known in two modifications; at 250 °C in vacuum it is dehydrated to g-Mn 2 O 3; not soluble in water Nature manganite does not decompose with HNO 3 and diluted H 2 SO 4, but reacts slowly with H 2 SO 3, artificially obtained is easily decomposed by mineral acids; O 2 is oxidized to b-MnO 2. See also Manganates.

MANGANESE OXIDE. toxic; MPC see Art. Manganese.

Chemical encyclopedia. Volume 2 >>

What is manganese? Properties of manganese. Applications of manganese

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Analytical review

MANGANESE OXIDES

Manganese(II) oxide

Physical properties

Chemical properties

Geological properties

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Application

Manganese(II,III) oxide

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· The mineral occurs in nature hausmannite -- Mn3O4 with impurities.

Manganese(II,IV) oxide

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· Oxidation manganese(II) oxide or manganese(II,III) oxide:

Physical properties

Chemical properties

Manganese(III) oxide

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· Minerals found in nature braunite, kurnakite and bixbyite - manganese oxide with various impurities.

· Oxidation of manganese(II) oxide:

Reduction of manganese(IV) oxide:

Physical properties

Chemical properties

Manganese(IV) oxide

Chemical properties

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Manganese(VII) oxide

Manganese(VI) oxide

manganese dioxide production chemical

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· Formed by condensation of violet vapors released when the solution is heated potassium permanganate in sulfuric acid:

Physical properties

Patterns of changes in the properties of manganese oxides

methods for producing manganese dioxide

Example 1

Example 2

experimental part

Conclusion

Application

Manganese

Prevalence in nature

Literature

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Properties

Precautionary measures

Application

general review

Physical properties

Chemical properties

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Application

Magrane oxides

Manganese(II) compounds

Manganese(IV) compounds

Applications of MnO 2

Manganese(VI) and (VII) compounds