General methods of obtaining metals.

Methods for obtaining metals are usually divided into:

• pyrometallurgical (reduction at high temperatures);
• hydrometallurgical (reduction from salts in solutions);
• electrometallurgical (electrolysis of solution or melt);
• biometallurgical.

I. Pyrometallurgical method for obtaining metals.

1. Carbothermic method of obtaining metals − reduction of metals from oxides with coal or carbon monoxide

Me x O y + C = CO 2 + Me,

Me x O y + C = CO + Me,

Me x O y + CO = CO 2 + Me

For example,

ZnO+ C = CO + Zn

Fe 3 O 4 + 4CO = 4CO 2 + 3Fe

MgO + C = Mg + CO

2. Roasting of sulfides followed by reduction(if the metal is in the ore in the form of a salt or base, then the latter are first converted into oxide)

Stage 1 – Me x S y +O 2 = Me x O y +SO 2

Stage 2 − Me x O y + C = CO 2 + Me or Me x O y + CO = CO 2 + Me

For example,

2ZnS + 3O 2 = 2ZnO + 2SO 2

MgCO 3 = MgO + CO 2

3. Metallothermic method ( a method of producing metals in which metals are used as a reducing agent )

In this method, active metals are used as a reducing agent. Examples of metallothermic reactions:

A) Aluminothermy (in cases where it is impossible to reduce with coal or carbon monoxide due to the formation of carbide or hydride)

Me x O y + Al = Al 2 O 3 + Me

For example,

4SrO + 2Al = Sr(AlO 2) 2 + 3Sr

3MnO 2 + 4Al = 3Mn + 2Al 2 O 3

3BaO + 2Al = 3Ba + Al 2 O 3 (high purity barium is obtained)

Cr 2 O 3 + 2Al = 2Cr + Al 2 O 3

B) Magniethermy:

Me x O y + Mg = MgO + Me

TiCl 4 + 2Mg = Ti + 2MgCl 2

Metallothermic experiments in the production of metals were first carried out by the Russian scientist N. N. Beketov in the 19th century.

4. Hydrothermy − for the production of high purity metals

Me x O y + H 2 = H 2 O + Me

For example,

WO 3 + 3H 2 = W + 3H 2 O

MoO 3 + 3H 2 = Mo + 3H 2 O

II. Hydrometallurgical method for obtaining metals.

The hydrometallurgical method is based on the dissolution of a natural compound in order to obtain a solution of a salt of this metal and the displacement of this metal by a more active one. For example, the ore contains copper oxide and is dissolved in sulfuric acid:

CuO + H 2 SO 4 = CuSO 4 + H 2 O,

then carry out the substitution reaction:

CuSO 4 + Fe = FeSO 4 + Cu.

In this way, silver, zinc, molybdenum, gold, and vanadium are obtained.

If a metal oxide is required for reduction, then the oxide is first obtained during the processing process:

a) from sulfide – by firing in oxygen:

2ZnS + 3O 2 = 2ZnO + 2SO 2

b) from carbonate – by decomposition when heated:

CaCO 3 = CaO + CO 2

III. The electrometallurgical method of producing metals is the reduction of metals by electric current (electrolysis).

1. Alkali and alkaline earth metals obtained in industry by electrolysis molten salts (most often chlorides):

2NaCl – melt, elect. current → 2Na + Cl 2

CaCl 2 – melt, electric. current. → Ca + Cl 2

hydroxide melts:

4NaOH – melt, elect. current. → 4Na + O 2 + 2H 2 O (!!! used occasionally for Na)

2. Aluminum in industry it is obtained by electrolysis aluminum oxide melt in Na 3 AlF 6 cryolite (from bauxite):

2Al 2 O 3 – melt in cryolite, elect. current. → 4Al + 3O 2

3. Electrolysis of aqueous salt solutions use to obtain metals of intermediate activity and inactive:

2CuSO 4 +2H 2 O – solution, elect. current → 2Cu + O 2 + 2H 2 SO 4

Metals in nature.

Metals occur in nature in three forms.

1) Gold and platinum are found in free form; gold occurs in a dispersed state, and sometimes collects into large masses of nuggets. So in Australia in 1869 they found a block of gold weighing one hundred kilograms. Three years later, they discovered an even larger block weighing about two hundred and fifty kilograms. Our Russian nuggets are much smaller, and the most famous one, found in 1837 in the Southern Urals, weighed only about thirty-six kilograms. In the middle of the 17th century in Colombia, the Spaniards, panning for gold, found heavy silver metal along with it. This metal seemed as heavy as gold, and it could not be separated from gold by washing. Although it resembled silver, it was almost insoluble and stubbornly resisted smelting; it was considered an accidental harmful impurity or a deliberate counterfeit of precious gold. Therefore, the Spanish government ordered at the beginning of the 18th century to throw this harmful metal back into the river in front of witnesses. Platinum deposits are also located in the Urals. It is a massif of dunite (igneous rock consisting of iron and magnesium silicates with an admixture of iron ore). It contains inclusions of native platinum in the form of grains. In native form and in the form of compounds, silver, copper, mercury and tin can be found in nature.

2) All metals. Metals of medium and low activity, which are up to tin in the voltage series, are found in natural conditions only in the form of compounds - they form oxides and sulfides. Less commonly, they can be found in complex acid-metal compounds.

3) Chemically active elements are found either in the form of simple salts or in the form of polyelement compounds, which have a very complex chemical structure, but generally quite simply decompose into their components under a certain influence.

Most often, metals are found in nature in the form of salts of inorganic acids:

sylvinite chlorides KCl NaCl, rock salt NaCl;

nitrates – Chilean saltpeter NaNO 3;

sulfates - Glauber's salt Na 2 SO 4 10 H 2 O, gypsum CaSO 4 2H 2 O;

carbonates - chalk, marble, limestone CaCO 3, magnesite MgCO 3, dolomite CaCO 3 MgCO 3;

sulfides sulfur pyrite FeS 2, cinnabar HgS, zinc blende ZnS;

phosphates - phosphorites, apatites Ca 3 (PO 4) 2;

oxides - magnetic iron ore Fe 3 O 4, red iron ore Fe 2 O 3, brown iron ore containing various hydroxides of iron (III) Fe 2 O 3 H 2 O.

Back in the middle of the 2nd millennium BC. e. In Egypt, the production of iron from iron ores was mastered. This marked the beginning of the Iron Age in human history, which replaced the Stone and Bronze Ages. On the territory of our country, the beginning of the Iron Age dates back to the turn of the 2nd and 1st millennia BC. e.

Minerals and rocks containing metals and their compounds and suitable for the industrial production of metals are called ores.

The industry that deals with the extraction of metals from ores is called metallurgy. The same name is given to the science of industrial methods for obtaining metals from ores.

Metallurgy is divided into ferrous (production of iron and its alloys) and non-ferrous (production of other metals).

Most metals are found in nature as part of compounds in which the metals are in a positive oxidation state, which means that in order to obtain them in the form of a simple substance, it is necessary to carry out a reduction process.

But before restoring a natural metal compound, it is necessary to convert it into a form accessible for processing, for example, the oxide form, followed by the reduction of the metal.

3. Industrial methods for producing metals.

When developing technology for the production of chemicals, the laws of thermodynamics, kinetics, heat engineering, physical and chemical analysis, etc. are used. Naturally, economic conditions are also taken into account. If the reaction is reversible, apply Le Chatelier's principle:

If a system in equilibrium is influenced from the outside, then the equilibrium in the system will shift towards the reaction (direct or reverse) that leads to partial compensation of this influence.

Chemical methods are also used in the purification of emissions and wastewater from chemical industries.

There are several ways to obtain metals in industry. Their use depends on the chemical activity of the element obtained and the raw materials used. Some metals occur in nature in pure form, while others require complex technological procedures to isolate them. The extraction of some elements takes several hours, while others require many years of processing under special conditions. Common methods for obtaining metals can be divided into the following categories: reduction, roasting, electrolysis, decomposition.

There are also special methods for obtaining rare elements, which involve the creation of special conditions in the processing environment. This may include ionic decrystallization of the structural lattice or, conversely, a controlled polycrystallization process that allows the production of a specific isotope, radioactive irradiation and other non-standard exposure procedures. They are used quite rarely due to the high cost and lack of practical application of the selected elements. Therefore, let us dwell in more detail on the main industrial methods of producing metals. They are quite varied, but all are based on the use of chemical or physical properties of certain substances.

11.3. Chemical properties of metals

11.4.

Various types of naturally occurring minerals suitable for producing metals on an industrial scale are called ores.

All methods for extracting metals from ores are based on their recovery according to the equation

Men+ + n e → Me0,

where n is the valency of the metal.

Graphite, carbon monoxide (II) CO, hydrogen, active metals, electric current, etc. are used as reducing agents.

There are the following methods for obtaining metals from ores.

1) pyrometallurgical− carbothermic, metallothermic;

2) electrometallurgical;

3) hydrometallurgical.

Pyrometallurgical The method involves using high temperatures during the metal reduction process. Most often, these are reduction processes with more active metals: Al, Mg, Ca, Na, etc. (metallothermy), silicon (silicothermy), reduction with hydrogen, metal hydrides, etc.

Carbothermic method - reduction of metal oxides with carbon or carbon monoxide CO at high temperatures:

Cu2O + C→ 2Cu + CO

In blast furnaces, carbon oxide is used as a reducing agent.

Fe2 O3 + 3CO → 2Fe + 3CO2

In metallothermic method, more active metals at high temperatures (Al, Mg, Ca, etc.) are used as reducing agents. This method is used to obtain titanium, uranium, and vanadium:

TiCl4 + 2Mg → Ti + 2MgCl2

Not all metals can be obtained by reduction of carbon or carbon monoxide (II) CO. For example, the reaction Cr2 O3 + 3CO = 2Cr+3CO2, G ° = 274.6 kJ/mol, cannot occur even at fairly high temperatures, while aluminothermy is easily feasible.

Chemistry. Textbook allowance

11. GENERAL CHARACTERISTICS OF METALS

11.4. Methods for obtaining metals from ores

If aluminum is used as a reducing agent, then this method is called aluminothermy:

Cr2 O3 + 2Al→ 2Cr + 2Al2 O3

Some metals (for example, manganese) form carbides with carbon, so in this case, silicon is a more economical method.

catothermy:

MnO2 + Si T → Mn + SiO2

Reduction with hydrogen It is carried out, as a rule, when it is necessary to obtain a relatively pure metal. Hydrogen is used, for example, to obtain pure iron, tungsten from WO3, rhenium from

NH4 ReO4, osmium from (NH4 )2 OsCl6, etc.

Pyrometallurgy usually includes chlorine metallurgy. The essence of the method is the chlorination of raw materials in the presence of a reducing agent or without it and further processing of the resulting metal chlorides, for example:

TiO2 + C + 2Cl2 = TiCl4 + CO2

TiCl4 + 2Mg = Ti + 2MgCl2

The advantages of the chlorination method are: high speed of the process, complete use of raw materials, the ability to separate a large number of components due to the different volatility and thermal stability of chlorides.

Electrometallurgy– a technology based on the use of electrical energy for the recovery of metals.

Electrometallurgy includes processes for producing metals using electrothermal and electrolysis methods.

In the first case, electric current serves as a source of high temperatures (for example, steel smelting in electric furnaces); in the second, it is used for the direct isolation of metals from compounds.

Active metals such as K, Na, Ca, Mg, Al, etc. are obtained by electrolysis of melts of their compounds. For example, the electrolysis of molten sodium chloride produces sodium metal and chlorine gas:

molten salt NaCl, anode C (graphite):

(− ) K Na+ + e → Na0 − reduction,

(+) A 2Cl− − 2 e → Cl2 − oxidation.

Chemistry. Textbook allowance

11. GENERAL CHARACTERISTICS OF METALS

11.4. Methods for obtaining metals from ores

Producing aluminum is a complex process fraught with great difficulties. The main raw material - aluminum oxide Al2 O3 - does not conduct electric current and has a very high melting point (about 2,050 o C). Therefore, a molten mixture of cryolite Na3 AlF6 and aluminum oxide is subjected to electrolysis. A mixture containing about 10% wt. Al2 O3 melts at 960 o C and has electrical conductivity, density and viscosity that are most favorable for the process. To further improve these characteristics, additives AlF3, CaF2, MgF2 are added to the mixture. Thanks to this, electrolysis is possible at 950 o C.

The electrolyzer for smelting aluminum is an iron casing lined with refractory bricks on the inside. Its bottom (under), assembled from blocks of compressed coal, serves as a cathode. Anodes (one or more) are located on top: these are aluminum frames filled with coal briquettes. Electrolyzers are installed in series, each series consisting of 150 or more electrolyzers.

During electrolysis, aluminum is released at the cathode and oxygen at the anode. Aluminum, which has a higher density than the original melt, is collected at the bottom of the electrolyzer; from here he is periodically released. As the metal is released, new portions of aluminum oxide are added to the melt. The oxygen released during electrolysis interacts with the carbon of the anode, which burns out, forming CO and CO2.

Hydrometallurgy– a technology that produces metals from ores using aqueous solutions of special reagents (acids, alkalis, salts), which transform metals from an insoluble state in the ore to a water-soluble one. Next, the metal is isolated from aqueous solutions either by reducing it with a more active metal, or by electrolysis (if the metal is inactive), or by extraction with organic compounds.

For example, consider the production of copper:

CuO (s) + H 2SO 4 (l) = CuSO 4 (l) + H 2O (l)

Copper can be isolated from the resulting solution, for example, by reduction with iron:

CuSO4 + Fe = Cu + FeSO4

Ag, Au, Pb and other metals are separated from the waste rock contained in the ore using the hydrometallurgical method:

4Au + O2 + 8NaCN + 2H2 O = 4Na + 4NaOH

2Na + Zn = Na2 + 2Au

Chemistry. Textbook allowance

11. GENERAL CHARACTERISTICS OF METALS

11.4. Methods for obtaining metals from ores

A special place in hydrometallurgy is occupied by extraction - the extraction of a valuable component of a solution using a solvent that is immiscible with the solution. Currently, an entire branch of metallurgy has been created that uses various chemical extractants to separate metals from mixtures.

11.5. Obtaining metals of high purity

WITH By increasing the purity of metals, their characteristics significantly improve. They become more plastic, thermally and electrically conductive, more difficult to corrode, etc.

Obtaining high-purity metals is a very complex problem, which has not been solved for all metals. There are a number of cleaning methods, let's look at some of them.

At vacuum melting– the metal is melted in a vacuum, which allows you to get rid of a number of highly volatile and fusible impurities of various metals, non-metals, and gases. This method does not give a very high degree of metal purity.

Thermal decomposition of metal iodides used for purifying very refractory metals that form volatile compounds with iodine, such as zirconium, titanium, chromium, etc. The metal to be cleaned is placed in a crucible

And add iodine. When heated, the metal interacts with io-

house. In this case, a volatile metal iodide is formed (for example, TiJ4), which, in contact with a red-hot mesh of pure titanium, decomposes under the influence of high temperature, and purified titanium settles on it:

TiJ 4 1,300− 1,500 D С→ Ti + 2J 2

IN The result is pure metal, and the iodine is captured and returned to the process.

This method makes it possible to selectively isolate individual metals from their mixtures and obtain metals of a sufficiently high degree of purity.

Electrochemical refining based on the use of process

owls of electrolysis with a soluble anode, for example, when purifying blister copper from impurities.

IN copper sulfate solution CuSO is poured into the electrolytic bath 4 and install a massive anode made of blister copper, and a cathode made of refined copper in the form of a thin plate. During electrolysis, the copper of the anode passes

V solution and then reduced at the cathode:

CuSO4 solution, anode – blister copper, cathode – refined copper,

(+)A Cu0 – 2 e = Cu2+ (in solution),

(–)K Cu2+ + 2 e = Cu0 (remains on the cathode).

Chemistry. Textbook allowance

11.5. Obtaining high purity metals

Electrolysis is carried out at low speeds to ensure selective deposition of copper on the cathode, while impurities of other metals remain in the electrolyte solution.

Electrolysis is carried out until the anode is completely dissolved, and the cathode from a thin plate turns into a massive bar of pure refined copper.

Zone melting makes it possible to obtain metals of a very high degree of purity.

A metal ingot in the form of a rod placed in a crucible is moved at low speed (5−10 mm/h) through an electric furnace. In this case, a very small area of ​​the ingot located in the heating zone at the moment melts. As the crucible moves, the molten zone moves from one end of the ingot to the other.

The purification process is based on the fact that the solubility of impurities in the liquid phase is much higher than in the solid phase. As the ingot, and therefore the melt zone, moves slowly along the ingot, impurities are removed by the molten zone and moved to the end of the ingot.

By repeating the described process many times, a high-purity metal is obtained with impurities collected at one end of the ingot, which is cut off and subjected to further purification in order to more fully isolate the pure metal from them.

Test questions and assignments

1. What are the features of the electronic structure of atoms of metallic elements? What explains the relatively weak connection of the valence electrons of metal atoms with the nucleus?

2. Which elements are classified as metals in the periodic table of elements? How do their properties change by period, by group?

3. What determines the characteristic physical properties of metals? From

what do they depend on?

4. What is a metal bond? How is it accomplished?

5. What metals cannot be stored in air? Why? Write equations for the reactions of these metals with oxygen. What are the resulting compounds called?

6. Which metals are resistant to oxidation by atmospheric oxygen? Why?

7. What is the acid-base nature of metal oxides? How does it change in the period with an increase in the ordinal number of the element?

8. How does the nature of metal oxides depend on the oxidation state of the element forming these oxides?

9. Name methods for obtaining metals from ores.

Chemistry. Textbook allowance

11. GENERAL CHARACTERISTICS OF METALS

Test questions and assignments

10. What substances are used as metal reducing agents?

V pyrometallurgical method?

11. How does the degree of purity of a metal affect its physical properties?

12. Name the methods for obtaining pure metals and their features.

Competency student

know the classification of metals and their occurrence in nature; physical and chemical properties of metals; methods for obtaining metals from ores - pyrometallurgical, electrometallurgical, hydrometallurgical; methods for producing high purity metals;

be able to distinguish the features of the electronic structure of metals from non-metals; determine and explain the reason for changes in the chemical activity of metals by groups and periods of D.I. Mendeleev’s table; test experimentally the chemical activity of metals when they interact with acids, atmospheric oxygen and other oxidizing agents; explain the characteristic physical properties of metals in terms of metallic bonding; draw up equations of redox processes when producing metals by electrometallurgical, hydrometallurgical and other methods; explain the essence of the process of purifying metals using the electrolytic refining method and write down the equations of the corresponding chemical reactions.

Chemistry. Textbook allowance

How are metals obtained?

Pure metals from ores

With rare exceptions, metals are found in nature not in a pure, native state, but in the form of chemical compounds. These compounds arose during the history of the Earth due to the reactions of metals with other chemical elements. In most cases, the ores are oxides, sulfides or carbonates (Table 6). Metal-containing minerals in the earth's crust also contain undesirable mineral components, barren or vein rock. Therefore, using the methods of flotation, grinding, screening and agglomeration, the ore must first be brought to a state convenient for further metallurgical processing.

To extract pure metals from ores, they are subjected to appropriate chemical decomposition. As an example, let’s take an oxide, from which, through reduction, a crude contaminated material is first obtained, which is then processed through refining to pure or highly pure metal.

In metallurgical industries, either unoxidized ores are converted into metal oxides by heating in the presence of atmospheric oxygen and roasting, or the necessary metal compounds are removed from the ore by leaching with suitable solvents such as water, dilute acids, alkalis, salt solutions (hydrometallurgy).

The metal oxides can then be reduced with a substance that has a greater affinity for oxygen than the resulting material. These include, for example, carbon or its oxide at high temperatures (carbothermic method), aluminum (aluminothermy) or silicon (siliconthermy). These methods are united under the general concept of pyrometallurgy.

In electrometallurgy, a metal can be obtained electrolytically from a melt or an aqueous solution of its compound. Thermal decomposition of metal compounds is also known. The crude metal initially formed in all of the above methods is then purified by selective oxidation, electrolytic methods, evaporation and recondensation, or zone smelting.

Based on these principles, a wide variety of technological options for the production of metals have been developed. We will consider below those that are used to produce the most important metal materials.

Cast iron is a blast furnace product

For the production of cast iron, currently, mainly oxide ores are used in the form of agglomerate or pieces, which are reduced in blast furnaces using carbon or its oxide. The blast furnace (24) has a height of up to 40 m; at its widest point, the steam chamber, the diameter reaches from 3.5 to 10 m. Metal raw materials with additives (charge) and coke are poured into the furnace from the top platform in layers. Coke serves to carry out the chemical reduction reaction and at the same time helps to create the necessary temperature, which directly in the reaction zone, in the shoulders, reaches almost 2000 ° C. The air supplied to the furnace is preheated in air heaters (cowpers) to 800 °C, enters through a ring pipeline through nozzles (tuyeres) into the blast furnace and tends upward towards the flow of metal raw materials and coke. The loading mass is constantly replenished from the flue. During reduction, the metallurgical process produces liquid iron, which is carburized by the coke present, and slag. Liquid cast iron and slag are collected in the furnace, and, due to its low density, the slag floats on the metal. Slag is constantly removed from the furnace through slag tapholes, and cast iron is periodically, after 2-4 hours, taken through a taphole in the lower part of the furnace.

The blast furnace operates continuously for 10-15 years. From it, cast iron is produced containing 3.543% C, 1-3% Si, 0.5-1.5% Mn, 0.05-0.1% S and 0.05-0.1% P, as well as slag. This by-product is used in the production of gravel, small crushed stone, pavement material, cement, and slag wool. The fire-iron gas, which exits through the grate, heated to 300-400 °C, is supplied to heat the air heaters. Blast-furnace cast iron enters either an iron mixer and is further processed in liquid form at steel mills, or into a casting machine, which produces solid cast iron dies, which are then sent to steel mills or foundries.

From open hearth method to direct reduction

Iron-carbon alloys with a carbon content of less than 2% are called steel. Cast iron has a carbon content of more than 2.5%.

The essence of steel production is that by selective oxidation, part of the carbon and other undesirable elements are removed from blast furnace cast iron. An important process in steel production is therefore the so-called conversion of cast iron. This concept combines all the oxidation reactions of carbon and other iron satellites (silicon, manganese, phosphorus, sulfur) occurring inside a metallurgical furnace in the molten blast iron and scrap metal obtained there or introduced there. Flue gases and oxygen are mixed with the air required for oxidation.

All currently important methods of steel production can be classified as follows:

Steel production methods

Direct recovery

Forge methods

Converter method

In the open-hearth method, a metal charge (cast iron and scrap metal) in solid or liquid form is located in a tray-shaped hearth, along which a long torch heated to 1900 °C beats. This torch is formed during the combustion of generator gas in a stream of heated air (the principle of regenerative combustion). Open hearth furnaces operate for many months without interruption. Their capacity ranges from 10 to 600 tons of steel, which, depending on the size of the furnace and the features of the technology, is released from the furnace in the form of a finished melt after 5-20 hours. The oxygen necessary for converting cast iron into steel is present in the furnace in a chemically bound state in the form of carbon monoxide or metal oxides contained in the ore.

Steel production using electricity occurs most often in electric arc furnaces and less often in induction furnaces. Here the metal backfill is also located in a flat hearth. Electric arcs arise between the three graphite electrodes introduced from above and the metal charge. Electric arc furnaces operate for many months, and their capacity ranges from 5 to 100 tons of steel, the production of which requires from 4 to 10 hours.

In the converter (25) the metal charge is constantly in a liquid state. Oxygen comes either from air, which is blown from below through the melt (bottom blast), or in the form of pure oxygen through a small nozzle is pumped over the material (top, or oxygen blast). Due to the very intense oxidation reaction, the necessary heat is released during the process in the converter, so that there is no need to supply additional fuel. The capacity of such converters ranges from 5 to 100 tons, and the steel production time ranges from 20 to 60 minutes.

Most unalloyed steel is now produced using the open-hearth method. The earlier converter method (Thomas and Bessemer methods) also produces unalloyed steel, which, however, is enriched with nitrogen and is therefore of low quality. Modern methods of air or oxygen blasting make it possible to produce steels that are not inferior in quality to open-hearth steel. Methods using electricity make it possible to produce superior quality unalloyed steels, as well as low- and high-alloy steels. Appendix 3 allows you to get acquainted with classical and modern methods of steel production.

Finished steel is mostly cast in the form of ingots of round, square or rectangular cross-section, from which blanks (sheets, rods, profiles) are then produced on a rolling mill. A small portion of steel is processed directly in foundries into shaped steel castings (for example, machine parts).

The newest trend in steel production is the direct reduction of prepared iron ore with a reducing gas, bypassing blast furnace processes. In this case, sponge iron appears, the composition of which, unlike blast-furnace cast iron, is very close to steel.

In the GDR, unalloyed steels are produced mainly by the open-hearth method, and when producing alloyed ones, electric arc furnaces are used. The old converter method has practically lost its significance. Progressive methods of air and oxygen blasting have already found their application in the GDR and in the future they will play an increasingly important role in steel production.

Production of aluminum by electrolysis

Non-ferrous metals used in industry, such as aluminum, copper, magnesium, zinc, lead, due to the variety of ores containing them, are obtained in a variety of ways. However, each of them is based on one of the above principles for obtaining metals. Let's take a closer look at electrothermy using the example of aluminum production.

Aluminum is obtained from bauxite ore containing about 55-65% Al2O3, no more than 28% Fe2O3 and up to 24% SiO2. Crushed, dried and ground bauxite is converted into sodium aluminate. This is done either by exposing it to caustic soda under pressure 6-8 times greater than atmospheric pressure (Bauer's method), or by sintering with soda in rotary tube kilns (Lewieg's method). Aluminum hydroxide can be precipitated from an aluminate solution, which is then converted into pure alumina (Al2O3) in the same furnaces at 1300-1400°C. After dissolving the alumina thus obtained in salt (cryolite), the most important stage of the aluminum production process begins, electrolysis of the melt (26). In this case, slag aluminum falls to the bottom of the electrolysis cell, from which pure aluminum (up to 99-99.8% A1) is obtained by remelting. Another specific method of electrolysis leads to the production of ultra-pure aluminum (99.99% A1).

Lesson #26.

Topic: General methods of obtaining metals.

Objective of the lesson: repeat and systematize information about the main methods of obtaining metals in industry.

Tasks:

TRAINING

ensure the assimilation of concepts about the main methods of obtaining metals: pyrometallurgy, hydrometallurgy and electrometallurgy;

Consider and compare various methods for obtaining metals from natural raw materials.

Consider the essence of electrolysis, features of the electrolysis of electrolyte solutions.

Strengthen the ability to compose redox reactions.

DEVELOPING

develop the ability to think logically,

analyze, make generalizations and conclusions,

make comparisons;

EDUCATING

develop the ability to find the main thing,

promote the development of interest in learning.

Lesson type : combined.

Equipment and materials:

didactic handouts;

multimedia projector;

presentation.

Progress of the lesson.

I. Organizational stage.

Greetings. Checking readiness for the lesson.

II. Repetition of learned material.

Carrying out independent work.

III. Learning new material.

1. Metals in nature. Metallurgy.

Gold and platinum are found only in free form. Both in native form and in the form of compounds, silver, copper, mercury and tin can be found in nature. All other metals that are in the voltage series up toSn , are found in nature only in the form of compounds.

Among these connections:

chlorides (sylvin, halite, or rock salt, sylvinite);

nitrates (Chilean saltpeter);

sulfates (Glauber's salt, gypsum);

carbonates (chalk, marble, limestone; magnesite, dolomite);

silicates, including those containing aluminum - aluminosilicates (white clay, or kaolin, feldspars, mica);

sulfides (sulfur pyrites, cinnabar, zinc blende);

phosphates.

Minerals and rocks containing metals or their compounds and suitable for the industrial production of metals are called ores.

If ores contain compounds of two or more metals, then they are called polymetallic. For example, copper-molybdenum, lead-silver, etc.

Metallurgy is a branch of industry that deals with the extraction of metals from ores. The same name is given to the science of industrial methods for obtaining metals from ores.

2. General methods of obtaining metals.

1) Pyrometallurgy – recovery of metals from ores at high temperatures using reducing agents (carbon, carbon monoxide (II), hydrogen, metals - aluminum, magnesium).

Showing a video - producing copper from its oxide using a reducing agent - hydrogen.

Showing a video - producing lead from its oxide using a coal reducing agent.

Write the equation for this reaction.

Showing a video - producing chromium by aluminothermy.

Write the equation for this reaction.

2) Hydrometallurgy - reduction of less active metals by more active metals from solutions of their salts.

This is the production of metals, which takes place in two stages:

A natural compound is “dissolved” in a suitable reagent to produce a solution of a salt of that metal.

From the resulting solution, this metal is displaced by a more active metal or reduced by electrolysis.

For example, to obtain copper from ore containing copper (II) oxide CuO:

WITHuO+H 2 SO 4 = CuSO 4 +H 2 O

CuSO 4 + Fe = FeSO 4 + Cu

Silver, zinc, molybdenum, gold, uranium, etc. are obtained in the same way.

3) Electrometallurgy - These are methods of producing metals using electric current (electrolysis).

Let's remember what it is: electrolysis, electrolyte, electrode, cathode, anode, cations, anions.

In electrolysis, the oxidizing agent and reducing agent is electric current.

The processes of oxidation and reduction are separated in space; they occur not when particles come into contact with each other, but when they come into contact with the electrodes of an electrical circuit.

3. Electrolysis of aqueous solutions of electro-casting.

Cathodic processes in aqueous solutions of electrolytes: cations or water molecules accept electrons and are reduced.

1. Metal cations with a standard electrode potential greater than that of HYDROGEN are located in the voltage series after it: Cu 2+ ,Hg 2+ , Ag+, Pt 2+ , ..., to Pt 4+ . During electrolysis, they are almost completely reduced at the cathode and released as metal.

2H 2 O+2e - = H 2 +2OH -

2. Metal cations with a low standard electrode potential (metal cations of the beginning of the voltage range Li + ,Na + , K + , Rb + , ..., to Al 3+ inclusive). During electrolysis at the cathode, they are not reduced; instead, water molecules are reduced.

2H 2 O+2e - = H 2 +2OH -

3. Metal cations with a standard electrode potential less than that of HYDROGEN, but greater than that of aluminum (Mn 2+ , Zn 2+ , Cr 3+ , Fe 2+ , ..., to H). During electrolysis, these cations, characterized by average values ​​of electron-withdrawing ability, are reduced at the cathode simultaneously with water molecules.

Zn 2+ + 2e = Zn0

2H 2 O+2e - = H 2 +2OH -

Let's consider the electrolysis of a melt and a solution of sodium chloride.

Let's watch a video clip - electrolysis of a solution of copper (II) chloride.

Write the equation for this reaction.

IV. Reinforcing the material learned

View the video fragment (electronic appendix to the textbook) to paragraph 26

paragraph 26 p. 123 (tests)

V. Conclusion.

Let's summarize today's lesson.

Analysis of personal results (p. 123)

VI. Homework.

paragraph 26 pp. 122-123 task 1-3 (oral)

Individual task: 3 students (p. 123 task 7).

And in the form of various compounds. In a free state, there are metals in nature that are difficult to oxidize with atmospheric oxygen, for example, platinum, gold, silver, and much less commonly, mercury, copper, etc.

Native metals are usually found in small quantities as grains or inclusions in rocks. Occasionally there are also quite large pieces of metal - nuggets. Thus, the largest copper nugget found weighed 420 tons, silver - 13.5 tons, and gold - 112 kg.

Most metals in nature exist in a bound state in the form of various chemical natural compounds - minerals. Very often these are oxides, for example iron minerals: red iron ore, brown iron ore, magnetic iron ore Fe3O4. Often the minerals are sulfide compounds, for example lead luster PbS, zinc blende, or galena ZnS, cinnabar HgS.

Minerals are part of rocks and ores. Ores are natural formations containing minerals in which metals are found in quantities technologically and economically suitable for the production of metals in industry.

Based on the chemical composition of the mineral included in the ore, oxide, sulfide and other ores are distinguished.

Usually, before obtaining metals from ore, it is pre-enriched - waste rock, impurities, etc. are separated, resulting in the formation of a concentrate that serves as raw material for metallurgical production.

Metallurgy is the science of methods and processes for the production of metals from ores and other metal-containing products, the production of alloys and the processing of metals. The most important branch of heavy industry involved in the production of metals and alloys has the same name.

Depending on the method of obtaining metal from ore (concentrate), there are several types of metallurgical production.

Pyrometallurgy - methods of ore processing based on chemical reactions occurring at high temperatures (Greek pyros - fire).

Pyrometallurgical processes involve roasting, whereby metal compounds contained in ores, in particular sulfides, are converted into oxides, and sulfur is removed in the form of sulfur oxide (1V) SO2, for example:

2СuS + 3O2 = 2СuО + 2SO2

and smelting, in which the reduction of metals from their oxides occurs with the help of coal, hydrogen, carbon monoxide (P), a more active metal, for example:

2СuО + С = 2Сu + СO2

Сr2O3 + 2Аl = Аl2O3 + 2Сr

If aluminum is used as the reducing metal, the corresponding reduction process is called aluminothermy. This method of obtaining metals was proposed by the Russian scientist N. N. Beketov.

Nikolai Nikolaevich Beketov

Russian physical chemist. Contributed to the development of physical chemistry as an independent field of science. He discovered the chemical process of displacement of metals from solutions of their salts under the influence of other metals and hydrogen.

Hydrometallurgy- methods for obtaining metals based on chemical reactions occurring in solutions.

Hydrometallurgical processes include the stage of transferring insoluble metal compounds from ores into solutions, for example, copper, zinc and uranium salts are transferred into solution by the action of sulfuric acid, and molybdenum and tungsten compounds are transferred by treatment with a soda solution, followed by the reductive separation of metals from the resulting solutions using other metals or electric current.

Electrometallurgy- methods for producing metals based on electrolysis, i.e., the separation of metals from solutions or melts of their compounds by passing a direct electric current through them. This method is used mainly for the production of very active metals - alkali, alkaline earth and aluminum, as well as for the production of alloy steels. It was by this method that the English chemist G. Davy first obtained potassium, sodium, barium and calcium.

Humphry Davy

(1778-1829)

English chemist and physicist. One of the founders of electrochemistry. By electrolysis of salts and alkalis he obtained potassium, sodium, barium, calcium, amalgam (a solution of metal in mercury) of strontium and magnesium.

Microbiological methods for obtaining metals, which use the vital activity of certain types of bacteria, deserve great attention. For example, so-called thionic bacteria are capable of converting insoluble sulfides into soluble sulfates. In particular, this bacterial method is used to extract copper from its sulfide ores directly at their location. Next, the working solution enriched with copper(II) sulfate is supplied for hydrometallurgical processing.

1. Native metals.

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