Metals are found in nature mainly in the form of compounds. Only metals with low chemical activity (noble metals) are found in nature in a free state (platinum metals, gold, copper, silver, mercury). Of the structural metals, only iron, aluminum, and magnesium are found in sufficient quantities in nature in the form of compounds. They form thick deposits of relatively rich ores. This makes them easier to harvest on a large scale.
Since the metals in the compounds are in an oxidized state (have a positive oxidation state), obtaining them in a free state comes down to a reduction process:
This process can be carried out chemically or electrochemically.
In chemical reduction, carbon or carbon (II) monoxide is most often used as a reducing agent, as well as hydrogen, active metals, and silicon. With the help of carbon monoxide (II), iron is produced (in the blast furnace process), many non-ferrous metals (tin, lead, zinc, etc.):
Hydrogen reduction is used, for example, to produce tungsten from tungsten(VI) oxide:
The use of hydrogen as a reducing agent ensures the highest purity of the resulting metal. Hydrogen is used to produce very pure iron, copper, nickel and other metals.
A method for producing metals in which metals are used as a reducing agent is called metallothermic . In this method, active metals are used as a reducing agent. Examples of metallothermic reactions:
aluminothermy:
Magniethermy:
Metallothermic experiments in the production of metals were first carried out by the Russian scientist N. N. Beketov in the 19th century.
Metals are most often obtained by the reduction of their oxides, which in turn are isolated from the corresponding natural ore. If the source ore is sulfide minerals, then the latter are subjected to oxidative roasting, for example:
Electrochemical production of metals is carried out by electrolysis of melts of the corresponding compounds. In this way, the most active metals, alkali and alkaline earth metals, aluminum, and magnesium are obtained.
Electrochemical reduction is also used for refining (purification) of “raw” metals (copper, nickel, zinc, etc.) obtained by other methods. During electrolytic refining, a “rough” (with impurities) metal is used as an anode, and a solution of compounds of this metal is used as an electrolyte.
Methods for producing metals carried out at high temperatures are called pyrometallurgical (in Greek pyr - fire). Many of these methods have been known since ancient times. At the turn of the XIX-XX centuries. begin to develop hydrometallurgical methods of obtaining metals (in Greek hydor - water). With these methods, the components of the ore are transferred into an aqueous solution and the metal is then isolated by electrolytic or chemical reduction. This is how copper is obtained, for example. Copper ore containing copper (II) oxide CuO is treated with dilute sulfuric acid:
To reduce copper, the resulting solution of copper (II) sulfate is either subjected to electrolysis or the solution is exposed to iron powder.
The hydrometallurgical method has a great future, as it makes it possible to obtain a product without extracting ore from the ground. (Compare the advantages of the hydrometallurgical method for obtaining metals with underground gasification of coal.)
In his daily life he is surrounded by various metals. Most of the items we use contain these chemicals. This all happened because people found various ways to obtain metals.
What are metals
Inorganic chemistry deals with these valuable substances for people. The production of metals allows man to create ever more advanced technology that improves our lives. What are they? Before you consider general methods To obtain metals, you need to figure out what they are. Metals are a group of chemical elements in the form of simple substances with characteristic properties:
Thermal and electrical conductivity;
High plasticity;
Shine.
A person can easily distinguish them from other substances. A characteristic feature of all metals is the presence of a special shine. It is obtained by reflecting the incident rays of light onto a surface that does not transmit them. Luster is a common property of all metals, but it is most pronounced in silver.
To date, scientists have discovered 96 such chemical elements, although not all of them are yet recognized by official science. They are divided into groups depending on their characteristic properties. The following metals are distinguished:
Alkaline - 6;
Alkaline earth - 6;
Transitional - 38;
Lungs - 11;
Semi-metals - 7;
Lanthanides - 14;
Actinoids - 14.
Obtaining metals
In order to make an alloy, you must first obtain the metal from natural ore. Native elements are those substances that are found in nature in a free state. These include platinum, gold, tin, and mercury. They are separated from impurities mechanically or using chemical reagents.
Other metals are extracted by processing their compounds. They are found in various fossils. Ore is minerals and rocks, which contain metal compounds in the form of oxides, carbonates or sulfides. To obtain them, chemical processing is used.
Reduction of oxides with coal;
Obtaining tin from tin stone;
Burning sulfur compounds in special furnaces.
To facilitate the extraction of metals from ore rocks, various substances called fluxes are added to them. They help remove unwanted impurities such as clay, limestone, sand. As a result of this process, low-melting compounds called slag are obtained.
If there is a significant amount of impurities, the ore is enriched before smelting the metal by removing most of the unnecessary components. The most widely used methods of this processing are flotation, magnetic and gravitational methods.
Alkali metals
Mass production of alkali metals is a more complex process. This is due to the fact that they occur in nature only in the form of chemical compounds. Since they are reducing agents, their production is accompanied by high energy costs. There are several ways to extract alkali metals:
Lithium can be obtained from its oxide in a vacuum or by electrolysis of a melt of its chloride formed during the processing of spodumene.
Sodium is obtained by calcining soda with coal in tightly closed crucibles or by electrolysis of a chloride melt with the addition of calcium. The first method is the most labor-intensive.
Potassium is obtained by electrolysis of a melt of its salts or by passing sodium vapor through its chloride. It is also formed by the interaction of molten potassium hydroxide and liquid sodium at a temperature of 440°C.
Cesium and rubidium are mined by reducing their chlorides with calcium at 700-800 °C or zirconium at 650 °C. Producing alkali metals in this way is extremely energy-intensive and expensive.
Differences between metals and alloys
There is practically no fundamentally clear boundary between metals and their alloys, since even the purest, simplest substances have some amount of impurities. So what is the difference between them? Almost all metals used in industry and other sectors of the national economy are used in the form of alloys, purposefully obtained by adding other components to the main chemical element.
Alloys
Equipment requires a variety of metal materials. At the same time clean chemical elements are practically not used because they do not have the properties necessary for people. For our needs, we have invented different methods for producing alloys. This term refers to a macroscopically homogeneous material that consists of 2 or more chemical elements. In this case, metal components predominate in the alloy. This substance has its own structure. The following components are distinguished in alloys:
A base consisting of one or more metals;
Small additions of modifying and alloying elements;
Unremoved impurities (technological, natural, accidental).
Metal alloys are the main structural materials. There are more than 5,000 of them in technology.
Despite such a variety of alloys, those based on iron and aluminum are of greatest importance to people. They are the ones that are most often encountered in everyday life. There are different types of alloys. Moreover, they are divided according to several criteria. Thus, various methods of producing alloys are used. According to this criterion they are divided into:
Cast, which are obtained by melt crystallization of mixed components.
Powder, created by pressing a mixture of powders and subsequent sintering at high temperature. Moreover, often the components of such alloys are not only simple chemical elements, but also their various compounds, such as titanium or tungsten carbides in hard alloys. Their addition in certain quantities changes the materials.
Methods for producing alloys in the form of a finished product or billet are divided into:
Foundry (silumin, cast iron);
Deformable (steel);
Powder (titanium, tungsten).
Alloy types
There are different methods for producing metals, and the materials produced through them have different properties. In the solid state of aggregation, alloys are:
Homogeneous (homogeneous), consisting of crystals of the same type. They are often called single-phase.
Heterogeneous (non-uniform), called multiphase. When producing them, a solid solution (matrix phase) is taken as the basis of the alloy. The composition of heterogeneous substances of this type depends on the composition of its chemical elements. Such alloys may contain the following components: solid solutions introduction and substitution, chemical compounds (carbides, intermetallic compounds, nitrides), crystallites of simple substances.
Properties of alloys
Regardless of what methods of producing metals and alloys are used, their properties are completely determined by the crystalline structure of the phases and the microstructure of these materials. Each of them is different. The macroscopic properties of alloys depend on their microstructure. In any case, they differ from the characteristics of their phases, which depend solely on the crystal structure of the material. Macroscopic homogeneity of heterogeneous (multiphase) alloys is obtained as a result of the uniform distribution of phases in the metal matrix.
The most important property of alloys is weldability. Otherwise they are identical to metals. Thus, alloys have thermal and electrical conductivity, ductility and reflectivity (brilliance).
Types of alloys
Various methods for producing alloys have allowed man to invent a large number of metal materials with different properties and characteristics. According to their purpose, they are divided into the following groups:
Structural (steel, duralumin, cast iron). This group also includes alloys with special properties. So they differ in intrinsic safety or anti-friction properties. These include brass and bronze.
For filling bearings (babbitt).
For electric heating and measuring equipment (nichrome, manganin).
For the production of cutting tools (will win).
In production, people also use other types of metal materials, such as fusible, heat-resistant, corrosion-resistant and amorphous alloys. Magnets and thermoelectrics (telurides and selenides of bismuth, lead, antimony and others) are also widely used.
Iron alloys
Almost all the iron smelted on Earth is used for the production of simple and iron. It is also used in the production of cast iron. Iron alloys gained their popularity due to the fact that they have properties beneficial to humans. They were obtained by adding various components to a simple chemical element. So, despite the fact that various iron alloys are made on the basis of the same substance, steel and cast iron have different properties. Thanks to this, they find different areas of application. Most steels are harder than cast iron. Different methods for obtaining these metals make it possible to obtain different grades (grades) of these iron alloys.
Improving the properties of alloys
By fusing certain metals and other chemical elements, materials with improved characteristics can be obtained. For example, pure aluminum is 35 MPa. When producing an alloy of this metal with copper (1.6%), zinc (5.6%), magnesium (2.5%), this figure exceeds 500 MPa.
By combining different chemicals in different proportions, metallic materials with improved magnetic, thermal or electrical properties can be obtained. The main role in this process is played by the structure of the alloy, which is the distribution of its crystals and the type of bonds between atoms.
Steels and cast irons
These alloys are obtained by carbon (2%). When producing alloyed materials, nickel, chromium, and vanadium are added to them. All ordinary steels are divided into types:
Low-carbon (0.25% carbon) is used for the manufacture of various structures;
High carbon (more than 0.55%) is intended for the production of cutting tools.
Various grades of alloy steels are used in mechanical engineering and other products.
An alloy of iron and carbon, the percentage of which is 2-4%, is called cast iron. This material also contains silicon. Various products with good mechanical properties are cast from cast iron.
Non-ferrous metals
In addition to iron, other chemical elements are used to make various metal materials. As a result of their combination, non-ferrous alloys are obtained. In people's lives, materials based on:
Copper, called brass. They contain 5-45% zinc. If its content is 5-20%, then brass is called red, and if it is 20-36%, it is called yellow. There are alloys of copper with silicon, tin, beryllium, and aluminum. They are called bronzes. There are several types of such alloys.
Lead, which is ordinary solder (tertiary). In this alloy, 1 part of this chemical substance contains 2 parts of tin. In the production of bearings, Babbitt is used, which is an alloy of lead, tin, arsenic and antimony.
Aluminum, titanium, magnesium and beryllium, which are lightweight non-ferrous alloys with high strength and excellent mechanical properties.
Methods of obtaining
The main methods for producing metals and alloys:
Foundry, in which the solidification of various molten components occurs. To obtain alloys, pyrometallurgical and electrometallurgical methods for producing metals are used. In the first option, thermal energy obtained during fuel combustion is used to heat the raw material. The pyrometallurgical method produces steel in open-hearth furnaces and cast iron in blast furnaces. In the electrometallurgical method, raw materials are heated in induction or electric arc furnaces. In this case, the raw materials are melted very quickly.
Powder, in which powders of its components are used to make the alloy. Thanks to pressing, they are given a certain shape and then sintered in special ovens.
Technology of production of metals and alloys
The technology for the production of metals and their alloys is called metallurgy . Metallurgy is divided into ferrous - the production of iron and its alloys and non-ferrous - the production of other metals
The raw materials for obtaining metals are ores. Rudami are rocks that are technically possible and economically feasible to process to extract the metals they contain.
Typically, metal production occurs in two main stages:
Preliminary preparation of raw materials.
In the process of preliminary preparation of raw materials, an important stage is ore enrichment - removal of waste rock impurities (for example, quartz, feldspar, etc.). After enrichment, the content of the useful component in the ore increases.
To purify ore from waste rock, physical methods are used to separate mixtures of substances based on the differences in the properties of the components of the mixture. When beneficiating iron ore, magnetite (Fe 3 O 4) is separated from gangue using magnet.
Some ores can be enriched using the method flotation, based on the difference in wettability of the useful component of the ore and waste rock.
Many metals occur in nature as sulfide ores. Then, at the first stage, such raw materials are subjected to roasting. For example, when firing iron pyrites, iron (II) oxide is formed, which enters the next stage of production, and sulfur dioxide: 4FeS 2 + 11O 2 = 2Fe 2 O 3 + +8SO 2
2. Recovery of the metal itself from raw materials .
In the second stage, an oxidation-reduction reaction is carried out, as a result of which a metal is formed. Coal (coke), carbon monoxide (CO) and hydrogen are used as reducing agents. In some cases, reduction is carried out by electrolysis.
Methods for producing metals and alloys
Metals and alloys are obtained different ways. (from the Greek “pyro” - fire and metallurgy).
1. Pyrometallurgical method (from the Greek “pyro” - fire and metallurgy). In this way, the production of metals and alloys is based on the use of thermal energy, which is released during the combustion of fuel or the occurrence of chemical reactions in raw materials. During fuel combustion, thermal energy is released and CO is formed. Thermal energy is used to heat and melt raw materials, and CO is used to restore metals from their compounds (oxides). The pyrometallurgical method produces cast iron in blast furnaces, steel in open-hearth furnaces, etc.
2. Electrometallurgical method. In the electrometallurgical process, metals and alloys are produced in arc, induction and other types of electric furnaces. In electric furnaces, raw materials are heated to higher temperatures than in the pyrometallurgical process. The raw material melts very quickly.
3. Plasma method. The essence of plasma metallurgy is that at a temperature of 10,000 C, metal oxides are converted into plasma with a certain degree of ionization. Since the ionization energy of metal atoms is less than the ionization energy of oxygen atoms, in such a plasma the metal atoms are ionized, and the oxygen atoms remain neutral.
Metal ions are removed from the resulting mixture using a magnetic field. Plasma furnaces produce tungsten, molybdenum, synthesize titanium carbide, etc. This method is used to produce very high-quality metals and alloys.
4. Chemical-metallurgical method. This method combines chemical and metallurgical processes. Titanium is produced in this way: titanium tetrachloride (TiCI 4) is obtained from titanium ore, which is reduced with magnesium (Mg).
5. Hydrometallurgical method. With this method, metals are removed from ores, concentrates and production waste using solvents. Metals are then obtained from these solutions by electrolysis. This is how non-ferrous metals are produced and refined: copper, zinc, nickel, cobalt, chromium, silver, gold, etc.
The production of metals by the hydrometallurgical method consists of the following stages: preparation of ore for dissolution; dissolving ore and concentrate in a solvent; purification of the resulting solution from impurities harmful to electrolysis; electrolysis.
6. Powder metallurgy. This method combines processes that result in the production of powders of metals and non-metallic compounds, from which products (blanks, parts, etc.) are made by pressing (to give shape and size) followed by sintering.
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 (barium is obtained high purity)
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. Electrometallurgical method for obtaining metals - metal recovery electric shock(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, elect. 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, found in 1837 on 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 extraction of iron from iron ores. This marked the beginning of the Iron Age in the history of mankind, which replaced the Stone Age and Bronze Age. 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 science of industrial methods 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 that can be processed, 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 to clean up emissions, as well as Wastewater chemical production
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. 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 creating 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 their high cost and lack of practical application 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 certain substances.
In nature, chemical elements metals can be found both in free form (in the form of a simple substance) and in bound form (part of complex substances). In this regard, there are different methods and methods for obtaining metal; let’s consider the main ones.
Chemically low-active metals that are in the voltage series after hydrogen (for example, copper, mercury, gold, silver, platinum) are found on Earth in both free and bound forms. Metals in the voltage range up to hydrogen under natural conditions are usually found in a bound form. Metal compounds found in nature are also called minerals.
An accumulation of metal-containing minerals that are part of rocks and sedimentary rocks suitable for industrial processing are called ores..
If the metal is in a free form under natural conditions, then its production is reduced only to its separation with waste rock. In this case, well-known physical methods for separating mixtures are used.
In compounds, metals are in oxidized form and therefore reduction processes must be used to isolate them from ores. The extraction of metals from ores is carried out by the metallurgical industry or metallurgy. Moreover, depending on the method used for the recovery of metals from compounds, pyrometallurgy, hydrometallurgy and electrometallurgy are distinguished.
Pyrometallurgy covers methods for obtaining metals from ores using reduction reactions carried out at high temperatures.
The raw materials for the production of metals are mainly ores containing their oxides. Coal or CO (carbothermy), active metals (metallothermy), H2 (hydrogenothermy) and Si (siliconthermy) are used as a reducing agent.
ZnO + C = Zn + CO
Fe 2 O 3 + 3CO = 2Fe + 3CO 2
Cr 2 O 3 + 2Al = 2Cr + Al 2 O 3
Ca + 2CsCl = CaCl 2 + 2Cs
TiCl 4 + 2Mg = Ti + 2MgCl 2
MoO 3 + 3H 2 = Mo + 3H 2 O
WO 3 + 3H 2 = W + 3H 2 O
Carbon, used in the form of coke, at appropriate high temperatures can reduce almost any metal, even such an active one as alkali, alkaline earth, magnesium or aluminum. However, in practice, these metals are not obtained by carbothermy, since they form strong chemical compounds - carbides - with excess carbon.
Carbothermy usually produces metals such as Fe, Cu, Zn, Co, Ni, Mn, Cr. The carbides of these metals are fragile and easily decompose when heated.
Carbon(II)-oxide as a reducing agent is more effective than coke, since it is in a gaseous state and is able to provide a large area of contact of the reacting substances.
Using hydrogenothermy, the following metals are obtained - molybdenum, tungsten, rhenium. The advantage of this method is that it produces metals of high purity.
In metallothermy, one of the most active reducing agents is aluminum, which is explained by the high enthalpy of formation of its oxide
H(Al 2 O 3) = –1700 kJ/mol. Aluminum is used to produce metals such as chromium, iron, cobalt, and nickel.
It can even be used to obtain alkali and alkaline earth metals, since the enthalpies of formation of their oxides are significantly lower than H(Al 2 O 3). But, as a rule, these metals are obtained by other methods, since their oxides with Al 2 O 3 easily form aluminates:
3CaO + 2Al = Al 2 O 3 +3Ca
CaO + Al 2 O 3 = Ca(AlO 2) 2
summary equation
4 CaO + 2Al = Ca(AlO 2) 2 + 3Ca
If the ore contains metal sulfide, it is converted into oxide by oxidative roasting:
2ZnS + 3O 2 = 2ZnO + 2SO 2
4FeS 2 + 11O 2 = 2Fe 2 O 3 + 8SO 2
Carbonate ores are also pre-calcined for the same purpose:
ZnCO 3 = ZnO + CO 2
FeCO 3 = FeO + CO 2
Hydrometallurgy covers methods for obtaining metals from solutions of their salts. In this case, the metal compound included in the ore or feedstock is first transferred into solution using suitable reagents, and then this metal is extracted from this solution chemically.
For example, when copper ore containing copper(II)-oxide is treated with dilute sulfuric acid, copper goes into solution in the form of sulfate:
CuO + H 2 SO 4 = CuSO 4 + H 2 O
Then the copper is removed from the solution by displacement using iron powder:
CuSO 4 + Fe = Cu + FeSO 4
Au, Ag, Zn, Cd, Mo and other metals are obtained using a similar method.
4Au + O 2 + 8NaCN + 2H 2 O = 4Na + 4NaOH
2Na + Zn = Na 2 + 2Au
Electrometallurgy covers methods for producing metals by electrolysis of solutions or melts of their compounds:
2Al 2 O 3 = 4Al + 3O 2
2NaCl = 2Na + Cl2
2KCl = 2K + Cl 2
In this way, the most active metals are obtained, which, when reduced with hydrogen, coal, and aluminum, form chemical compounds with these substances.
Electrolysissolutions of salts, low-active metals are obtained, which are in the series of voltages after hydrogen:
CuCl 2 = Cu + Cl 2
Electrolysis of solutions is used to obtain low-active metals of high purity.
Navigation
- Solving combined problems based on quantitative characteristics of a substance
- Problem solving. The law of constancy of the composition of substances. Calculations using the concepts of “molar mass” and “chemical amount” of a substance
- Solving calculation problems based on quantitative characteristics of matter and stoichiometric laws
- Solving calculation problems based on the laws of the gas state of matter
- Electronic configuration of atoms. The structure of the electron shells of atoms of the first three periods
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