The atomic mass of zinc. Interaction with water. and the structure of the atom

Zinc is a silvery-white metal that has been widely used in an alloy with copper (brass) since ancient times in Egypt, China, Greece and India. In the middle of the 18th century, the substance was isolated in its pure form. Zinc received its modern name only in the 1920s. In nature, it is represented by salts that are part of minerals. In this article, you will learn more about what zinc is and how it can be used.

general characteristics

Zinc is an element of a side subgroup of the 2nd group of the 4th period of the periodic table, with serial number 30. The atomic mass of zinc is 65.39. It owes its name to Paracelsus, in whose writings there are the words zinken and zincum, apparently derived from the word zinke, meaning a tooth. From here came the chemical formula of zinc - Zn. Being a very common element, zinc is found in the earth's crust in almost all water resources of the planet and in the lion's share of living organisms. To date, more than six dozen minerals of this substance are known. The bulk of zinc is mined in Bolivia, Australia, Kazakhstan and Iran.

Physical and chemical properties

Let's find out what zinc is in terms of science. This element is a brittle and ductile transition metal. When exposed to air, the silvery-white substance tarnishes. Zinc burns to form a white oxide. When a plate of this material is bent, a crackling sound can be heard due to the friction of the crystals. Zinc heated to 100-150 °C becomes very ductile.

Industrial use

Metallic zinc has found wide application in industry. With its help, gold and silver are mined by underground leaching. Zinc is also used to protect steel from corrosion (galvanizing and plating). In batteries and accumulators, this substance acts as a material for the negative electrodes.

Zinc plates are widely used in printing, mainly for printing illustrations. Brass is made from copper and zinc. Alloys of this substance with magnesium and aluminum are widely used in mechanical engineering. Zinc is introduced into the composition of solid solders to reduce their melting point. Its oxide is an antiseptic and anti-inflammatory agent, therefore it is popular in medicine. It is also used to produce paints - the so-called zinc white.

Zinc selenide, phosphide, sulfide and telluride are widely used semiconductors. In addition, phosphide is used as a poison for rodents, sulfide is used as a part of phosphors, and selenide is used in the manufacture of optical glasses.

Zinc in the body

The action of the macronutrient is due to the fact that it is part of a large number of enzymes. Thus, zinc plays an important role in the human body. Even in ancient Egypt, it was used to heal wounds. To date, scientists have proven that this macronutrient is directly involved in strengthening the immune system and maintaining normal hormonal levels, and also stabilizes growth.

In the human body, this chemical can be found in: muscle tissues, bones, kidneys, liver, blood cells, and even the retina of the eye. Zinc not only contributes to longevity, but also helps to maintain youth and get rid of signs of fatigue.

Today, even young people suffer from a lack of antioxidants, one of which is zinc. This has an extremely negative effect on female reproduction and the endocrine system. Girls who are deficient in zinc suffer from insufficient production of sex hormones and grow more than they should. They have excessively long limbs, a violation of the deposition of fat cells and the menstrual cycle, and external infantilism.

For men, zinc is also very important. It regulates the growth of the prostate gland, and is also responsible for the prevention of male infertility and prostate adenoma. In addition, this microelement activates the activity of sex hormones and spermatozoa.

In old age, a lack of zinc leads to hearing loss, the development of atherosclerosis and frequent infectious diseases. With sufficient use of this substance, memory, attention and other brain functions improve.

A huge amount of zinc is found in our hair. Therefore, problems with the hairline (brittleness, dullness, loss) are the first signal of its deficiency. Many people know that vitamin A is a guarantee of healthy nails, skin and hair. However, even its enhanced intake may be ineffective if you do not take zinc, which acts as an activator of vitamins E and A.

In addition, it allows you to get rid of acne, rheumatism, and infectious diseases of the oral cavity. Studies have shown that the high mortality of newborn boys may be caused by maternal zinc deficiency during pregnancy. This problem is exacerbated by the fact that women's need for this substance is much less than men's. For the same reason, preeclampsia and miscarriages are possible.

Due to its antioxidant and regenerative properties, this macronutrient has been used for over 5000 years to heal wounds and burns. It is still added to ointments, lotions and creams to this day.

Daily rate

The norm of zinc consumption was determined only in 1970. In men, it is 15 mg per day, and in women - 12 mg. However, many experts insist that these figures should be at least doubled. Statistics show that the majority of the world's population does not receive even the indicated amounts of macronutrients. In some cases, the dose of zinc is definitely worth increasing. These are: psychological stress, pregnancy and feeding, physical activity, vegetarianism.

It must also be borne in mind that with cortisone treatment, the use of contraceptives, and the abuse of too sweet and salty foods, the absorption of zinc decreases. But the use of magnesium and vitamin B6, on the contrary, increases the activity of this macronutrient. Therefore, magnesium and zinc are often presented in tandem in medicines.

Signs of deficiency

The lack of zinc in the body can be due to a number of reasons: insufficient intake from food, poor absorption, disorders in the thyroid gland, liver disease. In addition, the reason for the deficiency of this macronutrient may be an excess of proteins, phytin and selenium consumed with food. The cause of this problem and a decrease in the quality of life in general can also be moral and physical stress, an unstable lifestyle, stressful situations, and bad habits.

Overconsumption of zinc in the body occurs during inflammation and oncology. The reason is that in the treatment of these diseases, cell growth is activated, in which zinc plays an important role.

The lack of this macronutrient in the body is a rather serious problem. It can lead to problems like this:

Pathology of the gastrointestinal tract.
Sleep disturbances, fatigue, nervousness.
Tendency to alcohol dependence, depressive states.
Hyperactivity.
Loss of smell, appetite and taste sensations.
Decreased visual acuity.
Anemia.
Acne, dermatitis, eczema, psoriasis and other skin diseases.
Hair and nail damage.
The development of diabetes.
Delayed puberty, which can lead to prostate adenoma and impotence.
Pathologies during pregnancy or even infertility.
Weakened immunity and, as a result, allergic and respiratory diseases.
Premature aging.

As recent studies have shown, if there is a lack of zinc and taurine in the human body, then epilepsy may begin to develop.

Zinc is especially important for children, as a lack of it can lead to stunted growth. In some eastern countries, because of this reason, there are many people of dwarf growth.

Excess zinc

An overabundance of a macronutrient occurs when using more than two grams per day. If you take more than 200 g of zinc, it will cause vomiting. Long-term use of the substance in an amount of more than 100 grams per day leads to a deterioration in immunity and contributes to the development of stomach ulcers. Acute poisoning is accompanied by gag reflexes, diarrhea and the appearance of a specific taste in the mouth.

The cause of an excess of zinc can be taking medications that are not agreed with the doctor, metabolic disorders at the cellular level, working in hazardous industries, and even improper use of galvanized dishes.

Symptoms of the initial stages of poisoning with this macroelement are: pathologies of the skin, nails and hair, weakening of the immune system, stomach pain, disorders in the liver, pancreas and prostate. With more severe poisoning, pain in the lumbar region, increased heart rate and pain when urinating can occur. There is also a high probability of increasing the level of cholesterol in the vessels.

Positive is the fact that, according to many scientists, an overdose of zinc is practically impossible, since it does not have toxicity and cannot accumulate in tissues in the form of excess. This is especially true of the macronutrient contained in its natural form in food. But the lack of a substance in the diet of many people is indeed a serious problem.

Sources in food

It would seem that if zinc is found in foods almost everywhere, why do people have problems with a deficiency of this macronutrient. There are a number of nuances here. First, the amount of zinc in plant sources is extremely small. Secondly, macronutrients that enter the body with food are not always absorbed in full. And thirdly, culinary processing and cultivation on depleted soils (as applied to plants) can affect the decrease in the nutritional value of products. Therefore, before compiling a comprehensive diet, it is worth understanding what zinc is and how much it is in a particular product. Vegetarians should be especially careful.

By the way, in folk medicine there is a simple but effective remedy for replenishing zinc deficiency - an infusion of birch leaves.

Interaction of zinc with other substances

Zinc has both "enemies" and "helpers". The first category of substances includes: copper, iron, mercury and calcium. Zinc is poorly absorbed under the influence of: tannin, alcohol, anabolics, diuretics and contraceptives. Such an important substance for the body as fiber can reduce the effectiveness of zinc up to 80%. Here, again, it is worth being attentive to vegetarians who consume a lot of vegetables and fruits that contain fiber.

Zinc assistants include: vitamins of groups A, E, C and B6, fluorine and picolinic acid. By the way, a complex of zinc, manganese and vitamin B6 is used to prevent certain types of schizophrenia.

Zinc-based preparations

Having figured out what zinc is and how it is used, we will briefly consider in which medical preparations it is presented. Here it is immediately worth mentioning that it is highly undesirable to use medicines without consulting a doctor. Most often, patients are prescribed zinc solutions, powders, ointments (for example, Bureau Plus, Desitin, Glutamol, zinc ointment), as well as oxides and sulfates in the form of drops. Zinc-containing vitamins are also popular (Centrum, Selinitsink Plus, Zincteral, Zinkit). In addition, zinc suppositories are used to treat hemorrhoids, and tablets are used to combat baldness.

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Introduction

Atomic number 30

Atomic mass 65.409

Density, kg/m³ 7140

Melting point, °С 419.5

Boiling point, °С 906.2

Heat capacity, kJ/(kg °C) 0.383

Electronegativity 1.6

Covalent radius, E 1.25

1st ionization potential, ev 9.39

Zinc is an element of a secondary subgroup of the second group, the fourth period of the periodic system of chemical elements of D. I. Mendeleev, with atomic number 30. It is denoted by the symbol Zn (lat. Zincum). Under normal conditions, it is a brittle bluish-white transition metal (tarnishes in air, becoming covered with a thin layer of zinc oxide). During crystallization, it has a hexagonal lattice. The element has five stable isotopes with mass numbers 64, 66, 67, 68 and 70. The most common is 64Zn (48.89%).

Zinc is one of the metals widely used in various fields of the national economy, science, technology, and medicine.

The different uses of zinc account for:

galvanizing -- 45-60%

medicine (zinc oxide as an antiseptic) - 10%

alloy production -- 10%

production of rubber tires -- 10%

oil paints - 10%

it is also necessary for the vital activity of plants, animals and humans, since it is part of some enzymes and hormones.

1. History of discovery

The word "zinc" is found in the writings of Paracelsus and other researchers of the 16th-17th centuries. and goes back, perhaps, to the ancient German "zinc" - plaque, an eyesore. The name of this metal has changed several times in its history. The word "zinc" in Russia was introduced by M. V. Lomonosov in 1742.

When metallic zinc was first smelted is not precisely established, but historical documents indicate that it was obtained in India as early as the 5th century BC. BC. An alloy of zinc with copper - brass - was known in Ancient Greece, Ancient Egypt, India, China.

In the XVI century. the first attempts were made to smelt it in the factory. But the production "did not go." Technological difficulties proved insurmountable. They tried to obtain zinc in the same way as other metals - the ore was burned, turning zinc into oxide, then this oxide was reduced with coal. Zinc, of course, was reduced by interacting with coal, but was not smelted because this metal had already evaporated in the melting furnace - its boiling point was only 906 ° C. And there was air in the oven. Meeting him, active zinc vapor reacted with oxygen, and the original product, zinc oxide, was formed again.

It was possible to establish zinc production in Europe only after the ore began to be reduced in closed retorts without air access. Approximately the same "rough" zinc is obtained now, and it is purified by refining.

On an industrial scale, zinc smelting also began in the 18th century. In 1743, the first zinc plant, founded by William Champion, went into operation in Bristol, where zinc was obtained by distillation. The products quickly penetrated into Belgium and Silesia. In 1746, A. S. Marggraf in Germany developed a distillation method similar to Champion’s method for obtaining pure zinc by calcining a mixture of its oxide and coal without air in refractory clay retorts, followed by condensation of zinc vapor in refrigerators. Marggraf described his method in detail and thus laid the foundations for the theory of zinc production. Therefore, he is often called the discoverer of zinc.

2. Zinc deposits in nature

Zinc is present not only in rocks and soil, but also in air, water and the biosphere. The average content of zinc in the earth's crust is 8.3 10-3%, in the main igneous rocks it is slightly higher (1.3 10-2%) than in acidic ones (6 10-3%), in the water of the World ocean - 0.01 mg / l. Zinc, as one of the biogenic elements, is constantly present in the tissues of animals and plants. The average content of this metal in most living organisms of the planet is 5*10-4%.

Native zinc is not found in nature. Zinc occurs in ores mainly in the form of compounds. Compounds of this metal are part of polymetallic ores. Only after enrichment, zinc concentrates contain from 48 to 65% zinc, up to 12% iron, up to 2% copper, up to 2% lead, and, in addition, a fraction of a percent of scattered and rare metals.

The main minerals of zinc:

ZnS - sphalerite (zinc blende), contains 67.1% zinc, color - yellow, brown, black;

nZnS mFeS - marmatite, contains more than 60% zinc, brownish-black color;

ZnO - zincite, contains 80.3% zinc, dark red color;

ZnCO3 - smithsonite, contains 64.8% ZnO, white, gray, greenish color;

Zn2SiO4(2ZnO SiO2) - willemite, contains 73% ZnO, white, yellow, greenish color;

H2Zn2SiO5(2ZnO SiO2 H2 O) - calamine, contains 67.5% ZnO, white, yellow, color;

ZnSO4 - zincosite, contains 50.3% ZnO, is rare in nature;

ZnSO4 7H2O - goslarite, contains 28.2% ZnO, white or reddish color.

Zinc is actively transported by water flows, especially such migration of this metal is typical for thermal waters, where zinc is transported together with lead. Subsequently, zinc sulfides, which occupy an important place in industry, are precipitated from such streams.

Zinc ore deposits are widespread throughout the world. Zinc ores are mined in more than 50 countries.

China, Australia, Peru, Europe and Canada are the world's leading zinc producers.

In ores, zinc usually coexists with lead and other metals, including copper, gold, and silver.

The most common zinc mineral is sphalerite (ZnS), also known as zinc sphalerite, which is present in virtually all currently mined zinc deposits. Zinc ores located close to the earth's surface are often oxides and carbonates.

World reserves of zinc on Earth are about 1900 million tons, reserves (available for extraction) - about 250 million tons. The largest zinc reserves are in Australia (22.4% of the total) and China (17.2%).

Reserves at zinc deposits in 2010, thousand tons

Raw resources of Russia

Despite the fact that Russia's share in world zinc reserves is 14%, its share in the world production of this metal is much more modest and amounts to only about 3%. This is due to the insufficient development of existing deposits.

Approximately 82% of the reserves are located in the fields of the East Siberian and Ural regions, the other 18% - within the West Siberian, Far East and North Caucasus regions. The largest zinc deposits in Russia are: Kholodninskoye, Ozernoye, Korbalikhinskoye, Gayskoye, Uzelginskoye, Uchalinskoye and Nikolaevskoye.

About 80% of zinc deposits are underground, 8% are located on the surface, and the rest are of a combined type. However, in terms of production volume, 15% is mined from quarries, 64% of ore is produced from underground mines, and 21% of mining is combined mining.

Currently, only approximately 60% of the world's zinc consumed comes from mined ores, the remaining 40% is obtained from the processing of zinc-containing waste and metal scrap. The level of recycling in the world is increasing every year. In the world today, more than 90% of zinc-containing waste is collected and processed. Usually these are production waste, or buildings, structures, machines, equipment and household appliances that have served their time.

3. Physical properties

Zinc in its purest form is a fairly ductile silvery-white metal. It has a hexagonal lattice. It is brittle at room temperature, when the plate is bent crackling is heard from the friction of crystallites, in the cast state it is of little plasticity, but already at 100--150 ° C it is easily subjected to pressure treatment - pressing, stamping and deep drawing, rolled into thin sheets, foil about hundredths thick fractions of a millimeter, wire. With further heating (above 200 ° C), zinc becomes very brittle - up to thinning into a powder. Impurities, even minor ones, sharply increase the fragility of zinc.

Properties:

atomic radius of this element: -1.37E, ionic - Zn2 + -0.83E;

has a hexagonal lattice with parameters:

a = 0.26649 nm, c = 0.49468 nm;

density, g/cm3: in the solid state at 20°C - 7.1 - 7.2, in the liquid state at 450°C - 6.6;

temperature, melting, ° С: - 419.4, boiling - 905.4;

heat, kJ/kg: melting - 100.8, evaporation - 1.75;

heat capacity, J / (kg.K): in the solid state at 20 ° C -394, in the liquid state at 450 ° C -502;

thermal conductivity, W / (m.K): in the solid state at 20 ° C - 111, in the liquid state at 450 ° C - 60;

specific electrical conductivity, at 20°C, (MSm/m) -15.9;

electrical resistivity, μ Ohm.m: in the solid state at 20°C - 0.059, in the liquid state at 420°C - 0.354;

coefficient of linear expansion in the temperature range 20-200°C, K-1 -29.8.10-6

temperature coefficient of thermal conductivity, K-1 - 0D5.10-3

temperature coefficient of electrical resistance, K "1 - 4.17.10-3

magnetic characteristics - diamagnetic;

4. Chemical properties

The external electronic configuration of the Zn atom is 3d104s2. The oxidation state in compounds is +2. The normal redox potential of 0.76 V characterizes zinc as an active metal and an energetic reducing agent. In air at temperatures up to 100 ° C, zinc quickly tarnishes, becoming covered with a surface film of basic carbonates. In moist air, especially in the presence of CO2, metal is destroyed with the formation of basic zinc bicarbonate even at ordinary temperatures.

At a temperature of red heat, it can be oxidized by water vapor with the release of hydrogen and carbon dioxide. When heated sufficiently in air, it burns with a bright greenish-blue flame to form zinc oxide with a significant release of energy.

In accordance with the place occupied by zinc in the series of voltages, it readily dissolves in dilute acids with evolution of hydrogen. In this case, concentrated acid is reduced to nitrogen oxides, diluted acid is reduced to ammonia. Dissolution in conc. H3S04 is accompanied by the release of not hydrogen, but sulfur dioxide.

A mixture of zinc powder and sulfur reacts explosively when heated.

Zinc does not interact with nitrogen even in vapors, but rather easily reacts with ammonia at a red-hot temperature, forming zinc nitride - Zn3Na.

Zinc carbide ZnC, formed by heating zinc in a stream of acetylene, decomposed by water and dilute acids.

When metallic zinc is heated in phosphorus vapor to 440–780°C, phosphides, Zn3Ps and ZnP2, are formed.

In the molten state, zinc is infinitely miscible with many metals: Cu, Ag, Au, Cd, Hg, Ca, Mg, Mn, Fe, Co, Ni, Al, Sn.

Zinc forms compounds with many metals, for example: Cu, Ag, Au, Mn, Fe, Co, Ni, Pf, Pd, Rh, Sb, Mg, Ca, Li, Na, K.

Zinc is quite easily soluble in alkalis, as well as aqueous solutions of ammonia and ammonium chloride, especially when heated. The rate of dissolution of zinc not only in alkalis, but also in acids depends on its purity. Very pure zinc dissolves slowly, and to speed up the process, it is recommended to introduce a few drops of a highly dilute solution of copper sulfate into the solution (the appearance of galvanic couples).

Interaction with non-metals

When strongly heated in air, it burns with a bright bluish flame to form zinc oxide:

When ignited, it reacts vigorously with sulfur:

It reacts with halogens under normal conditions in the presence of water vapor as a catalyst:

Zn + Cl2 = ZnCl2

Under the action of phosphorus vapor on zinc, phosphides are formed:

Zn + 2P = ZnP2 or

3Zn + 2P = Zn3P2

Zinc does not interact with hydrogen, nitrogen, boron, silicon, carbon.

Interaction with water

Reacts with water vapor at red heat to form zinc oxide and hydrogen:

Zn + H2O = ZnO + H2

Interaction with acids

In the electrochemical series of voltages of metals, zinc is before hydrogen and displaces it from non-oxidizing acids:

Zn + 2HCl = ZnCl2 + H2

Zn + H2SO4 = ZnSO4 + H2

Reacts with dilute nitric acid to form zinc nitrate and ammonium nitrate:

4Zn + 10HNO3 = 4Zn(NO3)2 + NH4NO3 + 3H2O

Reacts with concentrated sulfuric and nitric acids to form a zinc salt and acid reduction products:

Zn + 2H2SO4 = ZnSO4 + SO2 + 2H2O

Zn + 4HNO3 = Zn(NO3)2 + 2NO2 + 2H2O

Interaction with alkalis

Reacts with alkali solutions to form hydroxo complexes:

Zn + 2NaOH + 2H2O = Na2 + H2

when fused, it forms zincates:

Zn + 2KOH = K2ZnO2 + H2

Interaction with ammonia

With gaseous ammonia at 550-600°C it forms zinc nitride:

3Zn + 2NH3 = Zn3N2 + 3H2

dissolves in an aqueous solution of ammonia, forming tetraamminzinc hydroxide:

Zn + 4NH3 + 2H2O = (OH)2 + H2

Interaction with oxides and salts

Zinc displaces metals in the stress row to the right of it from solutions of salts and oxides:

Zn + CuSO4 = Cu + ZnSO4

Zn + CuO = Cu + ZnO

5. Zinc compounds

Zinc oxide is the most important industrial zinc-containing compound. As a by-product of brass production, it was known before the metal itself. Zinc oxide is obtained by burning in air the vapors of zinc formed during the smelting of ore. A cleaner and whiter product is produced by burning vapors obtained from pre-purified zinc.

Usually zinc oxide is a white fine powder. When heated, its color changes to yellow as a result of the removal of oxygen from the crystal lattice. By adding a 0.02-0.03% excess of metallic zinc to zinc oxide, a whole range of colors can be obtained - yellow, green, brown, red, however, reddish shades of the natural form of zinc oxide - zincite - appear for a different reason: due to the presence manganese or iron. Zinc oxide ZnO is amphoteric; it dissolves in acids to form zinc salts and in alkalis to form hydroxozincates such as - and 2-.

The main industrial use of zinc oxide is in the manufacture of rubber, in which it shortens the cure time of the original rubber.

Zinc oxide increases the life of glass and is therefore used in the production of special glasses, enamels and glazes. Another important area of application is in the composition of neutralizing cosmetic pastes and pharmaceutical preparations.

Zinc hydroxide is formed as a gelatinous white precipitate when alkali is added to aqueous solutions of zinc salts. Zinc hydroxide, like oxide, is amphoteric:

Zn(OH)2 + 2OH- = 2-

Zinc sulfide is released as a white precipitate during the interaction of soluble sulfides and zinc salts in an aqueous solution. In an acidic environment, zinc sulfide does not precipitate. Hydrogen sulfide water precipitates zinc sulfide only in the presence of anions of weak acids, such as acetate ions, which reduce the acidity of the medium, which leads to an increase in the concentration of sulfide ions in the solution.

Sphalerite is the most common mineral of zinc and the main source of the metal, but a second natural, although much rarer, form, wurtzite, is also known, which is more stable at high temperatures. Pure zinc sulfide is white and, like zinc oxide, is used as a pigment; for this, it is often obtained together with barium sulfate by reacting aqueous solutions of zinc sulfate and barium sulfide.

Freshly precipitated zinc sulfide readily dissolves in mineral acids with the release of hydrogen sulfide:

ZnS + 2H3O+ = Zn2+ + H2S + 2H2O

However, baking makes it less reactive, and therefore it is a suitable pigment in children's toy paints, as it is harmless if swallowed. In addition, zinc sulfide has interesting optical properties. It turns gray when exposed to ultraviolet radiation.

Zinc chloride is one of the important zinc compounds in industry. It is obtained by the action of hydrochloric acid on secondary raw materials or burnt ore.

Concentrated aqueous solutions of zinc chloride dissolve starch, cellulose (therefore they cannot be filtered through paper) and silk. It is used in the production of textiles, in addition, it is used as a wood preservative and in the manufacture of parchment.

Since zinc chloride easily dissolves oxides of other metals in the melt, it is used in a number of metallurgical fluxes. Using a zinc chloride solution, metals are cleaned before soldering.

6. Zinc production

It is known that pure zinc ores are almost never found in nature. Zinc compounds are part of polymetallic ores, usually containing 1-5% Zn, so they are pre-enriched to obtain zinc concentrate, which can contain 50-65% zinc, up to 12% iron, up to 2% copper, up to 2% lead, plus fractions of a percent of scattered and rare metals. Such a complex composition of zinc concentrates and ores is one of the reasons why zinc production took so long to develop. Modern technologies still face the problems of processing polymetallic zinc ores.

Zinc concentrates are subjected to roasting, while zinc sulfide is converted into oxide:

2ZnS + 2O2 = 2ZnO + 2SO2^

Obtaining pure metallic zinc from oxide is possible in two ways.

At the moment, electrolytic or hydrometallurgical is the main method for obtaining zinc. It consists in the electrolytic separation of zinc from sulfate, which is obtained by treating calcined concentrates with sulfuric acid. The resulting sulfate solution is purified from impurities - by precipitating them with zinc dust - and then electrolyzed in special baths, the surface of which is lined with lead or vinyl plastic. Then zinc is deposited on aluminum cathodes, from where it is removed daily for further remelting in induction furnaces.

With this method of obtaining zinc, it is possible to work out the ore by 93-94% (if waste is processed), that is, the extraction of zinc occurs by almost 100%. Moreover, the purity of the resulting metal is 99.95%. From the waste of such production, you can get zinc sulfate, as well as cadmium, lead, copper, and even gold and silver. Sometimes get In, Ga, Ge, Tl.

Another method (which has existed for a long time) for obtaining metallic zinc is pyrometallurgical or distillation. This method is as follows. Through a layer of crushed ore (powdered state) placed on a grate, air or some gas is fed from below at such a speed that its jets pass through the material, intensively mixing it. It turns out, as it were, "boiling" of powdered ore, which is in a "fluidized" state, because only liquids can boil. Zinc is extracted from the calcined concentrate by reducing it with coke at a temperature of 1200-1300°C and condensing the resulting zinc vapors with their subsequent pouring into molds.

Previously, the restoration was carried out in fired clay retorts, which had to be maintained manually, later they were replaced by vertical mechanized retorts made of refractory material - carborundum.

Due to the close contact of solid particles of ore and gas, chemical reactions in the "fluidized bed" proceed at a very high speed. The use of firing in a "fluidized bed" gives an increase in the productivity of furnaces by 3-4 times with a more thorough extraction of zinc from the concentrate.

This method is very effective in roasting sulfide ores and concentrates, sublimating relatively volatile metals, calcining, cooling and drying various substances.

Zinc is obtained from lead-zinc concentrates in shaft furnaces. Distillation zinc is purified by segregation (separation of liquid zinc from iron and part of lead at a temperature of 500°C). With such cleaning, it is possible to achieve a metal purity of 98.7%.

Sometimes a more complex and expensive distillation purification is used, which gives the metal a purity of 99.995%, allowing the extraction of valuable cadmium.

chemical distillation zinc

7. Application

Demand for metal in recent years has been growing, which is primarily due to the extensive use of zinc in various sectors of the economy - automotive, metallurgy, aviation, pipe industry, mechanical engineering, construction, medicine and in the production of rubber products and paints and varnishes.

More than half of the zinc produced in the world is used to protect steel from corrosion - galvanizing. The mechanism of this protection is different than that of other anti-corrosion coatings: cobalt, nickel, cadmium, tin - all these elements in the series of metal activity are after iron. This means that they are chemically more resistant than iron, they "cover" the steel surface from environmental influences. Zinc, on the contrary, is more chemically active than iron; it reacts with aggressive atmospheric components earlier. It turns out that zinc not only mechanically protects iron from external influences, it also protects it chemically. The resulting electrochemical process breaks down the zinc, keeping the base metal safe. Such a coating will work effectively even if there is a violation of integrity - a chip or scratch.

Galvanized sheet is used as a roofing material, goes to the manufacture of items that are in frequent contact with water (buckets, tanks).

Great value and alloys of zinc with other metals. So long-known brass (an alloy of copper and zinc) is used to manufacture condenser tubes, cartridge cases, various valves, radiators and much more. Zinc introduced in certain concentrations always improves the mechanical properties of copper (its strength, ductility, corrosion resistance). In addition, such an introduction reduces the cost of the alloy - after all, zinc is much cheaper than copper.

Zinc alloys began to be used in printing, gradually replacing the antimony-tin-lead alloy for casting fonts. Alloy No. 3, containing 95% zinc, 3% aluminum and magnesium, is now increasingly used. Zinc is used to make clichés that allow drawings and photographs to be reproduced in print.

Pure zinc in the form of dust is used to displace gold and silver from cyanide solutions; for purification of zinc sulfate solution from copper and cadmium. Zinc is used in the separation of lead from noble metals, since it forms intermetallic compounds with them that are insoluble in liquid lead.

In pyrotechnics, zinc dust is used to produce blue flames. Powdered zinc is used in the preparation of a special protective paint for technical objects and buildings.

Sheets of pure zinc are widely used in the production of galvanic cells.

Zinc compounds are widely used. The main industrial application of zinc oxide ZnO is in the production of rubber, in which it shortens the curing time of the original rubber. When mixed with drying oil, zinc oxide turns into zinc white used by painters. In addition, ZnO increases the life of glass and is therefore used in the production of special glasses, enamels and glazes. Another important area of application is in the composition of neutralizing cosmetic pastes and pharmaceutical preparations.

Zinc chloride ZnCl2 is used in the production of textiles, in addition, it is used as an antiseptic for wood and in the manufacture of parchment.

Zinc chloride is used in a number of metallurgical fluxes. Using a ZnCl2 solution, metals are cleaned before soldering.

8. Zinc toxicity

Zinc exhibits toxic properties at a dose of 150-600 mg, a lethal dose is 6 g. Under production conditions, wherever zinc is heated above its melting point (419.5 ° C), zinc oxide can be in the air; it is poisonous, when inhaled it causes the so-called foundry fever, which is expressed in chills, headache, nausea, cough. The maximum allowable concentration for zinc oxide is 0.5 mg/m3. Pure zinc is not dangerous for humans; rarely observed cases of poisoning are usually associated with industrial zinc contaminated with arsenic, antimony and lead impurities. From the point of view of physiology, zinc is an essential element for both humans and animals, as well as for plants.

9. Zinc and its role in the human body

Zinc is essential for the normal functioning of every cell in the body. Normally, the human body should contain about 2-3 g of zinc. Most of it is found in the skin, liver, kidneys, retina, hair, and in men, in addition, in the prostate gland.

Zinc is one of the vital trace elements:

is part of more than 40 metalloenzymes associated with respiration and other physiological processes. They catalyze the hydrolysis of peptides, proteins, some esters and aldehydes;

is a component of such vital hormones as insulin;

necessary for the formation of red blood cells and other blood cells;

plays a significant role in the synthesis of messenger RNA molecules on the corresponding DNA segments (transcription), in the functioning of the T-cell link of immunity, in the metabolism of lipids and proteins, in the stabilization of ribosomes and biopolymers;

participates in the metabolism of carbohydrates due to insulin, in addition, vitamin A is absorbed by the body only in the presence of zinc, vitamins C and E are poorly digestible without this element;

is part of enzymes and complexes that provide the most important physiological functions of the body:

Formation, growth and metabolism (metabolism) of cells, protein synthesis, wound healing;

Activation of immune responses directed against bacteria, viruses, tumor cells;

Assimilation of carbohydrates and fats;

Maintaining and improving memory;

Maintaining gustatory and olfactory sensitivity;

Bone formation

Ensuring the stability of the retina and the transparency of the lens of the eye;

Normal development and functioning of the genital organs.

A person receives zinc mainly from food. The body needs 10-20 mg of this mineral per day. It is found in foods such as: carrots, beets, potatoes, cherries, plums, apples, cabbage, garlic, mushrooms, legumes, grains, nuts, eggs, cheese, milk, seafood, meat.

A low level of zinc in the blood is characteristic of a number of diseases: atherosclerosis, cirrhosis of the liver, cancer, heart disease, rheumatism, arthritis, diabetes, peptic ulcer of the stomach and duodenum, ulcers on the body.

With an overdose of zinc, attacks of weakness are observed, the danger of poisoning, since zinc exhibits toxic properties at a dose of 150-600 mg, a lethal dose is 6 g. It may be carcinogenic. Zinc oxide and its metal dust cause pathological changes in the lungs. When compounds of this metal come into contact with the skin, eczema and dermatitis occur.

The need for zinc in human life

Zinc is one of the most common metals in industry. Due to its characteristics, it is very easy to process by pressure or high temperatures, and is widely used in a wide variety of fields of the national economy, science, technology, and medicine.

Demand for metal remains strong, thanks to the rapid growth in the production of anti-corrosion coatings. Zinc coating is often more reliable than others, because zinc does not just mechanically protect iron from external influences, it protects it chemically.

Zinc is also one of the most important biologically active elements and is necessary for all forms of life.

The human body contains about 2 g of zinc. Although zinc-containing enzymes are present in most cells, its concentration is very low, and therefore it became quite late to understand how important this element is; the necessity and indispensability of zinc for humans was established 100 years ago.

Zinc research is still ongoing. Although this metal is inconspicuous, cheap, zinc has found thousands of applications in the world.

Bibliography

1. Painters V.P., Selezneva E.A. Analytical chemistry of elements. "Science" Moscow 1975.- 543p.

2. Popular library of chemical elements. M., Nauka, 1977

3. Properties of chemical elements - Chemist's Handbook. Zinc - chem100.com

4. Kazakov B.I. Metal from Atlantis (about zinc). M.: Metallurgy, 1984 - 128s.

5. Popular library of chemical elements. Zinc - http://n-t.ru/ri/ps/

6. Zefirov N. S. (editor-in-chief) Chemical Encyclopedia: in 5 volumes - Moscow: Great Russian Encyclopedia, 1999. - T. 5. - 378 p.

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Role in metallurgy

Hydro- and pyrometallurgical processes are the most common ways to produce zinc metal from ore. In its properties, it is in no way inferior to chromium as an anti-corrosion coating. Half of all zinc produced is spent precisely on the application of a protective layer for iron and steel.

Anti-corrosion application of zinc.

Due to the low melting point of zinc and its alloys with other metals, there is a problem of sensitivity to overheating. Therefore, excessive overheating in production causes a disruption in the process with subsequent oxidation of the alloy. The most common are alloys with copper (brass), as well as with lead. They are widely used in engineering, alkaline batteries, galvanic cells and alloys with other noble metals.

The characteristic of the properties of an element changes under the influence of impurities. For example: the triple eutectic of an alloy of lead and zinc with an admixture of tin melts much easier than zinc itself and collapses under hot pressure. The addition of only 0.2% iron to the composition of zinc increases its brittleness several times. Bismuth and arsenic, sparingly soluble in the element, generally have a negative effect on the technological characteristics of the resulting substance.

In industry, the reducing properties of an element have an important function. He takes part in the precipitation of gold from solutions, in the production of hydrosulfite, in the extraction of copper and cadmium from ore.

Reactions with elements

Interaction with acids

The good reaction of zinc with most acids is due to its position in relation to hydrogen in the electrochemical series of activity of metals. This forms many important zinc salts. These salts are predominantly colorless, they are hygroscopic crystals, the solutions of which, due to hydrolysis, have an acidic environment. In the case of salts of other metals, it will also displace them from solution if they are in the voltage row to the right of the element.

When interacting with acids, zinc salts are formed.

In a solution of an element with sulfuric acid at a temperature below 38 ° C, zinc sulfate is formed, the scientific name of which is ZnSO4 sulfate. It is used in the production of viscose, some branches of metallurgy, in medicine as a disinfectant. ZnCl2 chloride is obtained from a solution of hydrochloric acid with zinc. It is used in the manufacture of batteries, antiseptic impregnation of wood and paper fibers.

Derived compounds

Zinc and its amphoteric properties are transferred to zinc hydroxides Zn(OH)2. These substances are inherent in the chemical behavior of acids and bases at the same time. Hydroxide can be obtained in the form of a white precipitate by the action of alkali on sulfate. In its natural state, hydroxide is a crystalline substance that decomposes at temperatures above 130 °C. It is used for the synthesis of zinc salts.
The old method of extracting ZnO oxide, previously referred to as the "French process", can be called spectacular. In the presence of highly heated air around the cell plate, zinc vapor will begin to evolve, which then ignites with a bluish light, forming an oxide. In large-scale production, it is mined from the natural mineral zincite. In addition, thermal decomposition of more complex compounds, such as hydroxide, is widely used to produce oxide.
Colorless white oxide powder, insoluble in water, expresses its chemical duality. When zinc oxide is fused with alkalis, zincates are obtained. When fused with oxides - silicates. Its own thermal conductivity allows it to be a semiconductor, the band gap of which is 3.36 eV. Oxide has a wide range of applications in the chemical industry, becoming a filler in many plastics. In electronics, not a single ray tube of a TV can do without it. It is also found in most dermatological ointments.

Introduction

The element zinc (Zn) in the periodic table has serial number 30. It is in the fourth period of the second group. Atomic weight - 65.37. Distribution of electrons in layers 2-8-18-2

The origin of the element's name is unclear, but it seems plausible that it is derived from Zinke (German for "point" or "tooth"), due to the appearance of the metal.

Zinc is a bluish-white metal, melting at 419 C, and turning into steam at 913 C; its density is 7.14 g/cm3. At ordinary temperatures, zinc is rather brittle, but at 100-110 C it bends well and rolls into sheets. In air, zinc is covered with a thin layer of oxide or basic carbonate, which protects it from further oxidation.

Water has almost no effect on zinc, although it is in the series of voltages much to the left of hydrogen. This is explained by the fact that the hydroxide formed on the surface of zinc during its interaction with water is practically insoluble and prevents the further course of the reaction. In dilute acids, however, zinc readily dissolves to form the corresponding salts.

In addition, zinc, like beryllium and other metals that form amphoteric hydroxides, dissolves in alkalis. If zinc is heated in air to the boiling point, then its vapor ignites and burns with a greenish-white flame, forming zinc oxide.

When heated, zinc interacts with non-metals (except hydrogen, carbon and nitrogen). Actively reacts with acids:

Zn + H2SO4 (dec.) = ZnSO4 + H2

Zinc is the only element of the group that dissolves in aqueous solutions of alkalis with the formation of ions (hydroxozincates):

Zn + 2OH + 2H2O = + H2

1. Raw material for zinc production

Research Institute "Uralmekhanobr" (owned by UMMC) has developed a technology for the extraction of metallized pellets and zinc concentrate from electric steel production waste. The new method will allow metallurgists to obtain inexpensive raw materials and solve environmental problems.

The source of zinc production is ore raw materials, which are usually in the sulfide state, and zinc is represented mainly by sphalerite (ZnS). The ores are always complex, they contain, in addition to zinc, lead, copper, iron, silver, etc. Recently, secondary raw materials have been used in countries with high consumption.

The raw material is zinc concentrate. As a starting material, not only mineral and secondary, but also zinc-containing products of other industries are used: slag and dust from the metallurgical industries of lead, copper, tin, cast iron. These products are much poorer in zinc than zinc concentrates and yet they are included in zinc raw materials. Until recently, zinc slags were considered waste products, although they contain a significant amount of zinc, especially in lead slags (10-17% zinc).

Distribution of zinc in nature and its industrial extraction. The content of zinc in the earth's crust is 7.6 10-3%, it is distributed approximately the same as rubidium (7.8 10-3%), and slightly more than copper (6.8 10-3%) .

The main zinc minerals are zinc sulfide ZnS (known as zincblende or sphalerite) and zinc carbonate ZnCO3

Canada occupies the first place in the world in terms of production (16.5% of world production, 1113 thousand tons, 1995) and zinc reserves. In addition, rich zinc deposits are concentrated in China (13.5%), Australia (13%), Peru (10%), USA (10%), Ireland (about 3%).

Zinc is mined in 50 countries. In Russia, zinc is extracted from copper pyrite deposits in the Urals, as well as from polymetallic deposits in the mountains of Southern Siberia and Primorye. Large reserves of zinc are concentrated in Rudny Altai (Eastern Kazakhstan), which accounts for more than 50% of zinc production in the CIS countries. Zinc is also mined in Azerbaijan, Uzbekistan (Almalyk deposit) and Tajikistan.

The innovativeness of the technology is that it allows you to simultaneously obtain zinc and metallic iron from waste. Previously, this was not possible. The essence of the process was explained by Samuil Melamud, head of the ore and concentrate agglomeration department at Uralmekhanobr: “Dust, together with blast-furnace slag and other iron-containing waste, is pelletized and loaded into a specially designed rotary kiln. It creates a special atmosphere and firing mode (it is in them that the know-how lies), which allow the extraction of zinc and the metallization of iron present in the oxide form. Zinc is captured in fabric bag filters, and the pellets are cooled, processed and transferred to the metallurgical process.”

According to scientists, on average, from one ton of dust it is possible to obtain 300 - 350 kg of metallic iron and 50 - 70 kg of zinc. A new method of waste recycling will allow the use of cheap recyclable materials, reduce the cost of storing hazardous waste and environmental payments. As a result, the cost of zinc produced will be 15-20% lower than its current world prices (1.9 thousand tons at the London Metal Exchange). The payback period for new installations with a volume of 20 - 30 thousand tons of processing per year is no more than four years.

Currently, an economic justification is being prepared for the feasibility of introducing the technology at the UMMC enterprises: Metallurgical Plant named after. A.K. Serov, Vtortsvetmete (Sukhoi Log), Mednogorsk copper and sulfur plant. In the future, it is planned to sell licenses for the right to use know-how to other steel companies.

The scientists of OAO Uralmekhanobr (an enterprise of the UMMC scientific complex), together with the specialists of the UMMC, have developed a new technology for the domestic and foreign ferrous metallurgy enterprises for the extraction of zinc and iron from the dusts of electric steelmaking. The innovation of the technology lies in the fact that it allows simultaneously obtaining zinc and metallic iron from raw materials, which was not possible before.

According to Samuil Melamud, head of the ore and concentrate agglomeration department at OAO Uralmekhanobr, one of the authors of the development, the technology ensures the extraction of metallized pellets and zinc concentrate by reductive roasting of zinc-containing dusts. Preliminary results showed that from a ton of dust from the Metallurgical Plant named after. A.K. Serov, you can get 300–350 kg of metallic iron and 50–70 kg of zinc.

“Growing costs for the extraction of ore raw materials and scrap, limited natural resources and the expected increase in penalties for environmental pollution naturally lead to the fact that industrialists are starting to take recycling of industrial waste more seriously,” says Samuil Melamud. “Especially since modern technologies are already able to be cost-effective.”

In April of this year, the Mednogorsk copper-sulfur plant (Orenburg region, an enterprise of the UMMC metallurgical complex) successfully passed pilot tests of the new technology. Currently, a feasibility study is being prepared for the implementation of technology at one of the UMMC enterprises.

2. Methods for obtaining zinc

With a sharp cooling, zinc vapor immediately, bypassing the liquid state, turn into solid dust. It is often necessary to store zinc in the form of dust, and not to melt it into ingots.

Zinc does not appear in nature as a native metal. Zinc is mined in two ways:

1) pyrometallurgical method

2) hydrometallurgical method from polymetallic ores containing 1-4% Zn in the form of sulfide, as well as Cu, Pb, Ag, Au, Cd, Bi. Ores are enriched by selective flotation, obtaining zinc concentrates (50-60% Zn) and simultaneously lead, copper, and sometimes also pyrite concentrates. Zinc concentrates are fired in fluidized bed furnaces, converting zinc sulfide into ZnO oxide; the resulting sulfur dioxide SO2 is used to produce sulfuric acid. There are two routes from ZnO to Zn.

1) According to the pyrometallurgical (distillation) method, which has existed for a long time, the calcined concentrate is subjected to sintering to impart grain size and gas permeability, and then reduced with coal or coke at 1200 - 1300 ° C:

ZnO + C = Zn + CO.

The resulting metal vapors are condensed and poured into molds. At first, the restoration was carried out only in hand-operated fired clay retorts; later, vertical mechanized retorts made of carborundum began to be used, then - shaft and electric arc furnaces; from lead-zinc concentrates, zinc is obtained in shaft furnaces with blast. Productivity gradually increased, but zinc contained up to 3% impurities, including valuable cadmium. Distillation zinc is purified by segregation (that is, by settling the liquid metal from iron and part of lead at 500 ° C), reaching a purity of 98.7%. The sometimes more complex and expensive purification by rectification, which is sometimes used, gives a metal with a purity of 99.995% and allows the extraction of cadmium.

The main method of obtaining zinc is electrolytic (hydrometallurgical). Calcined concentrates are treated with sulfuric acid; the resulting sulfate solution is purified from impurities (by deposition with zinc dust) and subjected to electrolysis in baths tightly lined inside with lead or vinyl plastic. Zinc is deposited on aluminum cathodes, from which it is daily removed (stripped off) and melted in induction furnaces. Usually the purity of electrolytic zinc is 99.95%, the completeness of its extraction from the concentrate (taking into account waste processing) is 93-94%. Production wastes produce zinc sulfate, Pb, Cu, Cd, Au, Ag; sometimes also In, Ga, Ge, Tl.

2) The hydrometallurgical method of processing calcined zinc concentrates consists in dissolving zinc oxide with an aqueous solution of sulfuric acid and subsequent precipitation of zinc by electrolysis. Therefore, the hydrometallurgical method is sometimes called electrolytic. In the production of zinc by electrolysis, the zinc concentrate is preliminarily subjected to oxidative roasting.

ZnSO4 → Zn 2+ + SO4 2-

2+ (–) cathode Zn , H2O (+) anode: SO42–, H2O

Zinc got its name from the light hand of Paracelsus, who called this metal "zincum" ("zinken"). Translated from German, this means "tooth" - this is the shape of the crystallites of metallic zinc.

In its pure form, zinc is not found in nature, but it is found in the earth's crust, in water, and even in almost every living organism. Its extraction is most often carried out from the minerals: zincite, willemite, calamine, smithsonite and sphalerite. The latter is the most common, and its main part is ZnS sulfide. Sphalerite in translation from Greek means snag. It got its name because of the difficulty of identifying the mineral.

Zn can be found in thermal waters, where it constantly migrates, precipitating as the same sulfide. Hydrogen sulfide acts as the main precipitator of zinc. As a biogenic element, zinc is actively involved in the life of many organisms, and some of them concentrate this element in themselves (certain types of violets).

Bolivia and Australia have the largest deposits of minerals containing Zn. The main zinc deposits in Russia are located in the East Siberian and Ural regions. The total projected reserves of the country are 22.7 million tons.

Zinc: production

The main raw material for the extraction of zinc is a polymetallic ore containing Zn sulfide in an amount of 1-4%. In the future, this raw material is enriched by selective flotation, which makes it possible to obtain zinc concentrate (up to 50-60% Zn). It is placed in furnaces, converting the sulfide into ZnO oxide. Then, a distillation (pyrometallurgical) method is usually used to obtain pure Zn: the concentrate is fired and sintered to a state of grain size and gas permeability, after which it is reduced with coke or coal at a temperature of 1200-1300°C. A simple formula shows how to get zinc from zinc oxide:

ZnO+С=Zn+CO

This method allows you to achieve 98.7 percent purity of the metal. If a purity of 99.995% is required, a technologically more complex purification of the concentrate by rectification is used.

Physical and chemical properties of zinc

The element Zn, with an atomic (molar) mass of 65.37 g / mol, occupies cell number 30 in the periodic table. Pure zinc is a blue-white metal with a characteristic metallic luster. Its main characteristics:

density - 7.13 g / cm 3
melting point - 419.5 ° C (692.5 K)
boiling point - 913 o C (1186 K)
specific heat capacity of zinc - 380 j / kg
specific electrical conductivity - 16.5 * 10 -6 cm / m
specific electrical resistance - 59.2 * 10 -9 ohm / m (at 293 K)

Contact of zinc with air leads to the formation of an oxide film and tarnishing of the metal surface. The element Zn easily forms oxides, sulfides, chlorides and phosphides:

2Zn + O 2 \u003d 2ZnO

Zn+S=ZnS

Zn+Cl 2 = ZnCl 2

3Zn + 2P \u003d Zn 3 P 2

Zinc interacts with water, hydrogen sulfide, is highly soluble in acids and alkalis:

Zn + H 2 O \u003d ZnO + H 2

Zn+H 2 S=ZnS+H 2

Zn + H 2 SO 4 \u003d ZnSO 4 + H 2

4Zn + 10НNO 3 \u003d 4Zn (NO 3) 2 + NH 4 NO3 + 3 H 2 O

Zn + 2KOH + 2H 2 O \u003d K2 + H 2

Zinc also interacts with the CuSO 4 solution, displacing copper, since it is less active than Zn, which means that it is the first to be removed from the salt solution.

Zinc can be present not only in solid or dusty form, but also in the form of a gas. In particular, zinc vapors arise during welding. In this form, Zn is a poison that causes zinc (metal) fever.