- soft, malleable, chemically inert metal is very resistant to corrosion. It is these qualities that mainly determine its widest application in the national economy. In addition, the metal has a fairly low melting point and easily forms a variety of alloys.
Let's talk today about its use in construction and industry: alloys, lead cable sheaths, paints based on it,
The first use of lead was due to its excellent malleability and corrosion resistance. As a result, the metal was used where it should not have been used: in the manufacture of dishes, water pipes, washbasins, and so on. Alas, the consequences of such use were the saddest: lead is a toxic material, like most of its compounds, and when it enters the human body, it causes a lot of serious damage.
- The real distribution of the metal received after the experiments with electricity moved to the widespread use of electric current. It is lead that is used in numerous chemical current sources. More than 75% of the total share of the smelted substance goes to the production of lead batteries. Alkaline batteries, despite their greater lightness and reliability, cannot displace them, since lead batteries create a higher voltage current.
- Lead forms many low-melting alloys with bismuth, cadmium, and so on, all of which are used to make electrical fuses.
Lead, being toxic, poisons the environment, and poses a considerable danger to humans. Lead batteries need to be recycled or, more promising, recycled. Today, up to 40% of the metal is obtained by recycling batteries.
- Another interesting application of metal is the winding of a superconducting transformer. Lead was one of the first metals that showed superconductivity, and at a relatively high temperature - 7.17 K (for comparison, the superconductivity temperature for - 0.82 K).
- 20% by volume of the substance lead is used in the production of lead sheaths for power cables for underwater and underground laying.
- Lead, or rather, its alloys - babbits, are anti-friction. They are widely used in the manufacture of bearings.
- In the chemical industry, metal is used in the production of acid-resistant equipment, since it reacts very reluctantly with acids and with a very small number of them. For the same reasons, it is used to produce pipes for pumping acids and sewage for laboratories and chemical plants.
- In military production, the role of lead is difficult to underestimate. Lead balls were thrown by the catapults of ancient Rome. Today it is not only ammunition for small arms, hunting or sporting weapons, but also initiating explosives, for example, the famous lead azide.
- Another well-known application is solders. provides a universal material for joining all other metals that are not alloyed in the usual way.
- Lead metal, although soft, is heavy, and not just heavy, but the most affordable to obtain. And this is connected with one of its most interesting properties, although relatively recently discovered - the absorption of radioactive radiation, and of any rigidity. Lead shielding is used wherever there is a threat of increased radiation - from an X-ray room to a nuclear test site.
Hard radiation has a greater penetrating power, that is, a thicker layer of material is required to protect it from it. However, lead absorbs hard radiation even better than soft radiation: this is due to the formation of an electron-positron pair near the massive nucleus. A layer of lead 20 cm thick is able to protect against any radiation known to science.
In many cases, there is simply no alternative to metal, so a suspension due to its environmental hazard cannot be expected. All efforts of this kind should be directed towards the development and implementation of efficient methods of cleaning and recycling.
This video will tell you about the extraction and use of lead:
Its use in construction
Metal in construction work is used infrequently: its toxicity limits the range of applications. However, in the composition of alloys or in the construction of special structures, the substance is used. And the first thing we'll talk about is lead roofing.
Roof
Lead has been used since time immemorial. In Ancient Russia, churches and bell towers were covered with lead sheet, since its color was perfect for this purpose. The metal is plastic, which makes it possible to obtain sheets of almost any thickness, and, most importantly, shape. When covering non-standard architectural elements, constructing complex cornices, a lead sheet is just perfect, so it is constantly used.
Rolled lead is produced for roofing, usually in rolls. In addition to sheets with a standard flat surface, there is also a corrugated material - pleated, painted, tinned and even self-adhesive on one side.
In air, the lead sheet quickly becomes covered with a patina consisting of a layer of oxide and carbonates. The patina protects the metal from corrosion. But if for some reason you don’t like its appearance, the roofing material can be coated with a special patinating oil. This is done manually or in a production environment.
Sound absorption
Soundproofing a home is one of the persistent problems of old, and many modern houses. There are many reasons for this: the structure itself, where walls or floors conduct sound, the material of floors and walls that does not absorb sound, an innovation in the form of a new design elevator, which is not provided for in the project and creates additional vibration and many other factors. But in the end, the occupant of the apartment is forced to cope with these problems on his own.
At an enterprise, in a recording studio, in a stadium building, this problem becomes much larger, and is solved in the same way - by installing a sound-absorbing finish.
Lead, oddly enough, is used in this particular role - a sound absorber. The construction of the material is almost the same. A lead plate of small thickness - 0.2-0.4 mm is covered with a protective polymer layer, since the metal is still hazardous, and organic material - foamed rubber, polyethylene, polypropylene - is fixed on both sides of the plate. The sound insulator absorbs not only sound, but vibration.
The mechanism is as follows: a sound wave, passing through the first polymer layer, loses some of the energy and excites vibrations of the lead plate. Part of the energy is then absorbed by the metal, and the remainder is quenched in the second foamed layer.
It should be noted that the direction of the wave in this case does not matter.
This video will tell you how lead is used in construction and the economy:
X-ray rooms
X-ray radiation is extremely widely used in medicine, in fact, forming the basis of instrumental examination. But if in minimal doses it does not pose a particular danger, then receiving a large dose of radiation is a threat to life.
When arranging an X-ray room, it is lead that is used as a protective layer:
- walls and doors;
- floor and ceiling;
- mobile partitions;
- personal protective equipment - aprons, shoulder pads, gloves and other items with lead inserts.
Protection is provided due to a certain thickness of the shielding material, which requires accurate calculations, taking into account the size of the room, the power of the equipment, the intensity of use, and so on. The ability of a material to reduce radiation is measured in terms of "lead equivalent" - the value of the thickness of such a layer of pure lead, which is able to absorb the calculated radiation. Such protection is considered effective if it exceeds the specified value by ¼ mm.
X-ray rooms are cleaned in a special way: the timely removal of lead dust is important here, since the latter is dangerous.
Other destinations
Lead is a heavy, malleable, corrosion-resistant metal, and most importantly, it is readily available and fairly cheap to manufacture. In addition, the metal is indispensable for radiation protection. So a complete rejection of its use is a matter of a rather distant future.
Elena Malysheva will tell about the health problems caused by the use of lead in the video below:
Lead- a rare mineral, a native metal of the class of native elements. Malleable, relatively fusible metal of silver-white color with a bluish tint. Known since ancient times. Very plastic, soft (cut with a knife, scratched with a fingernail). Nuclear reactions produce numerous radioactive isotopes of lead.
See also:
STRUCTURE
Lead crystallizes in a face-centered cubic lattice (a = 4.9389Å) and has no allotropic modifications. Atomic radius 1.75Å, ionic radii: Pb 2+ 1.26Å, Pb 4+ 0.76Å. Twinned crystals according to (111). It occurs in small rounded grains, scales, balls, plates and filamentous formations. PROPERTIES
Lead has a rather low thermal conductivity of 35.1 W/(m K) at 0°C. The metal is soft, cut with a knife, easily scratched with a fingernail. On the surface, it is usually covered with a more or less thick film of oxides; when cut, a shiny surface opens, which fades with time in air. Melting point - 600.61 K (327.46 ° C), boils at 2022 K (1749 ° C). Belongs to the group of heavy metals; its density is 11.3415 g/cm 3 (+20 °C). As the temperature rises, the density of lead decreases. Tensile strength - 12-13 MPa (MN / m 2). At a temperature of 7.26 K, it becomes a superconductor.
RESERVES AND PRODUCTION
The content in the earth's crust is 1.6 10 −3% by weight. Native lead is rare, the range of rocks in which it is found is quite wide: from sedimentary rocks to ultrabasic intrusive rocks. In these formations, it often forms intermetallic compounds (for example, zvyagintsevite (Pd,Pt) 3 (Pb,Sn), etc.) and alloys with other elements (for example, (Pb + Sn + Sb)). It is part of 80 different minerals. The most important of them are: galena PbS, cerussite PbCO 3 , anglesite PbSO 4 (lead sulfate); of the more complex ones - tillite PbSnS 2 and betekhtinite Pb 2 (Cu,Fe) 21 S 15, as well as lead sulfosalts - jamsonite FePb 4 Sn 6 S 14, boulangerite Pb 5 Sb 4 S 11. It is always contained in uranium and thorium ores, often having a radiogenic nature.
Ores containing galena are mainly used to obtain lead. First, a concentrate containing 40-70 percent lead is obtained by flotation. Then, several methods of processing the concentrate into werkbley (blister lead) are possible: the previously widespread method of mine reduction smelting, the method of oxygen-weighted cyclone electrothermal smelting of lead-zinc products (KIVTsET-TSS) developed in the USSR, the Vanyukov smelting method (melting in a liquid bath) . For melting in a shaft (water jacket) furnace, the concentrate is sintered beforehand, and then it is loaded into a shaft furnace, where lead is reduced from oxide.
Werkbley, which contains more than 90 percent lead, undergoes further purification. First, seigerization is used to remove copper, followed by sulfur treatment. Then alkaline refining removes arsenic and antimony. Next, silver and gold are isolated using zinc foam and the zinc is distilled off. Bismuth is removed by treatment with calcium and magnesium. As a result, the content of impurities drops to less than 0.2%[
ORIGIN
Forms dissemination in igneous, mainly acidic rocks; in Fe and Mn deposits, it associates with magnetite and hausmanite. Occurs in placers with native Au, Pt, Os, Ir.
Under natural conditions, it often forms large deposits of lead-zinc or polymetallic ores of the stratiform type (Kholodninskoe, Transbaikalia), as well as skarn (Dalnegorskoe (formerly Tetyukhinskoe), Primorye; Broken Hill in Australia) type; galena is also often found in deposits of other metals: pyrite-polymetallic (Southern and Middle Urals), copper-nickel (Norilsk), uranium (Kazakhstan), gold ore, etc. Sulfosalts are usually found in low-temperature hydrothermal deposits with antimony, arsenic, as well as in gold deposits (Darasun, Transbaikalia). Sulfide-type lead minerals have a hydrothermal genesis, oxide-type minerals are frequent in the weathering crusts (oxidation zones) of lead-zinc deposits. In clarke concentrations, lead is found in almost all rocks. The only place on earth where there is more lead in rocks compared to uranium is the Kohistan-Ladakh arc in northern Pakistan.
APPLICATION
Lead nitrate is used to produce powerful mixed explosives. Lead azide is used as the most widely used detonator (initiating explosive). Lead perchlorate is used to prepare a heavy liquid (density 2.6 g/cm³) used in flotation beneficiation of ores, it is sometimes used in powerful mixed explosives as an oxidizing agent. Lead fluoride alone, as well as together with bismuth, copper, silver fluoride, is used as a cathode material in chemical current sources.
Lead bismuth, lead sulfide PbS, lead iodide are used as cathode material in lithium batteries. Lead chloride PbCl 2 as a cathode material in backup current sources. Lead telluride PbTe is widely used as a thermoelectric material (thermo-emf 350 μV/K), the most widely used material in the production of thermoelectric generators and thermoelectric refrigerators. Lead dioxide PbO 2 is widely used not only in a lead battery, but also many backup chemical current sources are produced on its basis, for example, a lead-chlorine element, a lead-fluorine element, and others.
White lead, basic carbonate Pb (OH) 2 PbCO 3 , dense white powder, is obtained from lead in air under the action of carbon dioxide and acetic acid. The use of white lead as a coloring pigment is now not as common as before, due to their decomposition under the action of hydrogen sulfide H 2 S. Lead white is also used for the production of putty, in the technology of cement and lead carbon paper.
Lead arsenate and arsenite are used in the technology of insecticides for the destruction of agricultural pests (gypsy moth and cotton weevil).
Lead borate Pb (BO 2) 2 H 2 O, an insoluble white powder, is used to dry paintings and varnishes, and, together with other metals, as coatings for glass and porcelain.
Lead chloride PbCl 2 , white crystalline powder, soluble in hot water, solutions of other chlorides and especially ammonium chloride NH 4 Cl. It is used for the preparation of ointments in the treatment of tumors.
Lead chromate PbCrO4, known as chrome yellow, is an important pigment for the preparation of paints, for dyeing porcelain and textiles. In industry, chromate is mainly used in the production of yellow pigments.
Lead nitrate Pb (NO 3) 2 is a white crystalline substance, highly soluble in water. It is a binder of limited use. In industry, it is used in matchmaking, textile dyeing and stuffing, antler dyeing, and engraving.
Since lead is a good absorber of γ-radiation, it is used for radiation shielding in X-ray machines and in nuclear reactors. In addition, lead is considered as a coolant in the projects of advanced fast neutron nuclear reactors.
Lead alloys are widely used. Pewter (tin-lead alloy), containing 85-90% Sn and 15-10% Pb, is moldable, inexpensive and used in the manufacture of household utensils. Solder containing 67% Pb and 33% Sn is used in electrical engineering. Alloys of lead with antimony are used in the production of bullets and typographic type, and alloys of lead, antimony and tin are used for figure casting and bearings. Lead-antimony alloys are commonly used for cable jackets and electric battery plates. There was a time when a significant part of the lead produced in the world was used for cable sheathing, due to the good moisture-proof properties of such products. However, subsequently lead was largely replaced by aluminum and polymers from this area. Thus, in Western countries, the use of lead for cable sheaths fell from 342,000 tons in 1976 to 51,000 tons in 2002. Lead compounds are used in the manufacture of dyes, paints, insecticides, glass products and as additives to gasoline in the form of tetraethyl lead (C 2 H 5) 4 Pb (a moderately volatile liquid, the vapors of which have a sweetish fruity odor in low concentrations, and an unpleasant odor in large concentrations; Тmelt = 130 °C, Тboil = +80 °С/13 mm Hg; density 1.650 g/cm³; nD2v = 1.5198; insoluble in water, miscible with organic solvents; highly toxic, easily penetrates through the skin; MPC = 0.005 mg/m³ LD50 = 12.7 mg/kg (rats, oral)) to increase the octane number.
Used to protect patients from X-ray radiation.
Lead (English Lead) - Pb
CLASSIFICATION
| Strunz (8th edition) | 1/A.05-20 |
| Nickel-Strunz (10th edition) | 1.AA.05 |
| Dana (7th edition) | 1.1.21.1 |
| Dana (8th edition) | 1.1.1.4 | Hey's CIM Ref | 1.30 |
Lead (Latin name plumbum) is a chemical element, a metal with atomic number 82. In its pure form, the substance has a silvery, slightly bluish tint.
Due to the fact that lead is widely distributed in nature, it is easy to mine and process, this metal has been known to mankind since ancient times. It is known that people used lead as early as the 7th millennium BC. Lead was mined and processed in ancient Egypt and later in ancient Rome. Lead is quite soft and pliable, so even before the invention of smelting furnaces, it was used to make metal objects. For example, the Romans made pipes from lead for the water supply network.
In the Middle Ages, lead was used as a roofing material and for the production of seals. For a long time, people did not know about the dangers of the substance, so it was mixed into wine and used in construction. Even into the 20th century, lead was added to printing ink and gasoline additives.
Lead properties
In nature, lead is most often found in the form of compounds that are part of ores. Ores are mined, and then a pure substance is isolated industrially. The metal itself, as well as its compounds, have unique physical and chemical properties, which explains the widespread use of lead in various industries.
Lead has the following properties:
- very soft, obedient metal that can be cut with a knife;
- heavy, denser than iron;
- melts at relatively low temperatures (327 degrees);
- oxidizes rapidly in air. A piece of pure lead is always covered with a layer of oxide.
Lead toxicity
Lead has one unpleasant feature: it and its compounds are toxic. Lead poisoning is chronic: with constant intake into the body, the element accumulates in the bones and organs, causing serious disorders. 
For a long time, the volatile compound tetraethyl lead was used to improve gasoline, which caused environmental pollution in cities. Now in civilized countries the use of this additive is prohibited.
Lead Application
The toxicity of lead is now well known. At the same time, lead and its compounds can be of great benefit if used rationally and competently.
The efforts of scientists and developers are aimed at making the most of the beneficial properties of lead, reducing its danger to humans. Lead is used in a variety of industries, including:
— in medicine and other areas where radiation protection is needed. Lead does not transmit any radiation well, so it is used as a shield. In particular, lead plates are sewn into aprons that are worn by patients for safety during x-ray examinations. The protective properties of lead are used in the nuclear industry, science, and the production of nuclear weapons;
— in the electrical industry. Lead is not very susceptible to corrosion - this property is actively used in electrical engineering. Lead-acid batteries are the most widely used. Lead plates are installed in them, immersed in an electrolyte. The galvanic process makes it possible to obtain an electric current sufficient to start a car engine. The battery industry is the largest consumer of lead in the world. In addition, lead is used to protect cables, the production of cable cabins, fuses, superconductors;
— in the military industry. Lead is used to make bullets, shot, and shells. Lead nitrate is part of explosive mixtures, lead azide is used as a detonator;
— in the production of dyes and building mixtures. Lead white, extremely common before, is now giving way to other paints. Lead is used in the production of putties, cement, protective coatings for and ceramics. 
Due to the toxicity of lead, they try to limit the use of this metal, replacing it with alternative materials. Much attention is paid to the safety of production related to lead, the disposal of products containing this element, as well as to reduce the contact of lead parts with humans and the release of substances into the environment.
(nm, coordination numbers are given in brackets) Рb 4+ 0.079 (4), 0.092 (6), Рb 2+ 0.112 (4), 0.133(6).
The content of lead in the earth's crust is 1.6-10 3% by mass, in the World Ocean 0.03 µg/l (41.1 million tons), in rivers 0.2-8.7 µg/l. Known ca. 80 containing lead, the most important of which is galena, or lead luster, PbS. Small prom. anglesite PbSO 4 and cerus-site PbSO 3 are important. Lead is accompanied by Cu, Zn; Cd, Bi, Te and other valuable elements. Natural background in 2·10 -9 -5·10 -4 µg/m 3 . The body of an adult contains 7-15 mg of lead.
Properties. Lead is a bluish-gray metal that crystallizes into facets. cubic Cu type lattice, a - = 0.49389 nm, z = 4, spaces. Fm3m group. Lead is one of the fusible, heavy; m.p. 327.50 °С, b.p. 1751 °С; density, g / cm 3: 11.3415 (20 ° C), 10.686 (327.6 ° C), 10.536 (450 ° C), 10.302 (650 ° C), 10.078 (850 ° C);26.65 J/( K); 4.81 kJ / ,177.7 kJ/; 64.80 JDmol K); , Pa: 4.3 10 -7 (600 K), 9.6 10 -5 (700 K), 5.4 10 -2 (800 K). 1.2 10 -1 (900 K), 59.5 (1200 K), 8.2 10 2 (1500 K), 12.8 10 3 (1800 K). Lead is a poor conductor of heat and electricity; 33.5 W/(m K) (less than 10% of Ag); temperature coefficient. linear expansion of lead (purity 99.997%) in the range of t-r 0-320 ° C is described by the equation: a \u003d 28.15 10 -6 t + 23.6 10 -9 t 2 ° C -1; at 20°C r 20.648 μOhm cm (less than 10% of r Ag), at 300°C and 460°C, respectively. 47.938 and 104.878 μΩ cm. At -258.7°C r lead drops to 13.11·10 -3 µOhm·cm; at 7.2 K it passes into the superconducting state. Lead is diamagnetic, magnetic. susceptibility -0.12·10 -6 . In the liquid state, lead is fluid, h in the range of t-r 330-800 ° C varies within 3.2-1.2 mPa s; g in the range of 330-1000 ° C is in the range (4.44-4.01) 10 -3 N / m.
With wine is soft, plastic, easily rolled into the thinnest sheets. according to Brinell 25-40 MPa; s rast 12-13 MPa, s compress approx. 50 MPa; relates. elongation at break 50-70%. Significantly increase and lead Na, Ca and Mg, but reduce its chemical. durability. increases the anti-corrosion resistance of lead (to the action of H 2 SO 4). With Sb, the acid resistance of lead to H 2 SO 4 also increases. Reduce the acid resistance of lead Bi and Zn, and Cd, Te and Sn increase the fatigue resistance of lead. In lead, practically no sol. N 2 , CO, CO 2 , O 2 , SO 2 , H 2 .
In chem. lead is rather inert. The standard lead is -0.1265 V for Pb 0 /Pb 2+ . In the dry, it does not oxidize, in the wet, it fades, becoming covered with a film that turns into a presence. CO 2 in the main 2РbСО 3 ·Рb(OH) 2 . Lead forms a series: Pb 2 O, PbO (), PbO 2, Pb 3 O 4 () and Pb 2 O 3 (see). At room temperature, lead does not react with razb. sulfuric and hydrochloric to-tami, since the sparingly soluble films of PbSO 4 and PbC1 2 formed on its surface prevent further. Conc. H 2 SO 4 (> 80%) and HC1 at loading. interaction with lead to form p-rimy Comm. Pb(HSO 4) 2 and H 4 [PbCl 6 ]. Lead is resistant to hydrofluoric acid, aqueous solutions of NH 3 and to many others. org. to-there. The best solutions for lead-razb. HNO 3 and CH 3 COOH. In this case, Pb (NO 3) 2 and Pb (CH 3 COO) 2 are formed. Lead markedly sol. also in lemon, formic and wine to-tah.
Pb + PbO 2 + 2H 2 SO 4: 2PbSO 4 + 2H 2 O
When interacting Pb(IV) and Pb(II) with salts are formed, respectively. plumbates(IV) and plumbites(II),e.g. Na 2 PbO 3, Na 2 PbO 2. Lead slowly sol. in conc. solutions with the release of H 2 and the formation of M 4 [Pb (OH) 6].
When heated, lead reacts with to form. With hydrazoic acid, lead gives Pb (N 3) 2, with loading - PbS (see Lead chalcogenides). lead is not typical. In some districts, tetrahydride RbH 4 is found - bestsv. , easily decomposed into Pb and H 2 ; formed by the action of hydrochloric to-you on Mg 2 Pb. See also, Organic lead compounds.
Receipt. Main source of lead-sulfide polymetallic. . Selective from containing 1-5% Pb, lead and other concentrates are obtained. Lead concentrate usually contains 40-75% Pb, 5-10% Zn, up to 5% Cu, and also Bi. OK. 90% of lead is obtained by technology, including stages: sintering of sulfide concentrates, mine recovery. smelting of sinter and crude lead. Autogenous smelting processes are being developed to make use of the heat of combustion.
Agglomerating with traditional the production of lead is carried out on straight-line machines with blowing or by sucking it. In this case, PbS is oxidized predominantly. in liquid state: 2PbS + 3O 2: 2PbO + 2SO 2. Fluxes (SiO 2 , CaCO 3 , Fe 2 O 3 ) are added to the charge, to-rye, reacting with each other and with PbO, form a liquid phase that cements the charge. In the finished agglomerate lead in DOS. concentrated in lead silicate glass, which occupies up to 60% of the volume of the agglomerate. Zn, Fe, Si, Ca crystallize in the form of complex compounds, forming a heat-resistant framework. Effective (working) area of the agglomeration machines 6-95 m2.
The finished agglomerate contains 35-45% Pb and 1.2-3% S, part of which is in the form. The productivity of the agglomeration agglomerate machines depends on the S content in the charge and ranges from 10 (poor concentrates) to 20 t/(m 2 day) (rich concentrates); according to the burnt S, it is in the range of 0.7-1.3 t / (m 2 · day). Part containing 4-6% SO 2 is used to produce H 2 SO 4. The degree of utilization S is 40-50%.
The resulting agglomerate is sent to restore. smelting in mines. for smelting lead is a rectangular shaft formed by water-cooled boxes (caissons). (or air-oxygen mixture) is fed into through a special. nozzles (tuyeres) located along the entire perimeter in the lower. row of caissons. In the melting charge are included in the main. agglomerate and, sometimes lumpy recycled and secondary raw materials are loaded. Oud. melting of sinter 50-80 t/(m 2 day). Direct extraction of lead in the draft 90-94%.
The purpose of melting is to extract lead as much as possible into rough, and Zn and empty into slag. Main p-tion of mine smelting of lead agglomerate: PbO + CO: Pb + + CO 2. As the charge is introduced. Part of the lead is recovered by him directly. Lead requires a weak reduction. (O 2 10 -6 -10 -8 Pa). Consumption to the weight of the agglomerate in mine melting 8-14%. Under these conditions, Zn and Fe are not reduced and pass into slag. present in the agglomerate in the form of CuO and CuS. under the conditions of mine smelting, it is easily reduced to and passes into lead. With a high content of Cu and S in the agglomerate during shaft melting, an independent sinter is formed. phase-matte.
Main slag-forming components of slag (80-85% by weight of slag) - FeO, SiO 2 , CaO and ZnO - are sent for further processing to extract Zn. Up to 2-4% Pb and ~20% Cu pass into the slag, the content of these resp. 0.5-3.5 and 0.2-1.5%. Formed during mine smelting (and agglomeration) serves as a feedstock for the extraction of rare and.
At the heart of autogenous lead smelting processes is exothermic. p-tion PbS + O 2: Pb + SO 2, consisting of two stages:
2PbS + 3O2 : 2PbO + 2SO 2 PbS + 2PbO: 3Pb + SO 2
The advantages of autogenous methods over traditional ones. technology: agglomeration is excluded. , eliminates the need to dilute the concentrate with fluxes, which reduces the yield of slag, uses heat from and eliminates (partially) consumption, increases SO 2 recovery, which simplifies their use and improves plant safety. Two autogenous processes are used in the industry: KIVCET-TSS, developed in the USSR and implemented at the Ust-Kamenogorsk plant and in Italy at the Porto-Vesme plant, and the American QSL process.
Smelting technology according to the KIVCET-TSS method: finely divided, well-dried charge containing concentrate, circulating and, using a burner, is injected with technical O 2 into the melting chamber, where lead is obtained and slag is formed. (contain 20-40% SO 2) after cleaning from the smelting returned to the charge, they go to the production of H 2 SO 4. Draft lead and slag will separate through. partition flow in electrothermal. settling furnace, from where they are released through tap holes. served in the mixture for excess in the melting zone.
The QSL process is carried out in a converter-type unit. divided by a partition into zones. In the melting zone, the granular is loaded. concentrate, smelting and technical O 2 . The slag enters the second zone, where it is blown with a pulverized coal mixture for lead using lances. In all methods of melting the main the amount of Zn (~80%) passes into the slag. To extract Zn, as well as the remaining lead and some rare lead, the slag is processed by fuming or rolling.
Blister lead, obtained in one way or another, contains 93-98% Pb. Impurities in black lead: Cu (1-5%), Sb, As, Sn (0.5-3%), Al (1-5 kg/t), Au (1-30%), Bi (0.05 -0.4%). Purification of crude lead is carried out pyrometallurgical or (sometimes) electrolytically.
Pyrometallurgical the method is sequentially removed from black lead: 1) copper-two operations: segregation and using elemental S, forming Cu 2 S. Preliminary. (rough) purification from Cu to a content of 0.5-0.7% is carried out in reflective or electrothermal with deep lead, having a temperature difference in height. interaction on the surface with lead sulfide concentrate to form Cu-Pb matte. The matte is sent to copper production or to independent production. hydrometallurgical. processing.
2) Tellurium-action metallic. Na in the presence NaOH. selectively interact. with Te, forming Na 2 Te, floating on the surface and dissolving in NaOH. The melt goes for processing to extract Te.
3), and antimony-oxidation of them or O 2 in reflect. at 700-800 °C, or NaNO 3 in the presence. NaOH at 420°C. Alkaline melts are sent to hydrometallurgical. processing of NaOH from them and extraction of Sb and Sn; As is removed in the form of Ca 3 (AsO 4) 2 , which is sent for burial.
4) and gold - with the help of Zn, selectively reacting with those dissolved in lead; AuZn 3 , AgZn 3 are formed, floating on the surface. The resulting removals are removed from the surface for the last. processing them into
(first electron)
(according to Pauling)
Pb←Pb 4+ 0.80 V
| Pb | 82 |
| 207,2 | |
| 4f 14 5d 10 6s 2 6p 2 | |
| Lead | |
Lead- an element of the main subgroup of the fourth group, the sixth period of the periodic system of chemical elements of D. I. Mendeleev, with atomic number 82. It is designated by the symbol Pb (lat. Plumbum). The simple substance lead (CAS number: 7439-92-1) is a malleable, relatively low-melting gray metal.
The origin of the word "lead" is unclear. In most Slavic languages (Bulgarian, Serbo-Croatian, Czech, Polish) lead is called tin. A word with the same meaning, but similar in pronunciation to "lead", is found only in the languages of the Baltic group: švinas (Lithuanian), svins (Latvian).
The Latin plumbum (also of obscure origin) gave the English word plumber - a plumber (once pipes were minted with soft lead), and the name of the Venetian prison with a lead roof - Piombe, from which, according to some reports, Casanova managed to escape. Known since ancient times. Products from this metal (coins, medallions) were used in Ancient Egypt, lead water pipes - in Ancient Rome. An indication of lead as a certain metal is found in the Old Testament. Lead smelting was the first metallurgical process known to man. Prior to 1990, a large amount of lead was used (along with antimony and tin) for casting typographic fonts, as well as in the form of tetraethyl lead - to increase the octane number of motor fuel.
Finding lead in nature
Getting lead
Countries - the largest producers of lead (including secondary lead) for 2004 (according to ILZSG), in thousand tons:
| EU | 2200 |
| USA | 1498 |
| China | 1256 |
| Korea | 219 |
Physical properties of lead
Lead has a rather low thermal conductivity, it is 35.1 W/(m·K) at 0°C. The metal is soft and easy to cut with a knife. On the surface, it is usually covered with a more or less thick film of oxides; when cut, a shiny surface opens, which fades over time in air.
Density - 11.3415 g / cm³ (at 20 ° C)
Melting point - 327.4 ° C
Boiling point - 1740 ° C
Chemical properties of lead
Electronic formula: KLMN5s 2 5p 6 5d 10 6s 2 6p 2, according to which it has oxidation states +2 and +4. Lead is not very reactive chemically. On a metal section of lead, a metallic sheen is visible, gradually disappearing due to the formation of a thin PbO film.
With oxygen, it forms a number of compounds Pb2O, PbO, PbO2, Pb2O3, Pb3O4. Without oxygen, water at room temperature does not react with lead, but at high temperatures lead oxide and hydrogen are produced by the interaction of lead and hot water vapor.
PbO and PbO2 oxides correspond to the amphoteric hydroxides Pb(OH)2 and Pb(OH)4.
The reaction of Mg2Pb and dilute HCl yields a small amount of PbH4. PbH4 is an odorless gaseous substance that decomposes very easily into lead and hydrogen. At high temperatures, halogens form compounds of the form PbX2 with lead (X is the corresponding halogen). All these compounds are slightly soluble in water. Halides of the PbX4 type can also be obtained. Lead does not directly react with nitrogen. Lead azide Pb (N3) 2 is obtained indirectly: by the interaction of solutions of Pb (II) salts and NaN3 salts. Lead sulfides can be obtained by heating sulfur with lead, PbS sulfide is formed. Sulfide is also obtained by passing hydrogen sulfide into solutions of Pb (II) salts. In the series of voltages, Pb is to the left of hydrogen, but lead does not displace hydrogen from dilute HCl and H2SO4, due to the overvoltage of H2 on Pb, and films of sparingly soluble chloride PbCl2 and sulfate PbSO4 are formed on the metal surface, protecting the metal from further action of acids. Concentrated acids such as H2SO4 and HCl, when heated, act on Pb and form with it soluble complex compounds of the composition Pb(HSO4)2 and H2[PbCl4]. Nitric, as well as some organic acids (for example, citric) dissolve lead to form Pb(II) salts. By solubility in water, lead salts are divided into insoluble (for example, sulfate, carbonate, chromate, phosphate, molybdate and sulfide), slightly soluble (like chloride and fluoride) and soluble (for example, lead acetate, nitrate and chlorate). Pb (IV) salts can be obtained by electrolysis of solutions of Pb (II) salts strongly acidified with sulfuric acid. Salts of Pb (IV) add negative ions to form complex anions, for example, plumbates (PbO3) 2- and (PbO4) 4-, chloroplumbates (PbCl6) 2-, hydroxoplumbates [Pb (OH) 6] 2- and others. Concentrated solutions of caustic alkalis, when heated, react with Pb with the release of hydrogen and hydroxoplumbites of the X2[Pb(OH)4] type. Eion (Me => Me ++ e) \u003d 7.42 eV.
Basic lead compounds
lead oxides
Lead oxides are predominantly basic or amphoteric in nature. Many of them are painted in red, yellow, black, brown colors. In the photo at the beginning of the article, on the surface of the lead casting, tint colors are visible in its center - this is a thin film of lead oxides formed due to the oxidation of hot metal in air.
Lead halides
Lead chalcogenides
Lead chalcogenides - lead sulfide, lead selenide and lead telluride - are black crystals that are narrow-gap semiconductors.
lead salts
Lead sulfate
lead nitrate
lead acetate- lead sugar, refers to very toxic substances. Lead acetate, or lead sugar, Pb (CH 3 COO) 2 3H 2 O exists in the form of colorless crystals or a white powder, slowly weathering with the loss of water of hydration. The compound is highly soluble in water. It has an astringent effect, but since it contains poisonous lead ions, it is used externally in veterinary medicine. Acetate is also used in analytical chemistry, dyeing, cotton-printing, as a filler for silk, and for the production of other lead compounds. Basic lead acetate Pb (CH 3 COO) 2 Pb (OH) 2 - less water-soluble white powder - is used to decolorize organic solutions and purify sugar solutions before analysis.
Lead Application
Lead in the national economy
lead nitrate used for the production of powerful mixed explosives. Lead azide is used as the most widely used detonator (initiating explosive). Lead perchlorate is used to prepare a heavy liquid (density 2.6 g/cm³) used in flotation beneficiation of ores, it is sometimes used in powerful mixed explosives as an oxidizing agent. Lead fluoride alone, as well as together with bismuth, copper, silver fluoride, is used as a cathode material in chemical current sources. Lead bismuth, lead sulfide PbS, lead iodide are used as cathode material in lithium batteries. Lead chloride PbCl2 as a cathode material in backup current sources. Lead telluride PbTe is widely used as a thermoelectric material (thermo-emf with 350 μV/K), the most widely used material in the production of thermoelectric generators and thermoelectric refrigerators. Lead dioxide PbO2 is widely used not only in a lead battery, but also many backup chemical current sources are produced on its basis, for example, a lead-chlorine element, a lead-fluorine element, etc.
White lead, basic carbonate Pb (OH) 2.PbCO3, dense white powder, - obtained from lead in air under the action of carbon dioxide and acetic acid. The use of white lead as a coloring pigment is now not as common as it used to be, due to their decomposition by the action of hydrogen sulfide H2S. Lead white is also used for the production of putty, in the technology of cement and lead-carbonate paper.
Lead arsenate and arsenite are used in the technology of insecticides for the destruction of agricultural pests (gypsy moth and cotton weevil). Lead borate Pb(BO2)2 H2O, an insoluble white powder, is used to dry paintings and varnishes and, together with other metals, as coatings on glass and porcelain. Lead chloride PbCl2, white crystalline powder, soluble in hot water, solutions of other chlorides and especially ammonium chloride NH4Cl. It is used for the preparation of ointments in the treatment of tumors.
Lead chromate PbCrO4, known as chrome yellow, is an important pigment for the preparation of paints, for dyeing porcelain and textiles. In industry, chromate is mainly used in the production of yellow pigments. Lead nitrate Pb(NO3)2 is a white crystalline substance, highly soluble in water. It is a binder of limited use. In industry, it is used in matchmaking, textile dyeing and stuffing, antler dyeing, and engraving. Lead sulfate Pb(SO4)2, a water-insoluble white powder, is used as a pigment in batteries, lithography, and printed fabric technology.
Lead sulfide PbS, a black, water-insoluble powder, is used in pottery firing and to detect lead ions.
Since lead is a good absorber of γ-radiation, it is used for radiation shielding in X-ray machines and in nuclear reactors. In addition, lead is considered as a coolant in the projects of advanced fast neutron nuclear reactors.
Lead alloys are widely used. Pewter (tin-lead alloy), containing 85-90% Sn and 15-10% Pb, is moldable, inexpensive and used in the manufacture of household utensils. Solder containing 67% Pb and 33% Sn is used in electrical engineering. Alloys of lead with antimony are used in the production of bullets and typographic type, and alloys of lead, antimony and tin are used for figure casting and bearings. Lead-antimony alloys are commonly used for cable jackets and electric battery plates. Lead compounds are used in the production of dyes, paints, insecticides, glass products and as additives to gasoline in the form of tetraethyl lead (C2H5) 4Pb (moderately volatile liquid, vapors in small concentrations have a sweetish fruity odor, in large concentrations, an unpleasant odor; Tm = 130 °C, Тbp = 80°С/13 mmHg; density 1.650 g/cm³; nD2v = 1.5198; insoluble in water, miscible with organic solvents; highly toxic, easily penetrates through the skin; MPC = 0.005 mg/m³ LD50 = 12.7 mg/kg (rats, oral)) to increase the octane number.
Lead in medicine
Economic indicators
Prices for lead bullion (grade C1) in 2006 averaged $1.3-1.5/kg.
Countries, the largest consumers of lead in 2004, in thousand tons (according to ILZSG):
| China | 1770 |
| EU | 1553 |
| USA | 1273 |
| Korea | 286 |
Physiological action
Lead and its compounds are toxic. Once in the body, lead accumulates in the bones, causing their destruction. MPC in the atmospheric air of lead compounds is 0.003 mg/m³, in water 0.03 mg/l, in soil 20.0 mg/kg. The release of lead into the World Ocean is 430-650 thousand tons/year.
