What Are the Properties of Lead?

Lead is a metal chemical element with the element symbol Pb (Latin Plumbum; English name lead), an atomic number of 82 and an atomic weight of 207.2. Lead metal is a face-centered cubic crystal. [1]

Lead is a metal chemical element with the element symbol Pb (Latin Plumbum; English name lead), an atomic number of 82 and an atomic weight of 207.2. Lead metal is a face-centered cubic crystal. [1]
Metal lead is a corrosion-resistant heavy non-ferrous metal material. The original color of lead was cyan-white, and the surface was quickly covered with a layer of dark gray oxide in the air. Lead has the advantages of low melting point, high corrosion resistance, X-ray and -ray are not easy to penetrate, good plasticity, etc. It is often processed into plates and pipes, and is widely used in industrial sectors such as chemical industry, cables, batteries and radiation protection. [1]
On July 23, 2019, lead was included in the list of toxic and harmful water pollutants (the first batch) [2] .
Chinese name
lead
English name
lead
nickname
Black tin, turquoise, gold in water
Molecular weight
207.2
CAS Registry Number
7439-92-1
Melting point
327
Boiling point
1525 [3]
Water soluble
not soluble in water
Density
11.3437 g / cm3
Exterior
Blue-gray metal
Application
Lead-acid batteries, radiation protection materials, etc.
Risk description
poisonous
Average specific heat capacity
129.8J / (kg · K)
Hardness
1.5
Element symbol
Pb

Introduction to lead

Lead (Pb) is a high-density, soft blue-gray metal with a melting point of 327 ° C and a boiling point of 1750 ° C [1] . When the temperature exceeds 400 ° C, a large amount of lead vapor escapes and rapidly oxidizes into lead oxide smoke in the air. Common lead-containing substances include PtO, Pb 2 O 3 , Pb 3 O 4 , lead white (Pb (OH) 2 · 2PbCO 3 ), and lead sulfate (PbSO 4 )Wait. Nature exists mainly in the form of galena (PbS) and white lead (PbCO 3 ), but also in lead alum (PbSO 4 ). Occasionally, there is natural lead. Lead ore is often mixed with zinc, silver, copper and other elements. Lead and its compounds are used in a wide range of applications. Metallurgy, storage batteries, printing, pigments, paints, glazes, soldering and other operations can be exposed to lead and its compounds. [4]
The crystal structure of lead is a cubic lattice. Lead has high density, low hardness, low melting point, high boiling point, poor conductivity to electricity and heat, and can absorb radiation. Therefore, lead is used to make containers for radioactive materials and used as protective materials. [5]
This metal is highly resistant to corrosion, and some lead pipes installed by the Romans are still intact. Lead is mostly used in pipes (though it is now replaced by plastic). Lead is also used to shield X-rays, used in the manufacture of arms, as a cable jacket, in crystallized glass (as lead oxide), and as an anti-knock agent (such as tetraethyl lead, (C 2 H 5 ) 4 Pb ). Most lead salts are insoluble in water, with the exception of nitrate (Pb (NO 3 ) 2 ) and acetate (Pb (CH 3 COO) 2 ). Severe lead poisoning can cause diarrhea and vomiting, but lead poisoning is usually chronic with symptoms of abdominal pain, muscle pain, anemia, and nerve and brain damage. Children are particularly susceptible to inhaling excessive lead from the exhaust gases of cars. [6] The daily maximum allowable concentration of lead in the atmosphere of residential areas is 0.00007mg / m, and the maximum allowable concentration in surface water is 0.1mg / L. [4]

Physical and chemical properties of lead

Lead is located in Group IVA in the sixth period, with an atomic radius of 146pm, a Pb radius of 84pm, a first ionization energy of 718.96kJ / mol, an electronegativity of 1.8, and a major oxidation number of +2, +4. Silver-gray shiny heavy metal, easily oxidized in the air and loses its luster, becomes dark, soft in quality, weak in ductility and strong in ductility. The density is 11.34g / cm, the melting point is 327.5 ° C, and the boiling point is 1525 ° C [3] . Has strong resistance to radiation penetration.
The recrystallization temperature of lead is below room temperature, which has excellent press workability and does not cause work hardening. The strength and hardness of lead and lead alloys, especially the fatigue and creep strengths are relatively low, and they are susceptible to fatigue and creep damage. Attention should be paid to the design and use of components. [1]
The main physical and mechanical properties of lead are as follows:
performance data
Density (20 ) / g · cm -3 11.68
Melting point / 327.4
Boiling point / 1525 [3]
Average specific heat capacity (0 100 ) / J · (kg · K) -1 129.8
Heat of fusion / kJ · mol -1 4.98
Gasification heat / kJ · mol -1 178.8
Thermal conductivity (0 100 ) / W · (m · K) -1 34.9
Resistivity (20 ° C) / · cm 20.6
Tensile strength / MPa 14.7
Elongation/% 60 70
Brinell hardness / MPa 30 48 [1]
Lead has four stable isotopes: Pb-204 (1.4% abundance), Pb-206 (24.1% abundance), Pb-207 (22.1% abundance), and Pb-208 (52.4% abundance). The last three are the final products of uranium-238, uranium-235, and plutonium-232 after a series of fission. Only Pb is a naturally occurring, non-decaying product. [7] Pb-208 has the highest mass among stable isotopes.

Chemical activity of lead

At normal temperature in the air, a layer of lead oxide or basic lead carbonate is easily formed on the surface of lead, which will tarnish the lead and prevent further oxidation. Easily combine with halogen and sulfur to form PbCl 4 , PbI 2 , PbS, etc. The molten lead air reacts to produce lead monoxide, which can be obtained by heating lead in pure oxygen. It reacts with hydrochloric acid to give off hydrogen and generate slightly soluble PbCl 2 , which covers the surface of lead and stops the reaction. Reacts with hot concentrated hydrochloric acid to form HPbCl 3 and H 2 . The reaction with dilute sulfuric acid releases hydrogen and forms a poorly soluble PbSO 4 coating, which stops the reaction. However, hot concentrated sulfuric acid generates Pb (HSO 4 ) 2 and releases SO 2 . Reaction with dilute nitric acid or concentrated nitric acid can generate lead nitrate Pb (NO 3 ) 2 . Under aerobic conditions, it can be dissolved in organic acids such as acetic acid to form soluble lead salts. Slow reaction with strong alkali solution gives off hydrogen to lead acid. [8] Reacts with water in the presence of oxygen to form insoluble Pb (OH) 2 .
The lead is oxidized to PbO 2 when it is heated and melted, and then decomposes to PbO at elevated temperature. When the temperature rises to 603 to 723K, Pb 3 O 4 (ie, lead dan) is formed. Pb 2 O 3 or Pb 3 O 4 easily dissociates at high temperatures to form stable PbO. [5]
Lead is very stable in SO 2 , lead hardly interacts with pure CO 2 , and ordinary water corrodes lead slightly. Lead is easily soluble in nitric acid, borofluoric acid, silicofluoric acid, and acetic acid. It is hardly soluble in sulfuric acid, hydrochloric acid, and hydrofluoric acid at room temperature. NH 4 OH solution or air-dilute dilute NaOH solution can slowly dissolve lead. Lead is soluble in silver nitrate solution. Other nitrates and chlorides corrode lead. Potassium, sodium, iron, ammonia sulfate and potassium carbonate and cyanide solutions have no effect on lead. [5]

Lead corrosion resistance mechanism

Lead forms a dense lead oxide film on the surface of the air, a lead carbonate film in humid air containing carbon dioxide, and a lead sulfate film in sulfuric acid. These formed films play a good protective role. Therefore, lead has excellent corrosion resistance in many media, especially sulfuric acid. The corrosion rate in the atmosphere of the lead industrial zone is 0.00043 to 0.00068 mm / a; the corrosion rate in natural seawater is 0.01 to 0.015 mm / a; when the sulfuric acid concentration reaches 70% to 80% and the temperature is 50 ° C, the lead is Has good corrosion resistance. [1]

Lead production method

Lead smelting lead raw materials

The crust of lead is less abundant than copper, zinc, and tin. The main lead ore in nature is sulfide ore, followed by lead oxide ore. The main composition of lead sulfide is native galena (PbS). But there are few single lead sulfides, often associated with sphalerite, collectively called lead-zinc ore. Other associated minerals are often silver ore (Ag 2 S), pyrite (FeS 2 ), chalcopyrite (CuFeS 2 ), pyrite (FeAsS), and bismuth ore (Bi 2 S 3 ) And minerals of rare elements such as indium, germanium, gallium, thallium, tellurium. The composition of lead-zinc ore is complicated, and it should be smelted before being enriched by beneficiation. The lead oxide ore is mainly composed of white lead ore (PbCO 3 ) and lead vanadium (PbSO 4 ). It is a secondary ore, which mostly appears in the upper layer of sulfide ore, or coexists with sulfide ore. Leaded miscellaneous materials are also an important resource for the production of lead. [5]

Lead extraction metallurgy

The extraction of lead metallurgy is divided into two types: metallurgical and wet lead smelting. The former is widely used in industrial production. The traditional pyrometallurgical lead smelting method generally includes three major links: sintering and roasting of lead concentrate, lead smelting, crude lead pyrometallurgy refining or (lead electrolytic refining). The traditional lead smelting method is the most widely used for smelting lead by blast furnace reduction smelting. Lead produced by this method accounts for 85% of total lead production. The smelting furnace smelting method is a method of reducing lead oxide to crude lead by using coke as a reducing agent. This method requires sintering and roasting to convert most of the PbS in the lead sulfide concentrate to PbO and sinter. The calcined material is sintered into pieces. The crude lead produced by lead smelting also contains many impurities, which need to be refined by pyrolysis or electrolytic refining to obtain refined lead that meets product quality standards and meets user requirements, and recover valuable metals in crude lead. Crude lead fire refining is dominant in today's lead refining. [5]
The traditional fire method of lead smelting has serious problems such as serious environmental pollution, difficult recovery of sulfur in raw materials, high energy consumption, and low production efficiency. Since the 1950s, some countries in the world have competed to study the direct lead smelting method to replace the traditional fire method. Method of smelting lead. Industrial production or semi-industrial tests that have been carried out by the 1990s include the Kivset-CS, the oxygen bottom-blown lead (QSL), the Isa smelting (ISA), and the flash smelting. Lead etc. The common features of these direct lead smelting methods are that they do not undergo a separate sintering and roasting process, and basically achieve self-heating smelting. The flue gas is convenient for acid production and has a low degree of environmental pollution. From the perspective of development, it may replace the traditional fire smelting method. [5]

Lead smelting in China

(1) Transformation of lead smelting technology
With the continuous development of China's industry, the demand for lead products is increasing. However, due to the limitations of China's lead smelting technology, the supply of lead products is far below the actual demand for lead products. This requires China's lead smelting technology to be further improved. With the continuous progress of smelting technology and the accumulation of practical experience, China's lead smelting technology has been improved to a certain extent. Lead producers are transforming lead smelting technology to further improve the lead product Yield and quality. In the production process of lead products in China, the production of lead products is being transformed toward the bottom blowing furnace + side blowing reduction furnace + smoke furnace. The transformation of lead product smelting technology has not only greatly improved the output and quality of lead products, but also reduced the energy consumption in the lead smelting process, further improving energy efficiency. It is believed that with the continuous progress of lead smelting technology, the supply of lead products in China will gradually meet the needs of our industry for lead products. [9]
(2) There are problems
The problems existing in the lead smelting process in China have restricted the advancement of lead smelting technology in China, thereby affecting the supply of lead products in China. The problems in China's lead smelting process are mainly divided into three aspects. First of all, the shortage of lead resources in China has restricted the supply of lead products in China. From the perspective of the distribution of lead resources in China, although the distribution of lead resources is relatively wide, the reserves of lead resources are relatively low and cannot provide sufficient raw materials for lead smelting. In addition, the waste of lead products during the smelting process is relatively serious and the energy consumption is large. This has also caused the lead resources to be underutilized and the supply of lead cannot meet the demand. Secondly, the inadequate supervision of lead smelting in China has led to serious waste of lead resources. [9]
In the production process of lead products in China, the relevant departments do not pay attention to the supervision of lead smelting. On the one hand, some enterprises have not produced lead products in accordance with the production standards, resulting in a waste of lead resources. On the other hand, due to insufficient supervision, lead manufacturers often do not pay attention to energy consumption and environmental pollution, resulting in energy waste. At the same time, pollution in the production of lead products has caused environmental damage. In addition, due to insufficient supervision, some companies use backward smelting technology to meet foreign demand for lead products, which has further exacerbated China s resource shortage and environmental pollution. Finally, the environmental pollution caused by the lead smelting process has increased the environmental pressure in China. Due to the restrictions of China's lead smelting technology level, dust and exhaust gas will be generated during the production of lead products. These dusts and exhaust gases have not been properly disposed of, resulting in serious environmental pollution during the production process of lead products. [9]
Sulfur dioxide is produced during the production of lead products. Sulfur dioxide can cause acid rain, cause great damage to crops and buildings, and cause economic losses. Pollution caused by lead smelting also restricts the supply of lead products. [9]

Modern lead smelting technology

(1) Oxygen top-blown melting technology
Both the Isaac (ISA) and Ausmelt methods are oxygen top-blown methods. The ISA method (ISA) is used as an example to further explain the technical characteristics of the oxygen top-blown melting technology. The Isaac method is different from the Kivset method. It requires less charge, but the method has a higher smoke rate. Another advantage of Isafa is that the furnace equipment covers a relatively small area, which can save space for lead smelting, reduce the cost of lead smelting to a certain extent, and increase the economic benefits of the enterprise. [9]
(2) Oxygen bottom blowing smelting technology
The QSL method and the SKS method are both bottom-blown melting tank melting technologies. The QSL method is taken as an example to further explain the technical characteristics of the oxygen bottom-blown melting technology. The QSL method is the same as the ISA method. The smoke and dust rate is relatively high. The QSL method also has a relatively small area of furnace equipment. Economic benefits. [9]
(3) Oxygen side blowing smelting technology
Oxygen side-blown smelting technology is a direct lead smelting technology developed in China by molten pool smelting. The equipment required for this technology is relatively simple and the amount of investment is relatively small. The metal recovery rate is also very high, and the economic benefits created are relatively good. However, this technology does not control the heat dissipation well, resulting in a large energy consumption during lead smelting. This technology is widely used in China because the required cost is relatively low. However, the widespread use of this technology has also caused great pressure on China's energy resources and is not conducive to sustainable development. This is the problem that our country must solve for the next step of this technology. [9]

Lead compounds

There are many types of lead compounds. The main compounds with industrial value are PbS, PbO, PbSO 4 and lead chloride. [5]

Lead monoxide

(1 Introduction
Also known as yellow lead oxide, commonly known as Huang Dan or Mi Tuo. The chemical formula is PbO, and the formula is 223.19. There are many variations. The tetragonal crystals are yellow-red with a density of 9.53g / cm 3 ; the orthorhombic crystals are yellow with a density of 8.0g / cm 3 ; the amorphous ones are yellow to red-yellow with a density of 9.2-9.5g / cm 3 . Melting point is 888 ° C. [10]
(2) Solubility
Lead monoxide is hardly soluble in water and ethanol, soluble in nitric acid and acetic acid to form the corresponding lead salt, and dissolved in hot strong alkali solution to produce lead acid salt. [10]
(3) Chemical activity
Lead monoxide can absorb carbon dioxide in the air to produce lead carbonate, and when heated to 500 ° C in the air, it can produce lead trioxide. When heated, it can be reduced to lead by carbon, hydrogen, carbon monoxide, and mixed with glycerol to form a hard substance, which can be used as a binder. [10]
(4) Preparation method and use
Lead monoxide is usually produced by oxidizing molten lead in air or heating lead carbonate and lead nitrate to decompose. It is commonly used as a drier for pigments, paints, and metallurgical fluxes. It is also used to make special lead glass, enamel, battery electrodes, and rubber. . [10]

Lead sulfide

(1 Introduction
The chemical formula is PbS, the formula is 239.25, blue with metallic luster cubic crystal or brown-black powder. It has a density of 7.5 g / cm 3 and a melting point of 1114 ° C. It starts to partially evaporate at 860 ° C. [11]
(2) Solubility
Insoluble in water and alkaline solutions. Soluble in nitric acid. [11]
(3) Chemical activity
Burn in the air to produce lead monoxide and sulfur dioxide. [11]
(4) Preparation method and use
The artificial preparation of lead sulfide usually involves passing hydrogen sulfide into an acidic lead nitrate solution. The main ore of lead sulfide in nature is galena, which is the raw material for smelting lead. After the lead sulfide is purified, it can be used as a semiconductor. [11]

Lead chloride

Lead chloride mainly includes PbCl 2 and PbCl 4. PbCl 2 is the most important of lead chloride.
(1) Lead dichloride
Lead dichloride, with a molecular weight of 278.11, is white crystals and is toxic. The relative density is 5.85, the melting point is 501 ° C, and the boiling point is 950 ° C. Slightly soluble in cold water, soluble in hot water, difficult to dissolve in dilute hydrochloric acid, but soluble in concentrated hydrochloric acid and concentrated solutions of alkali metal chlorides, forming tetrachlorolead (II) anion complex ions. Hardly soluble in alcohol, can form basic salts and double salts. It is usually prepared by the reaction of lead monoxide or basic lead carbonate with hydrochloric acid, and can also be obtained by precipitating lead nitrate with hydrochloric acid. It is used to make pigments and can also be used as solder or flux. [12] It is also used to produce various lead salts and lead-containing pigments. The minimum lethal dose to rats is 2000 mg / kg. Lead that enters the human body can be incorporated into bones and hair, but is only harmful when concentrated in the liver. [13]
(2) Lead tetrachloride
Lead tetrachloride, also known as high lead chloride. Molecular weight is 349.01, yellow volatile oily liquid, poisonous. The relative density is 3.18 (0 ° C), the melting point is -15 ° C, and it is stable only at low temperatures [13] . It decomposes (generates lead dichloride and chlorine gas) at normal temperature, and violently decomposes and explodes at 105 ° C. It is easily hydrolyzed into lead dioxide and hydrogen chloride in the presence of moisture and water, and emits strong smoke. Soluble in concentrated hydrochloric acid to form lead (IV) hexachloride acid. Insoluble in concentrated sulfuric acid. It is usually obtained by dissolving lead dioxide in cold concentrated hydrochloric acid or by reacting concentrated sulfuric acid with ammonium hexachlorolead (IV) acid. [14]

Lead sulfate

(1 Introduction
Lead sulfate, also known as lead alum, has a molecular weight of 303.26, usually white crystals or powder, a relative density of 6.2, and decomposition at 1000 ° C, and a melting point of about 1170 ° C. [15]
(2) Solubility
Slightly soluble in water, difficult to dissolve in ethanol and dilute sulfuric acid, soluble in hot concentrated sulfuric acid, concentrated hydrochloric acid, concentrated nitric acid, concentrated lye, ammonium acetate, ammonium tartrate and other solutions. [15]
(3) Preparation method and use
Lead sulfate is usually formed by the action of lead monoxide and sulfuric acid, or by the reaction of a soluble lead salt solution with dilute sulfuric acid. Commonly used as a raw material for white pigments, batteries and quick-drying paints. [15]

Lead application

Lead is the raw material for making batteries, cables, bullets and ammunition, and it is also an additive to gasoline. Lead compounds are used as raw materials for pigments, glass, plastics and rubber. Because metal lead has excellent acid and alkali corrosion resistance, it is widely used in manufacturing chemical and metallurgical equipment. Lead alloys are used as bearings, movable gold and solder. In addition, lead has also opened up some new uses. For example, it can be used as a stabilizer for asphalt to prolong the service life of pavement; used in the manufacture of nuclear power station shields and nuclear waste storage tanks; high-power battery packs used by the electric industry department to adjust the load; and magnetic fluid dynamic devices. [5]

A brief history of lead applications

Lead is one of the metals that humans extracted earlier, and it was discovered and used by humans as early as about 3,000 BC. During the pre-Egypt period of Egypt (earlier than 3000 BC), small figures made of lead were used. Mesopotamia was made into small containers or hammered with lead in Urak III (Uru III, 3000 BC). The thinnest piece of lead found in China is the lead block unearthed from Erlitou Site, Yanshi, Henan Province. It exists about 3500 to 4,000 years ago. In the tombs of the Shang Dynasty and the Western Zhou Dynasty, unearthed Jie, Xi, Zun, Ding and Ge of the lead were unearthed. The lead of the Western Zhou Dynasty (11th century BC ~ 771 years) contained 99.75% lead. [8] Lead was not more common in Palestine until after the 15th century BC. However, large-scale production of lead did not begin until the 17th to 18th centuries. The main lead-producing countries were the United States, the former Soviet Union, Japan, Germany, the United Kingdom, and China. [8]

Lead- acid battery

Lead-acid batteries (referred to as lead-acid batteries) have a history of more than 150 years since their introduction. Due to their low price, mature technology, and reliable performance, they have become the largest and most widely used secondary batteries in chemical power sources. Since then, it has been widely used in various occasions of social production and life. [16]
Lead-acid batteries are charged and discharged by using solid-phase reactions of different valences of lead. When the battery is discharged, the active material of the two electrodes becomes PbSO 4 respectively. When charged, the reaction proceeds in the reverse reaction direction. The electrolyte sulfuric acid is an active material. . The positive-negative electrode reaction applies a dissolution-precipitation mechanism rather than a solid-state ion transfer or film formation mechanism. The standard cell voltage of a lead-acid battery at room temperature is 2.1 V. [16]

Lead cable sheath

The sheath material is mainly chemical lead, lead alloy containing 1% antimony or arsenic, and lead alloy containing 0.03% calcium or hoof. Lead is used as cable sheath to protect it from moisture, corrosion and shielding. The lead used in the cable industry is mainly power cables and communication cables. Although the lead sheath of domestic power communication cables has been mostly replaced by other materials such as plastic, there are still a small number of cables with lead sheaths. Due to environmental concerns abroad, there has been much controversy over the use of lead in transoceanic cable sheaths, but lead consumption in this field still accounts for a large part of its use. [17]

Lead chemical products

Currently, there are quite a few lead compounds used in the chemical industry. Only a few widely used products are introduced here. Lead oxide is widely used in the pasty mixture of lead-acid battery grids, as well as in cement, glass, and ceramics, and can be used to prepare other lead compounds. Hongdan is an important antirust coating, used as a primer and an internal paint layer to prevent Corrosion of steel.
Industrially important white anticorrosive pigments are monobasic lead carbonate, dibasic lead phosphite, dibasic phosphorous silicate and monobasic lead silicate. Lead borate can be used in glass manufacturing, fire-resistant coatings, and paint drier; lead nitrate is used in pharmaceuticals and ore flotation. In addition, lead chemical products are also used as light emitting materials in electronic powder materials and color electronic ultra-black picture tubes. [17]

Lead solder

Lead alloy solder is commonly referred to as soft solder. Among them, lead-tin alloy solder is the most widely used and has a long history in all soldering materials. It has a low melting point, and can be connected to most metals with a simple heating method without damaging the heat-sensitive components.
The application of traditional alloy solders should pay special attention to the manufacturers: the alloys with different tin contents should be used according to the specific welding objects and requirements. In order to achieve the purpose of meeting the requirements of use, save expensive tin and reduce costs. For example, solder with a tin content of not less than 5% is mainly used for sealing. It is commonly used to seal pre-soldering containers, coating and welding metals, and can also be used for service temperatures exceeding 120 ° C. [17]

Lead lead

(1) lead plate
Generally, lead material is rolled into a thin lead plate with a width of less than 3.6m and an arbitrary thickness, and a 0.4mm thick lead plate weighs. As a structural material, lead plate is a very important corrosion-resistant material in the chemical and related industries. This is mainly because lead has the ability to resist a variety of corrosive environments. Of course, it can also be used as building structural materials, such as roof anti-corrosion boards and bathroom floors. The lead plate is in contact with cement, etc., and is generally coated with a layer of asphalt. As a shielding layer for x-rays and gamma rays, it is a familiar application. Taking advantage of the excellent shock absorption and sound insulation performance of lead, there are also a large number of lead plates used for shock absorption and sound insulation. For example, steel and lead damping pads installed under the foundation of a building to prevent the transmission of vibration; pure lead can absorb most of the vibration energy released during an earthquake, and this type of shock absorber has been tested in an earthquake in Japan in recent years. [17]
(2) Lead tube
Lead pipes in lead materials are also a major aspect and are widely used in the chemical industry and drainage pipes. Extruded with chemical lead or 6% antimony into a seamless tube. With diameters ranging from thin tubes to 300mm or larger, tubes of almost any thickness are available for production.
(3) Wire mesh lead
In the construction of lead materials, in addition to lead plates, tubes, and solder, there is also lead mesh for plugging; a considerable part of the above-mentioned lead-tin solders are used as low-melting fusible alloys (lead and tin, bismuth, cadmium (Alloys such as Pylon, Indium, etc.) are almost all wire. The lowest melting point in the latter is below 100 ° C and is used for automatic arc extinguishing, electric fuses, boiler plugs, etc.
In developed countries, lead has constituted an independent consumption destination, especially in the United Kingdom. Lead skin has been used as a roof material to prevent radiation from atmospheric atoms in the atmosphere. However, the production of lead in China is very small, with an annual output of about 10,000 tons. With the improvement of people's lives, lead materials may become one of the main consumer uses of lead. [17]

Lead lead casting material

The most important of the lead casting materials are bearing alloys and lead alloys; the casting products include bearings, type plates, counterweights, gaskets, warheads, ballast counterweights, and even integral castings for large nuclear power plants' radiation protection layers. [17]

Lead- lead composite

A lead sheet is sandwiched between two tin sheets, and rolled into a tightly-bonded Sn-Pb-Sn composite foil with a thickness of 0.01 mm or less, which is generally referred to as "lead foil". In the construction industry, it is used to prevent moisture, or as an antioxidant foil for grapes and champagne bottles. Some are also used in the electronics industry. This "lead foil" is produced in large quantities abroad and is widely used. However, there are gaps in production and application in China. Of course, the more common and more used lead composite is made by combining lead with a harder material, and its performance is better than that of both materials. Lead can be compounded with steel, concrete, wood, brick, or other suitable materials. The structural composite material has excellent corrosion resistance and high strength. Although the strength of lead and plastic is slightly lower, the composite has excellent sound insulation properties.
Composite materials made from the combination of lead and stronger materials include:
Basic lead composite structure: cast or extruded lead or lead alloy on a limited composite base. Such as cast antimony-containing lead valves, pumps, anodes and containers.
Lead compounded on high-strength substrate: sheet, tube, or other extruded lead and its alloys are firmly compounded with steel, wood, concrete, copper or other metals, and used as heating pipes, conveyors, floors, cable sheaths, Roof with anode plate.
Paste composite lead materials: Sheets, tubes, or other forms of lead and their alloys, which are connected with steel, concrete, wood, or other materials with an adhesive, and are used as lead skin acid storage containers.
Metallurgically bonded lead composites: heavy lead or lead alloy composites combined with steel, copper or other metallurgical metallurgy, used as leaded steel reaction tanks, leaded copper cooling and heating coils.
Inorganic material composite lead: lead sheet is embedded between concrete or steel and tile material, and the lead sheet is mechanically or chemically connected to the inner and outer layers. For example, a cushion material is embedded between the steel sheet and the inner layer for sulfuric acid mist washing, sedimentation, collection, storage, etc.
Lead-coated composite material: The coating is connected to the equipment surface, mechanically or metallurgically, and has corrosion resistance. Paint Pb-Sn on steel for roofs, sinks and chutes. The above 6 kinds of lead composite materials all have the advantages of low material cost, low installation and maintenance cost, excellent corrosion resistance, long service life, and suitable for various operating conditions. [17]

Lead Industry Development

China's lead metal market

China's Refined Lead Production, 2001-2014
China has abundant lead ore resources. With the increase of domestic lead demand, China's lead ore mining volume has reached the world's number one. However, the concentration of China's lead smelting industry is relatively low. The total output of the top ten lead companies in the country's lead production is less than 50% of the country's total, and 65% of the lead battery production capacity is in the hands of several major manufacturers in Zhejiang. Concentration makes the right to speak firmly in the hands of the buyer, so the buyer's market is an important feature of the domestic lead market. [18]
According to data released by the National Bureau of Statistics of China, China's refined lead output in 2014 totaled 4.22 million tons, a year-on-year decrease of 5.5%. China's refined lead output from 2001 to 2014 is shown in the figure on the right:
The data also shows that the total output of China's lead concentrate in 2014 reached 2.997 million tons, a year-on-year decrease of 4.84%. During 2010-2014, the growth rate of China's lead concentrate output decreased year by year. The output of lead concentrate from 2008 to 2014 is shown on the right:
China's Lead Concentrate Production, 2008-2014
Lead is one of the most important basic metals in the national economy. It is widely used in batteries, cable jackets, automobile manufacturing, military industries and other industries. Lead-acid batteries are the main consumer area of lead, and lead consumption accounts for more than 80% of the entire lead demand. With the rapid development of the national economy, the social demand for industrial raw materials is increasing. Driven by the strong demand of the lead-acid battery industry, the consumption of lead in China has surpassed that of the United States, ranking first in the world. [18]

China's lead industry distribution

China's lead and zinc industry production layout, based on the distribution of lead and zinc mines and construction conditions, after more than 40 years of development and construction, has now formed five major northeast, Hunan, Guangdong, Guangdong, Guangdong, Yunnan, Sichuan and Northwest five lead and zinc mining and smelting and processing supporting Production base, its lead output accounts for more than 85% of the total national output, and zinc output accounts for 95% of the total national output. [19]
(1) Northeast Production Base
Northeast China is one of China's earlier developed lead and zinc production bases. As early as the early 1950s, its lead production accounted for more than 80% of the country's lead output, and it played an important role in China's lead and zinc production. Northeast base is mainly composed of No. 7 mine and two factories, namely Qingchengzi lead-zinc mine, Bajiazi lead-zinc mine, Chaihe lead-zinc mine (now closed), Huanren copper-zinc mine, Hongtuoshan copper-zinc mine, Xilin Lead-zinc mine (now bankrupted and closed pit), Tianbaoshan lead-zinc mine, Shenyang smelter, Huludao zinc plant. The No. 7 Plant and the No. 2 Plant are not only pillar pillars and mines of the Northeast Lead and Zinc Production Base, but also a base for cultivating scientific and technological talents. In the 1960s and 1970s, it sent a large number of experienced scientific and technological and managerial personnel and production technical workers to newly-built lead and zinc enterprises nationwide, and made positive contributions to the development of China's lead and zinc industry. [19]
(2) Hunan Production Base
Hunan is rich in lead and zinc mineral resources and rich in minerals. Most of the mineral resources can be developed and used. The lead-zinc plant and mine in this base was built in the 1950s and 1960s. It is a Hunan lead-zinc production base consisting of Shuikoushan Mining Bureau, Taolin Lead-zinc Mine, Huangshaping Lead-zinc Mine, Dongpo Lead-Zinc Mine, and Zhuzhou Smelter. It was the largest lead-zinc production base in the country at that time, and occupied an important position in the national output. [19]
(3) Production bases in Guangdong and Guangxi
Guangdong and Guangxi provinces are rich in lead and zinc resources. The two provinces are one of China's large lead and zinc production bases formed in the 1970s. Guangdong is mainly based on the Fankou lead-zinc mine and Shaoguan smelter, followed by Bingcun lead-zinc mine, Changhua lead-zinc mine, and Dajianshan lead-zinc mine. Guangxi has Siding Lead-Zinc Mine, Daxin Lead-Zinc Mine, Hesan Lead-Zinc Mine, Liuzhou Zinc Products Factory and Dachang Mining Bureau. [19]
(4) Dianchuan Production Base
Yunnan's lead and zinc mineral resources are very rich, and the lead and zinc reserves currently rank first in the country. Lead and zinc enterprises in this base were also built in the 1950s and 1960s, mainly in Huize Lead and Zinc Mine, Lancang Old Factory Lead and Zinc Mine, Kunming Smelter and Gejiujie Smelter. Yunnan lead-zinc mineral resources have broad development prospects. In the 1990s, the construction of a super-large lead-zinc deposit, a gold-top mine, began. There are two major mines in Sichuan, the Huidong Lead-Zinc Mine, and the Huili Lead-Zinc Mine, as well as a number of small and medium-sized mines. The output of lead and zinc concentrates has soared. [19]
(5) Northwest Production Base
Northwest China is also rich in lead and zinc mineral resources, mainly distributed in the three provinces of Ganshan, Shaanxi, and Qinghai. Moreover, the reserves in the western metallogenic belt have increased significantly, and the resource prospects are very considerable. The base's lead-zinc production is dominated by silver and non-ferrous metals companies, including the Xiaoyinshan lead-zinc mine in the silver plant, the third smelter and the northwest lead-zinc smelter, Shaanxi's lead-shan lead-zinc mine, Erlihe lead-zinc mine, Yindongliang Lead-Zinc Mine, etc. and Qinghai Xitieshan Mining Bureau. Northwest lead and zinc production is small, but the development prospects are considerable. First, it has abundant lead-zinc mineral resources. It is located in the Xicheng-Fengtai ore belt on the border between Gansu and Shaanxi. More than 10 large and medium-sized lead-zinc-silver-gold deposits have been identified. Reach large. Second, the factory dam is stepping up the construction of a large-scale mine, which will become the main mineral raw material supply base of the Northwest smelter and one of the nation's large-scale lead-zinc mines.
In addition to the above-mentioned five major lead and zinc production bases, a number of small and medium-sized mines have also been constructed in Inner Mongolia, Jiangxi, Guizhou and other provinces. Among them, Inner Mongolia Wutonghua lead-zinc mine, Baiyinuo lead-zinc mine, Wengniute Banner, Zongzi lead-zinc mine, and other mines. Inner Mongolia is one of the major provinces and regions in the country for the production of lead and zinc concentrates, and has great development prospects. Jiangxi has Yinshan lead-zinc mine. Guizhou has Hezhang lead-zinc mine and Shanshulin lead-zinc mine. [19]

Harm of lead to human body

Lead is one of the three major heavy metal pollutants. It is a heavy metal element that seriously harms human health. The ideal lead content in the human body is zero. The human body mostly brings lead into the body by ingesting food and drinking tap water. 90% of the lead that enters the body is stored in the bones, and 10% is distributed to all tissues and organs of the body with blood circulation, affecting red blood cells and brain, kidney, and nerve System functions, especially after infants and young children absorb lead, more than 30% will remain in the body, affecting infants' growth and intellectual development. [20]
Because lead is a cumulative poisoning, only when the lead content in the human body reaches a certain level can it cause physical discomfort. After long-term intake of lead, it will cause serious damage to the blood system and nervous system of the body, especially to children. The hazards of health and intelligence have irreversible effects. [20]
In industrial production, lead is inhaled into the human body in the form of lead dust (smoke). Occupational lead poisoning is mostly chronic poisoning, and clinically has the general symptoms of nervous, digestive, blood and other systems. The nervous system is mainly manifested as neurasthenia, polyneuropathy and encephalopathy. Neurasthenia is one of the early and more common symptoms of lead poisoning, manifested as dizziness, headache, general weakness, memory loss, sleep disturbance, and dreaming. Polyneuropathy can be divided into sensory, motor, and mixed types: [21]
Sensory manifestations are numbness of the extremities and glove-sock-type sensory disturbances at the extremities; muscle-type weakness and muscle paralysis are present in the exercise-type. Lead poisoning encephalopathy is rarely seen. It is the most severe lead poisoning and manifests as headache, nausea, vomiting, high fever, irritability, convulsions, lethargy, mental disorders, coma and other symptoms. Mild digestive symptoms can be expressed as metallic taste in the mouth, loss of appetite, bloating and discomfort in the upper abdomen, abdominal pain and constipation; severe colic. The blood system is mainly lead that interferes with the hemoglobin synthesis process and causes anemia. In general, lead poisoning can recover quickly after lead flooding treatment, and there are few sequelae except lead poisoning encephalopathy. [twenty one]

Lead pollution

Source of lead pollution

(1) Direct pollution
Involving food production technology and utensils for food, direct contact with lead in the production process of food or direct addition of lead-containing raw materials due to the production process will lead to lead pollution. Now more common are lead-containing canned food, preserved eggs and This phenomenon exists in the production of food such as popcorn. [20]
The over-standard rate of lead in 2,766 foods in 16 categories monitored from 2001 to 2008 was 5.42%. Although the overall pollution is not serious, the lead content in foods such as preserved eggs is relatively high; the pollution of lead and cadmium in Guangdong food from 2009 to 2010 The test showed that lead contaminated food in the food was mainly kelp, laver, and preserved eggs, and their over-standard rates were 20%, 30%, and 28%, respectively. In addition, investigations showed that children who do not eat canned food, preserved eggs, popcorn, etc The IQ should be high, and the results of these surveys show that the direct harm of lead-contaminated food cannot be underestimated. [20]
(2) Indirect pollution
During the growth and production of food raw materials, lead pollution is caused by soil, air, and water. With the development of modern industry, the discharge of industrial "three wastes" has enabled the toxic heavy metal lead to enter the ecosystem through various channels. Data show that as early as 1997, the area of lead pollution in China has reached 20 million m 2 , accounting for 20% of the total cultivated land area in the country. With the increase of pollution in recent years, the area of pollution has exceeded the area of pollution in 1997; Lead has been reported to be contaminated by soil, air, and water. The blood lead incident in Zhongshan, Guangzhou in May 2011 was the result of water pollution. [20]

Lead control methods

(1) curb pollution sources
China is a big country in the production of lead. Now China's lead production has ranked first in the world. Therefore, if lead ore is not properly controlled during the production process, a large-scale lead pollution incident is likely to occur. The lead poisoning incident occurred in Fengxiang, Shaanxi Province in early 2012. It is because the nearby residents were not relocated in time before mining, resulting in a pollution incident in lead mining. [20]
(2) Controlling circulation channels
Transmission channels include contamination of food through water sources, tableware, cans, etc., regular detection of the level of lead in water in threatened areas, strict prevention of heavy metal lead entering food through normal circulation channels, and in addition, regular monitoring of lead content in food on the market at random And found that the excessive food was handled in time. [20]
(3) Treatment of victims
Lead is very harmful to the human body. When the lead content in children's body reaches about 10 g / dL, the intelligence of children will be 9% lower than that of children of the same age. Regular monitoring of blood lead in populations in threatened areas and timely treatment of poisoned patients is a current issue that must be considered. one. [20]

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