Knowledge about lead
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Lead is one of the earliest metals that humans extracted from lead-zinc ores. It is the softest heavy metal and one of the metals with a high density; it has a blue-gray color, a hardness of 1.5, a density of 11.34, a melting point of 327.4°C, and a boiling point of 1750°C. It possesses good ductility and can be easily alloyed with other metals such as zinc, tin, antimony, and arsenic. Zinc is a metal that was extracted from lead-zinc ores at a later time; it was the last of the seven ancient non-ferrous metals (copper, tin, lead, gold, silver, mercury, zinc). Zinc metal is blue-white in color, with a hardness of 2.0, a melting point of 419.5°C, and a boiling point of 911°C. When heated to 100–150°C, it exhibits good malleability; its specific gravity after rolling is 7.19. Zinc can be combined with various non-ferrous metals to form alloys or zinc-containing alloys; the most important of these are bronzes made from zinc together with copper, tin, lead, etc. It can also be used to create die-casting alloys with aluminum, magnesium, copper, and other metals. Lead and zinc have a wide range of applications, being used in fields such as the electrical industry, mechanical industry, **industry, metallurgical industry, chemical industry, light industry, and pharmaceutical industry. Furthermore, lead metal is also widely used in industries such as the nuclear industry and the oil industry. I. Characteristics of mineral raw materials: Lead and zinc are closely associated in nature, especially in primary ore deposits. They share a common source of mineralizing agents and very similar geochemical behaviors, have similar outer electron configurations, all exhibit strong thiol affinity, and form the same soluble complexes. Their degree of adsorption by ferromanganese, clay, or organic matter is also similar. The average lead content in the Earth’s crust is about 1510-6, while in relevant rocks it is 710-6 in sandstones, 910-6 in carbonate rocks, and 2010-6 in shales. The average zinc content in the Earth’s crust is about 8010-6. In various rocks, it ranges from 10510-6 in basalt, 6010-6 in granite, 1610-6 in sandstone, 2010-6 in carbonate rocks, and 9510-6 in shale. To date, about 250 different lead-zinc minerals have been discovered in the Earth’s crust, of which roughly one-third are sulfides and sulfates. Galena, sphalerite, etc. are the main industrial mineral raw materials for the smelting of lead and zinc. II. Requirements of the ore industry: Although more than 250 lead-zinc minerals have been discovered to date, only 17 are available for use in industrial applications. Among them, there are 11 minerals used in the lead industry and 6 minerals used in the zinc industry (Table 3.8.1), with galena and sphalerite being the most important. Ore industry types are based on the natural type of ore; according to the degree of oxidation, they can be classified as sulfide ores (with a lead or zinc oxidation rate of <10%), oxide ores (with a lead or zinc oxidation rate of >30%), and mixed ores (with a lead or zinc oxidation rate of 10%–30%) ； Based on the main useful components in the ore, they can be classified as: lead ore, zinc ore, lead-zinc ore, lead-zinc-copper ore, lead-zinc-sulfur ore, lead-zinc-copper-sulfur ore, lead-tin ore, lead-antimony ore, zinc-copper ore, etc ； Based on their structural characteristics, ores can be classified into: disseminated ores, dense massive ores, brecciated ores, banded ores, and fine-veined disseminated ores, among others. To meet the needs of geological exploration of lead-zinc mines and mine production and construction in China, the Ministry of Geology and Mineral Resources and the Ministry of Metallurgical Industry jointly formulated and issued the \"Specifications for Geological Exploration of Lead-Zinc Mines\" (provisional version) in 1983, based on the status of lead-zinc mineral resources in China as well as the technical conditions for mining, processing, and smelting. These specifications establish general industrial criteria for lead-zinc mines, which are used in preliminary exploration to assess whether a deposit has industrial value (Table 3.8.2). For a specific deposit, the industrial indicators to be used as the basis for mine construction, as outlined in the geological exploration reports, must first receive preliminary suggestions from the geological exploration agency, along with the necessary geological data. After the industrial department commissions the mine design agency to conduct economic analyses and comparative studies, these indicators are determined by the industrial authorities at or above the provincial level before they can be used as a basis for calculating the reserves of that deposit. During the mining of a deposit, the industrial indicators for the ore can be continuously adjusted based on a range of factors, including changes in the lead and zinc market conditions, the level of mining, processing, and smelting technologies, the economic benefits of mine development, and the need for rational resource protection. In order to carry out comprehensive development and utilization of the associated beneficial components, when the grade of these components in lead-zinc deposits reaches the levels specified in Table 3.8.3, it is necessary to conduct thorough sampling and chemical analysis, study the occurrence patterns of these components, and perform hydrometallurgical tests, so as to provide a basis for a rational comprehensive evaluation, development, and utilization. III. A Brief History of Mining: The ancestors of the Chinese nation made significant contributions to the mining, smelting, and utilization of lead and zinc ores. In ancient China, “lead” was written as “钅公”. Lead was already used in bronze casting during the middle period of the Shang Dynasty (16th–11th centuries BC), and the lead content in the spear blades from the Western Zhou Dynasty (11th century BC–771 BC) reached 99.75%. In ancient times, lead was often added to copper to form alloys, and it was also used to make lead white, lead tetroxide, and other substances. There were two types of raw materials used for lead smelting in ancient times: one was lead oxide, primarily cerusite, and the other was sulfide ores, primarily galena. In his work \"Shuyuan Zaji\", Lu Rong of the Ming dynasty described the method for smelting lead sulfide ores containing silver. In his work \"Tian Gong Kai Wu\", Song Yingxing mentioned three types of lead-zinc minerals that were mined at that time. One of them was called \"silver mine lead\", referring to galena that occurs together with minerals such as argentite ； The other type is “copper mountain lead,” referring to polymetallic ores containing galena, sphalerite, chalcopyrite, etc ； Another type is “grassy galena,” which may refer to galena with large crystals. Since lead ores often contain silver, in ancient times lead was mined and smelted on a large scale in order to extract silver. China was the first to invent zinc smelting. In ancient times, zinc was called “Wō qiān”. Zinc smelting could be carried out as early as the 10th century, during the Five Dynasties period, according to historical records. Records in the local history of Hezhang, Guizhou, indicate that zinc smelting began in the Magu area of this county during the Tianfu era of Emperor Gaozu of the Later Han Dynasty in the Five Dynasties period (947 AD). Song Yingxing of the Ming dynasty also described this in his work \"Tian Gong Kai Wu\", mentioning that calamine was used as the raw material and smelting took place in crucibles; the book includes illustrations to illustrate this. During the Ming and Qing dynasties, zinc was mainly used to make brass for coin casting and the production of various utensils. The export of zinc ingots to Europe began around the early 17th century. A ship that carried zinc ingots from Guangzhou in 1745 ran aground and sank off Gothenburg in Sweden; in 1872, some of the zinc ingots were recovered, and analysis showed that their zinc content was 98.99%, indicating that China’s level of zinc smelting at that time was quite high. In ancient China, not only were significant innovations made in the smelting and utilization of lead and zinc, but the zonal distribution of lead and zinc deposits was also recognized very early on. The “Guanzi: Earth Numbers” chapter states that “where there are mound stones above, there is lead, tin, and red copper below,” and “where there is lead above, there is silver below.” In the exploration of many modern lead-zinc deposits, numerous mining areas have been discovered through ancient mine shafts and remnants of smelting furnaces. Over the past century, during the period of old China, the lead and zinc industry was underdeveloped; there were only a few small mines and factories. Mining, processing, and smelting were carried out using traditional methods, with the highest annual production amounts reaching 8,900 tons of lead and 7,100 tons of zinc. After the founding of the People’s Republic of China, the lead and zinc industry developed rapidly. Through more than 40 years of extensive geological exploration, abundant lead and zinc mineral resources have been identified. A large number of state-owned large and medium-sized lead and zinc mines and smelters have been established, resulting in significant mining, processing, and smelting capabilities; the production volume ranks among the highest in the world. In 1996, the production of lead concentrate (metal content, the same below) was 643,000 tons, while the production of zinc concentrate (metal content, the same below) was 1.121 million tons. Lead and zinc metal production (including mineral production and by-product production): 706,000 tons of lead, ranking 2nd in the world ； Zinc: 1.184 million tons, ranking first in the world. It now not only meets domestic demand but also exports lead and zinc products, becoming one of the major producers of lead and zinc in the world. This post was last edited by The distance to happiness on 2009-3-5 10:33]
This post was last edited by cy1125915 on 2014-8-17 at 21:54. The mixer’s role is to combine various ores together, followed by sintering, crushing, and then feeding the mixture into the furnace to produce crude lead. The current shortage of mineral resources represents a challenge for lead smelting. Generally, several types of lead ores are used in combination for smelting. Among these ores, lead concentrate has the highest lead content; other ores such as silver-rich ores can also be used in combination. Those responsible for mixing these ores are known as mixers. They take advantage of the strengths of each ore while minimizing its weaknesses, thereby achieving the best recovery rates. The mixers prepare the ores in the optimal proportions. Once the ores are properly mixed, they are placed in special furnaces for sintering. After this process, the ores form large masses, which must then be crushed into smaller pieces before being fed into the furnace for further processing. The crude lead produced has a purity of over 95%. There are two types of waste products generated: water-quenched slag and matte. Blast furnace smelting has relatively low costs and is widely used in China, but it results in lower recovery rates and greater pollution. The oxygen-bottom-blown furnaces used at Hunan Shuikoushan Plant No. 8 represent modern manufacturing practices. These furnaces do not use lead sludge or lead oxide ores; instead, they use only concentrated ores, which are fed directly into the furnaces without going through a sintering process. This method eliminates pollution and increases recovery rates, though it incurs higher costs. An oxygen production facility is also required to supply the oxygen needed for smelting. Crude lead → Electrolysis → Pure lead → Anode slime → Decomposition → Gold, silver, bismuth, antimony
Rough calculation: Electricity cost + Labor cost + Coke + Coal + Water + Recovery rate + Logistics wages + Labor protection expenses = Lead smelting cost
Properties of zinc: Zinc is brittle at room temperature; it becomes softer when heated to 100–150°C, allowing it to be pressed into sheets or drawn into wires. But above 200°C, it becomes brittle and easily breaks into powder. Zinc is an active metal; at room temperature, a dense film of basic zinc carbonate forms on its surface in contact with air, preventing further oxidation of the underlying zinc. Zinc undergoes intense oxidation when heated to 225°C, producing a blue-green flame upon combustion. When heated, zinc reacts with fluorine, chlorine, bromine, and sulfur to form compounds. Zinc is a metal with a negative electrode potential; it dissolves easily in acids and can also displace certain metals from solutions, such as gold, silver, copper, and cadmium. Important compounds include zinc oxide, zinc sulfate, and zinc chloride. ■ Zinc resources: There are many mineral species of zinc in nature, with the common ones including sphalerite, wurtzite, zinc blende, smithsonite, zinc silicate, and hydrozincite. The world’s zinc reserves amount to 2.4 billion tons, and production is increasing year by year; in 1980, production was 6.14 million tons. China’s zinc reserves amount to 33 million tons, with production reaching 856,900 tons in 1993. ■ Production of zinc: The zinc concentrate obtained through the flotation of lead-zinc sulfide ores generally contains about 50% zinc, around 30% sulfur, and 5–14% iron. It also contains small amounts of lead, cadmium, copper, and precious metals, as well as trace amounts of rare metals such as indium, germanium, gallium, and thallium. The methods for producing zinc from zinc sulfide concentrate are wet process and pyrometallurgical process. The approximate proportion of zinc produced by various zinc smelting methods in the 1970s was: 74% from wet-process zinc smelting and 26% from dry-process zinc smelting (of which 5.6% came from vertical furnace methods, 2.2% from horizontal furnace methods, 11.4% from blast furnace methods, and 6.8% from electric heating methods). ■ Uses of zinc: Zinc is widely used in the manufacture of various alloys, such as brass, white brass, and bronze. Brass with a zinc content of 40% or less has the greatest practical value. By adding elements such as tin, nickel, manganese, iron, tungsten, and lead to brass, its physical properties can be altered; therefore, such alloys are known as special brasses. Another use of zinc is in galvanizing, and it is also used in the manufacture of dry batteries. Since zinc can fill even the smallest spaces within a mold during casting processes, it is often used as a material for precision castings in the automotive industry. Zinc compounds can be utilized in the textile industry, as well as in medicine and the rubber industry. It is used in the production of paints, pigments, dyes, etc.; in agriculture to make pesticides. Zinc is also employed in manufacturing microcrystalline zinc sheets, as well as in technologies such as fax plate production and die-casting alloys.
A chemical element. The chemical symbol for Pb is Pb; its atomic number is 82 and its atomic weight is 207.2. It belongs to group ⅣA of the periodic table. One of the first metals to be refined by humans. Lead figurines existed during Egypt’s Predynastic period. The ancient Romans already knew that lead was resistant to corrosion, and they used it extensively for water pipes. Ancient Egypt used lead compounds in ceramic glazes. During the middle period of the Shang Dynasty in China, lead was already added to bronze wares during their casting, and its content was also high in the lead-edged spears from the Western Zhou Dynasty. The abundance of lead in the Earth’s crust is 1.6×10-3%, and it rarely exists in its free state in nature; the main minerals are galena (PbS), cerussite (PbCO3), and lead sulfate (PbSO4). Lead is a decay product of uranium and thorium, and therefore is also present in various uranium and thorium ores. Silver-white metal, but with a slight blue tint; it loses its luster in air and turns dark gray. Its melting point is 327.502°C, boiling point is 1740°C, density is 11.3437 grams per cubic centimeter, and its Mohs hardness is 1.5 – it is quite soft. Lead is highly malleable and can be pressed into thin sheets, but it lacks ductility and cannot be drawn into wires. In humid air containing carbon dioxide, a lead carbonate basic film forms on the surface, preventing further oxidation of the lead. When heated, it can combine with oxygen, sulfur, and halogens to form corresponding compounds. There are 3 types of lead oxides: lead oxide (PbO), commonly known as litharge, which comes in red and yellow variants ； Lead dioxide (PbO2) is a brown solid with oxidizing properties ； Lead tetroxide (Pb3O4), commonly known as red lead, is a red powder. Lead hydroxide [Pb(OH)2] is an amphoteric hydroxide that is soluble in both acids and bases. It does not react with water; when it reacts with hydrochloric acid, lead chloride with low solubility is formed and coats the surface of the lead, thereby terminating the reaction. Its reaction with sulfuric acid is similar to that with hydrochloric acid. It is soluble in hot concentrated sulfuric acid, forming soluble lead bisulfate ； It dissolves in dilute nitric acid to form lead nitrate. Since lead nitrate is insoluble in concentrated nitric acid, its reaction with it comes to an end very quickly. The oxidation states of lead are +2 and +4. Lead and its compounds are toxic to the human body; once absorbed, they are primarily stored in the bones, where they partially replace calcium in calcium phosphate and are not easily excreted. Severe poisoning can cause damage to the nervous system; in extreme cases, it may lead to lead toxic encephalopathy, which is commonly seen in cases of tetraethyl lead poisoning. Vitamins B1 and C, as well as rutin, can improve metabolism in patients with lead poisoning and accelerate the excretion of lead. Calcium ethylenediaminetetraacetate disodium and similar compounds have lead-excreting effects. Decoctions of Chinese herbal medicines such as Lysimachia christinae can also treat lead poisoning. The production methods include: ① Converting the lead sulfide portion in galena into lead sulfate, and the two then react further to yield metallic lead. ②Lead sulfide is melted into lead oxide, and then it is smelted together with coke and limestone in a blast furnace to produce metallic lead. Refining methods include: ① pyrometallurgical refining. First, the crude lead is melted, and substances such as sulfur, sodium hydroxide, sodium chloride, and sodium nitrate are added to separate the impurities as slag. ②Electrorefining. Using thick lead as the anode and pure lead as the cathode, pure lead can be obtained. Corrosion-resistant, can be used as water pipes. Alloys of lead, antimony, and tin have a low melting point (around 240°C); they expand upon solidification and can be used as printing type. Lead glass is used as an X-ray shielding screen. Large amounts of lead are used in the production of tetraethyl lead, an anti-knock agent for gasoline, and battery plates. Lead is a chemical element whose chemical symbol is Pb (from Latin Plumbum), with an atomic number of 82. Lead is a soft, heavy metal that is toxic; it is a ductile group metal. Lead has a bluish-white color, and its surface is quickly covered with a layer of dark gray oxide in the air. Lead is used as a building material, in lead-acid batteries, for bullets and shells, and it is also present in solder, trophies, and some alloys. Lead has the highest atomic number among all stable chemical elements. Key features: Lead lacks an oxide layer, has a bright color, high density, very low hardness, and excellent ductility. It has quite low electrical conductivity but high corrosion resistance, which is why it is often used as a container for substances with strong corrosive properties, such as sulfuric acid. Adding a small amount of antimony or other metals can further enhance its corrosion resistance. Humans knew lead as early as 7,000 years ago. It is widely distributed, easy to extract, and easy to process; it has high ductility, is very soft, and has a low melting point. Lead was already mentioned in the Bible’s Book of Exodus. Ancient Rome used a great deal of lead. Some even believe that one of the reasons for the Roman invasion of Britain was that Cornwall contained the largest lead mines known at that time. Even in ice cores drilled from Greenland, an increase in lead levels in the atmosphere from the 5th century to the 3rd century BC can be measured. This elevation is considered to have been caused by the Romans today. Alchemists considered lead to be the oldest metal and associated it with Saturn. Throughout human history, lead has been a metal that was widely used. Starting from the mid-1980s, the use of lead began to decline sharply. The main reasons are the physiological effects of lead and its environmental pollution. Today, gasoline, dyes, solder, and plumbing pipes generally do not contain lead. Pure lead is rare in nature. Today, lead is mainly smelted and extracted together with metals such as zinc, silver, and copper. The main lead ore is galena (PbS), which contains 86.6% lead. Other common lead-containing minerals include lead carbonate (PbCO3) and lead sulfate (PbSO4). The largest lead-producing countries in the world are China, the United States, Australia, Russia, and Canada. Today, over half of the lead is recycled. Lead mines are generally mined by drilling or blasting. After being mined, the ore is ground and then mixed with water and other chemicals (such as the surfactant sodium xanthate). Bubbles rise in the container of this mixture, and the lead-containing minerals rise to the surface with these bubbles, forming a layer of foam. This layer of foam can be collected. This process can be repeated multiple times, and the result contains 50% lead. The collected foam was dried and melted to obtain lead at 97% purity. This melt is cooled slowly, and the impurities, being less dense, rise to the surface where they can be removed. The remaining lead was melted again. Cold air is blown into the melt; more impurities rise and are removed, resulting in 99.9% pure lead. Lead ore free of impurities is burned in air to form lead oxide, which is then reduced by heating it with carbon to obtain lead. Reaction equations: 2PbS + 3O₂ → 2PbO + 2SO₂; PbO + C → Pb + CO; PbO + CO → Pb + CO₂. Lead has four natural, stable isotopes: Pb-204 (1.4%), Pb-206 (24.1%), Pb-207 (22.1%), and Pb-208 (52.4%). The last three are the final products of uranium-238, uranium-235, and thorium-232 after a series of fissions. The half-lives of these reactions are 4.47×109 years, 7.04×108 years, and 1.4×1010 years, respectively. Only 204Pb is naturally occurring and not a decay product. The surface can form a lead basic carbonate film in air, preventing further oxidation inside. Lead bricks or lead aprons are manufactured to protect against X-rays and other radiation. Used to manufacture alloys. Solder rods made of equal amounts of lead and tin can be used to weld metals. Making type metal. Used as electrodes for batteries. Alloys of lead and antimony have a low melting point and are used to manufacture fuses. It can be used to manufacture lead bullets. It was once used to make pencils, which is how pencils got their name. Lead is a toxic metal that can particularly damage children’s nervous system, and it can cause diseases of the blood circulation system and the brain. Long-term exposure to lead and its salts (especially the soluble and highly oxidizing PbO2) can cause kidney disease and abdominal pain similar to colic. Some believe that the Alzheimer’s disease suffered by many ancient Roman emperors was caused by the use of lead in water pipes at that time (as well as lead salts being used as sweeteners in wine). Moreover, once lead accumulates in the body, it is difficult to eliminate on its own; it can only be removed through certain medications. There is a saying that seaweed and wood ear mushrooms have the ability to remove heavy metals ； Alternating between heavy consumption of meat and dairy products over a certain period of time (such as half a month) can help eliminate lead. Its use has been reduced due to suspicions that lead causes intellectual decline in children. In developed countries, **lead-based paint is no longer sold.** Ceramic products containing lead salts can cause poisoning, especially if the solution inside the container is acidic (such as fruit juice), as these solutions can dissolve the lead ions in the ceramics. The harm of lead, especially for girls and young women, can be very severe.