People studied the properties of copper, which is found in nature in the form of fairly large nuggets, back in ancient times, when dishes, weapons, jewelry, and various household products were made from this metal and its alloys. The active use of this metal for many years is due not only to its special properties, but also to the ease of processing. Copper, which is present in the ore in the form of carbonates and oxides, is quite easily reduced, which is what our ancient ancestors learned to do.
Initially, the process of recovering this metal looked very primitive: copper ore was simply heated over fires and then subjected to sudden cooling, which led to cracking of pieces of ore, from which copper could already be extracted. Further development This technology led to air being blown into the fires: this increased the heating temperature of the ore. Then the ore began to be heated in special structures, which became the first prototypes of shaft furnaces.
The fact that copper has been used by mankind since ancient times is evidenced by archaeological finds, as a result of which products made of this metal were found. Historians have established that the first copper products appeared already in the 10th millennium BC, and it began to be most actively mined, processed and used 8–10 thousand years later. Naturally, the prerequisites for such active use of this metal were not only the relative ease of its production from ore, but also its unique properties: specific gravity, density, magnetic properties, electrical, as well as specific conductivity, etc.
Nowadays, it is already difficult to find in the form of nuggets; it is usually mined from ore, which is divided into the following types.
- Bornite - this ore can contain copper in amounts up to 65%.
- Chalcocite, also called copper luster. Such ore can contain up to 80% copper.
- Copper pyrite, also called chalcopyrite (content up to 30%).
- Covelline (content up to 64%).
Copper can also be extracted from many other minerals (malachite, cuprite, etc.). They contain it in different quantities.
Physical properties
Copper in pure form is a metal whose color can vary from pink to red.
The radius of copper ions having a positive charge can take the following values:
- if the coordination index corresponds to 6 - up to 0.091 nm;
- if this indicator corresponds to 2 - up to 0.06 nm.
The radius of the copper atom is 0.128 nm, and it is also characterized by an electron affinity of 1.8 eV. When an atom is ionized, this value can take a value from 7.726 to 82.7 eV.
Copper is a transition metal with an electronegativity value of 1.9 on the Pauling scale. In addition, its oxidation state can take different meanings. At temperatures in the range of 20–100 degrees, its thermal conductivity is 394 W/m*K. The electrical conductivity of copper, which is surpassed only by silver, is in the range of 55.5–58 MS/m.
Since copper in the potential series is to the right of hydrogen, it cannot displace this element from water and various acids. Her crystal cell has a cubic face-centered type, its value is 0.36150 nm. Copper melts at a temperature of 1083 degrees, and its boiling point is 26570. The physical properties of copper are also determined by its density, which is 8.92 g/cm3.
Of its mechanical properties and physical indicators, the following are also worth noting:
- thermal linear expansion - 0.00000017 units;
- the tensile strength to which copper products correspond is 22 kgf/mm2;
- the hardness of copper on the Brinell scale corresponds to a value of 35 kgf/mm2;
- specific gravity 8.94 g/cm3;
- elastic modulus is 132000 Mn/m2;
- the elongation value is 60%.
The magnetic properties of this metal, which is completely diamagnetic, can be considered completely unique. It is these properties, along with physical parameters: specific gravity, specific conductivity and others, that fully explain the wide demand for this metal in the production of electrical products. Aluminum has similar properties, which is also successfully used in the production of various electrical products: wires, cables, etc.
The main part of the characteristics that copper has is almost impossible to change, with the exception of its tensile strength. This property can be improved almost twice (up to 420–450 MN/m2) if a technological operation such as hardening is carried out.
Chemical properties
The chemical properties of copper are determined by its position in the periodic table, where it has serial number 29 and is located in the fourth period. What is noteworthy is that it is in the same group with noble metals. This once again confirms its uniqueness chemical properties, which should be discussed in more detail.
In conditions of low humidity, copper exhibits virtually no chemical activity. Everything changes if the product is placed in conditions characterized by high humidity and high content carbon dioxide. Under such conditions, active oxidation of copper begins: a greenish film consisting of CuCO3, Cu(OH)2 and various sulfur compounds is formed on its surface. This film, called patina, performs the important function of protecting the metal from further destruction.
Oxidation begins to actively occur when the product is heated. If the metal is heated to a temperature of 375 degrees, then copper oxide is formed on its surface, if higher (375-1100 degrees) then two-layer scale.
Copper reacts quite easily with elements that are part of the halogen group. If a metal is placed in sulfur vapor, it will ignite. It also shows a high degree of affinity for selenium. Copper does not react with nitrogen, carbon and hydrogen even at high temperatures.
The interaction of copper oxide with various substances deserves attention. Thus, when it reacts with sulfuric acid, sulfate and pure copper are formed, with hydrobromic and hydroiodic acid - copper bromide and iodide.
The reactions of copper oxide with alkalis, which result in the formation of cuprate, look different. The production of copper, in which the metal is reduced to a free state, is carried out using carbon monoxide, ammonia, methane and other materials.
Copper, when interacting with a solution of iron salts, goes into solution, and the iron is reduced. This reaction is used to remove the deposited copper layer from various products.
Mono- and divalent copper is capable of creating complex compounds that are highly stable. Such compounds are double copper salts and ammonia mixtures. Both found wide application in various industries.
Applications of copper
The use of copper, as well as aluminum, which is most similar in properties to it, is well known - in the production of cable products. Copper wires and cables are characterized by low electrical resistance and special magnetic properties. For the production of cable products, types of copper characterized by high purity are used. If even a small amount of foreign metal impurities is added to its composition, for example, only 0.02% aluminum, then the electrical conductivity of the original metal will decrease by 8–10%.
Low and its high strength, as well as the ability to give in various types mechanical processing are those properties that make it possible to produce pipes from it that are successfully used for transporting gas, hot and cold water, pair. It is no coincidence that these pipes are used as part of the engineering communications of residential and administrative buildings in most European countries.
Copper, in addition to exceptionally high electrical conductivity, is distinguished by its ability to conduct heat well. Thanks to this property, it is successfully used as part of the following systems:
- heat pipes;
- coolers used to cool elements of personal computers;
- heating and air cooling systems;
- systems that provide heat redistribution in various devices (heat exchangers).
Metal structures in which copper elements are used are distinguished not only by their low weight, but also by their exceptional decorative effect. This is what caused them active use in architecture, as well as for creating various interior elements.
Copper is a ductile golden-pink metal with a characteristic metallic luster. In the periodic system of D.I. Mendeleev this chemical element designated as Cu (Cuprum) and is under serial number 29 in group I (side subgroup), in period 4.
The Latin name Cuprum comes from the name of the island of Cyprus. There are known facts that in Cyprus back in the 3rd century BC there were copper mines and local craftsmen smelted copper. Buy copper possible in the company "Kuproom".
According to historians, society has been familiar with copper for about nine thousand years. The most ancient copper products were found during archaeological excavations on the ground modern Turkey. Archaeologists have discovered small copper beads and plates used to decorate clothing. The finds date back to the turn of the 8th-7th millennium BC. In ancient times, copper was used to make jewelry, expensive dishes, and various tools with thin blades.
The great achievement of ancient metallurgists can be called the production of an alloy with copper base- bronze.
Basic properties of copper
1. Physical properties.
In air, copper acquires a bright yellowish-red hue due to the formation of an oxide film. Thin plates have a greenish-blue color when examined through them. In its pure form, copper is quite soft, malleable and easily rolled and drawn. Impurities can increase its hardness.
The high electrical conductivity of copper can be called the main property that determines its predominant use. Copper also has very high thermal conductivity. Impurities such as iron, phosphorus, tin, antimony and arsenic affect the basic properties and reduce electrical and thermal conductivity. According to these indicators, copper is second only to silver.
Copper has high values density, melting point and boiling point. An important property is also good resistance to corrosion. For example, at high humidity, iron oxidizes much faster.
Copper lends itself well to processing: it is rolled into copper sheet And copper rod, stretches into copper wire with a thickness brought to thousandths of a millimeter. This metal is diamagnetic, that is, it is magnetized against the direction of the external magnetic field.
Copper is a relatively low-active metal. Under normal conditions in dry air, its oxidation does not occur. It reacts easily with halogens, selenium and sulfur. Acids without oxidizing properties have no effect on copper. With hydrogen, carbon and nitrogen chemical reactions No. In humid air, oxidation occurs to form copper (II) carbonate - the top layer of platinum.
Copper is amphoteric, that is, earth's crust forms cations and anions. Depending on the conditions, copper compounds exhibit acidic or basic properties.
Methods for obtaining copper
In nature, copper exists in compounds and in the form of nuggets. The compounds are represented by oxides, bicarbonates, sulfur and carbon dioxide complexes, as well as sulfide ores. The most common ores are copper pyrite and copper luster. The copper content in them is 1-2%. 90% of primary copper is mined using the pyrometallurgical method and 10% using the hydrometallurgical method.
1.
The pyrometallurgical method includes the following processes: enrichment and roasting, smelting for matte, purging in a converter, electrolytic refining.
Copper ores are enriched by flotation and oxidative roasting. The essence of the flotation method is as follows: copper particles suspended in aquatic environment, stick to the surface of the air bubbles and rise to the surface. The method allows you to obtain copper powder concentrate, which contains 10-35% copper.
Copper ores and concentrates with a significant sulfur content are subject to oxidative roasting. When heated in the presence of oxygen, sulfides are oxidized, and the amount of sulfur is reduced by almost half. Poor concentrates containing 8-25% copper are roasted. Rich concentrates containing 25-35% copper are melted without resorting to roasting.
The next stage of the pyrometallurgical method for producing copper is smelting for matte. If lump copper ore with a large amount of sulfur is used as a raw material, then smelting is carried out in shaft furnaces. And for powdered flotation concentrate, reverberatory furnaces are used. Melting occurs at a temperature of 1450 °C.
In horizontal converters with side blowing, the copper matte is blown with compressed air in order for the oxidation of sulfides and ferrum to occur. Next, the resulting oxides are converted into slag, and sulfur into oxide. The converter produces blister copper, which contains 98.4-99.4% copper, iron, sulfur, as well as small amounts of nickel, tin, silver and gold.
Blister copper is subject to fire and then electrolytic refining. Impurities are removed with gases and converted into slag. As a result of fire refining, copper is formed with a purity of up to 99.5%. And after electrolytic refining, the purity is 99.95%.
2. The hydrometallurgical method involves leaching copper with a weak solution of sulfuric acid, and then separating copper metal directly from the solution. This method is used for processing low-grade ores and does not allow for the associated extraction of precious metals along with copper.
Copper Applications
Due to their valuable qualities, copper and copper alloys are used in the electrical and electrical engineering industries, in radio electronics and instrument making. There are alloys of copper with metals such as zinc, tin, aluminum, nickel, titanium, silver, and gold. Less commonly used are alloys with non-metals: phosphorus, sulfur, oxygen. There are two groups of copper alloys: brass (alloys with zinc) and bronze (alloys with other elements).
Copper is highly environmentally friendly, which allows its use in the construction of residential buildings. For example, a copper roof, due to its anti-corrosion properties, can last more than a hundred years without special care or painting.
Copper in alloys with gold is used in jewelry. This alloy increases the strength of the product, increases resistance to deformation and abrasion.
Copper compounds are characterized by high biological activity. In plants, copper takes part in the synthesis of chlorophyll. Therefore, it can be seen in the composition of mineral fertilizers. A lack of copper in the human body can cause deterioration in blood composition. It is found in many food products. For example, this metal is found in milk. However, it is important to remember that excess copper compounds can cause poisoning. This is why you should not cook food in copper cookware. During boiling, food may get into a large number of copper If the dishes inside are covered with a layer of tin, then there is no danger of poisoning.
In medicine, copper is used as an antiseptic and astringent. It is a component of eye drops for conjunctivitis and solutions for burns.
Copper(lat. Cuprum), Cu, chemical element of group I periodic table Mendeleev; atomic number 29, atomic mass 63.546; soft, malleable red metal. Natural Copper consists of a mixture of two stable isotopes - 63Cu (69.1%) and 65Cu (30.9%).
Receipt. Copper ores are characterized by high content Copper Therefore, before smelting, finely ground ore is subjected to mechanical enrichment; in this case, valuable minerals are separated from the bulk of the waste rock; As a result, a number of commercial concentrates (for example, copper, zinc, pyrite) and tailings are obtained.
In world practice, 80% of Copper is extracted from concentrates using pyrometallurgical methods based on melting the entire mass of the material. During the smelting process, due to the greater affinity of Copper for sulfur, and the components of waste rock and iron for oxygen, Copper is concentrated in the sulfide melt (matte), and the oxides form slag. The matte is separated from the slag by settling.
In most modern plants, smelting is carried out in reverberatory or electric furnaces. In reverberatory furnaces working space extended in the horizontal direction; the hearth area is 300 m2 or more (30 m ´ 10 m), the heat necessary for melting is obtained by burning carbonaceous fuel (natural gas, fuel oil, pulverized coal) in the gas space above the surface of the bath. In electric furnaces, heat is obtained by passing through molten slag. electric current(current is supplied to the slag through graphite electrodes immersed in it).
However, both reflective and electric melting, based on external heat sources, are imperfect processes. Sulfides, which make up the bulk of copper concentrates, have a high calorific value. Therefore, smelting methods are increasingly being introduced that use the heat of combustion of sulfides (oxidizer - heated air, air enriched with oxygen, or technical oxygen). Fine, pre-dried sulfide concentrates are blown with a stream of oxygen or air into a hot high temperature bake. Particles burn in suspension (oxygen-flash smelting). Sulfides can also be oxidized in the liquid state; these processes are being intensively studied in the USSR and abroad (Japan, Australia, Canada) and are becoming the main direction in the development of pyrometallurgy of sulfide copper ores.
Rich lump sulfide ores (2-3% Cu) with a high sulfur content (35-42% S) are in some cases directly sent for smelting in shaft furnaces (furnaces with a vertical working space). In one of the varieties of shaft smelting (copper-sulfur smelting), fine coke is added to the charge, which reduces SO2 to elemental sulfur in the upper horizons of the furnace. Copper is also concentrated in the matte in this process.
The resulting liquid matte (mainly Cu2S, FeS) is poured into a converter - a cylindrical tank made of sheet steel, lined with magnesite bricks on the inside, equipped with a side row of tuyeres for air injection and a device for rotating around an axis. Compressed air is blown through the matte layer. The conversion of mattes occurs in two stages. First, iron sulfide is oxidized, and quartz is added to the converter to bind the iron oxides; converter slag is formed. Copper sulfide is then oxidized to form metal copper and SO2. This rough Copper is poured into molds. Ingots (and sometimes directly molten blister Copper) are sent for fire refining in order to extract valuable satellites (Au, Ag, Se, Fe, Bi and others) and remove harmful impurities. It is based on the greater affinity of impurity metals for oxygen than copper: Fe, Zn, Co and partially Ni and others pass into slag in the form of oxides, and sulfur (in the form of SO2) is removed with gases. After removing the slag, Copper is “teased” to restore the Cu2O dissolved in it by immersing the ends of raw birch or pine logs in liquid metal, after which it is cast into flat shapes. For electrolytic refining, these ingots are suspended in a bath of CuSO4 solution acidified with H2SO4. They serve as anodes. When current is passed, the anodes dissolve, and pure Copper is deposited on the cathodes - thin copper sheets, also obtained by electrolysis in special matrix baths. To separate dense, smooth deposits, surface-active additives (wood glue, thiourea, and others) are introduced into the electrolyte. The resulting copper cathode is washed with water and melted. Noble metals, Se, Te and other valuable copper satellites are concentrated in the anode sludge, from which they are extracted through special processing. Nickel is concentrated in the electrolyte; By removing some of the solutions for evaporation and crystallization, Ni can be obtained in the form of nickel sulfate.
