Cobalt prices, history, occurrence, extraction and use

Cobalt (chemical jargon, Latin cobaltum, standard cobalt, named Cobalt Rex from the first describer after Cobalt ore) is a chemical element with the elementary symbol Co and atomic number 27. Cobalt is a ferromagnetic transition metal from the 9. Group or cobalt group of the periodic table. In the older counting it counts to the 8. Subgroup or iron-platinum group.

History

Cobalt salts and cobalt compounds have been known for a long time and were used as cobalt blue predominantly for coloring glass and ceramics. In the Middle Ages, they were often considered valuable silver and copper ores. However, since they could not be processed and because of the arsenic content on heating gave off bad odors, they were considered bewitched. Supposedly goblins had eaten the precious silver and eliminated in its place worthless silver ores. In addition to cobalt, these were also tungsten and nickel ores. These ores were then occupied by the miners with nicknames such as nickel, tungsten (such as "wolf foam", Latin lupi spuma) and just Kobolderz, so cobalt. 1735 discovered the Swedish chemist Georg Brandt in the preparation of cobalt salts the hitherto unknown metal, described its properties and gave it its present name. 1780 discovered Torbern Olof Bergman exploring the properties that cobalt is an element.

Physical Properties

Magnetization curves of 9 ferromagnetic materials.1. Sheet steel, 2. Electrical steel, 3. Cast steel, 4. Tungsten steel, 5. Magnetic steel, 6. Cast iron, 7. Nickel, 8. Cobalt, 9. Magnetite crystal structure of α-Co, a = 250,7 pm, c = 406,9 pm

Cobalt is a steel gray, very tough heavy metal with a density of 8,89 g / cm³. It is ferromagnetic with a Curie temperature of 1150 ° C. Cobalt occurs in two modifications: a hexagonal-dense (hcp) crystal structure in the space group P63 / mmc (space group number 194) with the lattice parameters a = 250,7 pm and c = 406,9 pm and two formula units per unit cell and a cubic face centered Form (fcc) with the grid parameter a = 354,4 pm. The hcp modification (α-cobalt, historically ε-cobalt) is more stable at lower temperatures and changes at about 450 ° C into the fcc modification (β-cobalt, historically α-cobalt).

As a typical metal it conducts heat and electricity well, the electrical conductivity is 26 percent of that of copper.

A special feature is the atomic mass of the naturally occurring cobalt; with 58,93 it is larger than the average atomic mass of nickel with 58,69, the next element in the periodic table. This peculiarity exists between argon and potassium as well as between tellurium and iodine.

Chemical properties

In chemical behavior it is similar to iron and nickel, resistant to air by passivation; it is only dissolved by oxidizing acids. Cobalt is one of the non-noble elements with a normal potential of -0,277 V. In compounds, it occurs predominantly in the oxidation states + II and + III. However, the oxidation states -I, 0, + I, + II, + III, + IV and + V are also represented in compounds. Cobalt forms a variety of mostly colored complexes. In this, unlike covalent compounds, the oxidation state + III is more abundant and stable than + II.

isotope

There are a total of 30 isotopes and 18 other core isomers between 47Co and 77Co known. Natural cobalt consists entirely of the isotope 59Co. The element is therefore one of the 22 pure elements. This isotope can be examined by NMR spectroscopy.

The nuclide 57Co decays via electron capture to 57Fe. The gamma radiation emitted during the transition to the ground state of the daughter nucleus has an energy of 122,06 keV (85,6%) and 14,4 keV (9,16%). The main application of 57Co is Mössbauer spectroscopy to distinguish bivalent and trivalent iron.

The most long-lived of the unstable isotopes is 60Co (Cobalt-60, Spin 5 +), with a half-life of 5,27 years under beta decay, first in an excited state of 60Ni (Spin 4 +) and then emitting gamma radiation (two energy 1,17 and 1,33 MeV) into the ground state (spin 0 +) of this nuclide decays. For this reason, 60Co is used as a source of gamma radiation for sterilizing or preserving food, for material examination (radiographic examination) and in cancer therapy ("cobalt gun"). In medicine, other isotopes such as 57Co or 58Co can be used as tracers.

60Co is exclusively obtained artificially by neutron activation from 59Co. Spontaneous fission sources such as 252Cf serve as the source of neutron for the production of smaller quantities. 59Co pellets are exposed to neutron flux in nuclear reactors to produce larger quantities.

The formation of 60Co from 59Co under neutron radiation could potentially also be used to enhance the effect of nuclear weapons that produce neutron radiation by being coated with cobalt (cobalt bomb). During the detonation, the strong gamma emitter would be formed, through which the environment would become more contaminated than by the nuclear explosion alone. If 60Co is not properly disposed of, but melted down with other cobalt and processed into steel, steel parts made from it can be harmful to radioactivity.

With 60Co, the Wu experiment was discovered, which discovered the parity violation of the weak interaction.

occurrence

Cobalt is a rare element with a frequency in the Earth's crust of 0,004 percent. This puts it in the thirtieth place in the list of frequency ordered items. Elemental it occurs only very rarely in meteorites and in the earth's core. Cobalt is present in many minerals, but usually occurs only in small amounts. The element is always associated with nickel, often with copper, silver, iron or uranium. Nickel is about three to four times as abundant as cobalt. Both metals belong to the siderophilic elements and are characteristic for basic and ultrabasic magmatites.

Cobalt is found as a trace element in most soils. There are a number of cobalt salts in which the cobalt has been enriched by weathering or other processes. The most important are: cobaltite (obsolete cobalt shine, CoAsS), linineit and siegenite (obsolete and misleading cobalt nickel gravel; (Co, Ni) 3S4), erythrin (obsolete cobalt blossom), asbolane (obsolete Erdkobalt), skutterudite (cobalt cobalt, Smaltin, CoAs3) and Heterogenite (CoOOH). The cobalt content of sulfide ores is low, usually only 0,1-0,3 percent.

The worldwide known cobalt reserves amount to 25 million tons. The main ore deposits are located in the Democratic Republic of the Congo and in Zambia, where the cobalt occurs together with copper, also in Canada, Morocco, Cuba, Russia, Australia and the United States. Another 120 million tonnes of cobalt are suspected in the earth's crust on the soils of the Atlantic, Pacific and Indian Oceans.

Extraction and presentation

Cobalt is mainly obtained from copper and nickel ores. The exact method of extraction depends on the composition of the parent ore. First, a portion of the existing iron sulfides is converted by roasting in iron oxide and slagged with silica as iron silicate. The result is the so-called rough stone, which in addition to cobalt nickel, copper and other iron as sulfide or arsenide. By further roasting with sodium carbonate and sodium nitrate further sulfur is removed. In this case, sulfates and arsenates are formed from part of the sulfur and arsenic, which are leached with water. There remain the corresponding metal oxides, which are treated with sulfuric or hydrochloric acid. Only copper does not dissolve, while nickel, cobalt and iron go into solution. With chlorinated lime then selectively cobalt can be precipitated as cobalt hydroxide and thus separated. By heating, this is converted into cobalt (II, III) oxide (Co3O4) and then reduced to cobalt with coke or aluminum powder:

The majority of cobalt is obtained by reducing the cobalt by-products of nickel and copper mining and the melt. Because cobalt is typically a by-product, cobalt supply is highly dependent on the economic viability of copper and nickel mining in a given market.

There are several ways to separate cobalt from copper and nickel, depending on the cobalt concentration and the exact composition of the ore used. One method is foam flotation, in which surfactants bind to various ore constituents, leading to an accumulation of cobalt salts. Subsequent roasting converts the ores into cobalt (II) sulfate and oxidizes copper and iron. By washing with water, the sulfate is extracted together with the arsenates. The residues are further leached with sulfuric acid, yielding a copper sulfate solution. Cobalt can also be leached from the molten copper.

Cobalt was first used in the form of oxides, sulfates, hydroxides or carbonates for heat-resistant paints and pigments, e.g. B. used for the painting of porcelain and ceramic (see also Smalte and Blaufarbenwerke). This was followed by the most famous decorative application in the form of blue cobalt glass. After 1800, the cobalt aluminate (CoAl2O4) was industrially produced as a strong pigment.

Cobalt is now used as an alloying component to increase the heat resistance of alloyed and high-alloy steels, in particular high-speed steel and superalloys, as a binder phase in hard metals and diamond tools (see: Widia). Its use as an alloying element and in cobalt compounds makes it a strategically important metal. (See Vitallium: implants, turbine blades, chemical apparatus.) Cobalt steels are used, for example. B. for highly stressed parts that must withstand high temperatures, such. B. valve seat inserts in internal combustion engines or vanes in gas turbines.

Cobalt-based superalloys have consumed most of the cobalt produced in the past. The temperature stability of these alloys makes them suitable for turbine blades of gas turbines and aircraft engines, although nickel-based single crystal alloys surpass their performance. Cobalt-based alloys are also corrosion and wear resistant, so like titanium, they can be used to make orthopedic implants that will not wear off over time. The development of wear-resistant cobalt alloys began in the first decade of the 20. Century with the Stellitlegierungen containing chromium with different proportions of tungsten and carbon. Alloys with chromium and tungsten carbides are very hard and wear-resistant. Special cobalt-chromium-molybdenum alloys such as vitallium are used for prosthesis parts. Cobalt alloys are also used for dentures as a useful replacement for nickel that may be allergenic. Some high speed steels also contain cobalt to increase their heat and wear resistance. The special alloys of aluminum, nickel, cobalt and iron, known as Alnico, as well as samarium and cobalt (samarium-cobalt magnet) are used in permanent magnets.

Cobalt is a component of magnetic alloys, as a drier (siccative) for paints and varnishes, as a catalyst for desulfurization and hydrogenation, as hydroxide or lithium-cobalt dioxide (LiCoO2) in batteries, in corrosion or wear-resistant alloys and as a trace element for medicine and agriculture. Cobalt is also used in the production of magnetic data carriers such as tape and video cassettes, where it improves the magnetic properties by doping. Cobalt has been used as an alloy component for guitar strings for some time.

Since the advent of lithium-ion batteries in the 1990 years, cobalt has been used for batteries, especially for mobile applications, since the lithium-cobalt-oxide battery has a particularly high energy density. The first commercially available lithium-ion battery came on the market as Sony lithium-cobalt dioxide accumulator in the year 1991. Due to the expected increasing importance of accumulators for mobile electronics and electromobility, the Federation of German Industries (BDI) advises: "Due to the high concentration of cobalt deposits on the politically unstable states of Congo and Zambia, increased research into manganese and iron phosphate electrodes and also in nickel electrodes, which contain no or only small amounts of cobalt, basically recommended ". A position paper by BDI on innovative drive technologies predicts: "The global demand for raw materials for cobalt could rise by 2030 times compared to 2006 due to the rising demand for lithium-ion batteries by the year 3,4".

Lithium cobalt (III) oxide is often used in lithium-ion battery cathodes. The material consists of cobalt oxide layers with intercalated lithium. During discharge, the lithium is released as lithium ions. Nickel-cadmium batteries and nickel-metal hydride batteries also contain cobalt to enhance the oxidation of nickel in the battery.

Although in the year 2018 most of the cobalt in batteries was used in a mobile device, rechargeable batteries for electric cars are a newer application for Cobalt. This industry has quintupled its demand for cobalt, making it urgent to find new resources in more stable areas of the world. Demand is expected to continue or increase as the spread of electric vehicles increases.

Cobalt-based catalysts are used in reactions with carbon monoxide. Cobalt is also a catalyst in the Fischer-Tropsch process for the hydrogenation of carbon monoxide to liquid fuels. In the hydroformylation of alkenes, cobalt octacarbonyl is often used as the catalyst, although it is often replaced by more efficient iridium and rhodium based catalysts, e.g. B the Cativa process.

Hydrodesulfurization of petroleum uses a catalyst derived from cobalt and molybdenum. This process helps to purify the petroleum of sulfur contaminants that affect the refining of liquid fuels.

physiology

Cobalt is part of vitamin B12, the cobalamin that is essential for humans to survive. In healthy people, this vitamin may possibly be produced by gut bacteria directly from cobalt ions. However, cobalamin needs to be bound by the gastric intrinsic factor to be ingested in the ileum. However, since the production site of the man-made cobalamin is located in the colon, a resorption is not possible according to the current state of knowledge. The vitamin must therefore be absorbed by the food. Nevertheless, a daily intake of 0,1 μg Cobalt is given as a trace element for the daily needs of adults. The lack of vitamin B12 can lead to a disturbed erythropoiesis and thus to anemia. In ruminants, such a deficiency is predominantly due to insufficient intake of cobalt. In animal production, cobalt is added to the feed in traces if the animals need to be fed on cobalt-poor grazing areas. This should be used to counteract growth and lactation disorders, anemia and loss of appetite.

Bacteria in the stomach of ruminants convert cobalt salts into vitamin B12, a compound that can only be produced by bacteria or archaea. Therefore, a minimal presence of cobalt in soils significantly improves the health of grazing animals.

Cobalamin-based proteins use corrin to hold the cobalt. Coenzyme B12 has a reactive C-Co bond involved in the reactions. In humans, B12 has two types of alkyl ligands: methyl and adenosyl. Methylcobalamin promotes the transfer of methyl groups. The adenosyl version of B12 catalyzes rearrangements in which a hydrogen atom is transferred directly between two adjacent atoms, with simultaneous replacement of the second substituent X, which may be a carbon atom with a substituent, an oxygen atom of an alcohol, or an amine. Methylmalonyl-CoA mutase converts methylmalonyl-CoA into succinyl-CoA, an important step in energy recovery from proteins and fats.

Although much less common than other metalloproteins (eg, zinc and iron), other cobaltoproteins are known besides B12. These proteins include methionine aminopeptidase 2, an enzyme found in humans and other mammals that does not use the corrin ring of B12, but directly binds cobalt. Another uncorrected cobalt enzyme is nitrile hydratase, an enzyme in bacteria that metabolizes nitriles.

While small overdoses of cobalt compounds are only slightly toxic to humans, larger doses from 25 to 30 mg per day lead to skin, lung, stomach disorders, liver, heart, kidney damage and cancerous ulcers.

In the mid-1960's there were a number of cases of cobalt-induced cardiomyopathy (cobalt cardiomyopathy) in Canada and the United States. In Quebec, 49 was registered, and in Omaha 64 patients. The symptoms included, among other things, stomach pain, weight loss, nausea, shortness of breath and cough. The mortality rate was 40 percent. Autopsies revealed severe damage to the heart muscle and liver. All patients were strong beer drinkers with a consumption of 1,5 to 3 liters per day. They preferred to consume varieties from local breweries, which had started adding cobalt (II) sulfate as a foam stabilizer about a month earlier. The limit values ​​for cobalt in food were not exceeded. The onset of the illnesses came to a halt immediately after the breweries had stopped the cobalt (II) sulfate admixtures.

Cobalt (II) salts activate the hypoxia-inducible transcription factors (HIF) and increase the expression of HIF-dependent genes. This includes the gene for erythropoietin (EPO). Cobalt (II) salts could be misused by athletes to promote the formation of red blood cells.

proof

A relatively meaningful pre-sample for cobalt is the phosphoric salt bead, which is colored intensely blue by cobalt ions. In the cation separation process, it can be detected next to nickel with thiocyanate and amyl alcohol, it forms when dissolved in amyl alcohol blue Co (SCN) 2. The reddish-violet cobalt (II) thiocyanate also turns blue when mixed with acetone.

Quantitatively, cobalt can be determined with EDTA in a complexometric titration against murexide as an indicator.

Connections

Cobalt usually occurs in its compounds in two or trivalent. These compounds often have bold colors. Important cobalt compounds are:

Oxide

Cobalt (II) oxide is an olive-green, water-insoluble salt. It forms a sodium chloride structure of the space group Fm3m (room group number 225). Cobalt (II) oxide is used as a raw material for the production of pigments, in particular for the production of the pigment Smalte, which is also used in the ceramics industry. It can also be used to make cobalt glass and Thénards Blue. Cobalt (II, III) oxide is a black solid and belongs to the group of spinels.

Cobalt (II, III) oxide is an important intermediate in the recovery of metallic cobalt. By roasting and leaching, cobalt (II, III) oxide is first obtained from various cobalt salts (usually sulfides or arsenides). This can now be reduced with carbon or aluminothermic to the element.

Cobalt (III) oxide is a gray-black solid which is practically insoluble in water. At a temperature above 895 ° C, it releases oxygen, forming cobalt oxides such as Co3O4 and CoO.

halides

Cobalt (II) chloride (anhydrous)
Cobalt (II) chloride hexahydrate

Cobalt (II) chloride is an anhydrous blue, hexahydrate pink salt. It has a trigonal cadmium (II) hydroxide type crystal structure with space group P3m1 (space group number 164). Anhydrous cobalt (II) chloride is very hygroscopic and easily absorbs water. It changes very characteristic its color from blue to pink. The opposite color change from pink to blue is also possible by heating the hexahydrate to temperatures above 35 ° C. Because of the typical color change, it served as a moisture indicator in desiccants such as silica gel. With the help of cobalt (II) chloride, water can also be detected in other solutions. It is also used as a so-called secret ink, as it is barely visible as a hexahydrate in aqueous solution on the paper, but when it is heated, appears deep blue writing.

Cobalt (II) bromide is a green hygroscopic solid that turns into the red hexahydrate in the air. In water, it is easily soluble in red color. Cobalt (II) iodide is a black graphite-like hygroscopic mass that slowly turns black in green in air. It is soluble in water, with dilute solutions appearing red, concentrated solutions red at low temperatures, and all shades from brown to olive green at higher temperatures. Cobalt (II) bromide and cobalt (II) iodide have a hexagonal cadmium iodide crystal structure of space group P63mc (space group number 186).

Further connections

Cobalt (II) nitrate is a salt of nitric acid formed from the cobalt cation and the nitrate anion. The brown-red and hygroscopic salt is usually hexahydrate, forming monoclinic crystals that are readily soluble in water, ethanol, and other organic solvents.

Cobalt (II) oxalate is a flammable, non-flammable, crystalline, pink solid that is virtually insoluble in water. It decomposes when heated above 300 ° C. It occurs in two allotropic crystal structures. One has a monoclinic crystal structure with the space group C2 / c (space group number 15), the other an orthorhombic crystal structure with the space group Cccm (space group number 66). Cobalt (II) oxalate is mainly used for the production of cobalt powder. The yellowish-pink tetrahydrate is used in the preparation of catalysts.

Cobalt (II) sulfate is a violet-red, hygroscopic salt in the anhydrous state. Cobalt (II) sulphate is used for the production of pigments, glazes, in porcelain painting, for the toning of papers (photography), in baths for cobalt electroplating and for trace element supplementation in aquaristics.

Cobalt yellow is a fine, light crystalline powder and is used as a pigment for oil and watercolor painting.

Thénards Blue is a blue pigment made by sintering cobalt (II) oxide with alumina at 1200 ° C. It is extremely stable and has been used in the past as a dye for ceramics (especially Chinese porcelain), jewelry and paints. Transparent glasses are tinted with the silica-based cobalt pigment smalt.

The pigment Rinmans Green is a turquoise green powder and is mainly used for oil paints and cement paints. Rinman's Green is a popular source of zinc. Zinc oxide or zinc hydroxide is mixed on a Magnesiarinne with a small amount of a highly diluted cobalt nitrate solution. The faint glow in the oxidizing flame creates Rinman's green.

cobalt complexes

Upon addition of ammonia solution, a cobalt (II) chloride solution initially precipitates cobalt (II) hydroxide, which dissolves in excess of ammonia solution and ammonium chloride in the presence of atmospheric oxygen as the oxidant to form different amine cobalt (III) complexes , In particular, the orange-yellow hexaammine cobalt (III) chloride and the red aquapentaammo cobalt (III) chloride are formed.

In addition, various Chloroammincobalt (III) complexes can form, such as Chloropentaammincobalt (III) chloride or Dichlorotetraammincobalt (III) chloride. Some of these compounds are eliminated from the solution. In addition, there are also ammine complexes of cobalt (II) salts, such as hexaammine cobalt (II) sulfate, which can be prepared by passing ammonia gas over anhydrous cobalt (II) sulfate.

In addition to the ammine complexes, a variety of compounds with different ligands exist. Examples are the potassium hexacyanocobaltate (II) (K4 [Co (CN) 6]), the potassium tetrathiocyanatocobaltate (II) (K2 [Co (SCN) 4]), the potassium hexanitritocobaltate (III) (Fischer's salt, cobalt yellow), and complexes with organic Ligands such as ethylenediamine or oxalation.

Noteworthy is a property of [Co (NH3) 5 (NO2)] Cl (NO3). When irradiated with UV light, the micrometer-to-millimeter-sized crystals in this cobalt coordination compound jump, leaving distances that are a thousand times their size. This is due to isomerization of the nitrite ligand (NO2), which leads to stresses in the crystal. This conversion of light into mechanical energy has been studied by scientists from the United Arab Emirates and Russia.

Cobalt prices

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