The cobalt It is a transition metal that belongs to group VIIIB of the periodic table and whose chemical symbol is Co. It is a grayish-blue solid (depending on its impurities), found throughout the earth's crust; although its concentration barely represents 25 ppm or 0.001% of it.
This metal is an essential trace element in ruminant nutrition. It is also part of the core of vitamin B12, necessary for the maturation of erythrocytes. Vitamin B12 It has a structure similar to that of the heme group of hemoglobin; but with Co instead of Fe.
In nature, cobalt is not usually found pure, but within complex mineral matrices such as: cobaltite, skutterudite, erythrite, etc. In these minerals, cobalt is usually combined with nickel, iron or arsenic..
The name 'cobalt' comes from the German kobalt, which in turn derived from kobolt, a name that miners gave to mineral ores that produced blue dyes and had few metals that they knew; ores that, it is worth mentioning, caused them poisoning.
Cobalt is found in ores along with nickel, iron, and copper, among other metals. Therefore, it cannot be obtained pure, and requires intense refining work to purify it until its use is practical..
It was discovered by the Swedish chemist Georg Brandt between 1730 and 1740. It was the first metal discovered since prehistory. Brandt pointed out that cobalt was responsible for the blue tint of ceramics and glass; and not bismuth, as was believed until then.
Cobalt has 29 isotopes. The 59Co is stable and represents almost 100% of the cobalt isotopes; the remaining 28 are radioisotopes. These include 60Co, used in cancer treatment. It is a magnetic element, conserving its magnetism at high temperatures. This property has allowed it to form alloys such as the so-called Alinco, used in loudspeakers, microphones, radio horns, etc..
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Cobalt was used as far back as 2,000 to 3,000 years BC. The Egyptians, the Persians and the Chinese dynasties used it in the elaboration of their sculptures and ceramics. It provided the blue coloration so appreciated in works of art and articles of use.
The Egyptians (1550 - 1292 BC) were probably the first people to use cobalt to give glass its blue color..
Cobalt is not isolated in ores, but in the presence of minerals with nickel, copper and arsenic.
When trying to melt copper with nickel, arsenic oxide was produced, a very poisonous gas that was the cause of the poisoning suffered by the miners.
Cobalt was discovered in approximately 1735 by the Swedish chemist Georg Brandt, who realized that cobalt, precisely, was the metal that provided the blue coloration of ceramics and glass.
It was the first metal discovered since ancient times. Since this time, man used numerous metals such as iron, copper, silver, tin, gold, etc ... In many cases it is unknown when they began to be used..
The first cobalt mining in the world began in Europe, with Norway being the first producer of cobalt blue; a compound of alumina and cobalt, in addition to enamel (powdered cobalt glass), used as a pigment in ceramics and in paint.
The preponderance in the production of cobalt, moved to New Caledonia (1864) and Canada (1904), in the Ontario region due to the discovery of deposits in those countries.
Later, the current Democratic Republic of the Congo (1913) became the world's leading producer of cobalt due to the discovery of large deposits in the Katanga region. Currently this country, together with Canada and Australia, is one of the main cobalt producers.
Meanwhile, the ROC is the world's leading producer of refined cobalt, as it imports the metal from the Democratic Republic of the Congo for refining..
In 1938, John Livinglood and Glenn Seaborg achieved production in an atomic reactor of the 60Co; radioactive isotope used in medicine to treat cancer.
Cobalt, like other metals, holds its atoms together through the metallic bond. The force and compression is such that they establish a metallic crystal, where there is a tide of electrons and conduction bands that explain their electrical and thermal conductivities..
Microscopically analyzing cobalt crystals, it will be found that they have a compact hexagonal structure; there are triangles of Co atoms arranged in ABAB ... layers, forming triangular prisms with interspersed layers, which in turn, represent the sixth part of a hexagon.
This structure is present for most cobalt samples at temperatures below 450ºC. However, when the temperature rises, a transition begins between two crystallographic phases: the compact hexagonal (hcp) and the face-centered cubic (fcc, for its acronym in English: face-centered cubic).
The transition is slow, so not all hexagonal crystals turn cubic. Thus, at high temperatures cobalt can exhibit both crystalline structures; and then, its properties are no longer homogeneous for all metal.
The crystal structure is not completely perfect; it can harbor irregularities, which define crystalline grains of different sizes. The smaller they are, the lighter the metal will appear or sponge-like. On the other hand, when the grains are large, the metal will become solid and solid..
The detail with cobalt is that not only the grains modify the external appearance of the metal: also its crystalline structure. Below 450 ° C the hcp structure should predominate; but when the grains are small, as in spongy cobalt, the dominant structure is the fcc.
The opposite occurs when the grains are large: the fcc structure dominates over the hcp. It makes sense since large grains are heavier and put greater pressure on each other. At higher pressures, the Co atoms compact more and choose to adopt the hcp structure.
At high temperatures (T> 1000ºC), the transitions just described occur; but in the case of spongy cobalt, a small portion of its crystals become hexagonal, while most continue to be cubic..
In a Spanish research work (Peña O'shea V. et al., 2009), it was shown that it was possible to synthesize hexagonal cobalt nanocrystals capable of withstanding temperatures close to 700ºC without undergoing transitions to the fcc phase..
To do this, the researchers reduced samples of cobalt oxides with CO and Htwo, finding that hcp nanocrystals owed their stability to a coating of carbon nanofibers.
The electron configuration of cobalt is:
[Ar] 3d74stwo
It can therefore theoretically lose up to nine electrons from its valence shell; but this does not occur (at least under normal conditions), nor is the Co cation formed9+.
Its oxidation states are: -3, -1, +1, +2, +3, +4, +5, with +2 and +3 being the main ones.
Solid, lustrous, blue-gray metal. Polished cobalt is silvery white with a bluish hue.
58.933 g / mol.
27.
It is a transition metal that belongs to group 9 (VIIIB), period 4.
1,768 K (1,495 ºC, 2,723 ºF).
3,200 K (2,927 ºC, 5,301 ºF).
8.90 g / cm3.
16.06 kJ / mol.
377 kJ / mol.
24.81 J / mol K
4,720 m / s (measured on a metal rod).
5.0 on the Mohs scale.
It is one of the three ferromagnetic elements at room temperature. Cobalt magnets retain their magnetism at temperatures as high as 1,121ºC (2,050ºF).
1.88 on the Pauling scale.
First ionization level: 740.4 kJ / mol.
Second ionization level: 1,648 kJ / mol.
Third ionization level: 3,232 kJ / mol.
125 pm.
6.7 cm3/ mol.
Cobalt slowly dissolves in dilute mineral acids. It does not combine directly with hydrogen or nitrogen, but it does combine with carbon, phosphorus, and sulfur by heating. Binds to oxygen present in water vapor at high temperatures.
Reacts vigorously with 15 M nitric acid, forming cobalt nitrate, Co (NO3)two. Reacts weakly with hydrochloric acid to form cobalt chloride, CoCltwo. Cobalt does not form hydrides.
Both the Co+two like the Co+3 form numerous coordination complexes, being considered one of the metals with the highest number of these complexes.
Cobalt alloys are used in the manufacture of jet engines and gas turbine engines. An alloy called Alinco, made up of aluminum, nickel, and cobalt, has strong magnetic properties. Alinco magnets are used in hearing aids, compasses and microphones.
The so-called cutting tools are made with stellite alloys, consisting of cobalt, chromium and tungsten. Superalloys have a melting point close to that of cobalt, and are characterized by their great hardness, being used in the manufacture of low expansion tools.
Since ancient times, cobalt has been used by numerous cultures to give their art and decorative works a blue tint. In this sense, the oxides have been used: cobalt, CoO, and cobalt, Co3OR4.
In addition to their use in the manufacture of ceramics, glasses and enamels, cobalt oxides are used in the preparation of catalysts..
Cobalt-60 (60Co), a radioactive isotope that emits beta (β) and gamma (γ) radiation, is used in the treatment of cancer. Γ radiation is electromagnetic radiation, so it has the ability to penetrate tissues and reach cancer cells, thus allowing their eradication.
Cancer cells are cells that divide at high speed, which makes them more susceptible to ionizing radiation that hits their nucleus, damaging genetic material.
The 60Co, like other radioisotopes, is used in the sterilization of materials that are used in medical practice..
Likewise, cobalt is used in the manufacture of orthopedic implants, along with titanium and stainless steel. Most hip replacements use cobalt-chrome femoral stems..
Cobalt is used to improve the performance of rechargeable batteries, playing a useful role in hybrid vehicles..
Cobalt is used to provide metal surfaces with a good finish that protects them against oxidation. Cobalt Sulfate, CoSO4, for example, it is the main cobalt compound used in this regard.
Cobaltous Chloride, CoCltwo.6HtwoOr, it is used as a moisture indicator in desiccators. It is a pink solid that changes to blue color as it is hydrated.
Cobalt is part of the active site of vitamin B12 (cyanocobalamin) involved in the maturation of erythrocytes. Its absence causes an anemia characterized by the appearance in the blood circulation of large erythrocytes known as megaloblasts..
Cobalt is widely distributed throughout the earth's crust; although its concentration is very low, estimating that it constitutes 25 ppm of the earth's crust. Meanwhile, in the Solar System as a whole, its relative concentration is 4 ppm..
It is found in small quantities in the nickel-iron complexes, being native to Earth and meteorites. It is also found in combination with other elements in lakes, rivers, seas, plants and animals..
In addition, it is an essential element for the nutrition of ruminants and is present in vitamin B12, necessary for the maturation of erythrocytes. Cobalt is not usually isolated in nature, but is found in different minerals combined with other elements.
Cobalt minerals include the following: cobaltite, in combination with arsenic and sulfur; erythrite, made up of arsenic and hydrated cobalt; the glaucodot formed by cobalt, iron, arsenic and sulfur; and the skutterudite formed by cobalt, nickel and arsenic.
In addition, the following additional cobalt minerals can be noted: linnaelite, enamel and heterogenite. Cobalt is accompanied in minerals mainly by nickel, arsenic and iron.
Most of the time, cobalt is not extracted from the ores that contain it, but is a by-product of the mining of nickel, iron, arsenic, copper, manganese and silver. A complex process is required to extract and isolate cobalt from these minerals.
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