Cobalt is a chemical element and ferromagnetic metal of Group 9 (VIIIb) of the periodic table, which can be used especially for heat-resistant and magnetic alloys. The symbol of Cobalt is Co. This metal was isolated (c.1735) by a Swedish chemist named Georg Brandt, though the cobalt compounds had been used for centuries to impart a blue colour to ceramics and glazes.
The oxidation number of cobalt in [Co(NH3)6]Cl2Br is given as +6, 0, +3, +2. Cobalt oxidation states are +2 and +3.
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Cobalt metal has been detected in the Persian necklace beads and Egyptian statuettes of the 3rd millennium BCE, in glass, which is found in the Pompeii ruins, and in China as early as the Tang dynasty (618–907 CE) and after that, in the blue porcelain of the Ming dynasty (from 1368–1644). The term kobold was first applied (in the 16th century) to the ores thought to contain copper, but eventually, it is found to be poisonous arsenic-bearing cobalt ores. Finally, in 1742, Brandt determined that the blue colour of those ores was because of the presence of cobalt.
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Characteristics of Cobalt
Cobalt is a ferromagnetic metal having a specific gravity of 8.9. The Curie temperature is given as 1,115 °C, and the magnetic moment is given as 1.6–1.7 Bohr magnetons per atom. Cobalt contains a relative permeability two-thirds that of iron. Metallic cobalt is found as two crystallographic structures: fcc and hcp. The ideal transition temperature between the fcc and hcp structures is given as 450 °C, but in practice, the energy difference between them is so small that the random intergrowth of the two is very common.
Occurrence of Cobalt
The stable form of the cobalt metal can be produced in supernovae through the r-process. It comprises a percentage of 0.0029 of the crust of Earth. Free cobalt (which is the native metal) is not found on Earth due to the chlorine in the ocean and oxygen in the atmosphere. Both of these are abundant enough in the upper layers of the crust of Earth to prevent native metal cobalt from producing. Pure cobalt metal in the native metal produced on Earth is unknown, except as recently delivered in meteoric iron. Also, this element contains a medium abundance, whereas the natural compounds of cobalt are numerous, and the small amounts are found in most soils, rocks, animals, and plants.
Production of Cobalt
The primary ores of cobalt metal are erythrite, cobaltite, skutterudite, and glaucodot, but most cobalt can be obtained by reducing the cobalt by-products of copper and nickel mining and smelting.
Since cobalt is generally formed as a by-product, the supply of this metal depends, to a large extent, on the economic viability of the nickel and copper mining operations in the relevant market. Demand for this cobalt metal is projected to increase in 2017 by 6%.
Extraction of Cobalt
The U.S. Geological Survey estimates the world's cobalt reserves at 7,100,000 metric tons. And, Democratic Republic of the Congo (DRC) is currently producing 63% of the world's cobalt. By 2025, this market share can reach 73% if planned expansions by mining producers such as Glencore Plc take place as expected. However, by 2030, global demand could be 47 times more than that of 2017, as estimated by Bloomberg New Energy Finance.
Applications of Cobalt
There are many applications concerning cobalt metal. Let us discuss a few of them below:
Superalloys of cobalt-based have historically consumed most of the cobalt formed. The stability of temperature of these alloys makes them suitable for turbine blades for aircraft jet engines and gas turbines, although the nickel-based single-crystal alloys will surpass them in performance. Also, the cobalt-based alloys are corrosion - and wear-resistant by making them, such as, useful for making orthopaedic implants that do not wear down over time.
Lithium cobalt oxide (LiCoO2) can be used widely in lithium-ion battery cathodes. This material is mixed with cobalt oxide layers with lithium intercalated. During the discharge, the lithium releases lithium ions. Nickel metal hydride (NiMH) and Nickel-cadmium (NiCd) batteries also include cobalt to improve the nickel oxidation present in the battery. Transparency Market Research has estimated the global lithium-ion battery market at ﹩30 billion in 2015, and it is predicted to increase to over US﹩75 billion by 2024.
Health Impacts of Cobalt
Cobalt is considered an essential element for minute amounts of life. The LD50 value for the soluble cobalt salts has been estimated to be in a range of 150 - 500 mg/kg. In the US, the OSHA - Occupational Safety and Health Administration has designated a permissible exposure limit (PEL) of cobalt in the workplace as a TWA - Time-Weighted Average of 0.1 mg/m3. Also, the NIOSH - National Institute for Occupational Safety and Health has set a recommended exposure limit (REL) to 0.05 mg/m3, a time-weighted average. The Immediately Dangerous to Life and Health - IDLH value is given as 20 mg/m3.