Cobalt, as a free element, is not found on earth other than in meteorite deposits. It is, however, found in compound form in the Earth’s crust along with copper, nickel, iron, silver and lead. It is a hard, shiny, brittle, silvery-grey metal. The largest deposits, by far, occur in the Democratic Republic of the Congo where 63,000 metric tons were produced in 2015 from both large-scale and artisanal operations. China is the second highest producer, but produces only 7,200 metric tons.
Although cobalt is known to have been used a few millennia ago, more modern usages include a range of manufacturing, medical and industrial applications. Let’s explore this interesting chemical element.
In the Beginning
There is no record of when, where or how cobalt was discovered, but it is known that Ancient Egyptians used cobalt compounds in their glazes. The color Cobalt Blue is a rich and dark blue – the same color as the SEGA and Bidvest logos. Other ancient relics and remnants of ceramics, glass and glazes, once used for sculptures, artwork, crockery and jewelry, date back to the times of Mesopotamia, Pompeii and the Tang and Ming dynasties.
The name “Kobold” was originally penned in 1735 by the Swedish chemist and mineralogist, George Brandt, who discovered cobalt. The name Kobold, meaning “goblin” or “evil spirit”, had first been used by superstitious German miners who believed that an evil spirit was preventing them from extracting copper from the ore. What they were really mining was cobalt, which is similar in appearance to copper ore. During his experiments, Brandt also proved that bismuth was not responsible for the blue color in the ore, as previously believed, and that cobalt was.
A number of processes are used to extract cobalt from copper and nickel. The preferred method depends on the composition of the ore and the concentrations therein.
In a nutshell, these include:
- Froth flotation, in which the finely ground minerals are separated from ore and floated to the top of the pulp.
- Roasting, to convert ore to cobalt sulfate.
- Leaching with water to extract the sulfate together with the arsenates. Cobalt can also be leached from the slag of copper smelting.
The products of these processes are transformed into cobalt oxide. This is then reduced to a metal by different types of heat treatments.
Ruminant animals need cobalt-rich soils to prevent a range of illnesses, such as loss of appetite, failure to thrive, vitamin deficiencies and Brucellosis, amongst others. Due to over-farming, the natural soil content of cobalt has been reduced and livestock feeds now incorporate this element. Plus, small amounts are also used in some fertilizers.
High performance alloys containing cobalt are heat, wear and corrosion resistant. This makes them ideal for applications such as turbine engines, exhaust valves, certain manufacturing parts, gun barrels, and orthopaedic and dental implants. These alloys are also used to manufacture permanent magnets.
Most rechargeable lithium-ion batteries, as found in cameras, laptops and mobile devices, are cobalt-based. They have a long run-time, but a low discharge current, and are considered to be better than both nickel-cadmium and nickel-metal-hydride batteries. Tesla’s electric cars run on lithium-ion batteries, whereas nickel-metal-hydride batteries are currently more commonly used in hybrid cars.
Cobalt is used as a catalyst in the petrochemical/oil & gas and plastics industries. Without going into in-depth details of their compositions, catalysts in the petrochemical industry are used for desulphurisation and hydrotreating, and for producing terephthalic acid and di-methyl terephthalate, in the production of plastic bottles and ultra-strong plastics.
Electroplating is the process whereby a DC current is passed through a solution in order to create a thin metallic film/coating on an object, e.g. industrial parts, metal supermarket trolleys and certain electrical and telecommunication components. It imparts a hard coating that has an attractive chrome-like appearance. The types of solution used vary depending on the material to be coated. Palladium-cobalt plating is used in the manufacture of electronics and semiconductors.
- Pigments and Coloring
As a colourant, cobalt was – as mentioned earlier – used for producing a specific blue colour for porcelain, ceramics, jewellery and art. The same holds true today where about 30% of the total global production is used by the ceramic and paint industries.
Gamma rays are produced using Cobalt-60. These rays are used for radiotherapy to treat cancers, food irradiation, and the sterilisation of medical equipment and waste. The half-life of Cobalt-60 is 5.7 years, compared to the half-life of Carbon-14 (used to date the age of archaeological and geological items), which is 5,730 years.
Cobalt in the Human Body
As with most things in life, too little and too much can be detrimental to human health.
Cobalt – as cobalamin – is a component of Vitamin B12 which is essential for the healthy functioning of all cells in the body, including the manufacture of red blood cells and DNA. Unlike ruminants that produce their own Vitamin B12 if there is enough cobalt in their diets, our only sources of this vitamin are from food and supplements.
A severe lack of Vitamin B12 can cause weakness, palpitations, gastric disorders, pernicious anemia, nerve problems, and even depression and memory loss.
People who work in close proximity to cobalt, without adequate safety protection and usually over a long period of time, could also experience a range of illnesses such as hard metal lung disease; deafness; heart, thyroid and nerve problems; tinnitus; and blood-thickening. Some cases of metal-on-metal poisoning have also been reported in people who had total hip replacements where the both the ball and the socket joints were manufactured from cobalt-based material.
So there we have it: a little-known element that the ancients knew for its colour and which man has taken to greater heights in our ongoing industrial development.