Researchers around the geoscientist Bram Murton have found large quantities of rare earths in the deep sea. The deposit is located about 480 kilometers from the coast of the Canary Islands. It is a gigantic submarine, which could be made of the semi-metal tellurium – 1000 meters below the surface. The first five centimeters of the crust are said to contain about 50,000 times more of the rare earth than any deposit on land.
The discovery story of the element tellurium took place in the last two decades of the 18th century. The Austrian chemist and mineralogist Franz Joseph Mueller von Reichenstein observed a lower gold yield than expected in 1782 on gold rulers from Sibiu, Romania. The additional minerals contained were believed to be antimony sulphide or bismuth sulphide, which, however, excluded Muller von Reichenstein on the basis of his experiments. He suspected a new metal, which he gave the names “problematic metal” and “paradoxical gold”.
The questions were clarified only about a decade later, after the Berlin chemist Martin Heinrich Klaproth had received the rehearsals. He succeeded in the extraction and first re-presentation of the new element. In 1798, however, Klaproth acknowledged Miller von Reichenstein as the discoverer, but named the element himself with the “Tellurium” borrowed from the old Mother Earth (lat. Tellus).
Tellurium is a very rare occurrence on earth. The proportion of the earth’s crust is only 0.001 ppm or 1 gram per thousand tons of rock. This makes it even rarer than gold. It is sometimes found in elementary form, but mainly in the form of tellurium minerals, of which the calaverite (gold ditelluride, AuTe2), the sylvanite (a mixed silver / goldtelluride, (Au, Ag) 2Te4) and tellurite (tellurium dioxide, TeO2).
The frequent socialization of the tellurium with ores of the noble metals copper, silver and gold ensures its enrichment in the production process. In the production of refined copper by the electrolytic refining of raw copper, tellurium is deposited in the anode sludge as water-insoluble precious metal stellurides M2Te (M = Cu, Ag, Au). Only 180 tonnes of tellurium are produced every year.
The rare semimetal is interesting for use in ultra-efficient solar cells. How harmful the degradation is to the environment can not be said yet.
Geoscientists have discovered large quantities of rare metal tellurium in an underwater reservoir off the coast of the Canary Islands, reports Technology Review in its online edition (“More green energy thanks to metals from the deep sea”). A mountain, 1000 meters in depth, is said to have a larger tellurium content in its crust than any deposit on the dry land.
Tellurium can be used in particularly efficient solar cells. The dilemma when drilling the deposit is now whether the related risk to the environment should be addressed. Such deep-sea fuels have aroused appetite for several years. China would very much like to promote metals under the Indian Ocean – and is about to start the corresponding processes.
For deep-sea mining, demand for rare earths and precious metals is growing steadily. They are used in numerous electronic devices, in electric cars and in technology for the production of renewable Green energy. The dismantling is by no means ethically clean – the issue of “conflict metals” as well as the poor working conditions in Africa, for example, are driving the industry out.
The promotion of deep sea water could provide a remedy here and still be extremely lucrative for the sponsoring companies. With the silvery shine and the sharp edges are crystals of tellurium of selected beauty. They let us think it was a metal. However, the crystals are soft and brittle. They are easily crushed to powder. If the electrical conductivity is determined, the electrical resistance decreases with increasing temperature, which is the typical behavior of a semiconductor and not of a metal.
The crystal structure of the tellurium provides an explanation for this. There are spiral chains of tellurium atoms with short distances within the chain of 284 pm. Each tellurium has four neighbors from adjacent spiral chains, each of 350 pm. Taking into account all six neighbors of each tellurium.
In the noesis structure, tellurium shows its character as a main group element. The formation of the two short, localized bonds of each tellurium atom prevents the metallic conductivity. On transition to the liquid phase, above the melting point of 450 ° C., the conductivity increases by a factor of 15. In the molten state, the bonding and electron localization is no longer present.
Tellurium treasure in the sea
Tellurium is extremely important for the green energy sector. The semi-metal is found in some of the most efficient solar cells on the planet. The fact that the rare earths – as the name implies – occur in relatively small quantities and can only be promoted with comparatively great effort makes the solar power generators more expensive. The new deposit in the deep sea could partly change this: at least 2670 tons are to be taken from the sea, which is a twelfth of the world’s production.
Growing demand for rare earths
For deep-sea mining, demand for rare earths and precious metals is growing steadily. They are used in numerous electronic devices, in electric cars and in technology for the production of renewable energy. The activity is by no means ethically clean – the issue of “conflict metals” as well as the poor working conditions in Africa, for example, are driving the industry out. The promotion of deep sea water could provide a remedy here and still be extremely lucrative for the sponsoring companies.
However, no one knows what impact the deep sea promotion could have on the underwater life. They could be very negative. An analysis of deep sea degradation work carried out recently showed that even test bores can damage marine ecosystems.
Maritime mining with consequences
Larger projects could be even more problematic. If the natural processes in the deep sea are disturbed, this could have a negative impact not only on the marine population, but possibly even on the influence of weather patterns.
Business and research: the question of what is more important is to reduce the resources needed to produce significant amounts of green energy? Or do not touch nature and avoid potentially major damage to our oceans? Whether the purpose here sanctifies means is not yet settled. What is clear is that there is a great potential under the ocean.