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Metal toxicity or metal poisoning is the toxic effect of certain metals in certain forms and doses on life.Some metals are toxic when they form poisonous soluble compounds. . Certain metals have no biological role, i.e. are not essential minerals, or are toxic when in a certain for
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Plants are exposed to toxic metals through the uptake of water; animals eat these plants; ingestion of plant- and animal-based foods are the largest sources of toxic metals in humans. [32] Absorption through skin contact, for example from contact with soil, or metal containing toys and jewelry, [ 33 ] is another potential source of toxic metal ...
Tantalum was discovered in Sweden in 1802 by Anders Ekeberg, in two mineral samples – one from Sweden and the other from Finland. [15] [16] One year earlier, Charles Hatchett had discovered columbium (now niobium). [17] In 1809, the English chemist William Hyde Wollaston compared the oxides of columbium and tantalum, columbite and tantalite.
Tantalum is one of the most corrosion-resistant substances available. Many important uses have been found for tantalum owing to this property, particularly in the medical and surgical fields, and also in harsh acidic environments. It is also used to make superior electrolytic capacitors.
Tantalum ores often contain significant amounts of niobium, which is itself a valuable metal.As such, both metals are extracted so that they may be sold. The overall process is one of hydrometallurgy and begins with a leaching step; in which the ore is treated with hydrofluoric acid and sulfuric acid to produce water-soluble hydrogen fluorides, such as the heptafluorotantalate.
Coltan is the colloquial name for the mineral columbite-tantalum ("col-tan"). In the early 21st century coltan mining is associated with human rights violations such as child labour, systematic exploitation of the population by governments or militant groups, exposure to toxic chemicals and other hazards as a result of lax environmental protection, and general safety laws and regulations. [1]
A piece of columbite–tantalite, size 6.0 × 2.5 × 2.1 cm. Coltan (short for columbite–tantalites and known industrially as tantalite) is a dull black metallic ore from which the elements niobium and tantalum are extracted.