Tantalum is a
chemical element
A chemical element is a species of atoms that have a given number of protons in their nuclei, including the pure substance consisting only of that species. Unlike chemical compounds, chemical elements cannot be broken down into simpler sub ...
with the
symbol Ta and
atomic number
The atomic number or nuclear charge number (symbol ''Z'') of a chemical element is the charge number of an atomic nucleus. For ordinary nuclei, this is equal to the proton number (''n''p) or the number of protons found in the nucleus of every ...
73. Previously known as ''tantalium'', it is named after
Tantalus
Tantalus ( grc, Τάνταλος ) was a Greek mythological figure, most famous for his punishment in Tartarus: he was made to stand in a pool of water beneath a fruit tree with low branches, with the fruit ever eluding his grasp, and the wate ...
, a villain in Greek mythology. Tantalum is a very hard,
ductile
Ductility is a mechanical property commonly described as a material's amenability to drawing (e.g. into wire). In materials science, ductility is defined by the degree to which a material can sustain plastic deformation under tensile stres ...
,
lustrous
Lustre (British English) or luster (American English; see spelling differences) is the way light interacts with the surface of a crystal, rock, or mineral. The word traces its origins back to the Latin ''lux'', meaning "light", and generally ...
, blue-gray
transition metal
In chemistry, a transition metal (or transition element) is a chemical element in the d-block of the periodic table (groups 3 to 12), though the elements of group 12 (and less often group 3) are sometimes excluded. They are the elements that ca ...
that is highly corrosion-resistant. It is part of the
refractory metals
Refractory metals are a class of metals that are extraordinarily resistant to heat and wear. The expression is mostly used in the context of materials science, metallurgy and engineering. The definition of which elements belong to this group dif ...
group, which are widely used as components of strong
high-melting-point alloys. It is a
group 5 element
Group 5 is a group of elements in the periodic table. Group 5 contains vanadium (V), niobium (Nb), tantalum (Ta) and dubnium (Db). This group lies in the d-block of the periodic table. This group is sometimes called the vanadium group or vanadi ...
, along with
vanadium and
niobium, and it always occurs in geologic sources together with the chemically similar niobium, mainly in the
mineral
In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid chemical compound with a fairly well-defined chemical composition and a specific crystal structure that occurs naturally in pure form.John P. Rafferty, ed. (2 ...
groups
tantalite
The mineral group tantalite Fe,_manganese.html"_;"title="iron.html"_;"title="iron">Fe,_manganese">Mn)Tantalum">Ta2oxygen.html" ;"title="manganese">Mn)Tantalum.html" ;"title="iron">Fe,_manganese.html" ;"title="iron.html" ;"title="iron">Fe, manga ...
,
columbite
Columbite, also called niobite, niobite-tantalite and columbate [], is a black mineral group that is an ore of niobium. It has a submetallic Lustre (mineralogy), luster and a high density and is a niobate of iron and manganese. This mineral group ...
and
coltan
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. The niobium-dominant mineral in coltan is columbite (after niobium's original ...
.
The chemical inertness and very high melting point of tantalum make it valuable for laboratory and industrial equipment such as
reaction vessels and
vacuum furnace
A vacuum furnace is a type of furnace in which the product in the furnace is surrounded by a vacuum during processing. The absence of air or other gases prevents oxidation, heat loss from the product through convection, and removes a source of co ...
s. It is used in
tantalum capacitor
A tantalum electrolytic capacitor is an electrolytic capacitor, a passive component of electronic circuits. It consists of a pellet of porous tantalum metal as an anode, covered by an insulating oxide layer that forms the dielectric, surrounde ...
s for
electronic
Electronic may refer to:
*Electronics, the science of how to control electric energy in semiconductor
* ''Electronics'' (magazine), a defunct American trade journal
*Electronic storage, the storage of data using an electronic device
*Electronic co ...
equipment such as
computers. Tantalum is considered a
technology-critical element
A technology-critical element (TCE) is a chemical element that is critical to modern and emerging technologies. Technology-critical elements are elements for which a striking acceleration in usage has emerged, relative to past consumption. Many adv ...
by the European Commission.
History
Tantalum was discovered in Sweden in 1802 by
Anders Ekeberg, in two mineral samples – one from Sweden and the other from Finland. One year earlier,
Charles Hatchett
Charles Hatchett FRS FRSE (2 January 1765 – 10 March 1847) was an English mineralogist and analytical chemist who discovered the element niobium, for which he proposed the name "columbium".
Hatchett was elected a Fellow of the Linnaean Soci ...
had discovered
columbium
Niobium is a chemical element with chemical symbol Nb (formerly columbium, Cb) and atomic number 41. It is a light grey, crystalline, and ductile transition metal. Pure niobium has a Mohs hardness rating similar to pure titanium, and it has sim ...
(now niobium), and in 1809 the English chemist
William Hyde Wollaston
William Hyde Wollaston (; 6 August 1766 – 22 December 1828) was an English chemist and physicist who is famous for discovering the chemical elements palladium and rhodium. He also developed a way to process platinum ore into malleable ingot ...
compared its oxide,
columbite
Columbite, also called niobite, niobite-tantalite and columbate [], is a black mineral group that is an ore of niobium. It has a submetallic Lustre (mineralogy), luster and a high density and is a niobate of iron and manganese. This mineral group ...
with a density of 5.918 g/cm
3, to that of tantalum,
tantalite
The mineral group tantalite Fe,_manganese.html"_;"title="iron.html"_;"title="iron">Fe,_manganese">Mn)Tantalum">Ta2oxygen.html" ;"title="manganese">Mn)Tantalum.html" ;"title="iron">Fe,_manganese.html" ;"title="iron.html" ;"title="iron">Fe, manga ...
with a density of 7.935 g/cm
3. He concluded that the two oxides, despite their difference in measured density, were identical and kept the name tantalum.
After
Friedrich Wöhler confirmed these results, it was thought that columbium and tantalum were the same element. This conclusion was disputed in 1846 by the German chemist
Heinrich Rose
Heinrich Rose (6 August 1795 – 27 January 1864) was a German mineralogist and analytical chemist. He was the brother of the mineralogist Gustav Rose and a son of Valentin Rose.
Rose's early works on phosphorescence were noted in the Quarte ...
, who argued that there were two additional elements in the tantalite sample, and he named them after the children of
Tantalus
Tantalus ( grc, Τάνταλος ) was a Greek mythological figure, most famous for his punishment in Tartarus: he was made to stand in a pool of water beneath a fruit tree with low branches, with the fruit ever eluding his grasp, and the wate ...
: niobium (from
Niobe
In Greek mythology, Niobe (; grc-gre, Νιόβη ) was a daughter of Tantalus and of either Dione, the most frequently cited, or of Eurythemista or Euryanassa, the wife of Amphion and the sister of Pelops and Broteas.
Her father was the r ...
, the goddess of tears), and pelopium (from
Pelops
In Greek mythology, Pelops (; ) was king of Pisa in the Peloponnesus region (, lit. "Pelops' Island"). He was the son of Tantalus and the father of Atreus.
He was venerated at Olympia, where his cult developed into the founding myth of the O ...
).
The supposed element "pelopium" was later identified as a mixture of tantalum and niobium, and it was found that the niobium was identical to the columbium already discovered in 1801 by Hatchett.
The differences between tantalum and niobium were demonstrated unequivocally in 1864 by
Christian Wilhelm Blomstrand,
and
Henri Etienne Sainte-Claire Deville
Henri is an Estonian, Finnish, French, German and Luxembourgish form of the masculine given name Henry.
People with this given name
; French noblemen
:'' See the 'List of rulers named Henry' for Kings of France named Henri.''
* Henri I de Montm ...
, as well as by
Louis J. Troost, who determined the empirical formulas of some of their compounds in 1865.
Further confirmation came from the Swiss chemist
Jean Charles Galissard de Marignac
Jean Charles Galissard de Marignac (24 April 1817 – 15 April 1894) was a Swiss chemist whose work with atomic weights suggested the possibility of isotopes and the packing fraction of nuclei. His study of the rare earth elements led to h ...
, in 1866, who proved that there were only two elements. These discoveries did not stop scientists from publishing articles about the so-called ''
ilmenium Ilmenium was the proposed name for a new element found by the chemist R. Hermann in 1847. During the analysis of the mineral samarskite, he concluded that it does contain an element similar to niobium and tantalum. The similar reactivity of niobium ...
'' until 1871. De Marignac was the first to produce the metallic form of tantalum in 1864, when he
reduced tantalum chloride by heating it in an atmosphere of
hydrogen
Hydrogen is the chemical element with the symbol H and atomic number 1. Hydrogen is the lightest element. At standard conditions hydrogen is a gas of diatomic molecules having the formula . It is colorless, odorless, tasteless, non-toxic ...
.
Early investigators had only been able to produce impure tantalum, and the first relatively pure ductile metal was produced by
Werner von Bolton in
Charlottenburg
Charlottenburg () is a locality of Berlin within the borough of Charlottenburg-Wilmersdorf. Established as a town in 1705 and named after Sophia Charlotte of Hanover, Queen consort of Prussia, it is best known for Charlottenburg Palace, the ...
in 1903. Wires made with metallic tantalum were used for
light bulb filaments until
tungsten
Tungsten, or wolfram, is a chemical element with the symbol W and atomic number 74. Tungsten is a rare metal found naturally on Earth almost exclusively as compounds with other elements. It was identified as a new element in 1781 and first isol ...
replaced it in widespread use.
The name tantalum was derived from the name of the mythological Tantalus, the father of Niobe in
Greek mythology
A major branch of classical mythology, Greek mythology is the body of myths originally told by the ancient Greeks, and a genre of Ancient Greek folklore. These stories concern the origin and nature of the world, the lives and activities ...
. In the story, he had been punished after death by being condemned to stand knee-deep in water with perfect fruit growing above his head, both of which eternally ''tantalized'' him. (If he bent to drink the water, it drained below the level he could reach, and if he reached for the fruit, the branches moved out of his grasp.) Anders Ekeberg wrote "This metal I call ''tantalum'' ... partly in allusion to its incapacity, when immersed in acid, to absorb any and be saturated."
For decades, the commercial technology for separating tantalum from niobium involved the
fractional crystallization of
potassium heptafluorotantalate
Potassium heptafluorotantalate is an inorganic compound with the formula K2 aF7 It is the potassium salt of the heptafluorotantalate anion aF7sup>2−. This white, water-soluble solid is an intermediate in the purification of tantalum from its ...
away from potassium oxypentafluoroniobate monohydrate, a process that was discovered by
Jean Charles Galissard de Marignac
Jean Charles Galissard de Marignac (24 April 1817 – 15 April 1894) was a Swiss chemist whose work with atomic weights suggested the possibility of isotopes and the packing fraction of nuclei. His study of the rare earth elements led to h ...
in 1866. This method has been supplanted by
solvent extraction
A solvent (s) (from the Latin '' solvō'', "loosen, untie, solve") is a substance that dissolves a solute, resulting in a solution. A solvent is usually a liquid but can also be a solid, a gas, or a supercritical fluid. Water is a solvent for ...
from fluoride-containing solutions of tantalum.
Characteristics
Physical properties
Tantalum is dark (blue-gray), dense, ductile, very hard, easily fabricated, and highly conductive of heat and electricity. The metal is renowned for its resistance to
corrosion
Corrosion is a natural process that converts a refined metal into a more chemically stable oxide. It is the gradual deterioration of materials (usually a metal) by chemical or electrochemical reaction with their environment. Corrosion engi ...
by
acids; in fact, at temperatures below 150 °
C tantalum is almost completely immune to attack by the normally aggressive
aqua regia. It can be dissolved with
hydrofluoric acid or acidic solutions containing the
fluoride ion and
sulfur trioxide, as well as with a solution of
potassium hydroxide
Potassium hydroxide is an inorganic compound with the formula K OH, and is commonly called caustic potash.
Along with sodium hydroxide (NaOH), KOH is a prototypical strong base. It has many industrial and niche applications, most of which exp ...
. Tantalum's high melting point of 3017 °C (boiling point 5458 °C) is exceeded among the elements only by
tungsten
Tungsten, or wolfram, is a chemical element with the symbol W and atomic number 74. Tungsten is a rare metal found naturally on Earth almost exclusively as compounds with other elements. It was identified as a new element in 1781 and first isol ...
,
rhenium
Rhenium is a chemical element with the symbol Re and atomic number 75. It is a silvery-gray, heavy, third-row transition metal in group 7 of the periodic table. With an estimated average concentration of 1 part per billion (ppb), rhenium is one ...
and
osmium for metals, and
carbon
Carbon () is a chemical element with the symbol C and atomic number 6. It is nonmetallic and tetravalent—its atom making four electrons available to form covalent chemical bonds. It belongs to group 14 of the periodic table. Carbon mak ...
.
Tantalum exists in two crystalline phases, alpha and beta. The alpha phase is relatively
ductile
Ductility is a mechanical property commonly described as a material's amenability to drawing (e.g. into wire). In materials science, ductility is defined by the degree to which a material can sustain plastic deformation under tensile stres ...
and soft; it has
body-centered cubic
In crystallography, the cubic (or isometric) crystal system is a crystal system where the unit cell is in the shape of a cube. This is one of the most common and simplest shapes found in crystals and minerals.
There are three main varieties of ...
structure (
space group
In mathematics, physics and chemistry, a space group is the symmetry group of an object in space, usually in three dimensions. The elements of a space group (its symmetry operations) are the rigid transformations of an object that leave it uncha ...
''Im3m'', lattice constant ''a'' = 0.33058 nm),
Knoop hardness 200–400 HN and electrical resistivity 15–60 µΩ⋅cm. The beta phase is hard and brittle; its crystal symmetry is
tetragonal
In crystallography, the tetragonal crystal system is one of the 7 crystal systems. Tetragonal crystal lattices result from stretching a cubic lattice along one of its lattice vectors, so that the cube becomes a rectangular prism with a squar ...
(space group ''P42/mnm'', ''a'' = 1.0194 nm, ''c'' = 0.5313 nm), Knoop hardness is 1000–1300 HN and electrical resistivity is relatively high at 170–210 µΩ⋅cm. The beta phase is metastable and converts to the alpha phase upon heating to 750–775 °C. Bulk tantalum is almost entirely alpha phase, and the beta phase usually exists as thin films obtained by magnetron
sputtering
In physics, sputtering is a phenomenon in which microscopic particles of a solid material are ejected from its surface, after the material is itself bombarded by energetic particles of a plasma or gas. It occurs naturally in outer space, and ca ...
,
chemical vapor deposition or
electrochemical deposition from a
eutectic molten salt solution.
Isotopes
Natural tantalum consists of two
isotope
Isotopes are two or more types of atoms that have the same atomic number (number of protons in their nuclei) and position in the periodic table (and hence belong to the same chemical element), and that differ in nucleon numbers (mass numb ...
s:
180mTa (0.012%) and
181Ta (99.988%).
181Ta is a
stable isotope
The term stable isotope has a meaning similar to stable nuclide, but is preferably used when speaking of nuclides of a specific element. Hence, the plural form stable isotopes usually refers to isotopes of the same element. The relative abundanc ...
.
180mTa (''m'' denotes a metastable state) is predicted to decay in three ways:
isomeric transition to the
ground state of
180Ta,
beta decay
In nuclear physics, beta decay (β-decay) is a type of radioactive decay in which a beta particle (fast energetic electron or positron) is emitted from an atomic nucleus, transforming the original nuclide to an isobar of that nuclide. For ...
to
180 W, or electron capture to
180 Hf. However, radioactivity of this
nuclear isomer
A nuclear isomer is a metastable state of an atomic nucleus, in which one or more nucleons (protons or neutrons) occupy higher energy levels than in the ground state of the same nucleus. "Metastable" describes nuclei whose excited states have ...
has never been observed, and only a lower limit on its
half-life
Half-life (symbol ) is the time required for a quantity (of substance) to reduce to half of its initial value. The term is commonly used in nuclear physics to describe how quickly unstable atoms undergo radioactive decay or how long stable at ...
of 2.0 × 10
16 years has been set. The ground state of
180Ta has a half-life of only 8 hours.
180mTa is the only naturally occurring
nuclear isomer
A nuclear isomer is a metastable state of an atomic nucleus, in which one or more nucleons (protons or neutrons) occupy higher energy levels than in the ground state of the same nucleus. "Metastable" describes nuclei whose excited states have ...
(excluding
radiogenic
A radiogenic nuclide is a nuclide that is produced by a process of radioactive decay. It may itself be radioactive (a radionuclide) or stable (a stable nuclide).
Radiogenic nuclides (more commonly referred to as radiogenic isotopes) form some ...
and
cosmogenic
Cosmogenic nuclides (or cosmogenic isotopes) are rare nuclides (isotopes) created when a high-energy cosmic ray interacts with the nucleus of an ''in situ'' Solar System atom, causing nucleons (protons and neutrons) to be expelled from the atom ...
short-lived nuclides). It is also the rarest primordial isotope in the Universe, taking into account the elemental abundance of tantalum and isotopic abundance of
180mTa in the natural mixture of isotopes (and again excluding radiogenic and cosmogenic short-lived nuclides).
Tantalum has been examined theoretically as a "
salting" material for
nuclear weapon
A nuclear weapon is an explosive device that derives its destructive force from nuclear reactions, either fission (fission bomb) or a combination of fission and fusion reactions ( thermonuclear bomb), producing a nuclear explosion. Both bom ...
s (
cobalt
Cobalt is a chemical element with the symbol Co and atomic number 27. As with nickel, cobalt is found in the Earth's crust only in a chemically combined form, save for small deposits found in alloys of natural meteoric iron. The free element, p ...
is the better-known hypothetical salting material). An external shell of
181Ta would be irradiated by the intensive high-energy neutron flux from a hypothetical exploding nuclear weapon. This would transmute the tantalum into the radioactive isotope
182Ta, which has a
half-life
Half-life (symbol ) is the time required for a quantity (of substance) to reduce to half of its initial value. The term is commonly used in nuclear physics to describe how quickly unstable atoms undergo radioactive decay or how long stable at ...
of 114.4 days and produces
gamma ray
A gamma ray, also known as gamma radiation (symbol γ or \gamma), is a penetrating form of electromagnetic radiation arising from the radioactive decay of atomic nuclei. It consists of the shortest wavelength electromagnetic waves, typically ...
s with approximately 1.12 million electron-volts (MeV) of energy apiece, which would significantly increase the radioactivity of the
nuclear fallout
Nuclear fallout is the residual radioactive material propelled into the upper atmosphere following a nuclear blast, so called because it "falls out" of the sky after the explosion and the shock wave has passed. It commonly refers to the radioac ...
from the explosion for several months. Such "salted" weapons have never been built or tested, as far as is publicly known, and certainly never used as weapons.
Tantalum can be used as a target material for accelerated proton beams for the production of various short-lived isotopes including
8Li,
80Rb, and
160Yb.
Chemical compounds
Tantalum forms compounds in oxidation states −III to +V. Most commonly encountered are oxides of Ta(V), which includes all minerals. The chemical properties of Ta and Nb are very similar. In aqueous media, Ta only exhibit the +V oxidation state. Like niobium, tantalum is barely soluble in dilute solutions of
hydrochloric
Hydrochloric acid, also known as muriatic acid, is an aqueous solution of hydrogen chloride. It is a colorless solution with a distinctive pungent smell. It is classified as a strong acid. It is a component of the gastric acid in the digestiv ...
,
sulfuric,
nitric and
phosphoric acid
Phosphoric acid (orthophosphoric acid, monophosphoric acid or phosphoric(V) acid) is a colorless, odorless phosphorus-containing solid, and inorganic compound with the chemical formula . It is commonly encountered as an 85% aqueous solution, w ...
s due to the precipitation of hydrous Ta(V) oxide.
In basic media, Ta can be solubilized due to the formation of polyoxotantalate species.
Oxides, nitrides, carbides, sulfides
Tantalum pentoxide
Tantalum pentoxide, also known as tantalum(V) oxide, is the inorganic compound with the formula . It is a white solid that is insoluble in all solvents but is attacked by strong bases and hydrofluoric acid. is an inert material with a high refract ...
(Ta
2O
5) is the most important compound from the perspective of applications. Oxides of tantalum in lower oxidation states are numerous, including many
defect structures, and are lightly studied or poorly characterized.
Tantalates, compounds containing
4">aO4sup>3− or
3">aO3sup>− are numerous.
Lithium tantalate
Lithium tantalate ( Li Ta O3) is a perovskite which possesses unique optical, piezoelectric and pyroelectric properties which make it valuable for nonlinear optics, passive infrared sensors such as motion detectors, terahertz generation and de ...
(LiTaO
3) adopts a perovskite structure.
Lanthanum
Lanthanum is a chemical element with the symbol La and atomic number 57. It is a soft, ductile, silvery-white metal that tarnishes slowly when exposed to air. It is the eponym of the lanthanide series, a group of 15 similar elements between lant ...
tantalate (LaTaO
4) contains isolated tetrahedra.
As in the cases of other
refractory metal
Refractory metals are a class of metals that are extraordinarily resistant to heat and wear. The expression is mostly used in the context of materials science, metallurgy and engineering. The definition of which elements belong to this group diff ...
s, the hardest known compounds of tantalum are nitrides and carbides.
Tantalum carbide
Tantalum carbides (TaC) form a family of binary chemical compounds of tantalum and carbon with the empirical formula TaC''x'', where ''x'' usually varies between 0.4 and 1. They are extremely hard, brittle, refractory ceramic materials with metall ...
, TaC, like the more commonly used
tungsten carbide
Tungsten carbide (chemical formula: WC) is a chemical compound (specifically, a carbide) containing equal parts of tungsten and carbon atoms. In its most basic form, tungsten carbide is a fine gray powder, but it can be pressed and formed into ...
, is a hard
ceramic
A ceramic is any of the various hard, brittle, heat-resistant and corrosion-resistant materials made by shaping and then firing an inorganic, nonmetallic material, such as clay, at a high temperature. Common examples are earthenware, porcelain ...
that is used in cutting tools. Tantalum(III) nitride is used as a thin film insulator in some microelectronic fabrication processes.
The best studied chalcogenide is TaS
2, a layered
semiconductor
A semiconductor is a material which has an electrical conductivity value falling between that of a conductor, such as copper, and an insulator, such as glass. Its resistivity falls as its temperature rises; metals behave in the opposite way. ...
, as seen for other
transition metal dichalcogenide : 220px, Cadmium sulfide, a prototypical metal chalcogenide, is used as a yellow pigment.
A chalcogenide is a chemical compound consisting of at least one chalcogen anion and at least one more electropositive element. Although all group 16 elements ...
s. A tantalum-tellurium alloy forms
quasicrystal
A quasiperiodic crystal, or quasicrystal, is a structure that is ordered but not periodic. A quasicrystalline pattern can continuously fill all available space, but it lacks translational symmetry. While crystals, according to the classical ...
s.
Halides
Tantalum halides span the oxidation states of +5, +4, and +3.
Tantalum pentafluoride (TaF
5) is a white solid with a melting point of 97.0 °C. The anion
7">aF7sup>2- is used for its separation from niobium.
The chloride
, which exists as a dimer, is the main reagent in synthesis of new Ta compounds. It hydrolyzes readily to an
oxychloride
In chemistry, molecular oxohalides (oxyhalides) are a group of chemical compounds in which both oxygen and halogen atoms are attached to another chemical element A in a single molecule. They have the general formula , where X = fluorine (F), chlor ...
. The lower halides and , feature Ta-Ta bonds.
Organotantalum compounds
Organotantalum compounds include
pentamethyltantalum, mixed alkyltantalum chlorides, alkyltantalum hydrides, alkylidene complexes as well as cyclopentadienyl derivatives of the same.
Diverse salts and substituted derivatives are known for the hexacarbonyl
6">a(CO)6sup>− and related
isocyanide
An isocyanide (also called isonitrile or carbylamine) is an organic compound with the functional group –. It is the isomer of the related nitrile (–C≡N), hence the prefix is ''isocyano''.IUPAC Goldboo''isocyanides''/ref> The organic fragme ...
s.
Occurrence
![Tantalite](https://upload.wikimedia.org/wikipedia/commons/c/c0/Tantalite.jpg)
Tantalum is estimated to make up about 1
ppm or 2
ppm of the
Earth's crust by weight. There are many species of tantalum minerals, only some of which are so far being used by industry as raw materials:
tantalite
The mineral group tantalite Fe,_manganese.html"_;"title="iron.html"_;"title="iron">Fe,_manganese">Mn)Tantalum">Ta2oxygen.html" ;"title="manganese">Mn)Tantalum.html" ;"title="iron">Fe,_manganese.html" ;"title="iron.html" ;"title="iron">Fe, manga ...
(a series consisting of tantalite-(Fe), tantalite-(Mn) and tantalite-(Mg))
microlite
Microlite was once known as a pale-yellow, reddish-brown, or black isometric mineral composed of sodium calcium tantalum oxide with a small amount of fluorine. Its chemical formula is. Today it is a name of a group of oxide minerals of a similar ...
(now a group name),
wodginite
Wodginite is a manganese, tin, tantalum oxide mineral with the chemical formula . It may also include significant amounts of niobium.
Background
Wodginite was first described in 1963 for an occurrence in the Wodgina pegmatite, Wodgina, Pilbara Re ...
,
euxenite
Euxenite, or euxenite-(Y) (the official mineralogical name), is a brownish black mineral with a metallic luster.
Chemistry
It contains calcium, niobium, tantalum, cerium, titanium, yttrium, and typically uranium and thorium, with some other meta ...
(actually euxenite-(Y)), and
polycrase
Polycrase or polycrase-(Y) is a black or brown metallic complex uranium yttrium oxide mineral with the chemical formula . It is amorphous. It has a Mohs hardness of 5 to 6 and a specific gravity of 5. It is radioactive due to its uranium content (a ...
(actually polycrase-(Y)).
Tantalite (
Fe,
Mn)Ta
2 O6 is the most important mineral for tantalum extraction. Tantalite has the same mineral structure as
columbite
Columbite, also called niobite, niobite-tantalite and columbate [], is a black mineral group that is an ore of niobium. It has a submetallic Lustre (mineralogy), luster and a high density and is a niobate of iron and manganese. This mineral group ...
(
Fe,
Mn) (Ta,
Nb)
2 O6; when there is more tantalum than niobium it is called tantalite and when there is more niobium than tantalum is it called columbite (or
niobite
Columbite, also called niobite, niobite-tantalite and columbate [], is a black mineral group that is an ore of niobium. It has a submetallic Lustre (mineralogy), luster and a high density and is a niobate of iron and manganese. This mineral group ...
). The high density of tantalite and other tantalum containing minerals makes the use of
gravitational separation the best method. Other minerals include
samarskite
Samarskite is a radioactive rare earth mineral series which includes samarskite-(Y), with the chemical formula and samarskite-(Yb), with the chemical formula . The formula for samarskite-(Y) is also given as .
Samarskite crystallizes in the orth ...
and
fergusonite
Fergusonite is a mineral comprising a complex oxide of various rare-earth elements. The general chemical formula of fergusonite is (Y,REE)NbO4, where REE = rare-earth elements in solid solution with Y. Yttrium is usually dominant (the mineral in ...
.
Australia was the main producer of tantalum prior to the 2010s, with
Global Advanced Metals Talison Minerals Pty Ltd was a mining company based in Australia. It was split into Talison Lithium (as of 2020 a 51:49 jv between Tianqi Lithium and Albemarle Corporation) and Talison Tantalum, now known as Global Advanced Metals, in 2009. The ...
(formerly known as
Talison Minerals Talison Minerals Pty Ltd was a mining company based in Australia. It was split into Talison Lithium (as of 2020 a 51:49 jv between Tianqi Lithium and Albemarle Corporation) and Talison Tantalum, now known as Global Advanced Metals, in 2009. The t ...
) being the largest tantalum mining company in that country. They operate two mines in Western Australia,
Greenbushes in the southwest and
Wodgina
The Wodgina mine is an exhausted iron ore mine located in the Pilbara region of Western Australia, 90 kilometres south of Port Hedland.
The mine was operated by Atlas Iron Limited. The facilities and tenements are shared, by contract, with Glo ...
in the
Pilbara
The Pilbara () is a large, dry, thinly populated region in the north of Western Australia. It is known for its Aboriginal peoples; its ancient landscapes; the red earth; and its vast mineral deposits, in particular iron ore. It is also a g ...
region. The Wodgina mine was reopened in January 2011 after mining at the site was suspended in late 2008 due to the
global financial crisis
Global means of or referring to a globe and may also refer to:
Entertainment
* ''Global'' (Paul van Dyk album), 2003
* ''Global'' (Bunji Garlin album), 2007
* ''Global'' (Humanoid album), 1989
* ''Global'' (Todd Rundgren album), 2015
* Bruno ...
. Less than a year after it reopened, Global Advanced Metals announced that due to again "... softening tantalum demand ...", and other factors, tantalum mining operations were to cease at the end of February 2012.
[
] Wodgina produces a primary tantalum concentrate which is further upgraded at the Greenbushes operation before being sold to customers.
Whereas the large-scale producers of niobium are in
Brazil
Brazil ( pt, Brasil; ), officially the Federative Republic of Brazil (Portuguese: ), is the largest country in both South America and Latin America. At and with over 217 million people, Brazil is the world's fifth-largest country by area ...
and
Canada
Canada is a country in North America. Its ten provinces and three territories extend from the Atlantic Ocean to the Pacific Ocean and northward into the Arctic Ocean, covering over , making it the world's second-largest country by tot ...
, the ore there also yields a small percentage of tantalum. Some other countries such as
China,
Ethiopia
Ethiopia, , om, Itiyoophiyaa, so, Itoobiya, ti, ኢትዮጵያ, Ítiyop'iya, aa, Itiyoppiya officially the Federal Democratic Republic of Ethiopia, is a landlocked country in the Horn of Africa. It shares borders with Eritrea to the ...
, and
Mozambique
Mozambique (), officially the Republic of Mozambique ( pt, Moçambique or , ; ny, Mozambiki; sw, Msumbiji; ts, Muzambhiki), is a country located in southeastern Africa bordered by the Indian Ocean to the east, Tanzania to the north, Malawi ...
mine ores with a higher percentage of tantalum, and they produce a significant percentage of the world's output of it. Tantalum is also produced in
Thailand
Thailand ( ), historically known as Siam () and officially the Kingdom of Thailand, is a country in Southeast Asia, located at the centre of the Indochinese Peninsula, spanning , with a population of almost 70 million. The country is b ...
and
Malaysia
Malaysia ( ; ) is a country in Southeast Asia. The federation, federal constitutional monarchy consists of States and federal territories of Malaysia, thirteen states and three federal territories, separated by the South China Sea into two r ...
as a by-product of the
tin
Tin is a chemical element with the symbol Sn (from la, stannum) and atomic number 50. Tin is a silvery-coloured metal.
Tin is soft enough to be cut with little force and a bar of tin can be bent by hand with little effort. When bent, t ...
mining there. During gravitational separation of the ores from placer deposits, not only is
cassiterite (SnO
2) found, but a small percentage of tantalite also included. The slag from the tin smelters then contains economically useful amounts of tantalum, which is leached from the slag.
![World Tantalum Production 2006](https://upload.wikimedia.org/wikipedia/commons/7/75/World_Tantalum_Production_2006.svg)
World tantalum mine production has undergone an important geographic shift since the start of the 21st century when production was predominantly from Australia and Brazil. Beginning in 2007 and through 2014, the major sources of tantalum production from mines dramatically shifted to the
Democratic Republic of the Congo
The Democratic Republic of the Congo (french: République démocratique du Congo (RDC), colloquially "La RDC" ), informally Congo-Kinshasa, DR Congo, the DRC, the DROC, or the Congo, and formerly and also colloquially Zaire, is a country in ...
,
Rwanda, and some other African countries. Future sources of supply of tantalum, in order of estimated size, are being explored in
Saudi Arabia
Saudi Arabia, officially the Kingdom of Saudi Arabia (KSA), is a country in Western Asia. It covers the bulk of the Arabian Peninsula, and has a land area of about , making it the fifth-largest country in Asia, the second-largest in the A ...
,
Egypt
Egypt ( ar, مصر , ), officially the Arab Republic of Egypt, is a transcontinental country spanning the northeast corner of Africa and southwest corner of Asia via a land bridge formed by the Sinai Peninsula. It is bordered by the Medit ...
,
Greenland
Greenland ( kl, Kalaallit Nunaat, ; da, Grønland, ) is an island country in North America that is part of the Kingdom of Denmark. It is located between the Arctic and Atlantic oceans, east of the Canadian Arctic Archipelago. Greenland i ...
, China, Mozambique, Canada, Australia, the
United States
The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territori ...
,
Finland
Finland ( fi, Suomi ; sv, Finland ), officially the Republic of Finland (; ), is a Nordic country in Northern Europe. It shares land borders with Sweden to the northwest, Norway to the north, and Russia to the east, with the Gulf of B ...
, and Brazil.
It is estimated that tantalum resources will run out around 2060, based on extraction at current rates, demonstrating the need for increased
recycling
Recycling is the process of converting waste materials into new materials and objects. The recovery of energy from waste materials is often included in this concept. The recyclability of a material depends on its ability to reacquire the p ...
.
Status as a conflict resource
Tantalum is considered a
conflict resource
The eastern Democratic Republic of the Congo (DRC) has a history of conflict, where various armies, rebel groups, and outside actors have profited from mining while contributing to violence and exploitation during wars in the region. The four mai ...
.
Coltan
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. The niobium-dominant mineral in coltan is columbite (after niobium's original ...
, the industrial name for a
columbite
Columbite, also called niobite, niobite-tantalite and columbate [], is a black mineral group that is an ore of niobium. It has a submetallic Lustre (mineralogy), luster and a high density and is a niobate of iron and manganese. This mineral group ...
–
tantalite
The mineral group tantalite Fe,_manganese.html"_;"title="iron.html"_;"title="iron">Fe,_manganese">Mn)Tantalum">Ta2oxygen.html" ;"title="manganese">Mn)Tantalum.html" ;"title="iron">Fe,_manganese.html" ;"title="iron.html" ;"title="iron">Fe, manga ...
mineral from which niobium and tantalum are extracted, can also be found in
Central Africa
Central Africa is a subregion of the African continent comprising various countries according to different definitions. Angola, Burundi, the Central African Republic, Chad, the Democratic Republic of the Congo, the Republic of the Congo ...
, which is why tantalum is being linked to
warfare in the Democratic Republic of the Congo (formerly
Zaire
Zaire (, ), officially the Republic of Zaire (french: République du Zaïre, link=no, ), was a Congolese state from 1971 to 1997 in Central Africa that was previously and is now again known as the Democratic Republic of the Congo. Zaire was, ...
). According to an October 23, 2003
United Nations
The United Nations (UN) is an intergovernmental organization whose stated purposes are to maintain international peace and security, develop friendly relations among nations, achieve international cooperation, and be a centre for harmoniz ...
report, the smuggling and exportation of coltan has helped fuel the war in the Congo, a crisis that has resulted in approximately 5.4 million deaths since 1998 – making it the world's deadliest documented conflict since
World War II
World War II or the Second World War, often abbreviated as WWII or WW2, was a world war that lasted from 1939 to 1945. It involved the vast majority of the world's countries—including all of the great powers—forming two opposing ...
. Ethical questions have been raised about responsible corporate behavior, human rights, and endangering wildlife, due to the exploitation of resources such as coltan in the armed conflict regions of the
Congo Basin. The
United States Geological Survey
The United States Geological Survey (USGS), formerly simply known as the Geological Survey, is a scientific agency of the United States government. The scientists of the USGS study the landscape of the United States, its natural resources, ...
reports in its yearbook that this region produced a little less than 1% of the world's tantalum output in 2002–2006, peaking at 10% in 2000 and 2008.
USGS data published in January 2021 indicated that close to 40% of the world's tantalum mine production came from the Democratic Republic of the Congo, with another 18% coming from neighboring
Rwanda and
Burundi.
The stated aim of the ''Solutions for Hope Tantalum Project'' is to "source conflict-free tantalum from the Democratic Republic of Congo"
Production and fabrication
![Tantalum world production](https://upload.wikimedia.org/wikipedia/commons/6/6a/Tantalum_world_production.svg)
Several steps are involved in the extraction of tantalum from tantalite. First, the mineral is
crushed
Crushed may refer to:
* "Crushed" (''Ms. Marvel''), a 2022 episode of the American television series ''Ms. Marvel''
* "Crushed" (Roland Lee Gift song) a 2009 single by Roland Lee Gift
* "Crushed" (''The Suite Life of Zack & Cody'' episode), an ...
and concentrated by
gravity separation
Gravity separation is an industrial method of separating two components, either a suspension, or dry granular mixture where separating the components with gravity is sufficiently practical: i.e. the components of the mixture have different specific ...
. This is generally carried out near the
mine
Mine, mines, miners or mining may refer to:
Extraction or digging
* Miner, a person engaged in mining or digging
*Mining, extraction of mineral resources from the ground through a mine
Grammar
*Mine, a first-person English possessive pronoun
...
site.
Refining
The refining of tantalum from its ores is one of the more demanding separation processes in industrial metallurgy. The chief problem is that tantalum ores contain significant amounts of
niobium, which has chemical properties almost identical to those of Ta. A large number of procedures have been developed to address this challenge.
In modern times, the separation is achieved by
hydrometallurgy
Hydrometallurgy is a technique within the field of extractive metallurgy, the obtaining of metals from their ores. Hydrometallurgy involve the use of aqueous solutions for the recovery of metals from ores, concentrates, and recycled or residual m ...
.
Extraction begins with
leaching
Leaching is the loss or extraction of certain materials from a carrier into a liquid (usually, but not always a solvent). and may refer to:
* Leaching (agriculture), the loss of water-soluble plant nutrients from the soil; or applying a small amou ...
the ore with
hydrofluoric acid together with
sulfuric acid or
hydrochloric acid
Hydrochloric acid, also known as muriatic acid, is an aqueous solution of hydrogen chloride. It is a colorless solution with a distinctive pungent smell. It is classified as a strong acid
Acid strength is the tendency of an acid, symbol ...
. This step allows the tantalum and niobium to be separated from the various non-metallic impurities in the rock. Although Ta occurs as various minerals, it is conveniently represented as the pentoxide, since most oxides of tantalum(V) behave similarly under these conditions. A simplified equation for its extraction is thus:
: Ta
2O
5 + 14 HF → 2 H
2 7">aF7+ 5 H
2O
Completely analogous reactions occur for the niobium component, but the hexafluoride is typically predominant under the conditions of the extraction.
: Nb
2O
5 + 12 HF → 2 H
6">bF6+ 5 H
2O
These equations are simplified: it is suspected that bisulfate (HSO
4−) and chloride compete as ligands for the Nb(V) and Ta(V) ions, when sulfuric and hydrochloric acids are used, respectively.
The tantalum and niobium fluoride complexes are then removed from the
aqueous
An aqueous solution is a solution in which the solvent is water. It is mostly shown in chemical equations by appending (aq) to the relevant chemical formula. For example, a solution of table salt, or sodium chloride (NaCl), in water would be re ...
solution by
liquid-liquid extraction into
organic solvents
A solvent (s) (from the Latin '' solvō'', "loosen, untie, solve") is a substance that dissolves a solute, resulting in a solution. A solvent is usually a liquid but can also be a solid, a gas, or a supercritical fluid. Water is a solvent for p ...
, such as
cyclohexanone,
octanol
Octanols are alcohols with the formula C8H17OH. A simple and important member is 1-octanol, with an unbranched chain of carbons. Other commercially important octanols are 2-octanol and 2-ethylhexanol.
There are 89 possible isomers
In che ...
, and
methyl isobutyl ketone Methyl isobutyl ketone (MIBK) is the common name for the organic compound 4-methylpentan-2-one, condensed chemical formula (CH3)2CHCH2C(O)CH3. This colourless liquid, a ketone, is used as a solvent for gums, resins, paints, varnishes, lacquers, and ...
. This simple procedure allows the removal of most metal-containing impurities (e.g. iron, manganese, titanium, zirconium), which remain in the aqueous phase in the form of their
fluorides and other complexes.
Separation of the tantalum ''from'' niobium is then achieved by lowering the
ionic strength of the acid mixture, which causes the niobium to dissolve in the aqueous phase. It is proposed that
oxyfluoride
In chemistry, molecular oxohalides (oxyhalides) are a group of chemical compounds in which both oxygen and halogen atoms are attached to another chemical element A in a single molecule. They have the general formula , where X = fluorine (F), chlor ...
H
2 5">bOF5is formed under these conditions. Subsequent to removal of the niobium, the solution of purified H
2 7">aF7is neutralised with aqueous
ammonia
Ammonia is an inorganic compound of nitrogen and hydrogen with the formula . A stable binary hydride, and the simplest pnictogen hydride, ammonia is a colourless gas with a distinct pungent smell. Biologically, it is a common nitrogenous wa ...
to precipitate hydrated tantalum oxide as a solid, which can be
calcined
Calcination refers to thermal treatment of a solid chemical compound (e.g. mixed carbonate ores) whereby the compound is raised to high temperature without melting under restricted supply of ambient oxygen (i.e. gaseous O2 fraction of air), gener ...
to
tantalum pentoxide
Tantalum pentoxide, also known as tantalum(V) oxide, is the inorganic compound with the formula . It is a white solid that is insoluble in all solvents but is attacked by strong bases and hydrofluoric acid. is an inert material with a high refract ...
(Ta
2O
5).
Instead of hydrolysis, the H
2 7">aF7can be treated with
potassium fluoride
Potassium fluoride is the chemical compound with the formula KF. After hydrogen fluoride, KF is the primary source of the fluoride ion for applications in manufacturing and in chemistry. It is an alkali halide and occurs naturally as the rare ...
to produce
potassium heptafluorotantalate
Potassium heptafluorotantalate is an inorganic compound with the formula K2 aF7 It is the potassium salt of the heptafluorotantalate anion aF7sup>2−. This white, water-soluble solid is an intermediate in the purification of tantalum from its ...
:
: H
2 7">aF7+ 2 KF → K
2 7">aF7+ 2 HF
Unlike H
2 7">aF7 the potassium salt is readily crystallized and handled as a solid.
K
2 7">aF7can be converted to metallic tantalum by
reduction with
sodium
Sodium is a chemical element with the symbol Na (from Latin ''natrium'') and atomic number 11. It is a soft, silvery-white, highly reactive metal. Sodium is an alkali metal, being in group 1 of the periodic table. Its only stable ...
, at approximately 800 °C in
molten salt
Molten salt is salt which is solid at standard temperature and pressure but enters the liquid phase due to elevated temperature. Regular table salt has a melting point of 801 °C (1474°F) and a heat of fusion of 520 J/g.Journal of Chemical T ...
.
: K
2 7">aF7+ 5 Na → Ta + 5 NaF + 2 KF
In an older method, called the
Marignac process, the mixture of H
2 7">aF7and H
2 5">bOF5was converted to a ''mixture'' of K
2 7">aF7and K
2 5">bOF5 which was then be separated by
fractional crystallization, exploiting their different water solubilities.
Electrolysis
Tantalum can also be refined by electrolysis, using a modified version of the
Hall–Héroult process
The Hall–Héroult process is the major industrial process for smelting aluminium. It involves dissolving aluminium oxide (alumina) (obtained most often from bauxite, aluminium's chief ore, through the Bayer process) in molten cryolite, and el ...
. Instead of requiring the input oxide and output metal to be in liquid form, tantalum electrolysis operates on non-liquid powdered oxides. The initial discovery came in 1997 when Cambridge University researchers immersed small samples of certain oxides in baths of molten salt and reduced the oxide with electric current. The cathode uses powdered metal oxide. The anode is made of carbon. The molten salt at is the electrolyte. The first refinery has enough capacity to supply 3–4% of annual global demand.
Fabrication and metalworking
All
welding
Welding is a fabrication process that joins materials, usually metals or thermoplastics, by using high heat to melt the parts together and allowing them to cool, causing fusion. Welding is distinct from lower temperature techniques such as bra ...
of tantalum must be done in an inert atmosphere of
argon
Argon is a chemical element with the symbol Ar and atomic number 18. It is in group 18 of the periodic table and is a noble gas. Argon is the third-most abundant gas in Earth's atmosphere, at 0.934% (9340 ppmv). It is more than twice as ...
or
helium
Helium (from el, ἥλιος, helios, lit=sun) is a chemical element with the symbol He and atomic number 2. It is a colorless, odorless, tasteless, non-toxic, inert, monatomic gas and the first in the noble gas group in the periodic table. ...
in order to shield it from contamination with atmospheric gases. Tantalum is not
solderable The solderability of a substrate is a measure of the ease with which a soldered joint can be made to that material. Good solderability requires wetting (low contact angle) of the substrate by the solder.
__TOC__ Of metals
Solderability varies depe ...
. Grinding tantalum is difficult, especially so for
annealed tantalum. In the annealed condition, tantalum is extremely ductile and can be readily formed as metal sheets.
Applications
Electronics
![Tantal-Perle-Wiki-07-02-25-P1040364b](https://upload.wikimedia.org/wikipedia/commons/f/fe/Tantal-Perle-Wiki-07-02-25-P1040364b.jpg)
The major use for tantalum, as the metal powder, is in the production of electronic components, mainly capacitors and some high-power resistors. tantalum capacitor, Tantalum electrolytic capacitors exploit the tendency of tantalum to form a protective oxide surface layer, using tantalum powder, pressed into a pellet shape, as one "plate" of the capacitor, the oxide as the dielectric, and an electrolytic solution or conductive solid as the other "plate". Because the Relative static permittivity, dielectric layer can be very thin (thinner than the similar layer in, for instance, an aluminium electrolytic capacitor), a high capacitance can be achieved in a small volume. Because of the size and weight advantages, tantalum capacitors are attractive for portable telephones, personal computers, automotive electronics and cameras.
Alloys
Tantalum is also used to produce a variety of alloys that have high melting points, strength, and ductility. Alloyed with other metals, it is also used in making carbide tools for metalworking equipment and in the production of superalloys for jet engine components, chemical process equipment, nuclear reactors, missile parts, heat exchangers, tanks, and vessels.
Because of its ductility, tantalum can be drawn into fine wires or filaments, which are used for evaporating metals such as aluminium. Since it resists attack by body fluids and is nonirritating, tantalum is widely used in making surgical instruments and implants. For example, porous tantalum coatings are used in the construction of orthopedic implants due to tantalum's ability to form a direct bond to hard tissue.
Tantalum is inert against most acids except
hydrofluoric acid and hot
sulfuric acid, and hot alkaline solutions also cause tantalum to corrode. This property makes it a useful metal for chemical reaction vessels and pipes for corrosive liquids. Heat exchanging coils for the steam heating of hydrochloric acid are made from tantalum.
Tantalum was extensively used in the production of ultra high frequency Vacuum tube, electron tubes for radio transmitters. Tantalum is capable of capturing oxygen and nitrogen by forming nitrides and oxides and therefore helped to sustain the high vacuum needed for the tubes when used for internal parts such as grids and plates.
Other uses
![Tantalio](https://upload.wikimedia.org/wikipedia/commons/7/70/Tantalio.png)
Tantalum was used by NASA to shield components of spacecraft, such as ''Voyager 1'' and ''Voyager 2'', from radiation. The high melting point and oxidation resistance led to the use of the metal in the production of
vacuum furnace
A vacuum furnace is a type of furnace in which the product in the furnace is surrounded by a vacuum during processing. The absence of air or other gases prevents oxidation, heat loss from the product through convection, and removes a source of co ...
parts. Tantalum is extremely inert and is therefore formed into a variety of corrosion resistant parts, such as thermowells, valve bodies, and tantalum fasteners. Due to its high density, shaped charge and explosively formed penetrator liners have been constructed from tantalum. Tantalum greatly increases the armor penetration capabilities of a shaped charge due to its high density and high melting point.
It is also occasionally used in precious watches e.g. from Audemars Piguet, F.P. Journe, Hublot, Montblanc (pens), Montblanc, Omega Watches, Omega, and Panerai. Tantalum is also highly bioinert and is used as an orthopedic implant material.
The high stiffness of tantalum makes it necessary to use it as highly porous foam or scaffold with lower stiffness for hip replacement implants to avoid stress shielding. Because tantalum is a non-ferrous, non-magnetic metal, these implants are considered to be acceptable for patients undergoing MRI procedures.
The oxide is used to make special high refractive index glass for camera lenses.
Environmental issues
Tantalum receives far less attention in the environmental field than it does in other geosciences. Upper Crust Concentration (UCC) and the Nb/Ta ratio in the upper crust and in minerals are available because these measurements are useful as a geochemical tool. The latest value for upper crust concentration is 0.92 ppm, and the Nb/Ta(w/w) ratio stands at 12.7.
Little data is available on tantalum concentrations in the different environmental compartments, especially in natural waters where reliable estimates of ‘dissolved’ tantalum concentrations in seawater and freshwaters have not even been produced.
Some values on dissolved concentrations in oceans have been published, but they are contradictory. Values in freshwaters fare little better, but, in all cases, they are probably below 1 ng L
−1, since ‘dissolved’ concentrations in natural waters are well below most current analytical capabilities. Analysis requires pre-concentration procedures that, for the moment, do not give consistent results. And in any case, tantalum appears to be present in natural waters mostly as particulate matter rather than dissolved.
Values for concentrations in soils, bed sediments and atmospheric aerosols are easier to come by.
Values in soils are close to 1 ppm and thus to UCC values. This indicates detrital origin. For atmospheric aerosols the values available are scattered and limited. When tantalum enrichment is observed, it is probably due to loss of more water-soluble elements in aerosols in the clouds.
Pollution linked to human use of the element has not been detected. Tantalum appears to be a very conservative element in biogeochemical terms, but its cycling and reactivity are still not fully understood.
Precautions
Compounds containing tantalum are rarely encountered in the laboratory. The metal is highly biocompatible
and is used for body implant (medicine), implants and coatings, therefore attention may be focused on other elements or the physical nature of the chemical compound.
People can be exposed to tantalum in the workplace by breathing it in, skin contact, or eye contact. The Occupational Safety and Health Administration (OSHA) has set the legal limit (permissible exposure limit) for tantalum exposure in the workplace as 5 mg/m
3 over an 8-hour workday. The National Institute for Occupational Safety and Health (NIOSH) has set a recommended exposure limit (REL) of 5 mg/m
3 over an 8-hour workday and a short-term limit of 10 mg/m
3. At levels of 2500 mg/m
3, tantalum is IDLH, immediately dangerous to life and health.
References
External links
Tantalum-Niobium International Study Center
{{Authority control
Tantalum,
Biomaterials
Chemical elements with body-centered cubic structure
Chemical elements
Native element minerals
Noble metals
Refractory metals
Transition metals