What Is Tellurium?
Tellurium, with atomic number 52, belongs to group 16 of the periodic table.
This nonmetallic element, symbolized as Te, has an atomic weight of 127.60 and exhibits isotopes ranging from mass numbers 105 to 132. Among these, eight are stable while the remainder are radioactive.
Classified under various safety laws, tellurium, and its compounds pose toxicity risks to humans.
Uses of Tellurium
Tellurium serves as an alloy additive in steel and other acid-resistant alloys to enhance workability and sulfuric acid resistance. Its compounds find uses in colorants for glass and ceramics, oxidizers, and thermoelectric elements, notably in thermocouples for electronic refrigeration systems. High-purity intermetallic Se-Te compounds are utilized in photosensitive drums for dry copying, offering high recovery and reuse rates.
Moreover, adding 0.01-1.0% metallic tellurium to steel improves its free-cutting features, toughness, and corrosion resistance, making such steel ideal for automotive and precision machine parts.
Properties of Tellurium
While many tellurium compounds emit a garlic-like odor, elemental tellurium is odorless. It has a melting point of 449.51°C, a boiling point of 988°C, and a specific gravity of 6.232. Chemically akin to sulfur and selenium, it burns in air with a blue-green flame to form tellurium dioxide (TeO2) and reacts violently with halogens. Tellurium exhibits oxidation states of 6, 5, 4, 2, and -2 and forms a weakly acidic oxide.
Structure of Tellurium
Tellurium’s metallic form is a silvery-white crystal with a hexagonal structure, and its electron configuration is [Kr] 4d10 5s2 5p4. It occurs naturally in various minerals, both as elemental tellurium and in compounds with gold, silver, copper, and lead.
Other Information on Tellurium
1. Production of Tellurium
Although tellurium’s environmental presence is minimal, it is primarily obtained from sulfide ores as tellurides and in minor quantities in gold and silver. Leading reserves are found in the United States, Peru, and Canada, with major producers being Canada, Belgium, the United States, Peru, and Japan, accounting for 82.3% of global production.
In Japan, tellurium is sourced from the Kawazu Mine in Shizuoka and the Tezu Mine in Hokkaido. Industrially, it is derived from anode mud in copper and lead refining processes, treated with soda ash to produce soluble tellurium salts, and then isolated as telluric acid (TeO2・nH2O).
2. Tellurium Isotopes
Of the 30 known tellurium isotopes, naturally occurring 128Te and 130Te are radioactive, undergoing double beta decay, with 128Te having the longest half-life of any radioactive isotope. A small fraction of 110Te decays to 106Sn via alpha decay. Artificially, 131I can be produced from neutron capture of 130Te.
3. Tellurium Toxicity
Both elemental tellurium and its compounds are toxic, metabolizing in the body to produce dimethyl telluride, which emits a garlic-like odor. Exposure to tellurium compounds can lead to symptoms such as loss of appetite, headaches, nausea, and difficulty breathing, among others. These can be mitigated by avoiding further exposure.