Zirconium is a transition metal discovered in 1789. It is a lustrous metal and is widely used in manufacturing of wide range of durable, strong and noncorrosive materials.
History and Discovery
Several zirconium related minerals, including Zircon have been mentioned in biblical writings. Zirconium was discovered by Martin Klaproth in 1789, and in 1824 Jacob Berzelius (Swedish chemist) isolated an impure form of this metal. Zirconium was isolated in pure form by Anton E. van Arkel and J.H. de Boer (1925). The name Zirconium has been originated from the Persian word zargun, that means “golden colored” [1]. Zirconium came into lime light after the 1940s, when its use in the nuclear power plants was identified.
Zirconium
| Periodic Table Classification | Group 4 Period 5 |
|---|---|
| State at 20C | Solid |
| Color | Whitish-silver |
| Electron Configuration | [Kr] 4d2 5s2 |
| Electron Number | 40 |
| Proton Number | 40 |
| Electron Shell | 2,8,18,10,2 |
| Density | 6.49 g.cm-3 at 20°C |
| Atomic number | 40 |
| Atomic Mass | 91.22 g.mol -1 |
| Electronegativity according to Pauling | 1.2 |
Occurrence
Zirconium is an abundant metal. The commercial source of zirconium are the alluvial deposits present in beaches of ocean, beds of old lakes and streams. The most abundant mineral form of zirconium is baddeleyite (zirconium dioxide). The most common impurity in zirconium metal is hafnium, but for commercial use (except in nuclear reactors), zirconium with 1% hafnium is considered as pure metal. Today, the biggest producers of zirconium include South Africa, Australia, Indonesia, India, China and Sri Lanka. And around 900,000 tons per year of zircon (ZiSO4) are produced in the world [2].
Physical Characteristics
Zirconium is a grey-white element. It is shiny, lustrous, and malleable transition metal. In powder form, zirconium exists in black color. The physical characteristics of pure and impure form of zirconium greatly vary, as impure zirconium is hard and brittle, while in pure form, it is soft and ductile [3]. Zirconium is lighter than steel (have density of 6.49 g.cm-3 at 20C). The atomic number of zirconium is 40 and its atomic mass is 91.22 g.mol-1. The melting point of zirconium is 1852°C and boiling point is 4400°C. Its oxidation state is +4. It is present in the Group 4 (IV)b of the periodic table [4].
Chemical Characteristics
Zirconium is a resistant metal, with outstanding ability to withstand corrosion and heat. It can absorb significant amounts of various gases, including nitrogen, hydrogen and oxygen. Zirconium reacts vigorously with air and in divided or powder form, it can lead to spontaneous and dangerous ignition. It is unreactive with alkalis and acids and does not dissolve in them. Zirconium does not form radioactive isotopes when bombarded with neutrons [5].
Significance and Uses
- The most common use of zirconium is in nuclear applications. It is used in the manufacturing of engineering material for nuclear reactors. For instance, zirconium based cladding fuel rods are being used and core structure of reactors is also made from zirconium. Further, zirconium does not readily absorb neutron and can withstand any mechanical damage caused from neutron bombardment in nuclear reactors.
- Zirconium readily absorbs oxygen which makes it desirable candidate for removing residual gases from electron tubes or vacuum tubes (used in making television or computer screens).
- Zirconium is used in making refractory materials, including crucibles, rocket launch structures, furnaces, incinerators and ovens.
- It is used in various ceramic industries for opacification purposes (adjustment of glaze content).
- Zirconium is used as hardening agent in making alloys, including magnesium and steel.
- It is widely used in fabrication of valves, and pumps due to its high resistant to corrosion.
- It is widely used in packaging and paper industry for making surface coats as zirconium have outstanding strength and resistance.
Health Hazards
Zirconium metal and its salts have low toxicity (environmental and biological) as they are scarcely soluble in water. If ingested, zirconium does not get absorbed in the tissues and passes the gut without causing any hazard. Plants also don’t absorb zirconium present in the soil. However, the radioactive isotopes zirconium 95 is a radionuclide with considerably high half-life and continue to persist in the environment and cause cancer risks for decades [5].
Isotopes of Zirconium
Zirconium have five natural isotopes, zirconium-90 (51.46 percent), zirconium-92 (17.11 percent), zirconium-91 (11.23 percent), zirconium-96 (2.80 percent) and zirconium-94 (17.40 percent). There are 28 artificial isotopes of zirconium, which range in atomic mass from 78 to 110. The zirconium-93 is the most stable artificial isotope of zirconium, while zirconium-110 is the least stable isotope (with half-life of around 30 milliseconds). 110Zr is the most radioactive isotope and the heaviest [6].
REFERENCES
[1]. Harper, Douglas. “zircon”. Online Etymology Dictionary.
[2]. Nielsen, Ralph (2005) “Zirconium and Zirconium Compounds” in Ullmann’s Encyclopedia of Industrial Chemistry, Wiley-VCH, Weinheim. doi:10.1002/14356007.a28_543
[3]. Emsley, John (2001). Nature’s Building Blocks. Oxford: Oxford University Press. pp. 506–510. ISBN 0-19-850341-5.
[4]. Lide, David R., ed. (2007–2008). “Zirconium”. CRC Handbook of Chemistry and Physics. 4. New York: CRC Press. p. 42. ISBN 978-0-8493-0488-0.
[5] https://www.lenntech.com/periodic/elements/zr.htm
[6]. https://www.britannica.com/science/zirconium