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Zirconium [Zr, 40]
56.1 INTRODUCTION
Zirconium (Zr), a lustrous, grayish-white metal of group 4 in the periodic table of
elements, is soft, ductile, and malleable, and exhibits both oxyphilic and lithophilic
tendencies. Its abundance in the Earth’s crust is within the range of 100–250 mg/kg
and is distributed fairly similar to that in various rocks. Its contents in coal are from
about 30 to 50 mg/kg.
The oxidation state of zirconium is mainly +4, but it may also be +2 and +3.
It occurs in several silicates and its principal source is the mineral zircon, ZrSiO 4 .
Also, baddeleyite (called zirconia), ZrO 2 , has technological importance and is used
as a diamond simulant in jewelry. It is associated with Ti and Hf minerals, and may
occur in several minerals, such as pyroxenes, amphiboles, micas, and ilmenites.
World mine Zr production (rounded), excluding the United States, in 2010 was
1190 kt, of which 481 kt was produced in Australia, 390 kt in South Africa, 140 kt in
China, 60 kt in Indonesia (USGS 2011). Zirconium deposits are often enriched in U
and Th. It is also obtained as a by-product of Ti mining.
The principal use of Zr is for atomic energy purposes. It is highly resistant to corrosion, especially due to impacts of alkalis and acids; thus, it is an important component of various alloys. However, at high temperature (~900°C), Zr properties are
changed, which may result in meltdown of some equipments, especially of nuclear
reactors, which happened in 1979 at Three Miles Island, central Pennsylvania, and in
2011 at Fukushima, Japan, after the Tōhoku earthquake and tsunami (Emsley 2014).
Zirconium is applied in glass and ceramic productions, as well as in various thermal
installations, dyes, and pyrotechnics. It is added to paints to replace small amounts
of Pb compounds, which are still used (Emsley 2014).
Zirconium application in medicine is relatively broad, mainly as an addition to
implant materials. It is also a component of some cosmetics and toothpastes.
56.2 SOILS
Zirconium contents of soils are mainly inherited from parent rocks, and therefore, its
distribution in soil profiles is often used in studies of soil genetic. Lower Zr amounts
are in glacial drift soils (mean 140 mg/kg), and higher are in residual soils, especially derived from Zr-rich rocks (mean 305 mg/kg). Increased Zr content in coarse
fraction of desert dusts reflects the presence of detrital zircon (Castillo et al. 2008;
Jaworska and Dąbkowska-Naskręt 2006).
Soils contain Zr within the range of 90–850 mg/kg, and the highest concentration
is in heavy loamy soils (Table 56.1). Soils of various countries contain Zr as follows
(mean and range, in mg/kg): Argentina, 100–550; Australia, 350; China, 219–500;
Denmark, 115; Russia, 200–550; the United States, 184–760 (Kabata-Pendias 2011).
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