29
Nickel [Ni, 28]
29.1 INTRODUCTION
Nickel (Ni) is a metal of group 10 in the periodic table of elements, which also
contains Pd and Pt (platinum group metals). Its mean abundance in the Earth’s crust
is around 20 mg/kg. The contents of Ni in ultramafic rocks are highly elevated and
range from 1400 to 2000 mg/kg. Its concentrations decrease with increasing acidity
of rocks, down to the range of 5–20 mg/kg in granites. Sedimentary rocks contain
Ni from 5 to 90 mg/kg in sandy and argillaceous sediments, respectively. The lowest
Ni contents are in limestones, around 5 mg/kg. In coal its amounts highly vary, up to
about 300 mg/kg, and in fly ash they are lower, around 90 mg/kg.
Nickel occurs mainly at +2 oxidation state, which may change up to +4. It reveals
both chalcophilic and siderophilic affinity, and readily combines with Fe. Therefore,
Ni–Fe compounds are common in both the Earth’s core and meteorites. The Ni–Fe
alloy of the Earth’s core (called barysphere or NIFE) is composed of Fe/Ni within
the ratio of 11:1. The great affinity of Ni for S results in their association with various compounds and minerals. The main ores of Ni are composed mainly of pentlandite, (Ni,Fe) 9 S 8 , and pyrrhotite, Fe 1–x Ni. In rocks, Ni occurs primarily as sulfides
(millerite, NiS), arsenides (nickeline, NiAs), and antimonides (ullmannite, NiSbS).
Nickel is also associated with several Fe minerals and forms sulfides and sulfarsenides with Fe and Co. During weathering, it is coprecipitated with Fe and Mn oxides,
and becomes included in their minerals (e.g., goethite, limonite). Nickel may also be
associated with carbonates, phosphates, and silicates. Organic matter (OM) and clay
minerals exhibit a strong ability to absorb Ni; thus, it may be concentrated in some
coals and oil, as well as in bottom sediments rich in OM.
World (excluding the United States) mine production of Ni (rounded) in 2010
was 1550 Mt, of which 265 Mt was mined in Russia, 232 Mt in Indonesia, 155 Mt
in Canada, 156 Mt in Philippines, and 139 Mt in Canada (USGS 2011). Nickel has
been broadly used in several industries, especially for the production of stainless
steels. Most of Ni is added to various alloys resistant to oxidation and corrosion. Ni
alloys are used for different tools and vessels used in medicine, food technology, and
kitchen equipments. Its compounds are used as dyes in ceramic and glass manufactures. Other uses of Ni have been recently limited, partly due to its relatively high
price.
29.2 SOILS
Soils throughout the world contain Ni in a very broad range; however, its mean contents reported for various countries are within the relatively low range of 13–37 mg/kg.
The lowest Ni contents are in sandy and organic soils, and the highest in heavy loamy
and calcareous soils (Table 29.1). However, it may be elevated in some organic soils,
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