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Antimony [Sb, 51]

2.1 INTRODUCTION
Antimony (Sb), a metalloid of the group 15 in the periodic table of elements, occurs in
the Earth’s crust up to 0.9 mg/kg, and in igneous rocks within the range 0.1–1 mg/kg.
Its content in sedimentary rocks, especially argillaceous, may be higher, up to 4 mg/kg.
Sb content in coal varies within the range 1–3 mg/kg; it may be concentrated in fly ash
(up to 100 mg/kg). Sb amount in crude oil is within the order of magnitude 0.0X–0.X mg/kg.
Antimony exhibits chalcophilic properties, and occurs with sulfur and some metal
deposits such as Cu, Pb, and Ag, and, therefore, is used as a pathfinder for the geochemical exploration. Antimony deposits often contain minor amounts of Ag, Au, and Hg.
It has various oxidation stages: −3, +3, +4, and +5. More than 100 minerals of
Sb are found naturally. It occurs in three types of minerals, namely, sulfides, oxides,
and mixed oxides-sulfides (e.g., kermesite, Sb 2 S 2 O). Its main minerals are stibnite,
Sb 2 S 3 , and valentinite, Sb 2 O 3 . Antimony is a component of several other minerals,
such as pyrargyrite (Ag 2 SbS 3 ) and bourmite (PbCuSbS 3 ). It may easily form soluble
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thiocomplexes (SbS 2 , SbS 4 ) in various aquatic environments.
Global (excluding the United States) Sb production was estimated at 135  kt in
2010, with the highest in China at 120 kt (USGS 2011). Sb production increased significantly in recent years. Antimony is also recovered from various recycled scraps.
It is an important product of the secondary lead smelting and lead–acid batteries.
Antimony trioxide (stibnite; Sb 2 O 3 ) is the most important Sb compound used in
the industry. It is used mainly as an alloying metal for Pb in batteries (Pb-acid), for
added strength and improved electrical properties. Sb alloys with Pb and Sn are used
in bullets, and for solders and bearings. A variety of compounds containing Sb as
the major constituents are used for other ammunition types and explosives. It is also
applied in some microelectronics. This metal is used in fire retardant formulations
for plastics, rubbers, textiles, paper, and paints. Antimony compounds, primarily
sodium antimonate, are also used in decolorizing and refining agents for optical
glass and cathode ray tube glass. In the electronics industry, the use of Sb grows for
diodes. It is also applied in several chemical industries and in cosmetic production.
Antimony and its compounds are considered to be serious pollutants, and their
concentration in sewage sludge is recently of concern. Especially, Sb released from
coal combustion is an important pollutant due to its small-sized aerial particles, high
solubility, and reactivity (Shotyk et al. 2005).
2.2 SOILS
Sb background level in soils ranges from 0.05 to 4.0 mg/kg (Table 2.1). Its average
content in worldwide soils is estimated at 0.67 mg/kg. Mean content calculated for
top soils in the United States is 0.66 mg/kg (Burt et al. 2003), whereas this value for
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