Environmental Engineering Reference
In-Depth Information
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Fig. 13.1
Relationship between annual production amounts (T) and Clarke's Numbers (K)
the global impact of a particular industrial activity, before devising strategies to en-
sure sustainability on this planet. One aspect of this is to address the basic resource
consumption of the key elements that are essential to support our current industrial
society. The previous chapter addressed issues related to the iron and steel industry,
and in this chapter we will turn to the non-ferrous metals and consider the poten-
tial for reducing their substantial environmental impact by increasing their rate of
recycling.
Metal resources have been classified geochemically by Goldschmidt (
1954
) ac-
cording to their preferred host phases into lithophile (rock-loving), siderophile (iron-
loving), and chalcophile (ore-loving or chalcogen-loving) nature. These groups can
be distinguished as shown in Fig.
13.1
where the annual production of metals is
plotted logarithmically against Clarke's numbers
1
(Masuko
1994
). The different
groups reflect major differences in their distribution and chemical behavior with
implications for their environmental impact. For instance, Siderophile elements are
the high-density transition metals which dissolve readily in iron, and sink towards
the core so that they are rare in the Earth's crust. Lithophile elements combine read-
ily with oxygen so remain near the surface but require energy-intensive electrolysis
for extraction. Chalcophile elements also remain close to the earth's surface because
they combine readily with sulfur and thus their refining requires reduction with
coke to remove the sulfur with its associated pollution.
The detrimental environmental impacts of metal extraction and refining can be
illustrated by the case of copper (chalcophile group) extraction. Firstly, copper min-
ing has direct impacts on the environment through mining. Secondly, non-ferrous
1
Clarke's numbers express the average content of the chemical elements in the earth's crust and
other geochemical and cosmo-chemical systems.
