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FIGURE 2.1 Flowsheet of pyrometallurgical copper production from sulfidic ores.
2.3 Cu-METALLURGICAL SLAGS
Ore processing heading towards recovery of valuable metals has been practised since
historical times (Themelis, 1994; Radetzki, 2009). Although the fact that smelting
technologies have been gradually improving, this industrial sector still generates various kinds
of waste materials including waste rocks, ashes, sludges and slags (Piatak et al., 2003; Piatak
et al., 2004). Slags are considered as important waste materials, because they are produced in
large quantities and additionally contain elevated amounts of metallic elements (Ettler et al.,
2001; Piatak et al., 2004; Lottermoser, 2005; Kierczak et al., 2010; Vítková et al., 2010; Ash
et al., 2013). Due to the fact that historical technologies were not as efficient as modern ones,
CHAPTER 2: COPPER METALLURGICLA SLAGS- CURRENT KNOWLEDGE AND FATE:
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slags originating from former smelting industry are expected to contain higher amounts of
metals and other impurities (Lottermoser, 2002). It is also important to notice that current
knowledge about the environmental behaviour of metallurgical slags has increased and it is
now commonly known that slags can pose environmental risk (Gee et al., 1997; Manz &
Castro, 1997; Sobanska et al., 2000; Ettler et al., 2003; Piatak et al., 2004; Reuter et al., 2004;
Ettler et al., 2009; Vítková et al., 2010; Piatak & Seal, 2010; Kierczak et al., 2013; Ettler &
Johan, 2014; Piatak et al., 2015).
For this reason, slags are nowadays classified as potentially hazardous materials in contrast to
historical times when they were considered as inert for the environment. Thus, in many
former industrial areas, these wastes were abandoned without any environmental monitoring.
At several sites, research evaluating environmental quality has revealed that slags occurring at
disposal sites are not as environmentally stable as previously assumed (Piatak et al., 2004). It
is noticed that local pollution of the environment is related to wastes storage concluding that
long-term disposal of slags and their exposition to weathering may lead to the mobilization of
metallic elements and their transfer to environmental components such as soils, sediments,
ground and surface waters (Parsons et al., 2001; Lottermoser, 2002; Ettler et al., 2003;
Vítková et al., 2010; Kierczak et al., 2013). The studies devoted to environmental aspects of
slag disposal have certainly contributed to improvement of knowledge about the stability of
these wastes. Therefore, waste management in modern industrial sites treats slags with a
greater caution. Regardless of the potential environmental risk, these wastes are still disposed
in many industrial sites, but their storage is done in accordance with strict standards of proper
isolation and frequent environmental monitoring.
Chemical, textural and mineralogical characterization of slags is particularly significant for
environmental risk assessment. As already mentioned, the susceptibility of slags to alterations
strongly depends on their composition. Elevated concentrations of metallic elements in slags,
greater porosity and the presence of phases susceptible to weathering increase the
environmental risk of slag disposal. For this reason, characterization of slags is recommended
as the first step of environmental investigations (Ettler et al., 2009; Piatak et al., 2015).
Numerous analytical methods can be used to study the chemical and phase composition of
slags. Bulk slag chemistry analysis may be done using inductively coupled plasma atomic
emission spectroscopy (ICP-AES), inductively coupled plasma optical emission spectroscopy
(ICP-OES), inductively coupled plasma atomic mass spectroscopy (ICP-MS) with prior
material digestion. Whereas commonly used methods such as optical microscopy, scanning
electron microscopy (SEM), electron microprobe analysis (EMPA), X-ray powder diffraction
(XRD), X-ray fluorescence spectroscopy (XRF) and Raman spectroscopy deliver sufficient
information about the phase composition of the material and the distribution of metallic
elements in different phases. Combination all of these analytical methods allows a detailed
slag characterization including bulk chemistry and mineralogy. These methods are considered
as useful tools for laboratory simulation of the weathering as well as the further assessment of
CHAPTER 2: COPPER METALLURGICLA SLAGS- CURRENT KNOWLEDGE AND FATE:
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environmental hazards through observing alteration of slag materials (Gbor et al., 2000;
Kierczak et al., 2010; Jamieson, 2011; Piatak et al., 2015).
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