195
For Oliveira (2012), several models of magnetic separators are widely used,
especially dry and wet devices, which are used to separate large and small particles,
respectively. Drum, magnetic roll, and cross-belt separators are some of the devices
used (CETEM 2004). Electrostatic separators are used to segregate conductor from
nonconductor materials, especially to recover Cu and metals from printed circuit
boards, in addition to the recovery of aluminum and copper from cables and wires
(Cui and Forssberg 2003; Veit 2005). Veit (2005) states that the large difference
between the electric conductivity of metals and nonmetal elements establishes an
excellent condition to use this technology successfully in the recycling of waste. For
the author, the first electrostatic separators were developed to process ores. Today,
these devices are used for other aims, like the recovery of nonferrous metals from
automobile scrap, the treatment of municipal solid waste, the processing of electrical and electronic equipment, and other applications.
10.3.2.4.3 Pyrometallurgical Processes
The pyrometallurgical processing of metals includes the melting and refining of
materials to produce pure metals, such as copper and lead. The refining steps produce secondary phases that are rich in other metals, like precious metals, which are
defined in specific equipment (Oliveira 2012).
The decomposition of organic material using pyrometallurgical processes is an
appropriate way to recover metals since most organic compounds decompose and
become volatile at high temperatures. However, this process may release halogen
compounds, dioxins, and furans, also producing scum due to the presence of ceramic
materials and glass in waste. Besides, pyrometallurgical processes are not very efficient to recover tin (Sn), lead (Pb), and present other disadvantages (Blazsó et al.
2002; Veit 2005; Kasper 2011; Oliveira 2012).
10.3.2.4.4 Hydrometallurgy
The word “hydrometallurgy” denotes extraction and solubilization processes of
metals in an aqueous medium, which are followed by the treatment of resulting
solutions until valued forms of metals are obtained (Oliveira 2012). In these processes, attack solutions are used to dissolve and separate solid materials. These
solutions are then submitted to processes like solvent extraction, precipitation, and
refining to improve the selection of materials (Veit 2005; de Moraes 2011).
For Silvas (2014), several hydrometallurgical techniques may be used to treat
rare earth elements, like chemical leaching with cyanide, thiosulfate, ligands (ethylenediaminetetraacetic acid (EDTA), diethylenetriaminepentaacetic acid (DTPA),
nitrile acetic acid (NTA), oxalate, sodium hypochlorite, as well as sulfuric, hydrochloric, nitric acids, and aqua regia). Hydrometallurgical pickling with organic solvents, iron chloride, copper chloride, and hydrochloric acid is also used, besides
bioleaching, which in turn consumes little energy, as microorganisms carry out
10 E-waste Management and the Conservation of Geochemical Scarce Resources
For Oliveira (2012), several models of magnetic separators are widely used,
especially dry and wet devices, which are used to separate large and small particles,
respectively. Drum, magnetic roll, and cross-belt separators are some of the devices
used (CETEM 2004). Electrostatic separators are used to segregate conductor from
nonconductor materials, especially to recover Cu and metals from printed circuit
boards, in addition to the recovery of aluminum and copper from cables and wires
(Cui and Forssberg 2003; Veit 2005). Veit (2005) states that the large difference
between the electric conductivity of metals and nonmetal elements establishes an
excellent condition to use this technology successfully in the recycling of waste. For
the author, the first electrostatic separators were developed to process ores. Today,
these devices are used for other aims, like the recovery of nonferrous metals from
automobile scrap, the treatment of municipal solid waste, the processing of electrical and electronic equipment, and other applications.
10.3.2.4.3 Pyrometallurgical Processes
The pyrometallurgical processing of metals includes the melting and refining of
materials to produce pure metals, such as copper and lead. The refining steps produce secondary phases that are rich in other metals, like precious metals, which are
defined in specific equipment (Oliveira 2012).
The decomposition of organic material using pyrometallurgical processes is an
appropriate way to recover metals since most organic compounds decompose and
become volatile at high temperatures. However, this process may release halogen
compounds, dioxins, and furans, also producing scum due to the presence of ceramic
materials and glass in waste. Besides, pyrometallurgical processes are not very efficient to recover tin (Sn), lead (Pb), and present other disadvantages (Blazsó et al.
2002; Veit 2005; Kasper 2011; Oliveira 2012).
10.3.2.4.4 Hydrometallurgy
The word “hydrometallurgy” denotes extraction and solubilization processes of
metals in an aqueous medium, which are followed by the treatment of resulting
solutions until valued forms of metals are obtained (Oliveira 2012). In these processes, attack solutions are used to dissolve and separate solid materials. These
solutions are then submitted to processes like solvent extraction, precipitation, and
refining to improve the selection of materials (Veit 2005; de Moraes 2011).
For Silvas (2014), several hydrometallurgical techniques may be used to treat
rare earth elements, like chemical leaching with cyanide, thiosulfate, ligands (ethylenediaminetetraacetic acid (EDTA), diethylenetriaminepentaacetic acid (DTPA),
nitrile acetic acid (NTA), oxalate, sodium hypochlorite, as well as sulfuric, hydrochloric, nitric acids, and aqua regia). Hydrometallurgical pickling with organic solvents, iron chloride, copper chloride, and hydrochloric acid is also used, besides
bioleaching, which in turn consumes little energy, as microorganisms carry out
10 E-waste Management and the Conservation of Geochemical Scarce Resources