5.7 Thermo-Chemical Methods for Metals Recovery
135
depend on the type of raw material that is being processed, but typically Cu (the
base metal in electric wires and cables) has the highest concentration in pyrolysis
solid product [16]. Pyrolysis could play an important role in decreasing the volume
of waste, which is beneficial for the environment. However, most of the pyrolysis
processes for e-waste treatment are still in the laboratory scale by far.
5.7.2 Gasification and Plasma Technology
Gasification is not normally used for metals recovery from e-waste. However, some
recent work reports successful steam gasification of printed circuit boards (PCB) and
other electronic waste [16]. PCBs are important components in e-waste. Due to the
presence of high concentrations of precious metals, recycling of PCBs has attracted
significant attention [19]. During gasification, the organic components of the waste
are converted into hydrogen-rich syngas.
Plasma technology is an environmentally friendly method for metals recovery
from e-waste. This process is performed at high temperatures (as high as several thousand °C) in an ionized or electrically charged gas environment. The process smelts and
separates the precious metals in a furnace while removing the non-metal elements.
Although different types of plasma technology have been developed, including the
high enthalpy plasma jet, plasma reactor and plasma torch and this method is being
used in PyroGenesis Canada Inc. [17], there are limited numbers of studies on metals
recovery from e-waste using plasma mainly due to the high energy cost.
5.8 Metallurgical Methods for Metals Recovery
5.8.1 Pyrometallurgical Processing
Pyrometallurgical processes are the most common method for the recovery of
precious metals from e-waste. Usually, the metals are in a complex matrix with
other non-metallic materials and it is very difficult to recover them through physical separation methods. The pyrometallurgical methods are beneficial to segregate
and concentrate the metals from e-waste [12, 17]. This process consists of melting
electronic wastes in a high-temperature furnace or in a molten bath to remove the
plastics and the refectory oxides by forming slags and metal oxides [20]. It is mostly
used to recover the Cu content of e-waste and other metals that dissolve in molten
copper such as Ag, Au, Pt, and Pd [11]. A pyrometallurgical process mainly includes
smelting, incineration and alkali fusion. Pyrometallurgical processes are economical,
eco-efficient and could maximize the recovery of precious metals, whereas they have
the following limitations [11, 20, 21]:
135
depend on the type of raw material that is being processed, but typically Cu (the
base metal in electric wires and cables) has the highest concentration in pyrolysis
solid product [16]. Pyrolysis could play an important role in decreasing the volume
of waste, which is beneficial for the environment. However, most of the pyrolysis
processes for e-waste treatment are still in the laboratory scale by far.
5.7.2 Gasification and Plasma Technology
Gasification is not normally used for metals recovery from e-waste. However, some
recent work reports successful steam gasification of printed circuit boards (PCB) and
other electronic waste [16]. PCBs are important components in e-waste. Due to the
presence of high concentrations of precious metals, recycling of PCBs has attracted
significant attention [19]. During gasification, the organic components of the waste
are converted into hydrogen-rich syngas.
Plasma technology is an environmentally friendly method for metals recovery
from e-waste. This process is performed at high temperatures (as high as several thousand °C) in an ionized or electrically charged gas environment. The process smelts and
separates the precious metals in a furnace while removing the non-metal elements.
Although different types of plasma technology have been developed, including the
high enthalpy plasma jet, plasma reactor and plasma torch and this method is being
used in PyroGenesis Canada Inc. [17], there are limited numbers of studies on metals
recovery from e-waste using plasma mainly due to the high energy cost.
5.8 Metallurgical Methods for Metals Recovery
5.8.1 Pyrometallurgical Processing
Pyrometallurgical processes are the most common method for the recovery of
precious metals from e-waste. Usually, the metals are in a complex matrix with
other non-metallic materials and it is very difficult to recover them through physical separation methods. The pyrometallurgical methods are beneficial to segregate
and concentrate the metals from e-waste [12, 17]. This process consists of melting
electronic wastes in a high-temperature furnace or in a molten bath to remove the
plastics and the refectory oxides by forming slags and metal oxides [20]. It is mostly
used to recover the Cu content of e-waste and other metals that dissolve in molten
copper such as Ag, Au, Pt, and Pd [11]. A pyrometallurgical process mainly includes
smelting, incineration and alkali fusion. Pyrometallurgical processes are economical,
eco-efficient and could maximize the recovery of precious metals, whereas they have
the following limitations [11, 20, 21]: