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8.1.3 Microscopic Management of E-Waste
8.1.3.1 Recycling of E-Waste to Recover Valuable Materials
Improved standard of living of citizens, fast economic growth and enhanced technological advancement has resulted in the production of a large amount of electrical
and electronic equipment (Lu and Xu 2016). The useful life of electronic and electrical equipment has been reduced over the years owing to the adjustment of consumer taste and technological innovations (Khaliq et al. 2014). This has led to the
accumulation of the resultant waste electrical and electronic equipment (WEEE) or
E-waste in the environment (Khaliq et al. 2014; Lekka et al. 2015; Akcil et al. 2015;
Cayumil et al. 2016; Heydarian et al. 2018). Within this waste stream, the major
interests are the printed wiring boards and the plastics (Lu and Xu 2016). Besides
environmental concerns, recycling of this waste is attractive and also viable since it
contains significant amounts of precious metals (Cayumil et al. 2016; Ebin and Isik
2016). The presence of precious metals such as palladium, platinum, gold, tantalum,
selenium, etc., in E-waste, makes recycling a desirable process (Khaliq et al. 2014;
Chen et al. 2018). Therefore, their availability is paramount for their inclusion as a
tool for economic sustainability (Isıldar et al. 2018). However, it is important to note
that E-waste could be hazardous due to the presence of heavy metals (lead, mercury,
cadmium, etc.) as well as brominated flame retardants (Kaya 2016). Therefore,
proper management options should be adopted to prevent human and environmental
health risks (Kaya 2016; Lu and Xu 2016). The technologies that have been successfully deployed in the recovery of metals are hydrometallurgy (use of aqueous
solution in extraction of metals from the waste), pyrometallurgy (application of heat
to melt appliances and recover metal) and biohydrometallurgy (bioleaching with
adapted microorganisms) methods (Cui and Zhang 2008; Chauhan et al. 2018). The
following section will briefly discuss these methods.
8.1.3.1.1 Pyrometallurgy for the Recovery of Metal and Energy from E-Waste
Pyrometallurgy involves the recovery of metal of interest by processing (e.g. melting, burning under high temperature) of pulverized E-waste (Cayumil et al. 2016;
Ebin and Isik 2016). Most full-scale pyrometallurgical processing of WEEE scrap
takes place using smelters designed for refining metals from ore or metal scrap
(Townsend 2011; Chauhan et al. 2018). However, the upgrade of final metal products recovered from WEEE is a challenging task due to a mixture of pure metals and
alloys after the pyrometallurgical process (Reck and Graedel 2012). Smelting of
E-waste could result in the emission of environmentally persistent compounds such
as dioxin from the plastic components of the waste. A large amount of slag
generation, loss of precious metals and difficulty in recovery of Al, Fe and other
metals are the additional problems associated with pyrometallurgical methods
(Chauhan et al. 2018). A modified form – vacuum metallurgy – utilizes variation in
C. O. Onwosi et al.
8.1.3 Microscopic Management of E-Waste
8.1.3.1 Recycling of E-Waste to Recover Valuable Materials
Improved standard of living of citizens, fast economic growth and enhanced technological advancement has resulted in the production of a large amount of electrical
and electronic equipment (Lu and Xu 2016). The useful life of electronic and electrical equipment has been reduced over the years owing to the adjustment of consumer taste and technological innovations (Khaliq et al. 2014). This has led to the
accumulation of the resultant waste electrical and electronic equipment (WEEE) or
E-waste in the environment (Khaliq et al. 2014; Lekka et al. 2015; Akcil et al. 2015;
Cayumil et al. 2016; Heydarian et al. 2018). Within this waste stream, the major
interests are the printed wiring boards and the plastics (Lu and Xu 2016). Besides
environmental concerns, recycling of this waste is attractive and also viable since it
contains significant amounts of precious metals (Cayumil et al. 2016; Ebin and Isik
2016). The presence of precious metals such as palladium, platinum, gold, tantalum,
selenium, etc., in E-waste, makes recycling a desirable process (Khaliq et al. 2014;
Chen et al. 2018). Therefore, their availability is paramount for their inclusion as a
tool for economic sustainability (Isıldar et al. 2018). However, it is important to note
that E-waste could be hazardous due to the presence of heavy metals (lead, mercury,
cadmium, etc.) as well as brominated flame retardants (Kaya 2016). Therefore,
proper management options should be adopted to prevent human and environmental
health risks (Kaya 2016; Lu and Xu 2016). The technologies that have been successfully deployed in the recovery of metals are hydrometallurgy (use of aqueous
solution in extraction of metals from the waste), pyrometallurgy (application of heat
to melt appliances and recover metal) and biohydrometallurgy (bioleaching with
adapted microorganisms) methods (Cui and Zhang 2008; Chauhan et al. 2018). The
following section will briefly discuss these methods.
8.1.3.1.1 Pyrometallurgy for the Recovery of Metal and Energy from E-Waste
Pyrometallurgy involves the recovery of metal of interest by processing (e.g. melting, burning under high temperature) of pulverized E-waste (Cayumil et al. 2016;
Ebin and Isik 2016). Most full-scale pyrometallurgical processing of WEEE scrap
takes place using smelters designed for refining metals from ore or metal scrap
(Townsend 2011; Chauhan et al. 2018). However, the upgrade of final metal products recovered from WEEE is a challenging task due to a mixture of pure metals and
alloys after the pyrometallurgical process (Reck and Graedel 2012). Smelting of
E-waste could result in the emission of environmentally persistent compounds such
as dioxin from the plastic components of the waste. A large amount of slag
generation, loss of precious metals and difficulty in recovery of Al, Fe and other
metals are the additional problems associated with pyrometallurgical methods
(Chauhan et al. 2018). A modified form – vacuum metallurgy – utilizes variation in
C. O. Onwosi et al.