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E-wastes: Mines of future. Waste management
... For recovery of metals from e-waste, various traditional metallurgical techniques, viz. pyrometallurgical processes using heat treatments like roasting, smelting, and hydrometallurgical processes based on chemical leaching by acid/alkali wash are proposed (Akcil et al. 2009;Cui and Zhang 2008;Yazici and Deveci 2009). However, both pyrometallurgical and hydrometallurgical techniques for e-waste processing are often demonstrated to be energy intensive, costly, and associated with serious secondary pollutions such as release of toxic gases, i.e., dioxins and furans metal dusts and discharge of high volume lixiviants (Cui and Zhang 2008;Dalrymple et al. 2007;Ilyas et al. 2010;Owens et al. 2007). ...
... The hierarchy of e-waste management recommends the reuse and/or remanufacture of whole EEE followed by recovery of materials by recycling techniques and disposal by incineration and landfilling as a last strategy. Severe secondary pollution by metal content of e-waste has been reported in the dumping areas, landfills, and incinerators (Akcil et al. 2009;Cui and Zhang 2008;Fujimori and Takigami 2014). Leachates from landfills potentially transport toxic substances into soil and water while combustion in incinerators can introduce toxic gases into the atmosphere (UNEP 2009). ...
Waste electrical and electronic equipment (WEEE) or electronic waste (e-waste) is one of the fastest growing waste streams in the urban environment worldwide. The core component of printed circuit board (PCB) in e-waste contains a complex array of metals in rich quantity, some of which are toxic to the environment and all of which are valuable resources. Therefore, the recycling of e-waste is an important aspect not only from the point of waste treatment but also from the recovery of metals for economic growth. Conventional approaches for recovery of metals from e-waste, viz. pyrometallurgical and hydrometallurgical techniques, are rapid and efficient, but cause secondary pollution and economically unviable. Limitations of the conventional techniques have led to a shift towards biometallurgical technique involving microbiological leaching of metals from e-waste in eco-friendly manner. However, optimization of certain biotic and abiotic factors such as microbial species, pH, temperature, nutrients, and aeration rate affect the bioleaching process and can lead to profitable recovery of metals from e-waste. The present review provides a comprehensive assessment on the metallurgical techniques for recovery of metals from e-waste with special emphasis on bioleaching process and the associated factors.
... Therefore, it is imperative to develop recycling projects to increase the public awareness and to increase the collection rates to manage an ever-increasing stream of WEEE in Turkey. 102 -104 It has been well known that both the electronic and electrical waste generated contains a lot of non-degradable materials mostly hazardous by nature. 105 the soil or earth crust. ...
Waste generated by the electrical and electronic devices is huge concern worldwide. With decreasing life cycle of most electronic devices and unavailability of the suitable recycling technologies it is expected to have huge electronic and electrical wastes to be generated in the coming years. The environmental threats caused by the disposal and incineration of electronic waste starting from the atmosphere to the aquatic and terrestrial living system have raised high alerts and concerns on the gases produced (dioxins, furans, polybrominated organic pollutants, and polycyclic aromatic hydrocarbons) by thermal treatments and can cause serious health problems if the flue gas cleaning systems are not developed and implemented. Apart from that there can be also dissolution of heavy metals released to the ground water from the landfill sites. As all these electronic and electrical waste do posses richness in the metal values it would be worth recovering the metal content and protect the environmental from the pollution. Cyanide leaching has been a successful technology worldwide for the recovery of precious metals (especially Au and Ag) from ores/concentrates/waste materials. Nevertheless, cyanide is always preferred over others because of its potential to deliver high recovery with a cheaper cost. Cyanidation process also increases the additional work of effluent treatment prior to disposal. Several non-cyanide leaching processes have been developed considering toxic nature and handling problems of cyanide with non-toxic lixiviants such as thiourea, thiosulphate, aqua regia and iodine. Therefore, several recycling technologies have been developed using cyanide or non-cyanide leaching methods to recover precious and valuable metals.
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... Therefore, it is imperative to develop recycling projects to increase the public awareness and to increase the collection rates to manage an ever-increasing stream of WEEE in Turkey. 102 -104 It has been well known that both the electronic and electrical waste generated contains a lot of non-degradable materials mostly hazardous by nature. 105 the soil or earth crust. ...
Research on biohydrometallurgy of secondary metal resources is primarily focussed on the leaching of valuable metals. For secondary metal resources biological processing can be an economically more effective and environmentally friendlier alternative to traditional hydrometallurgical and pyrometallurgical processes. Therefore, Bioydrometallurgy is a rapidly evolving biotechnology that has already provided revolutionary solutions to old problems associated with recovery of metals by conventional pyrometallurgy and chemical metallurgy. This review evaluates various pr
ocesses of recovery of metals from waste materials and commercial applications are di
scussed. Case studies and future technology directions are reviewed.
Keywords: Biohydrometallurgy; Metal recovery; Recycling; Secondary metal resources
... metal diversity and metal-non-metal associations) are the main obstacles for the recovery of metals from WEEE (Cui and Forssberg, 2003;Yazıcı et al., 2010). For recovery of metals from WEEE, various treatment options based on conventional mechanical, physical, pyrometallurgical and hydrometallurgical processes are proposed (Cui and Zhang, 2008;Akcil et al., 2009;Yazıcı and Deveci, 2009). A schematic flowsheet illustrating the processes available for recovery of metals from WEEE is shown in Fig. 1. ...
a b s t r a c t Waste of electric–electronic equipment (WEEE) with an annual growth rate of about 3–5% is the fastest growing waste stream in municipal wastes. Notwithstanding their environmental pollution potential, waste of electrical and electronic equipment (WEEE) with their high content of base and precious metals, in particular, are regarded as a potential secondary resource when compared with ores. For the recovery of metals from WEEE, various treatment options based on conventional physical, hydrometallurgical and pyrometallurgical processes are available. These process options with particular reference to hydromet-allurgical processes were reviewed in this study. With their relatively low capital cost, reduced environ-mental impact (e.g. no hazardous gases/dusts), potential for high metal recoveries and suitability for small scale applications, hydrometallurgical processes are promising options for the treatment of WEEE. Since the metals are present in native form and/or as alloys, an oxidative leaching process is required for the effective extraction of base and precious metals of interest. A two-stage process based on oxidative acid leaching of base metals (Cu in particular) followed by leaching of precious metals using cyanide, thiosulfate, thiourea or halide as lixiviant(s) can be suitably developed for the hydrometallurgical treat-ment of WEEE. However, further research is required to develop new, cost effective and environmentally friendly processes and/or refine existing ones for leaching and, in particular, downstream processes.
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