Metallurgical processes unveil the unexplored “sleeping mines” e- waste: a review

Thakur, Pooja; Kumar, Sudhir

doi:10.1007/s11356-020-09405-9

Cited by 38 publications

(19 citation statements)

References 59 publications

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“…The rapid turnover of electronic devices such as personal computers, mobile phones, wearables, and smart home devices boosts the production of electrical and electronic equipment waste (WEEE) [ 1 ]. This stream is trending to reach more than 12 million tons by 2020 in Europe [ 2 ] and more than 52.2 million tons by 2021 worldwide [ 3 ]. Although printed circuit boards (PCBs) represent up to 6% of the WEEE mass, they have the most important environmental restrictions but, at the same time, the most economic advantages and are a secondary source for rare earth elements [ 4 ].…”

Section: Introductionmentioning

confidence: 99%

“…Within the paradigm of a circular economy, urban mining of PCBs [ 6 ] could indeed become a source of secondary valuable raw materials such as the metals Cu, Zn, Pb, Ni, Cd, Au, Ag, and Sn [ 3 , 7 , 8 ]. Contrary to chemical, mechanical and pyrometallurgical processes, the use of microorganisms to solubilize metal oxides and sulfides (bioleaching) allows the recovering of metals from e-waste with environmentally friendly and cost-effective operations, reducing health concerns [ 9 ].…”

Section: Introductionmentioning

confidence: 99%

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Food Waste-Assisted Metal Extraction from Printed Circuit Boards: The Aspergillus niger Route

et al. 2021

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A low-energy paradigm was adopted for sustainable, affordable, and effective urban waste valorization. Here a new, eco-designed, solid-state fermentation process is presented to obtain some useful bio-products by recycling of different wastes. Urban food waste and scraps from trimmings were used as a substrate for the production of citric acid (CA) by solid state fermentation of Aspergillus niger NRRL 334, with a yield of 20.50 mg of CA per gram of substrate. The acid solution was used to extract metals from waste printed circuit boards (WPCBs), one of the most common electronic waste. The leaching activity of the biological solution is comparable to a commercial CA one. Sn and Fe were the most leached metals (404.09 and 67.99 mg/L, respectively), followed by Ni and Zn (4.55 and 1.92 mg/L) without any pre-treatments as usually performed. Commercial CA extracted Fe more efficiently than the organic one (123.46 vs. 67.99 mg/L); vice versa, biological organic CA recovered Ni better than commercial CA (4.55 vs. 1.54 mg/L). This is the first approach that allows the extraction of metals from WPCBs through CA produced by A. niger directly grown on waste material without any sugar supplement. This “green” process could be an alternative for the recovery of valuable metals such as Fe, Pb, and Ni from electronic waste.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Food Waste-Assisted Metal Extraction from Printed Circuit Boards: The Aspergillus niger Route

et al. 2021

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“…[21,22] The direct smelting of WPCBs in primary copper smelters (such as the Noranda process) is an efficient technique for recovering valuable metallic products that is actually used at the industrial scale. [23][24][25][26] Advantages of using the copper primary metal process elaborated for copper sulfide concentrates such as chalcopyrite, that is, pyrometallurgical smelting technologies, are numerous:…”

Section: Introductionmentioning

confidence: 99%

On the Investigation of the Thermal Degradation of Waste Printed Circuit Boards for Recycling Applications

Khalil

Chaouki

Harvey

2021

Advanced Sustainable Systems

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becoming obsolete, especially in electronic devices. In fact, these types of valuable metal concentrations are such that electronic wastes can nowadays be considered as urban mines that need to be exploited. Urban mining is a concept that is emerging in our modern society. According to the United Nations Environment Programme (UNEP), around 20-50 million metric tons of waste electrical and electronic equipment (WEEE) are generated worldwide each year from which approximately 8.9 million metric tons are collected and recycled (about 20%) whereas 1.7 million metric tons are dumped into landfill and incinerated in different countries. [1][2][3][4][5] Direct combustion and landfill are considered the worst handling techniques of WEEE but are still common practices in countries that have no effective regulations or lack of necessary facilities for waste management. [6][7][8] Waste printed circuit boards (WPCBs) are basic non-conductive structures on which different electronic components are layed and electrically connected via conductive materials. As can be seen from Table 1, a standard WPCB consists mostly of:

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“…E-waste is comprised of a range of valuable materials that can be recycled, including metals, plastics, and glass [4]. As such, this waste stream is often referred to as an urban mine [5]. The combined total value of all e-waste generated in 2019 was estimated to be USD 57 billion.…”

Section: Introductionmentioning

confidence: 99%

“…Range of metal composition of PCBs in the literature (adapted from [1,2,4,15]). 1 ES: electronic scrap, 2 AR: aqua regia, 3 AAS: atomic absorption spectrometry, 4 MP: mobile phone, 5 ICP-OES: inductively coupled plasma optical emission spectroscopy, 6 ICP-MS: inductively coupled plasma mass spectrometry.…”

Section: Introductionmentioning

confidence: 99%

A Comparison of Methods for the Characterisation of Waste-Printed Circuit Boards

Yken

Cheng

Boxall

et al. 2021

Metals

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Electronic waste is a growing waste stream globally. With 54.6 million tons generated in 2019 worldwide and with an estimated value of USD 57 billion, it is often referred to as an urban mine. Printed circuit boards (PCBs) are a major component of electronic waste and are increasingly considered as a secondary resource for value recovery due to their high precious and base metals content. PCBs are highly heterogeneous and can vary significantly in composition depending on the original function. Currently, there are no standard methods for the characterisation of PCBs that could provide information relevant to value recovery operations. In this study, two pre-treatments, smelting and ashing of PCB samples, were investigated to determine the effect on PCB characterisation. In addition, to determine the effect of particle size and element-specific effects on the characterisation of PCBs, samples were processed using four different analytical methods. These included multi-acid digestion followed by inductively coupled plasma optical emission spectrometry (ICP-OES) analysis, nitric acid digestion followed by X-ray fluorescence (XRF) analysis, multi-acid digestion followed by fusion digestion and analysis using ICP-OES, and microwave-assisted multi-acid digestion followed by ICP-OES analysis. In addition, a mixed-metal standard was created to serve as a reference material to determine the accuracy of the various analytical methods. Smelting and ashing were examined as potential pre-treatments before analytical characterisation. Smelting was found to reduce the accuracy of further analysis due to the volatilisation of some metal species at high temperatures. Ashing was found to be a viable pre-treatment. Of the four analytical methods, microwave-assisted multi-acid digestion offered the most precision and accuracy. It was found that the selection of analytical methods can significantly affect the accuracy of the observed metal content of PCBs, highlighting the need for a standardised method and the use of certified reference material.

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Metallurgical processes unveil the unexplored “sleeping mines” e- waste: a review

Cited by 38 publications

References 59 publications

Food Waste-Assisted Metal Extraction from Printed Circuit Boards: The Aspergillus niger Route

Food Waste-Assisted Metal Extraction from Printed Circuit Boards: The Aspergillus niger Route

On the Investigation of the Thermal Degradation of Waste Printed Circuit Boards for Recycling Applications

A Comparison of Methods for the Characterisation of Waste-Printed Circuit Boards

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