scholarly journals Recovery of base and precious metals from PCBs (Printed Circuit Boards) in waste electrical and electronic equipment (WEEE)

2022 ◽  
Vol 13 (1) ◽  
pp. 001-011
Yete Pélagie ◽  
Togbe FC Alexis ◽  
Yovo Franck ◽  
Suanon Fidèle ◽  
Sidohounde Assou ◽  

Natural minerals are a powerful tool in politics when some have a major role in production. Its depletion is now a hot topic worldwide. Thus, the safety of the environment, natural surface water, groundwater and the protection of soils from chronic contamination by metallic and inorganic elements is a global concern. Indeed, industrialization and development have led to the generation of huge and varied amounts of waste, including electronic waste (e-waste), which is released into the environment. Although e-waste is classified as hazardous, most of it is not recycled and developed countries with strict environmental protection legislation send most of their e-waste to developing countries where regulations are lax. These electronic devices and components after being used are simply dumped into the environment due to lack of treatment and recycling strategy. As a result, they become a threat to the environment, ecosystems and humans. African countries are among the most vulnerable nations. But they are unfortunately ignored and underestimated. To date, there is no e-waste recycling unit (factory) in most African countries and mainly in the Republic of Benin. In response to this challenge, this study explored the different techniques used for the recycling of waste electrical/electronic equipment in order to develop a new environmentally friendly approach in future work, for the extraction and recycling of the usual and valuable metallic elements contained in electronic waste (printed circuit boards) released into the environment. For this purpose, a bibliographic research was carried out from 20 April to 16 October 2021. The results obtained allowed us to identify the advantages and disadvantages of existing recycling methods.

Metals ◽  
2019 ◽  
Vol 9 (10) ◽  
pp. 1034 ◽  
Manivannan Sethurajan ◽  
Eric D. van Hullebusch

Printed circuit boards (PCBs), a typical end-of-life electronic waste, were collected from an E-waste recycling company located in the Netherlands. Cu and precious metal concentration analyses of the powdered PCBs confirm that the PCBs are multimetallic in nature, rich, but contain high concentrations of Cu, Au, Ag, Pd, and Pt. Ferric sulfate concentration (100 mM), agitation speed (300 rpm), temperature (20 °C), and solid-to-liquid ratio (10 g·L−1) were found to be the optimum conditions for the maximum leaching of Cu from PCBs. The ferric sulfate leachates were further examined for selective recovery of Cu as copper sulfides. The important process variables of sulfide precipitation, such as lixiviant concentration and sulfide dosage were investigated and optimized 100 ppm of ferric sulfate and (copper:sulfide) 1:3 molar ratio, respectively. Over 95% of the dissolved Cu (from the multimetallic leachates) was selectively precipitated as copper sulfide under optimum conditions. The characterization of the copper sulfide precipitates by SEM-EDS analyses showed that the precipitates mainly consist of Cu and S. PCBs can thus be seen as a potential secondary resource for copper.

Yeongran Hong ◽  
Damien Thirion ◽  
Saravanan Subramanian ◽  
Mi Yoo ◽  
Hyuk Choi ◽  

Urban mining of precious metals from electronic waste, such as printed circuit boards (PCB), is not yet feasible because of the lengthy isolation process, health risks, and environmental impact. Although porous polymers are particularly effective toward the capture of metal contaminants, those with porphyrin linkers have not yet been considered for precious metal recovery, despite their potential. Here, we report a porous porphyrin polymer that captures precious metals quantitatively from PCB leachate even in the presence of 63 elements from the Periodic Table. The nanoporous polymer is synthesized in two steps from widely available monomers without the need for costly catalysts and can be scaled up without loss of activity. Through a reductive capture mechanism, gold is recovered with 10 times the theoretical limit, reaching a record 1.62 g/g. With 99% uptake taking place in the first 30 min, the metal adsorbed to the porous polymer can be desorbed rapidly and reused for repetitive batches. Density functional theory (DFT) calculations indicate that energetically favorable multinuclear-Au binding enhances adsorption as clusters, leading to rapid capture, while Pt capture remains predominantly at single porphyrin sites.

2021 ◽  
Vol 9 (5) ◽  
pp. 895
Carlotta Alias ◽  
Daniela Bulgari ◽  
Fabjola Bilo ◽  
Laura Borgese ◽  
Alessandra Gianoncelli ◽  

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.

2021 ◽  
Vol 11 (6) ◽  
pp. 2808
Leandro H. de S. Silva ◽  
Agostinho A. F. Júnior ◽  
George O. A. Azevedo ◽  
Sergio C. Oliveira ◽  
Bruno J. T. Fernandes

The technological growth of the last decades has brought many improvements in daily life, but also concerns on how to deal with electronic waste. Electrical and electronic equipment waste is the fastest-growing rate in the industrialized world. One of the elements of electronic equipment is the printed circuit board (PCB) and almost every electronic equipment has a PCB inside it. While waste PCB (WPCB) recycling may result in the recovery of potentially precious materials and the reuse of some components, it is a challenging task because its composition diversity requires a cautious pre-processing stage to achieve optimal recycling outcomes. Our research focused on proposing a method to evaluate the economic feasibility of recycling integrated circuits (ICs) from WPCB. The proposed method can help decide whether to dismantle a separate WPCB before the physical or mechanical recycling process and consists of estimating the IC area from a WPCB, calculating the IC’s weight using surface density, and estimating how much metal can be recovered by recycling those ICs. To estimate the IC area in a WPCB, we used a state-of-the-art object detection deep learning model (YOLO) and the PCB DSLR image dataset to detect the WPCB’s ICs. Regarding IC detection, the best result was obtained with the partitioned analysis of each image through a sliding window, thus creating new images of smaller dimensions, reaching 86.77% mAP. As a final result, we estimate that the Deep PCB Dataset has a total of 1079.18 g of ICs, from which it would be possible to recover at least 909.94 g of metals and silicon elements from all WPCBs’ ICs. Since there is a high variability in the compositions of WPCBs, it is possible to calculate the gross income for each WPCB and use it as a decision criterion for the type of pre-processing.

2017 ◽  
Vol 71 (3) ◽  
pp. 271-279
Aleksandra Vucinic ◽  
Zeljko Kamberovic ◽  
Milisav Ranitovic ◽  
Tihomir Kovacevic ◽  
Irena Najcevic

This paper presents the analysis of the quantity of plastic and waste printed circuit boards obtained after the mechanical treatment of electrical and electronic waste (E-waste) in the Republic of Serbia, as well as the recycling of non-metallic fractions of waste printed circuit boards. The aim is to analyze the obtained recycled material and recommendation for possible application of recyclables. The data on the quantities and treatment of plastics and printed circuit boards obtained after the mechanical treatment of WEEE, were gained through questionnaires sent to the operators who treat this type of waste. The results of the questionnaire analysis showed that in 2014 the dismantling of E-waste isolated 1,870.95 t of plastic and 499.85 t of printed circuit boards. In the Republic of Serbia, E-waste recycling is performed exclusively by using mechanical methods. Mechanical methods consist of primary crushing and separation of the materials which have a utility value as secondary raw materials, from the components and materials that have hazardous properties. Respect to that, the recycling of printed circuit boards using some of the metallurgical processes with the aim of extracting copper, precious metals and non-metallic fraction is completely absent, and the circuit boards are exported as a whole. Given the number of printed circuit boards obtained by E-waste dismantling, and the fact that from an economic point of view, hydrometallurgical methods are very suitable technological solutions in the case of a smaller capacity, there is a possibility for establishing the facilities in the Republic of Serbia for the hydrometallurgical treatment that could be used for metals extraction, and non-metallic fractions, which also have their own value. Printed circuit boards granulate obtained after the mechanical pretreatment and the selective removal of metals by hydrometallurgical processes was used for the testing of the recycling potential. Granulometric analysis as well analysis of chemical composition of obtained fractions was performed. Subsequently, the manual classification of different types of polymeric material contained in the granulate was made, and both the apparent specific gravity and the chemical composition of the classified types of polymeric materials were determined. Chemical composition of granulate was determined by X-Ray Fluorescence (XRF) using Thermo Scientific Niton XL 3t, while the identification of residual polymers was determined by the FTIR (Fourier Transform Infrared Spectroscopy) method on the Bomen MB 100 device in range 4000 to 400 cm?1. Based on the results of this study, it can be concluded that after the hydrometallurgical treatment of printed circuit boards, and the separation of metals that have the highest value, the residual non-metallic fraction have the utility value and can be used for various purposes, such as developing new polymer materials for technical purposes that have been investigated by many researchers and mentioned in this article.

2020 ◽  
Vol 8 (51) ◽  
pp. 18975-18981
Mi Lin ◽  
Zhe Huang ◽  
Zhihui Yuan ◽  
Yonggao Fu ◽  
Jiaqi Hu ◽  

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