A cost-effective strategy for metal recovery from waste printed circuit boards via crushing pretreatment combined with pyrolysis: Effects of particle size and pyrolysis temperature

Chen, Ye; Liang, Sha; Xiao, Keke; Hu, Jingping; Hou, Huijie; Liu, Bingchuan; Deng, Huali; Yang, Jiakuan

doi:10.1016/j.jclepro.2020.124505

Cited by 48 publications

(19 citation statements)

References 53 publications

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“…During the pyrolysis process, the materials contained in the electronic waste are converted into flammable gases, pyrolytic oil, and solid residue. Pyrolytic oil and flammable gases can be used as energy sources [28]. The solid residue formed during pyrolysis is enriched with metals and fiber glass contained in electronic waste and carbon, which facilitates the recuperation of metals from electronic waste.…”

Section: Resultsmentioning

confidence: 99%

“…The great need to find an efficient method for WPCBs recycling has led to pyrolysis, an alternative energy-intensive but environmentally friendly method. Pyrolysis was shown to be a viable alternative to treat the nonmetallic fraction of WPCBs for resource recovery and causing less environmental problems associated with the final products [28]. Pyrolysis is a process in which resins from WPCBs are converted into flammable gases and tar, which can be used as a fuel for the pyrolysis process itself, while metals and glass remain as residues, which may be further recycled by the hydrometallurgical process [29].…”

Section: Introductionmentioning

confidence: 99%

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Recovery of Rare-Earth Elements from Printed Circuit Boards by Vacuum Pyrolysis and Multiple Electrostatic Separation

et al. 2022

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The influence of the multi-stage electrostatic separation (ESS) of mechanically treated and magnetically separated waste electronic material and the pyrolysis of the selected ESS fraction on the distribution of metal elements (MEs), elements contained in refractory oxides (EROs), bromine (Br), and rare-earth elements (REEs) contained in waste electronic material was studied. The concentration of MEs, Br, and EROs in the tested samples was determined by X-ray fluorescence analysis, and the concentration of REEs and uranium was determined by inductively coupled plasma mass spectrometry (ICP-MS). The analysis of the distribution of elements during the multi-stage ESS showed that MEs were predominantly distributed in the conductive fraction and Br, EROs, and REEs were distributed in the nonconductive fraction. The nonconductive fraction (NC2) of the two-stage ESS was subjected to a low-temperature vacuum pyrolysis (T = 550 °C, p = 10 mbar). The distribution of pyrolysis products of the NC2 fraction was determined. The main products of the vacuum pyrolysis experiments were the solid residue phase (54.4 wt.%) and oils (35.4 wt.%). It has been proven that pyrolysis can significantly increase the concentration of MEs, EROs, and REEs in raw materials, thereby providing a method for cost-effectively obtaining of REEs from waste printed circuit boards.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Recovery of Rare-Earth Elements from Printed Circuit Boards by Vacuum Pyrolysis and Multiple Electrostatic Separation

et al. 2022

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“…Pyrolysis is typically employed due to its energy conversion efficiencies and less severe environmental impacts as compared to combustion/incineration [64][65][66][67].…”

Section: Pyrolysismentioning

confidence: 99%

Assessment of Pre-Treatment Techniques for Coarse Printed Circuit Boards (PCBs) Recycling

et al. 2021

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Waste electrical and electronic equipment or e-waste generation has been skyrocketing over the last decades. This poses waste management and value recovery challenges, especially in developing countries. Printed circuit boards (PCBs) are mainly employed in value recovery operations. Despite the high energy costs of generating crushed and milled particles of the order of several microns, those are employed in conventional hydrometallurgical techniques. Coarse PCB pieces (of order a few centimetres) based value recovery operations are not reported at the industrial scale as the complexities of the internal structure of PCBs limit efficient metal and non-metal separation. Since coarse PCB particles’ pre-treatment is of paramount importance to enhance metal and non-metal separations, thermal, mechanical, chemical and electrical pre-treatment techniques were extensively studied. It is quite evident that a single pre-treatment technique does not result in complete metal liberation and therefore several pre-treatment flowsheets were formulated for coarse PCB particles. Thermal, mechanical and chemical pre-treatments integrated flowsheets were derived and such flowsheets are seldom reported in the e-waste literature. The potential flowsheets need to be assessed considering socio-techno-economic considerations to yield the best available technologies (BAT). In the wider context, the results of this work could be useful for achieving the United Nations sustainable development goals.

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“…Thermal treatments are also applied to remove the plastic fraction and concentrate the metal fraction into the char [18], which hence undergoes hydrometallurgical treatments to dissolve, separate, and refine the most valuable and concentrated metals. The hydrothermal, as the thermal ones, also have the important role of detoxification of the materials, as PCBs contain brominated flame retardants that have to be removed from flue gas [19].…”

Section: Introductionmentioning

confidence: 99%

Preliminary Study on Gold Recovery from High Grade E-Waste by Thiourea Leaching and Electrowinning

et al. 2021

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The present paper is focused on the extraction of gold from high-grade e-waste, i.e., spent electronic connectors and plates, by leaching and electrowinning. These connectors are usually made up of an alloy covered by a layer of gold; sometimes, in some of them, a plastic part is also present. The applied leaching system consisted of an acid solution of diluted sulfuric acid (0.2 mol/L) with thiourea (20 g/L) as a reagent and ferric sulfate (21.8 g/L) as an oxidant. This system was applied on three different high-grade e-waste, namely: (1) Connectors with the partial gold-plated surface (Au concentration—1139 mg/kg); (2) different types of connectors with some of which with completely gold-plated surface (Au concentration—590 mg/kg); and (3) connectors and plates with the completely gold-plated surface (Au concentration—7900 mg/kg). Gold dissolution yields of 52, 94, and 49% were achieved from the first, second, and third samples, respectively. About 95% of Au recovery was achieved after 1.5 h of electrowinning at a current efficiency of only 4.06% and current consumption of 3.02 kWh/kg of Au from the leach solution of the third sample.

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A cost-effective strategy for metal recovery from waste printed circuit boards via crushing pretreatment combined with pyrolysis: Effects of particle size and pyrolysis temperature

Cited by 48 publications

References 53 publications

Recovery of Rare-Earth Elements from Printed Circuit Boards by Vacuum Pyrolysis and Multiple Electrostatic Separation

Recovery of Rare-Earth Elements from Printed Circuit Boards by Vacuum Pyrolysis and Multiple Electrostatic Separation

Assessment of Pre-Treatment Techniques for Coarse Printed Circuit Boards (PCBs) Recycling

Preliminary Study on Gold Recovery from High Grade E-Waste by Thiourea Leaching and Electrowinning

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