Liberation enhancement and copper enrichment improvement for waste printed circuit boards by heating pretreatment

Gao, Yan; Guo, Junwei; Zhu, Guangqing; Zhang, Zhenxing; Zhao, Peng; Zhu, Xiangnan; Zhang, Bo

doi:10.1016/j.wasman.2020.03.023

Cited by 12 publications

(8 citation statements)

References 45 publications

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“…This indicates that microwave pretreatment effectively improves the enrichment of copper in WPCB, and copper was effectively enriched within 4–2 and 2–1 mm fraction, while the content of copper in +4 mm fraction and 1 mm fraction were reduced. Yan et al 22 investigated the effect of crushing time on copper enrichment in WPCB under crushing conditions only, showing that as crushing time increased, more copper in WPCB was enriched with finer particle sizes. Compared with the results of Yan et al, it was found that the copper in WPCB under microwave pretreatment was more enriched in the coarser particle size.…”

Section: Resultsmentioning

confidence: 99%

Effect of Microwave Pretreatment on the Leaching and Enrichment Effect of Copper in Waste Printed Circuit Boards

Huang

et al. 2023

ACS Omega

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The use of efficient and clean methods for the recycling of waste circuit boards is an ongoing challenge. In this research, the effect of microwave pretreatment on the leaching and enrichment of copper from waste print circuit board (WPCB) was studied. The morphology and chemical structure of WPCB particles before and after microwave pretreatment were analyzed by SEM/EDS and Fourier infrared spectroscopy. Leaching experiments and copper enrichment tests were designed to investigate the effect of different microwave irradiation powers and microwave irradiation times on the copper leaching rate and copper enrichment rate in WPCB. The leaching experiment results showed that microwave pretreatment can effectively improve the leaching rate of WPCB. When the microwave irradiation power was 700 W, the irradiation time was 120 s, and the leaching time was 15 min, the copper leaching rate in WPCB was 57.01%, which was 24.34% higher than that in the untreated condition. The results of copper enrichment experiment show that microwave pretreatment can effectively improve the copper enrichment of WPCB. After microwave pretreatment, copper was effectively enriched in the 4–2 and 2–1 mm particle sizes. When the microwave irradiation time was 120 s, the copper enrichment rates in the 4–2 and 2–1 mm particle sizes were 1.74 and 1.66, which increased by 0.63 and 0.32, respectively, compared to the untreated condition. Microwave pretreatment enables the effective separation of metallic copper from non-metallic components in WPCB, increasing the exposure area of copper and promoting the monomer separation of copper, thus improving the leaching and enrichment of copper.

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Section: Resultsmentioning

confidence: 99%

Effect of Microwave Pretreatment on the Leaching and Enrichment Effect of Copper in Waste Printed Circuit Boards

Huang

et al. 2023

ACS Omega

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“…The microstructure evolution at the interfaces is observed and vivid images of structural deformation are also illustrated [14,37,48,53]. The detachment of epoxy resin from the copper foil is observed, possibly due to the cohesive force failure during thermal shock pre-treatment (Figure 2c) [14,37].…”

Section: Thermal Shockmentioning

confidence: 87%

“…Besides that, the cracking mode is altered from transverse cracking to longitudinal cracking once PCBs are heat-treated prior to comminution (Section 3.2) [53]. PCBs that are treated with residual steam pre-processing showed similar results under the three-point bend test [48].…”

Section: Thermal Shockmentioning

confidence: 96%

“…On the other hand, the cracking mode is altered from transverse cracking to longitudinal cracking once the PCBs are heat-treated prior to comminution (Figure 6) [53]. It is presumed that the shear forces induced by a universal crusher in the longitudinal direction surpass the pre-weakening bonding force at the PCB interface after the heat treatment, which causes the de-bonding of PCBs [53]. Rodrigues et al [12] also employed pre-weakening effects of 2 cm PCB fragments by generating cracks with a jaw crusher to enhance metal leaching.…”

Section: Mechanical/physical Pre-treatment Techniquesmentioning

confidence: 99%

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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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“…A mechanical activation was discovered to trigger physicochemical changes in solid materials, such as structural defects, phase transformations, and amorphization, to improve their leaching activity [ 79 ]. A two-step crushing process has been developed, and heat pretreatment technology before the crushing process has been proposed, as well as for reducing particle size and improving the breakage and liberation effects of WPCBs [ 80 ]. During the crushing stage, it should be noted that the micro-cracks produced were beneficial for the growth of bacteria, thereby enhancing the bioleaching efficiency of copper [ 81 ].…”

Section: Biochemical Processmentioning

confidence: 99%

Bioleaching of Typical Electronic Waste—Printed Circuit Boards (WPCBs): A Short Review

Yang

Wan

et al. 2022

IJERPH

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The rapid pace of innovations and the frequency of replacement of electrical and electronic equipment has made waste printed circuit boards (WPCB) one of the fastest growing waste streams. The frequency of replacement of equipment can be caused by a limited time of proper functioning and increasing malfunctions. Resource utilization of WPCBs have become some of the most profitable companies in the recycling industry. To facilitate WPCB recycling, several advanced technologies such as pyrometallurgy, hydrometallurgy and biometallurgy have been developed. Bioleaching uses naturally occurring microorganisms and their metabolic products to recover valuable metals, which is a promising technology due to its cost-effectiveness, environmental friendliness, and sustainability. However, there is sparse comprehensive research on WPCB bioleaching. Therefore, in this work, a short review was conducted from the perspective of potential microorganisms, bioleaching mechanisms and parameter optimization. Perspectives on future research directions are also discussed.

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Liberation enhancement and copper enrichment improvement for waste printed circuit boards by heating pretreatment

Cited by 12 publications

References 45 publications

Effect of Microwave Pretreatment on the Leaching and Enrichment Effect of Copper in Waste Printed Circuit Boards

Effect of Microwave Pretreatment on the Leaching and Enrichment Effect of Copper in Waste Printed Circuit Boards

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

Bioleaching of Typical Electronic Waste—Printed Circuit Boards (WPCBs): A Short Review

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