Article

Electro dynamic fragmentation of printed wiring boards as a preparation tool for their recycling

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Abstract

The use of Electro Dynamic Fragmentation (EDF) enables selective fragmentation of materials through generating electrical discharges as a means of fracturing. Liberated materials can be thus processed downstream in a more efficient way especially when value-added End-of-Life (EoL) electronic equipment is recycled. The aim of this study was to assess the benefits of the EDF technology towards processing of EoL printed wiring boards (PWBs) in view their recyclability. Printed wiring boards were comminuted using EDF at three different settings and with a hammer mill for comparative experiment. The products coming out were characterized by optical microscopy, SEM and liberation oriented leaching. Subsamples from the various EDF stages were inspected to investigate the progress of cracks and degree of copper layers exposure. The different energy levels used during the EDF processing have resulted in different degrees of PWBs damages, starting from components removal to entire structure perturbation and size reduction. EDF has resulted in generation of a lesser amount of fines, however the optimal approach in view energy efficient post-processing of the studied PWBs was the combination between single-stage EDF for components removal only with subsequent shredding of the depopulated boards.

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... A significant metal liberation can also be achieved when coarse PCBs are treated with high voltage electrical pulse (HVEP) comminution. The use of electro dynamic fragmentation in the pre-treatment of PCBs is analogous to the HVEP comminution [89]. HVEP comminution does not result in size reduction to a greater extent since most of the applied electrical energy is allocated at the hetero-component interface for delamination (Figure 2). ...
... Comparison studies are performed to investigate the crushing impacts of HVEP comminution and hammer mill [89]. Delamination is observed on HVEP-treated PCBs with a negligible size reduction effect, which is absent for the hammer mill products. ...
... Martino et al. [89] performed HVEP comminution using populated motherboards and reported the sequential damage on the boards under increased electrical energy ( Table 2). This technique thus possesses the added advantage of electrical component removal in advance, which is one of the requirements for hydrometallurgical operations. ...
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... The researcher showed that hammering and shredding electronic waste reduced it to a suitable size, enhancing the efficiency of the recovery process (Kaya 2016). However, recent research by Martino et al. (2017) showed that reduction of the size and liberation using electrodynamic fragmentation is an unconventional process for the recovery of the metal due to fine grinding (typically < 200 mm) of the electronic waste (Martino et al. 2017). ...
... The researcher showed that hammering and shredding electronic waste reduced it to a suitable size, enhancing the efficiency of the recovery process (Kaya 2016). However, recent research by Martino et al. (2017) showed that reduction of the size and liberation using electrodynamic fragmentation is an unconventional process for the recovery of the metal due to fine grinding (typically < 200 mm) of the electronic waste (Martino et al. 2017). ...
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... PCBs have a complex multicomponent composition. Using the electric discharge method for PCB disintegration is interest because PCB have significant differences in density and electrical conductivity [9,10]. ...
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... This method was used by scientists from Belgium and Switzerland in the innovative crushing of electronic components. Researchers found that there is a possibility of obtaining the grain size of recycled material, similar to the grain size obtained in hammer mills [14]. After appropriate modifications, the method could be introduced to crumble existing concrete structures. ...
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... Shredders and hammer mills are extensively used for size reduction of WEEE (Dalrymple et al., 2007;Kaya, 2016). In a recent study, Electro Dynamic Fragmentation of PCB was demonstrated as an unconventional method for size reduction and liberation of components (Martino, Iseli, Gaydardzhiev, Streicher-Porte, & Weh, 2017). ...
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Chapter
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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.