Abstract
In the present study, a model of closed-loop recycling of copper from PCBs is demonstrated, which involves the sequential application of bioleaching and electrowinning to selectively extract copper. This approach is proposed as part of the solution to resolve the challenging ever-increasing accumulation of electronic waste, e-waste, in the environment. This work is targeting copper, the most abundant metal in e-waste that represents up to 20% by weight of printed circuit boards (PCBs). In the first stage, bioleaching was tested for different pulp densities (0.25–1.00% w/v) and successfully used to extract multiple metals from PCBs using the acidophilic bacterium, Acidithiobacillus ferrooxidans. In the second stage, the method focused on the recovery of copper from the bioleachate by electrowinning. Metallic copper foils were formed, and the results demonstrated that 75.8% of copper available in PCBs had been recovered as a high quality copper foil, with 99 + % purity, as determined by energy dispersive X-ray analysis and Inductively-Coupled Plasma Optical Emission Spectrometry. This model of copper extraction, combining bioleaching and electrowinning, demonstrates a closed-loop method of recycling that illustrates the application of bioleaching in the circular economy. The copper foils have the potential to be reused, to form new, high value copper clad laminate for the production of complex printed circuit boards for the electronics manufacturing industry.Graphic
Highlights
Every year, 72% of copper extracted from natural resources, with high cost and energy consumption, is used for the production of electrical and electronic equipment [1]
By combining bioleaching and electrowinning, a model of closed-loop recycling of metals from printed circuit boards (PCBs) was demonstrated, which selectively extracted and recovered copper. This includes the solubilisation of copper from PCBs using an environmentally friendly method of bioleaching, and copper foil production through electrowinning
In this single batch method, 75.8% of copper available in PCB was recovered as pure copper foil, suitable for multiple applications including the manufacturing of PCBs
Summary
72% of copper extracted from natural resources, with high cost and energy consumption, is used for the production of electrical and electronic equipment [1]. Within a few years, discarded equipment including the bulk of the metal content is predominantly sent to landfill, which demonstrates an environmentally unsustainable approach that is commonly practiced in the IT industry [3]. To address these issues, urban mining is being developed to promote a circular economy and the reuse of metals in electrical and electronic equipment. Urban mining is being developed to promote a circular economy and the reuse of metals in electrical and electronic equipment This new trend has transformed waste electrical and electronic equipment (WEEE) into a secondary source of metals [4]. Methods traditionally used for metal extraction from ores in the mining industry, including pyrometallurgy, hydrometallurgy and bioleaching, can be used to extract metals from secondary resources
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