Ultra-fast extraction of metals from a printed circuit board using high power ultrasound in a calcium chloride-based deep eutectic solvent

Marin Rivera, R., Elgar, C. E., Jacobson, B., Feeney, A. , Prentice, P. , Ryder, K. and Abbott, A. P. (2024) Ultra-fast extraction of metals from a printed circuit board using high power ultrasound in a calcium chloride-based deep eutectic solvent. RSC Sustainability, 2(2), pp. 403-415. (doi: 10.1039/D3SU00147D)

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The increase of digitization, alongside the growth in consumer electronics and shortened life cycles, has led to a significant global increase in the volume of electronic waste (e-waste). Printed circuit boards (PCBs) are the most valuable components within e-waste due to the higher content of valuable (critical) metals compared to ores. Although some of these metals can be recycled by traditional methodologies, e.g., pyro- and hydrometallurgy, the utilisation of deep eutectic solvents (DESs) offers the opportunity to recover metals from e-waste with higher selectivity and lower toxicity. Yet, DESs are often characterised by very high viscosity, which slows dissolution kinetics. This study investigates the effect of ultrasound on the catalytic dissolution of metals, in the deep eutectic solvent formed from calcium chloride hexahydrated and ethylene glycol. Copper(II) chloride was considered as an oxidising agent, which has high solubility and reversibility in this solvent. High ultrasonic power prevented passivation leading to an enhancement of copper dissolution at a rate 10 000-times faster than without ultrasound. Thus, leaching rates determined with an optical profiler showed that metals can be extracted from a PCB much faster (7 μm min−1) with high power ultrasound rather than in silent conditions (0.6 μm min−1), and this is discussed in terms of chemical oxidation, passivation and cavitation activity.

Item Type:Articles
Additional Information:This project has received funding from the European Union's Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement number 101026159, and also from the Engineering and Physical Sciences Research Council (EPSRC) under the Sonocat project (EP/W018632/1).
Keywords:Sonication, oxidising agent, metal recovery, deep eutectic solvents, electronic waste, ultrasound, cavitation.
Glasgow Author(s) Enlighten ID:Feeney, Dr Andrew and Prentice, Dr Paul and Jacobson, Mr Ben
Authors: Marin Rivera, R., Elgar, C. E., Jacobson, B., Feeney, A., Prentice, P., Ryder, K., and Abbott, A. P.
College/School:College of Science and Engineering > School of Engineering > Systems Power and Energy
Journal Name:RSC Sustainability
Publisher:Royal Society of Chemistry
ISSN (Online):2753-8125
Published Online:18 December 2023
Copyright Holders:Copyright © 2024 The Author(s)
First Published:First published in RSC Sustainability 2023 2(2): 403-415
Publisher Policy:Reproduced under a Creative Commons License

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Project CodeAward NoProject NamePrincipal InvestigatorFunder's NameFunder RefLead Dept
314779Recycling technology metals using focussed ultrasound and catalytic etchantsAndrew FeeneyEngineering and Physical Sciences Research Council (EPSRC)EP/W018632/1ENG - Systems Power & Energy