Jacobson, B., Li, S., Rivera, R. M., Daly, P., Elgar, C. E., Mulvihill, D. M. , Abbott, A. P., Feeney, A. and Prentice, P. (2023) A mechanistic study identifying improved technology critical metal delamination from printed circuit boards at lower power sonications in a deep eutectic solvent. Ultrasonics Sonochemistry, 101, 106701. (doi: 10.1016/j.ultsonch.2023.106701)
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Abstract
Deep eutectic solvents (DESs) are an emerging class of ionic liquids that offer a solution to reclaiming technology critical metals (TCMs) from electronic waste, with potential for improved life cycle analysis. The high viscosities typical of DESs, however, impose mass transport limitations such that passive TCM removal generally requires immersion over extended durations, in some cases in the order of hours. It is postulated that, through the targeted application of power ultrasound, delamination of key structures in electronic components immersed in DESs can be significantly accelerated, thereby enabling rapid recovery of TCMs. In this paper, we fully characterise cavitation in a Choline Chloride-Ethylene Glycol DES as a function of sonotrode input power, by the acoustic detection of the bubble collapse shockwave content generated during sonications at more than 20 input powers over the available range. This justifies the selection of two powers for a detailed study of ultrasonically enhanced TCM-delamination from printed circuit boards (PCBs). Dual-perspective high-speed imaging is employed, which facilitates simultaneous observation of TCM removal, and the cavitation evolution and interaction with the PCB surface. Bubble jetting is identified as a key contributor to initial pitting of the TCM layers, exposing the larger underlying copper layer, with the contributions of additional inertial cavitation-mediated phenomena such as bubble-collapse shockwaves also demonstrated as important for delamination. Optimal cavitation activity throughout the sonication then promotes etching of the copper base layer of the PCB structure targeted by the DES, liberating the overlaying TCMs in sections as large as 0.79 mm2. We report a thirtyfold improvement in processing time compared to passive delamination, with sonications at the lower power outperforming those at the higher power. The results demonstrate the potential for industrially scalable recovery of TCMs from the growing quantities of global e-waste, using combined power ultrasonics and DESs.
| Item Type: | Articles |
|---|---|
| Additional Information: | This work was financially supported by the SonoCat project (grant EP/W018632/1) funded by the UK Engineering and Physical Sciences Research Council (EPSRC). Ben Jacobson is supported by the Future of Ultrasonic Engineering CDT (grant EP/S023879/1), funded by EPSRC. |
| Status: | Published |
| Refereed: | Yes |
| Glasgow Author(s) Enlighten ID: | Feeney, Dr Andrew and Daly, Mr Paul and Li, Shida and Mulvihill, Dr Daniel and Prentice, Dr Paul and Jacobson, Ben |
| Creator Roles: | Jacobson, B.Conceptualization, Methodology, Data curation, Validation, Formal analysis, Investigation, Writing – original draft, Writing – review and editing Li, S.Data curation, Investigation Daly, P.Resources, Writing – review and editing Mulvihill, D.Resources, Writing – review and editing Feeney, A.Writing – review and editing, Supervision, Funding acquisition Prentice, P.Conceptualization, Methodology, Writing – original draft, Writing – review and editing, Supervision, Funding acquisition |
| Authors: | Jacobson, B., Li, S., Rivera, R. M., Daly, P., Elgar, C. E., Mulvihill, D. M., Abbott, A. P., Feeney, A., and Prentice, P. |
| College/School: | College of Science and Engineering > School of Engineering > Systems Power and Energy |
| Journal Name: | Ultrasonics Sonochemistry |
| Publisher: | Elsevier |
| ISSN: | 1350-4177 |
| ISSN (Online): | 1873-2828 |
| Published Online: | 23 November 2023 |
| Copyright Holders: | Copyright © 2023 The Authors |
| First Published: | First published in Ultrasonics Sonochemistry 101: 106701 |
| Publisher Policy: | Reproduced under a Creative Commons License |
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