Two-stage leaching strategy for the selective recovery of base and precious metals from waste motherboard PCBs: Kinetic study and process optimization

The rapid growth of electronic waste (e-waste), particularly discarded motherboard printed circuit boards (PCBs), poses both a serious environmental challenge and a promising source of valuable metals. This study develops an innovative two-stage hydrometallurgical leaching approach for the selective...

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Detalhes bibliográficos
Autores: Rahimi, Vahid, Gómez Díaz, Diego, Freire Leira, María Sonia, Lazzari, Massimo, González Álvarez, Julia
Formato: artículo
Fecha de publicación:2026
País:España
Recursos:Universidad de Santiago de Compostela (USC)
Repositorio:Minerva. Repositorio Institucional de la Universidad de Santiago de Compostela
Idioma:inglés
OAI Identifier:oai:minerva.usc.gal:10347/45634
Acesso em linha:https://hdl.handle.net/10347/45634
Access Level:acceso abierto
Palavra-chave:E-waste
Printed circuit boards
Metal Leaching
Hydrometallurgy
Kinetics
Thiourea
Optimization
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spelling Two-stage leaching strategy for the selective recovery of base and precious metals from waste motherboard PCBs: Kinetic study and process optimizationRahimi, VahidGómez Díaz, DiegoFreire Leira, María SoniaLazzari, MassimoGonzález Álvarez, JuliaE-wastePrinted circuit boardsMetal LeachingHydrometallurgyKineticsThioureaOptimizationThe rapid growth of electronic waste (e-waste), particularly discarded motherboard printed circuit boards (PCBs), poses both a serious environmental challenge and a promising source of valuable metals. This study develops an innovative two-stage hydrometallurgical leaching approach for the selective recovery of base (Cu, Pb) and precious (Au, Ag, Pd) metals from waste motherboard PCBs. In the first stage, Cu and Pb were selectively leached using a low-concentration HNO3 solution. A comprehensive kinetic assessment, applying both heterogeneous shrinking-core and homogeneous models, revealed that Cu dissolution was governed primarily by surface chemical reactions, whereas Pb leaching was controlled by product-layer diffusion, with corresponding activation energies of 22.46 and 37.28 kJ mol−1, respectively. The second stage targeted the leaching of Au, Ag, and Pd using thiourea in the presence of Fe3+ as an oxidant. A Central Composite Rotational Design (CCRD) was employed to optimize thiourea, Fe3+, and H2SO4 concentrations. Statistical analysis identified the optimal conditions for maximizing Au recovery (up to 89.73 %). In contrast, the leaching models for Ag and Pd exhibited less statistically significant dependencies on the studied variables. Validation experiments confirmed the Au model reliability with an experimental efficiency of 87.82 ± 3.07 %, showing only a 2.13 % deviation from the predicted value, while Ag and Pd recoveries reached 29.99 ± 1.23 % and 45.97 ± 6.75 %, respectively. Structural and compositional analyses (SEM-EDX, XRF, XRD) confirmed effective removal of metals and morphological changes. This sequential leaching process demonstrates high selectivity, improved metal recovery, and reduced environmental impact, offering a sustainable and economically viable pathway for e-waste valorizationElsevierUniversidade de Santiago de Compostela. Centro de Investigación en Química Biolóxica e Materiais Moleculares (CiQUS)Universidade de Santiago de Compostela. Departamento de Enxeñaría QuímicaUniversidade de Santiago de Compostela. Departamento de Química Física20262026-04-1720262026-04-17journal articlehttp://purl.org/coar/resource_type/c_6501VoRhttp://purl.org/coar/version/c_970fb48d4fbd8a85info:eu-repo/semantics/articleapplication/pdfhttps://hdl.handle.net/10347/45634reponame:Minerva. Repositorio Institucional de la Universidad de Santiago de Compostelainstname:Universidad de Santiago de Compostela (USC)InglésengAgencia Estatal de Investigación http://dx.doi.org/10.13039/501100011033 Plan Estatal de Investigación Científica y Técnica y de Innovación 2021-2023 PID2021-122923NB-I00 RECUPERACION DE METALES ESCASOS Y VALIOSOS DE RESIDUOS ELECTRONICOS MEDIANTE MATERIALES ADSORBENTES PREPARADOS A MEDIDAopen accesshttp://purl.org/coar/access_right/c_abf2© 2025 The Authors. Published by Elsevier B.V. This article is available under the Creative Commons CC-BY-NC-ND licensehttp://creativecommons.org/licenses/by-nc-nd/4.0/info:eu-repo/semantics/openAccessoai:minerva.usc.gal:10347/456342026-06-15T12:47:27Z
dc.title.none.fl_str_mv Two-stage leaching strategy for the selective recovery of base and precious metals from waste motherboard PCBs: Kinetic study and process optimization
title Two-stage leaching strategy for the selective recovery of base and precious metals from waste motherboard PCBs: Kinetic study and process optimization
spellingShingle Two-stage leaching strategy for the selective recovery of base and precious metals from waste motherboard PCBs: Kinetic study and process optimization
Rahimi, Vahid
E-waste
Printed circuit boards
Metal Leaching
Hydrometallurgy
Kinetics
Thiourea
Optimization
title_short Two-stage leaching strategy for the selective recovery of base and precious metals from waste motherboard PCBs: Kinetic study and process optimization
title_full Two-stage leaching strategy for the selective recovery of base and precious metals from waste motherboard PCBs: Kinetic study and process optimization
title_fullStr Two-stage leaching strategy for the selective recovery of base and precious metals from waste motherboard PCBs: Kinetic study and process optimization
title_full_unstemmed Two-stage leaching strategy for the selective recovery of base and precious metals from waste motherboard PCBs: Kinetic study and process optimization
title_sort Two-stage leaching strategy for the selective recovery of base and precious metals from waste motherboard PCBs: Kinetic study and process optimization
dc.creator.none.fl_str_mv Rahimi, Vahid
Gómez Díaz, Diego
Freire Leira, María Sonia
Lazzari, Massimo
González Álvarez, Julia
author Rahimi, Vahid
author_facet Rahimi, Vahid
Gómez Díaz, Diego
Freire Leira, María Sonia
Lazzari, Massimo
González Álvarez, Julia
author_role author
author2 Gómez Díaz, Diego
Freire Leira, María Sonia
Lazzari, Massimo
González Álvarez, Julia
author2_role author
author
author
author
dc.contributor.none.fl_str_mv Universidade de Santiago de Compostela. Centro de Investigación en Química Biolóxica e Materiais Moleculares (CiQUS)
Universidade de Santiago de Compostela. Departamento de Enxeñaría Química
Universidade de Santiago de Compostela. Departamento de Química Física
dc.subject.none.fl_str_mv E-waste
Printed circuit boards
Metal Leaching
Hydrometallurgy
Kinetics
Thiourea
Optimization
topic E-waste
Printed circuit boards
Metal Leaching
Hydrometallurgy
Kinetics
Thiourea
Optimization
description The rapid growth of electronic waste (e-waste), particularly discarded motherboard printed circuit boards (PCBs), poses both a serious environmental challenge and a promising source of valuable metals. This study develops an innovative two-stage hydrometallurgical leaching approach for the selective recovery of base (Cu, Pb) and precious (Au, Ag, Pd) metals from waste motherboard PCBs. In the first stage, Cu and Pb were selectively leached using a low-concentration HNO3 solution. A comprehensive kinetic assessment, applying both heterogeneous shrinking-core and homogeneous models, revealed that Cu dissolution was governed primarily by surface chemical reactions, whereas Pb leaching was controlled by product-layer diffusion, with corresponding activation energies of 22.46 and 37.28 kJ mol−1, respectively. The second stage targeted the leaching of Au, Ag, and Pd using thiourea in the presence of Fe3+ as an oxidant. A Central Composite Rotational Design (CCRD) was employed to optimize thiourea, Fe3+, and H2SO4 concentrations. Statistical analysis identified the optimal conditions for maximizing Au recovery (up to 89.73 %). In contrast, the leaching models for Ag and Pd exhibited less statistically significant dependencies on the studied variables. Validation experiments confirmed the Au model reliability with an experimental efficiency of 87.82 ± 3.07 %, showing only a 2.13 % deviation from the predicted value, while Ag and Pd recoveries reached 29.99 ± 1.23 % and 45.97 ± 6.75 %, respectively. Structural and compositional analyses (SEM-EDX, XRF, XRD) confirmed effective removal of metals and morphological changes. This sequential leaching process demonstrates high selectivity, improved metal recovery, and reduced environmental impact, offering a sustainable and economically viable pathway for e-waste valorization
publishDate 2026
dc.date.none.fl_str_mv 2026
2026-04-17
2026
2026-04-17
dc.type.none.fl_str_mv journal article
http://purl.org/coar/resource_type/c_6501
VoR
http://purl.org/coar/version/c_970fb48d4fbd8a85
dc.type.openaire.fl_str_mv info:eu-repo/semantics/article
format article
dc.identifier.none.fl_str_mv https://hdl.handle.net/10347/45634
url https://hdl.handle.net/10347/45634
dc.language.none.fl_str_mv Inglés
eng
language_invalid_str_mv Inglés
language eng
dc.relation.none.fl_str_mv Agencia Estatal de Investigación http://dx.doi.org/10.13039/501100011033 Plan Estatal de Investigación Científica y Técnica y de Innovación 2021-2023 PID2021-122923NB-I00 RECUPERACION DE METALES ESCASOS Y VALIOSOS DE RESIDUOS ELECTRONICOS MEDIANTE MATERIALES ADSORBENTES PREPARADOS A MEDIDA
dc.rights.none.fl_str_mv open access
http://purl.org/coar/access_right/c_abf2
http://creativecommons.org/licenses/by-nc-nd/4.0/
dc.rights.openaire.fl_str_mv info:eu-repo/semantics/openAccess
rights_invalid_str_mv open access
http://purl.org/coar/access_right/c_abf2
http://creativecommons.org/licenses/by-nc-nd/4.0/
eu_rights_str_mv openAccess
dc.format.none.fl_str_mv application/pdf
dc.publisher.none.fl_str_mv Elsevier
publisher.none.fl_str_mv Elsevier
dc.source.none.fl_str_mv reponame:Minerva. Repositorio Institucional de la Universidad de Santiago de Compostela
instname:Universidad de Santiago de Compostela (USC)
instname_str Universidad de Santiago de Compostela (USC)
reponame_str Minerva. Repositorio Institucional de la Universidad de Santiago de Compostela
collection Minerva. Repositorio Institucional de la Universidad de Santiago de Compostela
repository.name.fl_str_mv
repository.mail.fl_str_mv
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score 15,812429

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