The Effect of the Redox Potential of Aqua Regia and Temperature on the Au, Cu, and Fe Dissolution from WPCBs

Heini Elomaa; Sipi Seisko; Tero Junnila; Tuomas Sirviö; Benjamin Wilson; Jari Aromaa; Mari Lundström

doi:10.3390/recycling2030014

The Effect of the Redox Potential of Aqua Regia and Temperature on the Au, Cu, and Fe Dissolution from WPCBs

Heini Elomaa, Sipi Seisko, Tero Junnila, Tuomas Sirviö, Benjamin Wilson, Jari Aromaa, Mari Lundström

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Abstract

Constant growth in waste electrical and electronic equipment (WEEE) levels necessitates the development of new, commercially viable recycling processes. Waste printed circuit boards (WPCBs) are a sub-group of WEEE that are of increasing interest due to their relatively high level of valuable metal content including Au, Ag, and platinum group metals (PGMs). Currently, precious metals like gold are mainly recycled from WEEE streams through copper melting/refining; however, the possibility to peel gold from WPCBs prior to smelting, could offer advantages for recycling. In this study, the suitability of aqua regia for selective or partially selective gold leaching from un-crushed WPCBs was investigated. The redox potential of aqua regia solutions and the dissolution efficiencies of Au, Cu, and Fe from WPCBs were investigated at different temperatures (40–80 °C) and concentrations (2–32%) in batch leaching tests. The redox potential of aqua regia solution was found to depend on concentration and temperature. It is suggested that Au dissolution in aqua regiarequires dissolved Cu2+ ions originating from the WPCB material to work. Au extraction (>50%) was shown to require a redox potential >700 mV with [Cu2+] > 2500 ppm, as a potential >850 mV alone was insufficient without cupric ions. Significant amounts of Au and Cu could be dissolved with only minor Fe dissolution at >8% aqua regia at 80 °C. Results suggest that leaching of uncrushed WPCBs in 8% aqua regia (T = 80 °C) can provide the opportunity for partial Au recovery prior to further processing.

Original language	English
Article number	14
Number of pages	9
Journal	Recycling
Volume	2
Issue number	3
DOIs	https://doi.org/10.3390/recycling2030014
Publication status	Published - 1 Sept 2017
MoE publication type	A1 Journal article-refereed
Event	Quo Vadis Recycling - Nový Smokovec, Slovakia Duration: 9 Jun 2017 → 9 Jun 2017 Conference number: 6

Keywords

waste printed circuit boards (WPCBs)
Gold leaching
Copper leaching

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10.3390/recycling2030014Licence: CC BY

Elomaa_Recycling_2017Final published version, 1.64 MBLicence: CC BY

http://www.mdpi.com/2313-4321/2/3/14Licence: CC BY

CMEco: Circular Metal Ecosystem
Aji, A. (Project Member), Lundström, M. (Principal investigator), Agarwal, V. (Project Member), Hamuyuni, J. (Project Member), Khalid, M. K. (Project Member), Seisko, S. (Project Member), Halli, P. (Project Member), Sinisalo, P. (Project Member), Jafari, S. (Project Member), Peng, C. (Project Member), Wilson, B. (Project Member), Leikola, M. (Project Member), Elomaa, H. (Project Member), Partinen, J. (Project Member), Revitzer, H. (Project Member), Wang, Z. (Project Member) & Kalliomäki, T. (Project Member)
01/01/2017 → 30/04/2019
Project: Business Finland: Other research funding
NoWASTE: Novel Precious Metal Recovery from Waste Streams
Yliniemi, K. (Project Member), Lundström, M. (Principal investigator), Hannula, P.-M. (Project Member), Barranco Asensio, V. (Project Member), Wilson, B. (Project Member), Halli, P. (Project Member), Karppinen, A. (Project Member), Revitzer, H. (Project Member) & Wang, Z. (Project Member)
01/09/2016 → 31/12/2020
Project: Academy of Finland: Other research funding
CLEEN / ARVI COR
Lundström, M. (Principal investigator) & Elomaa, H. (Project Member)
01/07/2015 → 31/12/2017
Project: Business Finland: Strategic centres for science, technology and innovation (SHOK)

Raw Materials Research Infrastructure
Karppinen, M. (Manager)
School of Chemical Engineering
Facility/equipment: Facility

Cite this

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title = "The Effect of the Redox Potential of Aqua Regia and Temperature on the Au, Cu, and Fe Dissolution from WPCBs",

abstract = "Constant growth in waste electrical and electronic equipment (WEEE) levels necessitates the development of new, commercially viable recycling processes. Waste printed circuit boards (WPCBs) are a sub-group of WEEE that are of increasing interest due to their relatively high level of valuable metal content including Au, Ag, and platinum group metals (PGMs). Currently, precious metals like gold are mainly recycled from WEEE streams through copper melting/refining; however, the possibility to peel gold from WPCBs prior to smelting, could offer advantages for recycling. In this study, the suitability of aqua regia for selective or partially selective gold leaching from un-crushed WPCBs was investigated. The redox potential of aqua regia solutions and the dissolution efficiencies of Au, Cu, and Fe from WPCBs were investigated at different temperatures (40–80 °C) and concentrations (2–32%) in batch leaching tests. The redox potential of aqua regia solution was found to depend on concentration and temperature. It is suggested that Au dissolution in aqua regiarequires dissolved Cu2+ ions originating from the WPCB material to work. Au extraction (>50%) was shown to require a redox potential >700 mV with [Cu2+] > 2500 ppm, as a potential >850 mV alone was insufficient without cupric ions. Significant amounts of Au and Cu could be dissolved with only minor Fe dissolution at >8% aqua regia at 80 °C. Results suggest that leaching of uncrushed WPCBs in 8% aqua regia (T = 80 °C) can provide the opportunity for partial Au recovery prior to further processing.",

keywords = "waste printed circuit boards (WPCBs) , Gold leaching, Copper leaching",

author = "Heini Elomaa and Sipi Seisko and Tero Junnila and Tuomas Sirvi{\"o} and Benjamin Wilson and Jari Aromaa and Mari Lundstr{\"o}m",

year = "2017",

month = sep,

day = "1",

doi = "10.3390/recycling2030014",

language = "English",

volume = "2",

journal = "Recycling",

issn = "2313-4321",

publisher = "MDPI AG",

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note = "Quo Vadis Recycling ; Conference date: 09-06-2017 Through 09-06-2017",

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TY - JOUR

T1 - The Effect of the Redox Potential of Aqua Regia and Temperature on the Au, Cu, and Fe Dissolution from WPCBs

AU - Elomaa, Heini

AU - Seisko, Sipi

AU - Junnila, Tero

AU - Sirviö, Tuomas

AU - Wilson, Benjamin

AU - Aromaa, Jari

AU - Lundström, Mari

N1 - Conference code: 6

PY - 2017/9/1

Y1 - 2017/9/1

N2 - Constant growth in waste electrical and electronic equipment (WEEE) levels necessitates the development of new, commercially viable recycling processes. Waste printed circuit boards (WPCBs) are a sub-group of WEEE that are of increasing interest due to their relatively high level of valuable metal content including Au, Ag, and platinum group metals (PGMs). Currently, precious metals like gold are mainly recycled from WEEE streams through copper melting/refining; however, the possibility to peel gold from WPCBs prior to smelting, could offer advantages for recycling. In this study, the suitability of aqua regia for selective or partially selective gold leaching from un-crushed WPCBs was investigated. The redox potential of aqua regia solutions and the dissolution efficiencies of Au, Cu, and Fe from WPCBs were investigated at different temperatures (40–80 °C) and concentrations (2–32%) in batch leaching tests. The redox potential of aqua regia solution was found to depend on concentration and temperature. It is suggested that Au dissolution in aqua regiarequires dissolved Cu2+ ions originating from the WPCB material to work. Au extraction (>50%) was shown to require a redox potential >700 mV with [Cu2+] > 2500 ppm, as a potential >850 mV alone was insufficient without cupric ions. Significant amounts of Au and Cu could be dissolved with only minor Fe dissolution at >8% aqua regia at 80 °C. Results suggest that leaching of uncrushed WPCBs in 8% aqua regia (T = 80 °C) can provide the opportunity for partial Au recovery prior to further processing.

AB - Constant growth in waste electrical and electronic equipment (WEEE) levels necessitates the development of new, commercially viable recycling processes. Waste printed circuit boards (WPCBs) are a sub-group of WEEE that are of increasing interest due to their relatively high level of valuable metal content including Au, Ag, and platinum group metals (PGMs). Currently, precious metals like gold are mainly recycled from WEEE streams through copper melting/refining; however, the possibility to peel gold from WPCBs prior to smelting, could offer advantages for recycling. In this study, the suitability of aqua regia for selective or partially selective gold leaching from un-crushed WPCBs was investigated. The redox potential of aqua regia solutions and the dissolution efficiencies of Au, Cu, and Fe from WPCBs were investigated at different temperatures (40–80 °C) and concentrations (2–32%) in batch leaching tests. The redox potential of aqua regia solution was found to depend on concentration and temperature. It is suggested that Au dissolution in aqua regiarequires dissolved Cu2+ ions originating from the WPCB material to work. Au extraction (>50%) was shown to require a redox potential >700 mV with [Cu2+] > 2500 ppm, as a potential >850 mV alone was insufficient without cupric ions. Significant amounts of Au and Cu could be dissolved with only minor Fe dissolution at >8% aqua regia at 80 °C. Results suggest that leaching of uncrushed WPCBs in 8% aqua regia (T = 80 °C) can provide the opportunity for partial Au recovery prior to further processing.

KW - waste printed circuit boards (WPCBs)

KW - Gold leaching

KW - Copper leaching

U2 - 10.3390/recycling2030014

DO - 10.3390/recycling2030014

M3 - Article

SN - 2313-4321

VL - 2

JO - Recycling

JF - Recycling

IS - 3

M1 - 14

T2 - Quo Vadis Recycling

Y2 - 9 June 2017 through 9 June 2017

ER -

The Effect of the Redox Potential of Aqua Regia and Temperature on the Au, Cu, and Fe Dissolution from WPCBs

Abstract

Keywords

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Projects

CMEco: Circular Metal Ecosystem

NoWASTE: Novel Precious Metal Recovery from Waste Streams

CLEEN / ARVI COR

Equipment

Raw Materials Research Infrastructure

Cite this