10.1002/anie.201810447
Angewandte Chemie International Edition
COMMUNICATION
significant 95% of dissolved Au in 30 min (Fig. 3b, step II). As
the 4-PSH-assisted dissolution method is selective for Group 11
metals, the recovery of these metals from Pt and Pd mixtures is
also possible.
his support of the computational studies by the NSF under CHE-
1464828.
Data availability
Supplementary information and chemical compound information
are available in the online version of the paper. CCDC 1852214
(1) contains the supplementary crystallographic data for this
paper. These data can be obtained free of charge from The
Cambridge Crystallographic Data Centre via
Keywords: gold • gold recycling • desulfurization • pyridinethiol
chemistry • reaction mechanism
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b
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Figure 3. Dissolution of Au from thin film substrates and PCB samples. a)
Progress of the etching process from edges towards center of the film, b)
Dissolution of Au in PCB samples. Step I: extraction of Cu and Ag with
NH3/(NH4)2SO4/H2O2 and Step II: quantitative dissolution of Au in 30 min with
4-PSH/H2O2 method.
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As shown here, 4-PSH as a reactive ligand and hydrogen
peroxide as an oxidant forms together a highly efficient
combination for dissolution of metallic Au. The reaction is driven
by the ability of a thione isomer of 4-PSH to coordinate to an Au
surface and to lower oxidation potentials of the Au atoms on the
surface. Simultaneously, a part of 4-PSH is oxidized to S8 and to
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generated AuI species. The excess of 4-PSH can be significantly
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and quantitative dissolution of Au.
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The 4-PSH dissolution method was further applied to Cu0 and
Ag0 substrates resulting in high dissolution efficiencies. The
method possesses inherent selectivity towards metals which
undergo one-electron oxidation; Pt and Pd thin films remain
intact during the 4-PSH treatment. Furthermore, selectivity within
Group 11 was demonstrated by changing the ligand; 2-MBI as a
reactive ligand prefers only Cu0. This selectivity results from the
remarkably lower formation energy of the bisligand intermediate
Cu(2-MBI)2 in comparison to the Au and Ag species. The
dissolution was further implemented as an efficient method for
Au films and printed circuit board samples. Thus, the principles
learned from the studies reported herein could find future
applications in sustainable dissolution pathways for noble metals.
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Acknowledgements
The financial support of the Academy of Finland (#282555) is
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gratefully acknowledged. We thank Professor Filipp Furche for
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