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Article: Supramolecular Gold Stripping from Activated Carbon Using α-Cyclodextrin

TitleSupramolecular Gold Stripping from Activated Carbon Using α-Cyclodextrin
Authors
Issue Date2021
Citation
Journal of the American Chemical Society, 2021, v. 143, n. 4, p. 1984-1992 How to Cite?
AbstractWe report the molecular recognition of the Au(CN)2- anion, a crucial intermediate in today's gold mining industry, by α-cyclodextrin. Three X-ray single-crystal superstructures - KAu(CN)2α-cyclodextrin, KAu(CN)2(α-cyclodextrin)2, and KAg(CN)2(α-cyclodextrin)2 - demonstrate that the binding cavity of α-cyclodextrin is a good fit for metal-coordination complexes, such as Au(CN)2- and Ag(CN)2- with linear geometries, while the K+ ions fulfill the role of linking α-cyclodextrin tori together as a result of [K+···O] ion-dipole interactions. A 1:1 binding stoichiometry between Au(CN)2- and α-cyclodextrin in aqueous solution, revealed by 1H NMR titrations, has produced binding constants in the order of 104 M-1. Isothermal calorimetry titrations indicate that this molecular recognition is driven by a favorable enthalpy change overcoming a small entropic penalty. The adduct formation of KAu(CN)2α-cyclodextrin in aqueous solution is sustained by multiple [C-H···π] and [C-H···anion] interactions in addition to hydrophobic effects. The molecular recognition has also been investigated by DFT calculations, which suggest that the 2:1 binding stoichiometry between α-cyclodextrin and Au(CN)2- is favored in the presence of ethanol. We have demonstrated that this molecular recognition process between α-cyclodextrin and KAu(CN)2 can be applied to the stripping of gold from the surface of activated carbon at room temperature. Moreover, this stripping process is selective for Au(CN)2- in the presence of Ag(CN)2-, which has a lower binding affinity toward α-cyclodextrin. This molecular recognition process could, in principle, be integrated into commercial gold-mining protocols and lead to significantly reduced costs, energy consumption, and environmental impact.
Persistent Identifierhttp://hdl.handle.net/10722/333490
ISSN
2023 Impact Factor: 14.4
2023 SCImago Journal Rankings: 5.489
ISI Accession Number ID

 

DC FieldValueLanguage
dc.contributor.authorLiu, Wenqi-
dc.contributor.authorJones, Leighton O.-
dc.contributor.authorWu, Huang-
dc.contributor.authorStern, Charlotte L.-
dc.contributor.authorSponenburg, Rebecca A.-
dc.contributor.authorSchatz, George C.-
dc.contributor.authorStoddart, J. Fraser-
dc.date.accessioned2023-10-06T05:19:50Z-
dc.date.available2023-10-06T05:19:50Z-
dc.date.issued2021-
dc.identifier.citationJournal of the American Chemical Society, 2021, v. 143, n. 4, p. 1984-1992-
dc.identifier.issn0002-7863-
dc.identifier.urihttp://hdl.handle.net/10722/333490-
dc.description.abstractWe report the molecular recognition of the Au(CN)2- anion, a crucial intermediate in today's gold mining industry, by α-cyclodextrin. Three X-ray single-crystal superstructures - KAu(CN)2α-cyclodextrin, KAu(CN)2(α-cyclodextrin)2, and KAg(CN)2(α-cyclodextrin)2 - demonstrate that the binding cavity of α-cyclodextrin is a good fit for metal-coordination complexes, such as Au(CN)2- and Ag(CN)2- with linear geometries, while the K+ ions fulfill the role of linking α-cyclodextrin tori together as a result of [K+···O] ion-dipole interactions. A 1:1 binding stoichiometry between Au(CN)2- and α-cyclodextrin in aqueous solution, revealed by 1H NMR titrations, has produced binding constants in the order of 104 M-1. Isothermal calorimetry titrations indicate that this molecular recognition is driven by a favorable enthalpy change overcoming a small entropic penalty. The adduct formation of KAu(CN)2α-cyclodextrin in aqueous solution is sustained by multiple [C-H···π] and [C-H···anion] interactions in addition to hydrophobic effects. The molecular recognition has also been investigated by DFT calculations, which suggest that the 2:1 binding stoichiometry between α-cyclodextrin and Au(CN)2- is favored in the presence of ethanol. We have demonstrated that this molecular recognition process between α-cyclodextrin and KAu(CN)2 can be applied to the stripping of gold from the surface of activated carbon at room temperature. Moreover, this stripping process is selective for Au(CN)2- in the presence of Ag(CN)2-, which has a lower binding affinity toward α-cyclodextrin. This molecular recognition process could, in principle, be integrated into commercial gold-mining protocols and lead to significantly reduced costs, energy consumption, and environmental impact.-
dc.languageeng-
dc.relation.ispartofJournal of the American Chemical Society-
dc.titleSupramolecular Gold Stripping from Activated Carbon Using α-Cyclodextrin-
dc.typeArticle-
dc.description.naturelink_to_subscribed_fulltext-
dc.identifier.doi10.1021/jacs.0c11769-
dc.identifier.pmid33378203-
dc.identifier.scopuseid_2-s2.0-85100082007-
dc.identifier.volume143-
dc.identifier.issue4-
dc.identifier.spage1984-
dc.identifier.epage1992-
dc.identifier.eissn1520-5126-
dc.identifier.isiWOS:000618171900035-

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