Gold extraction at the molecular level using α- and β-cyclodextrins

Author(s)

S. Santos Braga

Sources

Beilstein J. Org. Chem. 2025, 21, 1116–1125.

Cyclodextrins (CDs) are known for their ability to form supramolecular interactions with a wide range of guest molecules. In this review, the focus is given on the inclusion of complex aurate ions such as tetrabromoaurate, dicyanoaurate, and a few other tetrahaloaurates. The review describes the properties of self-assembly of cyclodextrins with these ions, with a highlight to α-CD and, more recently, β-CD, requiring the use of a co-former/precipitating agent. Practical applications of this ability include the selective isolation of gold from a variety of sources, ranging from gold-rich mining ores and tailings/mining wastes to gold-bearing metal scraps obtained from discarded electronic devices. Moreover, it describes the development of a method based on the spontaneous complex formation between α-CD and tetrabromoaurate, as well as its current status of use in a few mining sites in the United States.

Figure: Schematic depiction of the α-CD channels containing the polyionic {[K(OH2)6]+[AuBr4]−}n chain inside. Reproduced from “Selective isolation of gold facilitated by second-sphere coordination with α-cyclodextrin © 2013 Z. Liu et al., published by Springer Nature, distributed under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs 3.0 Unported License, ttp://creativecommons.org/licenses/by-nc-nd/3.0).This content is not subject to CC BY 4.0.

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