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

TL;DR

This review explores how cyclodextrins can selectively extract gold from various sources using molecular interactions.

Contribution

The novelty lies in the detailed review of α- and β-cyclodextrins' ability to form complexes with aurate ions for gold extraction.

Findings

Cyclodextrins form stable complexes with aurate ions like tetrabromoaurate and dicyanoaurate.

α-CD and β-CD can be used with co-formers to isolate gold from ores and electronic scraps.

A method using α-CD and tetrabromoaurate is currently applied in some U.S. mining sites.

Abstract

Cyclodextrins (CDs) are known for their ability to form supramolecular interactions with a wide range of guest molecules. In this review, 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 highlight to α-CD and, more recently, β-CD, requiring the use of a co-former/precipitating agent. Practical applications of this ability are directed to the selective isolation of gold from a variety of sources, spanning from gold-rich mining ores and tailings/mining wastes to gold-bearing metal scraps obtained from disposed electronic devices. Moreover, it describes the development of a method based on spontaneous complex formation between α-CD and tetrabromoaurate and its current status of use in a few mining sites in the United States.

Figures