Going for gold: a new method for recycling metals

A team of researchers have developed a recyclable chemical reagent that separates valuable metals such as gold

A team of University of Edinburgh researchers from the Schools of Chemistry and Geosciences have developed a recyclable chemical reagent that separates valuable metals such as gold by direct and selective precipitation from various acidic, mixed-metal solutions of relevance to extraction and e-waste recycling industries. The team is comprised of PhD student Luke Kinsman, Professor Carole Morrison and Professor Jason Love from the School of Chemistry and Professor Bryne Ngwenya from the School of Geosciences.

This precipitation process overcomes hazards associated with the use of organic solvents in precious-metal separations, and the singular precipitation of gold is achieved directly from solutions derived from electronic waste, the recycling of which is an increasing global challenge. This method is subject to a patent application and could be incorporated into a variety of metal extraction and recycling processes due to its selectivity, recyclability, and relevance to various metal dissolution processes.

Commenting on the research, Professor Jason Love, Personal Chair of Molecular Inorganic Chemistry, said:

petri dishes

“This is a big leap forward from our previous research. The main advantage is that we can selectively precipitate gold (and other metals) directly from acidic leach solutions, so avoiding the use of the organic solvents common in separation processes using solvent extraction.”

“Perhaps the most eye-catching application is that we can dissolve electronic waste in aqua regia and precipitate gold directly and selectively from it, so simplifying the recycling process. We also show that we can separate other precious metals such as platinum by changing the acid concentration which should be applicable to current precious metal recycling processes.”

“We have exploited fundamental chemical recognition principles to design a new, tuneable, recyclable, and highly selective process of separating metals that could be integrated into current metal extraction and recycling industries.”

“Ligand design as achieved in this work represents a major step change in reducing the chemical environmental footprint of recycling metals from waste. The next step is to integrate the separation process with even more environmental friendly upstream processing such as microbiological leaching.”



L. M. M. Kinsman, C. A. Morrison, B. T. Ngwenya, J. B. Love, “Tuneable separation of gold by selective precipitation using a simple and recyclable diamide,” Nat. Commun., 2021, DOI: 10.1038/s41467-021-26563-7

L. M. M. Kinsman, C. A. Morrison, B. T. Ngwenya, J. B. Love, 2021, “Method of selective precipitation of metals using amide compounds,” UK Patent Application PE961477GB.

Link to article in Nature Communications: https://doi.org/10.1038/s41467-021-26563-7

Link for the patent NCD: https://edinburgh-innovations.ed.ac.uk/technology/reduced-data-transfer-framework-for-single-photon-lidar-2