University of Jyväskylä

06/06/2024 | Press release | Distributed by Public on 06/05/2024 21:14

Collaborative insight on the circular economy of gold, silver, and copper

Collaborative insight on the circular economy of gold, silver, and copper

Researchers at the University of Jyväskylä and the University of Helsinki have developed a new dissolution approach to recover gold, silver and copper from waste electrical and electronic equipment, and a theoretical model to understand and predict the dissolution process from the atomic scale. The development of new chemical methods is more important than ever because various industrial processes produce waste that cannot be recycled.
Professor Karoliina Honkala from Department of Chemistry was one of the researchers who participated in the study.

Gold, silver, and copper are widely used in modern electronics, and their recovery from waste electrical and electronic equipment (WEEE) is central to the circular economy of metals. The metal sequestration is, however, very challenging becomes WEEE contains several components and materials from which the wanted metals should be recovered in a selective, effective, economic, and environmentally friendly manner.

Joint experimental, theoretical, and computational research

Chemists from Helsinki and Jyväskylä Universities collaborated to investigate a novel method for recovering gold, silver, and copper from WEEEs. In the developed approaches the metals of interest are selectively dissolved in different mixtures of biobased ionic solvents and oxidants. The experiments carried out at the Department of Chemistry at the University of Helsinki showed that gold, silver, and copper can be sequentially dissolved and separated by judicious choice of solvent-oxidant couples, as shown in Figure 1.

Figure 1. Chart for the sequential and selective metal dissolution in different solvent-oxidant couples.

The experimental work demonstrated the efficiency of the sequential dissolution approach, but it remained unclear how and why different metals are dissolved in a given solvent-oxidant mixtures. The researchers at the Department of Chemistry at the University of Jyväskylä developed a theoretical model, which could explain the experimental results.

- Our theory is based on a rather simple thermodynamic model, which combines the electrochemical and dissolution properties of the considered metals. The model was parameterized through quantum chemical calculations of the metal ions in different ionic media, as shown in Figure 2. Our model and calculations could explain why different metals are dissolved in a given solvent-oxidant mixture. The approach was also extended to predict the dissolution rates in different media, tell University Researcher Timo Weckman and Academy of Finland Fellow Marko Melander from the Department of Chemistry of the University of Jyväskylä.

Figure 2. Computed solvation structures of copper in different media. From left to right: in water, lactic acid, and reline solutions.

A simple model for complex chemistry

The results showed that recycling and recovery of very complex and heterogeneous WEEEs can be understood, and even predicted, using rather traditional approaches of inorganic, physical, and computational chemistries.

- The dissolution of metals in ionic liquids is a very complicated process and understanding the atomic scale mechanisms with experiments alone is challenging. Computational models reduce the complexity as far as possible - often even to a point where the model no longer captures the experimental situation. It was therefore great to see that our model, which is based on rather basic chemical understanding, could rationalize the experimental findings. In the future we hope to further develop and apply similar theoretical-computational approaches to predict novel solvent-oxidant mixtures for our experimental partners, Weckman and Melander envision.

The results are now published in the renowned Angewandte Chemie International Edition journal.

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