Pilot installation for the return of precious metals into the economic cycle using innovative biotechnological process engineering

© m&k GmbH

Gold-plated materials for industrial applications, for example electronic contacts, usually consist of a copper carrier layer to which the precious metal has been applied in a thin layer. These coatings are usually only a few micrometers thick, which in most cases makes their recovery with conventional melting technologies economically unviable.

Bacterial leaching (bioleaching) uses bacteria that occur freely in nature and are harmless to humans and the environment to release metals from difficult-to-process or low-value ores, concentrates and fine-grained residues and sludges. The copper carrier material is dissolved in the leaching process. The gold coating accumulates as flakes, can be separated and fed into the smelting processes largely separately. In addition to the gold, the copper is recovered from the solution using electrochemical processes. The polymer carrier structures that would otherwise be burnt are retained during the biological treatment and can be recycled separately. Apart from the repeatedly usable biological leaching solution, the bacteria only require CO2, which they extract from the air.

The aim of the “GoldRecApp” project is to translate these processes, which already work in the laboratory and in a small testing facility, into an industrially usable scale. In the testing facility, essential apparatus elements are already connected with each other. The design is being tested under industrial operating conditions, and the interfaces between the individual facility components are the same as those for future implementation. The upscaling and piloting of the entire plant will follow.

This recovery of precious and valuable metals makes economic sense on the one hand because of their material value, and on the other hand it also reduces dependence on imports of raw materials. Moreover, it is possible to substitute significant quantities of primary raw materials (especially gold and copper) and, hence, to contribute to the conservation of resources.