The Brandenburgische Technische Universität (BTU) Cottbus‑Senftenberg carried out a two‑year joint research project (01 March 2016 – 30 June 2018) aimed at creating an efficient, environmentally friendly recycling technology for thin metallic coatings on polymer substrates. The goal was to separate and recover galvanised layers of chromium, nickel, gold, copper and other precious metals from plastic parts while simultaneously cleaning the polymer to a high purity suitable for reuse. The project was conducted in close collaboration with industrial partners and involved the university’s departments of Processing Technology and Technical Microbiology.

The scientific work began with a systematic assessment of bioleaching as a viable method for treating metallised polymers. Suitable bacterial strains were screened and characterised for their ability to dissolve metal layers without damaging the polymer matrix. Optimal reaction conditions—such as pH, temperature, agitation and exposure time—were identified, and the limits imposed by particle size and shape of the coated parts were quantified. With these fundamentals established, a laboratory‑scale biotechnological leaching unit was designed and built. The unit incorporated a controlled aeration system, a temperature‑regulated reactor, and a continuous feed of the selected bacterial culture. Experiments demonstrated selective dissolution of the metal layers while leaving the polymer largely intact. Subsequent precipitation steps, using selective reagents, recovered the dissolved metals as high‑purity powders or salts. The cleaned polymer fragments were then washed and characterised to confirm the removal of residual metal ions and bacterial biomass.

Building on the laboratory results, the team scaled the process to a pilot‑plant (Technikum) scale. The pilot apparatus retained the core features of the lab unit but was equipped with larger reactors, automated feeding and sampling systems, and a closed‑loop recirculation of the leaching solution. During pilot operation, the process consistently achieved metal recoveries above 90 % for chromium and nickel, while the polymer recovered exhibited a surface cleanliness level suitable for subsequent extrusion or injection moulding. The pilot plant also demonstrated the feasibility of regenerating the bacterial culture and leaching solution, reducing operational costs and waste generation.

The collaboration structure was defined by clear roles: the BTU provided the research expertise, laboratory facilities, and the design of the leaching and precipitation systems; the industrial partners supplied the coated polymer feedstock, industrial‑scale equipment, and practical insights into process integration. The project was funded through a German research grant (exact funding body not disclosed in the report), and the final report was prepared in a confidential format for the funding agency and consortium members.

In summary, the project delivered a fully integrated biotechnological recycling chain that separates and recovers precious metals from polymer composites with high efficiency and minimal environmental impact. The laboratory and pilot‑plant results confirm the technical feasibility of the approach and lay the groundwork for future industrial deployment. The collaboration between academia and industry, combined with the university’s strong background in material separation and microbiological processes, has produced a novel, scalable solution that advances circular economy goals for metallised plastic waste.