Chemical and Sustainable Approaches for the Recovery and Recycling of Copper from Waste

Metals can be recycled indefinitely without losing their chemical, physical, or mechanical properties. Turning this potential into reality is a major challenge for inorganic chemistry, which must develop sustainable and efficient recycling strategies, ideally within a circular economy framework. This is especially true for metals defined as critical (i.e. high economic importance and high supply risk) or strategic (i.e. high economic importance with lower supply risk), such as copper. Copper plays a key role in the energy transition from fossil fuels to electrification, particularly in electrical grids and electronics. Global demand continues to grow, reaching 26.5 Mt in 2023 and projected to hit 30 Mt by 2028, while only about 16 wt% of refined copper comes from recycling — despite an energy saving of ~85% compared to primary production. Copper losses during production are almost unavoidable and occur in slags, tailings, fabrication residues, and other process by-products. These residues still contain relevant amounts of copper and represent a valuable secondary resource. End-of-life products such as Waste Electrical and Electronic Equipment (WEEE) also contribute to the growing stream of Cu-bearing waste. Increasing recycling from such sources is crucial to lowering supply risk, especially in countries where there is no active copper mining industry. This Ph.D. thesis aims to develop innovative strategies for recovering copper from various waste sources, addressing both its oxidized form Cu(II) and metallic form Cu(0). Cu-bearing exhausted catalysts and custom multimetallic powders were investigated as Cu(II) sources, while brass scraps served as Cu(0) sources. Hydrometallurgical processes were designed based on coordination chemistry for the selective leaching of copper, and a biometallurgical approach was also explored. Across all processes, achieving high leaching efficiency with maximal selectivity was the main challenge. The coordination-based leaching strategies achieved near-complete copper extraction from Cu(II) sources with high selectivity over co-existing metals such as iron and aluminum. In the case of Cu(0) sources, the oxidation of copper and zinc from brass was achieved at room temperature by exploiting green oxidant. Then, copper and zinc were separated through different wet chemistry approaches. The biometallurgical approach, though slower, proved effective under milder conditions, offering a complementary route for copper leaching. Comprehensive characterization techniques were employed to evaluate both starting materials and intermediates: Inductively Coupled Plasma – Optical Emission Spectroscopy (ICP-OES) for elemental analysis, X-Ray Diffraction (XRD) for identifying crystalline phases, Fourier Transform Infrared Spectroscopy (FT-IR) and Raman spectroscopy for molecular insights, Ultraviolet-Visible (UV-Vis) spectroscopy to investigate coordination complexes formed during leaching, and electrochemical tools for the redox characterization of starting materials. The experimental results were further supported by theoretical and statistical tools, including speciation diagrams to model copper–ligand interactions across pH ranges, and Design of Experiment (DoE) methodologies for process optimization.