Hydrometallurgical recovery of copper from waste electrical cables and its transformation into copper borate: an integrated waste-to-product approach

The hydrometallurgical recovery of copper from end-of-life cables and its conversion into value-added materials represents a promising route for secondary resource utilisation. In this study, high-purity copper (98.8 wt.% Cu) obtained from mechanically processed waste cables was leached using sulfuric acid and hydrogen peroxide. Leaching kinetics were evaluated using the shrinking core model, indicating a mixed control mechanism involving chemical reaction and product layer diffusion, with an apparent activation energy of 22.99 kJ mol−¹. Under optimised conditions (4 M H₂SO₄, 90°C, solid/liquid ratio of 1:10, and 100 g L−¹ H₂O₂), copper dissolution reached 96.9% after 480 min. The resulting pregnant leach solution was directly utilised for copper borate synthesis without the addition of commercial CuSO₄, providing a closed-loop approach for copper valorisation. XRD, FT-IR, and SEM–EDS analyses confirmed that precipitation at pH 8.0 produced phase-pure, fine-grained crystalline copper borate (Cu₃(BO₃)₂) with a homogeneous morphology, whereas lower or higher pH values led to incomplete precipitation or secondary phase formation. The proposed waste-to-product route demonstrates the feasibility of converting cable-derived copper into functional copper borate for potential applications in wood preservation, agriculture, and optical technologies.