Removal of lead from copper alloy scraps by compound-separation method

Recently, the global scale environmental problems have become a critical issue. In metallic material, not only the cost reduction and improvement of mechanical properties but also the decrease in environmental load is required. In copper alloys, several mass%Pb was added to improve their machinability. However, due to the adverse toxicity of Pb, which is harmful to health, a new regulation to limit the amount of Pb permitted in drinking water supplies has been enforced. A huge amount of copper alloys scrap containing Pb will become industrial waste due to its unavailability as a raw material. In order to promote the recycle of copper alloys scrap containing Pb, we developed a new technique for removing Pb from copper alloys scrap. By adopting this new teclinique, Pb was removed from brass and bronze using compound-separation method. Copper alloys containing 2-6 mass% Pb were molten using a high-frequency induction furnace under nitrogen atmosphere. Ca-Si and NaF compounds were added into the molten copper alloys to form large particles of Pb compound. Then, these large particles of Pb compound were skimmed off from the molten copper alloys. Liquid metal extraction and casting was characterized by electron probe microanalyser (EPMA) and fluorescence X-ray (XRF) analysis. The results show that high percentage (83% in brass and 82% in bronze) of Pb removal can be achieved.