Recovery of copper and zinc from waste brass ashes by solvent extraction – Juiz de Fora, Brazil

Ing. Julia M. Martins, Ing. Sérgio de A. Penchel Jr, M.Sc. Pablo Pina, D.Sc Achilles Junqueira Bourdot Dutra

There are several small to large scale brass casting companies in Brazil. This industrial segment generates significant zinc and copper bearing residues that are suitable for treatment as secondary raw materials. However, most casting companies do not recycle the residues generated during casting of brass and other zinc bearing alloys. Some other companies purchase slags, ashes and other residues for evaluation, processing and production of some products, mainly Zinc PW and Zamac alloys. However, the most part of the material that is recycled during these processes is the metallic portion of it, therefore, the oxidized portion (also known as brass ashes) of the residues is not treated. Currently, the zinc smelter of Votorantim Metais Holding located at Juiz de Fora – Brazil, is processing 915 tons of zinc per year from brass ashes, through blending small quantities of this material in the feed of the roaster. However, high content of copper, the presence of metallic elements and other impurities limit the amount of brass ashes that can be treated in this circuit. Direct leaching is also not suitable for brass ashes treatment, mostly due to significant amounts of halogens (chlorine and fluorine), nickel and other minor contaminants, that are deleterious for the zinc electrowinning process. Therefore, a considerable amount of brass ashes is available in the market and cannot be treated considering the current process limitations. This study aims to evaluate a possible circuit for treatment of brass ashes by solvent extraction to recovery copper and zinc sulfate solution to compose the main production process of Votorantim Metais Holding zinc smelter situated in Juiz de Fora.