Recycling of brass melting slag through the high-temperature oxidation-leaching process

Abstract

Brass melting slag is a valuable secondary resource for the recovery of copper and zinc. The hydrometallurgical recovery process of this material is a challenge, because of its limited dissolution in sulfuric acid. The present study aimed at studying a combined pyro-hydrometallurgical treatment processes involving high temperature oxidation and sulfuric acid leaching to industrial brass melting slag to recover copper and zinc. The effect of temperature on the performance and efficiency of the high temperature oxidation process was investigated by isothermal thermogravimetry. The results revealed that by increasing the oxidation temperature, leachability improves due to the oxidation of metallic brass particles. The results obtained showed that 3 h oxidation of as-received slag at 900 °C, increased its percent leaching amount in 2 M sulfuric acid from 34 to 81%. The pregnant leach solution containing copper sulfate and zinc sulfate was subjected to the electrowining process to recover the copper as copper cathode. The zinc was also recovered as zinc sulfate via evaporation and crystallization process. Kinetic investigations showed that the 3D diffusion model has a good agreement with the isothermal oxidation results. In this model, the oxidation reaction is controlled by the outward diffusion of zinc from the brass particle. The activation energy of isothermal oxidation was obtained as 311 kJ mol− 1.