Copper recovery from sludges generated in the electrolyte treatment plant of a pyrometallurgical complex

• Published in: Hydrometallurgy 2021-12, Vol.206, p.105769, Article 105769
• Main Authors: Paz-Gómez, D.C., Pérez-Moreno, S.M., Ruiz-Oria, I., Ríos, G., Bolívar, J.P.
• Format: Article
• Language: English
• Subjects: Characterization; Copper recovery; Copper sulfate; Crystallization; Electrolytic sludge; Valorization
• ISSN: 0304-386X; 1879-1158
• DOI: 10.1016/j.hydromet.2021.105769

Electrolytic sludge is generated in the last stage of the electrolyte decontamination treatment plant in the manufacture of cathodic copper (> 99.99 % Cu). Currently, this sludge is recycled back to the process due to the high concentration of copper, although its recirculation involves a serious problem of arsenic accumulation in the industrial process. This negatively affects the quality of commercial copper. Therefore, the main focus of this study was the recovery of copper contained in the electrolyte sludge as copper (II) sulfate pentahydrate (CuSO4∙5H2O) for its return to the industrial process and/or commercialization. The remaining waste, which contains mainly As and other toxic chemical species, were eliminated in a controlled repository. To this end, an exhaustive characterization of the electrolytic sludge was performed to determine its chemical composition, mineral phases, and particle size. The main results indicated that the sludge was composed of very fine particles (~ 99 % < 100 μm), containing mostly Cu (~ 54 %) (Cu3As, Cu2O, Cu and CuSO4∙xH2O), As (~ 10 % as Cu3As) and S (~ 7 % as CuSO4∙xH2O). More than 90 % of the Cu contained in the sludge was recovered as very pure copper sulfate (≥ 99.5 %) by an evaporative crystallization process. In addition, around 70 % of the As was removed in the process as a solid (> 99 % in As2O3). The rest of pollutants remained in the final solution, which ultimately will be treated in the liquid effluent treatment plant. Therefore, valorization of the electrolytic sludge was achieved by copper recovery as CuSO4∙5H2O using evaporative crystallization; this process was an effective way for both recovering Cu and removing the As contained in the electrolytic sludge generated in the electrolyte treatment plant. •A physicochemical characterization of electrolytic sludge was carried out.•A high concentration of copper was found.•High copper recovery as copper sulphate pentahydrate was achieved.•High arsenic removal was obtained.