ABSTRACT Cyanidation is the main process for gold and silver recovery from its ores. In this study, a process is proposed to recover copper and cyanide from barren solutions from the Merrill-Crowe cementation process with zinc dust. This technology is based on inducing nucleated precipitation of copper and silver in a serpentine reactor, using sodium sulfide as the precipitator, and sulfuric acid for pH control. Results show that pH value has a significant effect on copper cyanide removal efficiency, and it was determined the optimal pH range to be 2.5 - 3. At this pH value, the copper cyanide removal efficiency achieved was up to 97 and 99%, when copper concentration in the influent was 636 and 900 ppm. respectively. In this process (sulphidization-acidification-thickening-HCN recycling), the cyanide associated with copper cyanide complexes, is released as HCN gas under weakly acidic conditions, allowing it to be recycled back to the cyanidation process as free cyanide. Cyanide recovery was 90%. Finally, this procedure was successfully run at Minera William in México.
Cite this paper
nullJ. Parga, J. Valenzuela, H. Moreno and J. Pérez, "Copper and Cyanide Recovery in Cyanidation Effluents," Advances in Chemical Engineering and Science, Vol. 1 No. 4, 2011, pp. 191-197. doi: 10.4236/aces.2011.14028.
 F. Habashi, “One Hundred Years of Cyanidation Historical Note,” CIM Bulletin, Vol. 80, No. 905, 1987, pp. 108- 114.
 J. R. Parga, J. L. Valenzuela and F. Cepeda, “Pressure Cyanide Leaching for Precious Metals Recovery,” Journal of Metals, Vol. 59, No. 10, 2007, pp. 43-47.
 F. Habashi, “Kinetics and Mechanism of Gold and Silver Dissolution in Cyanide Solution,” Bulletin No. 59, Bureau of Mines and Geology, State of Montana, 1967.
 J. R. Parga, H. M. Casillas, V. Vazquez and J. L. Valen- zuela, “Cyanide Detoxification of Mining Wastewaters with TiO2 Nanoparticles and Its Recovery by Electrocoagulation,” Chemical Engineering and Technology, Vol. 32, No. 12, 2009, pp. 1901-1908.
 D. M. Muir, “A Review of the Selective Leaching of Gold from Oxidised Copper-Gold Ores with Ammonia- cyanide and New Insights for Plant Control and Operation,” Minerals Engineering, Vol. 24, No. 6, 2011, pp. 576-582. doi:10.1016/j.mineng.2010.08.022
 C. A. Fleming, “Cyanide Recovery,” Developments in Mineral Processing, Vol. 15, 2005, pp. 703-727.
 C. W. Lawr, “Cyanide Regeneration as Practiced by Compa?ia Beneficiadora de Pachuca,” Mexico Technical Publication AIME, Vol. 6, No. 208, 1929, pp. 1-37.
 J. R. Parga and D. L. Cocke, “Enhance Cyanide Recovery by Using Air-Sparged Hydrocyclone,” Chemical Engineering and Technology, Vol. 26, No. 4, 2003, pp. 503- 507. doi:10.1002/ceat.200390075
 Z. M. Shareefdeen, W. Ahmed and A. Aidan, “Kinetics and Modeling of H2S Removal in a Novel Biofilter,” Advances in Chemical Engineering and Science, Vol. 1, No. 2, 2011, pp. 72-76. doi:10.4236/aces.2011.12012
 A. E. Lewis, “Review of Metal Sulphide Precipitation,” Hydrometallurgy, Vol. 104, No. 2, 2010, pp. 222-234.
 M. Adams, R. Lawrence and M. Bratty, “Biogenic Sulphide for Cyanide Recycle and Copper Recovery in Gold-Copper Ore Processing,” Minerals Engineering, Vol. 21, No. 6, 2008, pp. 509-517.