Document Type : Original Research Paper


Department of Mining, Tarbiat Modares University, Tehran, Iran


The presence of copper bearing minerals in cyanidation of gold ores may lead to several challenges in the CIP/CIL circuits. Many solutions have been proposed to address these problems, one being the use of glycine in the cyanidation process. Here, the experimental as well as molecular modelling studies using Density Functional Theory (DFT) have been conducted to investigate the glycine role in cyanidation of copper bearing gold ores. The results show that in the presence of glycine in the solution containing copper-cyanide species and in very low or zero free cyanide content, the dissolution rate of gold is significantly improved (3.02 vs. 0.23 ppm), while no improvement is observed in copper free or cyanide enriched solutions. Molecular modeling has been performed to interpret the laboratory results as well as to identify the mechanisms. The modeling results demonstrate that in cyanide deficient solutions, cyanide complex of copper complexes (E = -319 kCal.mol-1) is replaced by glycine, and the free cyanide produced results in higher gold cyanidation as well as lower copper cyanide formation.


Main Subjects

[1]. Marsden, J. and House, I. (2006). The Chemistry of Gold Extraction: Society for Mining, Metallurgy, and Exploration.
[2]. Zia, Y., Mohammadnejad, S. and Abdollahy, M. (2020). Destabilisation of gold cyanide complex by sulphur species: A computational perspective. Hydrometallurgy, 197, 105459.
[3]. Hilson, G. and Monhemius, A.J. (2006). Alternatives to cyanide in the gold mining industry: what prospects for the future? Journal of Cleaner Production, 14, 1158-1168.
[4]. Abbruzzese, C., Fornari, P., Massidda, R., Veglio, F., and Ubaldini, S. (1995). Thiosulphate leaching for gold hydrometallurgy. Hydrometallurgy, 39, 12.
[5]. Aylmore, M.G. (2005). Alternative lixiviants to cyanide for leaching gold ores. In M. D. Adams (Ed.), Developments in Mineral Processing (Vol. 15, pp. 1076): Elsevier.
[6]. Ghasemi, S., Mohammadnejad, S. and Khalesi, M.R. (2018). A DFT study on the speciation of aqueous gold and copper cyanide complexes. Computational and Theoretical Chemistry, 1124, 23-31.
[7]. Ghasemi, S., Mohammadnejad, S., and Khalesi, M.R. (2022). Role of Functional Groups in Selective Adsorption of Gold over Copper Cyano complexes by Activated Carbon: A DFT Study. Journal of Mining and Environment, 13(3), 891-901.
[8]. Bulatovic, S.M. (1997). Flotation behaviour of gold during processing of porphyry copper-gold ores and refractory gold-bearing sulphides. Minerals Engineering, 10 (9): 895-908.
[9]. Feng, D., and van Deventer, J.S.J. (2006). Ammoniacal thiosulphate leaching of gold in the presence of pyrite. Hydrometallurgy, 82 (3–4): 126-132.
[10]. Forrest, K., Yan, D., and Dunne, R. (2001). Optimisation of gold recovery by selective gold flotation for copper-gold-pyrite ores. Minerals Engineering, 14 (2): 227-241.
[11]. Bas, A.D., Ozdemir, E., Yazici, E.Y., Celep, O., and Deveci, H. (2011). Ammoniacal thiosulphate leaching of a copper-rich gold ore. Paper presented at the 15th International Conference on Environmental and Mineral Processing (EaMP), Ostrava, Czech Republic.
[12]. Kondos, P.D., Deschênes, G., and Morrison, R.M. (1995). Process optimization studies in gold cyanidation. Hydrometallurgy, 39 (1): 235-250.
[13]. Jiang, T., Zhang, Y., Yang, Y., and Huang, Z. (2001). Influence of copper minerals on cyanide leaching of gold. Journal of central south university of technology. 8 (1): 24-28.
[14]. Tao, Y. (1987). A review on treatment of copper-beating gold ores. Huang Jin (in Chinese), 3 (41).
[15]. BAS, A.D., Kucuk, A., Yazici, E.Y., and Deveci, H. (2012). Assessment of ammoniacal ammonium sulphate leaching as a pretreatment process for copper bearing gold ores. XIIIth International Mineral Processing Symposium (IMPS), Bodrum, Turkey.
[16]. Muir, D.M., La Brooy, S.R., and Fenton, K. (1991). Processing copper–gold ores with ammonia or ammonia–cyanide solutions. World Gold ’91, Cairns, Australia.
[17]. Deschênes, G., Gu, H., Xia, C., Pratt, A., Fulton, M., Choi, Y., and Price, J. (2012). A study of the effect of djurliete, bornite and chalcopyrite during the dissolution of gold with a solution of ammonia-cyanide. Minerals and Metallurgical Processing, 2, 459−472.
[18]. Deschênes, G. and Prud'homme, P.J.H. (1997). Cyanidation of a copper-gold ore. International Journal of Mineral Processing, 50 (3): 127-141.
[19]. Dai, X., Simons, A., and Breuer, P. (2012). A review of copper cyanide recovery technologies for the cyanidation of copper containing gold ores. Minerals Engineering, 25 (1): 1-13.
[20]. Eksteen, J. and Oraby, E.A. (2015). The leaching and adsorption of gold using low concentration amino acids and hydrogen peroxide: Effect of catalytic ions, sulphide minerals and amino acid type. Minerals Engineering, 70, 36-42.
[21]. Oraby, E. and Eksteen, J. (2014). The selective leaching of copper from a gold–copper concentrate in glycine solutions. Hydrometallurgy, 150, 14-19.
[22]. Oraby, E. and Eksteen, J. (2015). The leaching of gold, silver and their alloys in alkaline glycine– peroxide solutions and their adsorption on carbon. Hydrometallurgy, 152, 199- 203.
[23]. Oraby, E. and Eksteen, J. (2015). Gold leaching in cyanide-starved copper solutions in the presence of glycine. Hydrometallurgy, 156, 81-88.
[24]. Oraby, E., Eksteen, J., and Tanda, B. (2017). Gold and copper leaching from gold-copper ores and concentrates using a synergistic lixiviant mixture of glycine and cyanide. Hydrometallurgy, 169(Supplement C), 339-345.
[25]. Sarvar, M., Shafaei Tonkaboni, Z., Noaparast, M., Badiei, A.R., and Amiri, A. Application of amino acids for gold leaching: Effective parameters and the role of amino acid structure. Journal of Cleaner Production, 391, 136123.
[26]. Li, H., Deng, Z., Oraby, E., and Eksteen, J. (2023). Amino acids as lixiviants for metals extraction from natural and secondary resources with emphasis on glycine: A literature review. Hydrometallurgy, 216, 106008.
[27]. Li, H., Oraby, E., and Eksteen, J. (2022). Extraction of precious metals from waste printed circuit boards using cyanide-free alkaline glycine solution in the presence of an oxidant. Minerals Engineering, 181, 107501.
[28]. Oraby, E., Eksteen, J., and Tanda, B. (2017) Gold and copper leaching from gold-copper ores and concentrates using a synergistic lixiviant mixture of glycine and cyanide. Hydrometallurgy, 169, 339-345.
[29]. Rezaee, M., Saneie, R., Mohammadzadeh, A., Abdollahi. H., Kordloo, M., Rezaee, A., and Vahidi, E. (2023). Eco-friendly recovery of base and precious metals from waste printed circuit boards by step-wise glycine leaching: Process optimization, kinetics modeling, and comparative life cycle assessment. Journal of Cleaner Production, 389, 136016.
[30]. Delley, B. (2000). From molecules to solids with the DMol3 approach. The Journal of chemical physics, 113 (18): 7756-7764.
[31] Klamt, A. and Schüürmann, G. (1993). COSMO: a new approach to dielectric screening in solvents with explicit expressions for the screening energy and its gradient. Journal of the Chemical Society, Perkin Transactions 2, 799-805.
[32]. Hancock, R. and Bartolotti, L. (2005). Density functional theory-based prediction of the formation constants of complexes of ammonia in aqueous solution: indications of the role of relativistic effects in the solution chemistry of gold (I). Inorganic Chemistry, 44(20), 7175-83.
[33]. Gutten, O. and Rulíšek, L. (2013). Predicting the stability constants of metal-ion complexes from first principles. Inorganic Chemistry, 52 (18): 10347-10355.
[34]. Yin, X., Opara, A., Du, H., and Miller, J. (2011). Molecular dynamics simulations of metal–cyanide complexes: Fundamental considerations in gold hydrometallurgy. Hydrometallurgy, 106 (1-2): 64-70.