Irgiredmet JSC, Irkutsk, Russia:

A. A. Lukianov, Senior Researcher at the Metallurgy Laboratory, e-mail: laa@irgiredmet.ru
A. V. Bogorodskiy, Senior Researcher, Candidate of Technical Sciences, e-mail: bav@irgiredmet.ru
S. V. Balikov, Principal Researcher, Doctor of Technical Sciences

A technology for the recovery of gold from oxidized sulfide gold-copper flotation concentrates using a thiocyanate-based solvent has been developed. The technology involves low-temperature atmospheric oxidation (LTO) of sulfide gold-copper flotation concentrates with sulfuric acid, leaching of gold with a thiocyanate-based solvent, and adsorption of gold on activated carbon or ion-exchange resin. It was found that the recovery of gold into the leaching solution did not exceed 80% when using thiocyanate as a solvent. The recovery of gold from the LTO product of sulfide gold-copper flotation concentrates into the solution by the use of a mixture of thiocyanate and alkali metal cyanide was above 93%, which is comparable to conventional cyanidation. The technology includes preliminary leaching of the oxidized LTO product of flotation concentrates with a thiocyanate-cyanide mixture, at the pulp temperature of 95 oC and the designed concentrations of KSCN and NaCN of 1.0 and 0.5 g/L, correspondingly. Then, the pulp is transferred to adsorption leaching with the countercurrent flow of adsorbent and pulp streams. The main differences between the technology and conventional cyanidation are the elimination of alkaline treatment of the flotation concentrate LTO product; dissolution and adsorption of gold in acidic environments and at a high temperature; the maximum gold leaching time of 7 hours in total compared to 24 hours; the gold solvent (KSCN+NaCN) consumption of 4.5 kg/t of gold concentrate compared to 10 kg (NaCN). An engineering and economical comparison of cyanide and thiocyanate-cyanide for the recovery of gold from oxidized sulfide gold-copper flotation concentrates shows that the technology reduces the capital and operating costs for processing of the LTO product of sulfide gold-copper flotation concentrates by at least 20%.

1. Lodeyshchikov V. V. Processes to recover gold and silver from refractory ores: In 2 volumes. Irkutsk : Izdatelstvo Irgiredmet, 1999. Vol. 1. 342 p.; Vol. 2. 452 p.
2. Kholmogorov A. G., Pashkov G. L., Kononova O. N. Noncyanic solvents for extracting gold from gold-bearing products. Khimiya v interesakh ustoychivogo razvitiya. 2001. No. 9. pp. 293–298.
3. Strizhko L. S. The metallurgy of gold and silver. Moscow : MISIS, 2001. 336 p.
4. Azizitorghabeh A., Wang J., Ramsay J. A., Ghahreman A. A review of thiocyanate gold leaching – Chemistry, thermodynamics, kinetics and processing. Minerals Engineering. 2021. Vol. 160. p. 106689.
5. La Brooy S. Fixing the Cyanide Issue – Alleviation or Replacement. The 22^nd International Conference ALTA. 2017.
6. Li J., Safarzadeh M. S., Moats M. S., Miller J. D., LeVier K. M. et al. Thiocyanate hydrometallurgy for the recovery of gold. Part I: Chemical and thermodynamic considerations. Hydrometallurgy. 2012. Vol. 113–114. pp. 1–9.
7. Li J., Wan R. Y., LeVier K. M., Miller J. D. Thiocyanate process chemistry for gold recovery. Proceedings of the 6th International Symposium on Hydrometallurgy. 2008. Phoenix Arizona. pp. 824–836.
8. Aylmore M. G. Alternative Lixiviants to Cyanide for Leaching Gold Ores. Gold Ore Processing. (Editor) Mike D. Adams. Chapter 27. 2016. pp. 447–484. DOI: 10.1016/B978-0-444-63658-4.00027-X.
9. Wan R. Y., Brierley J. A., Acar S., LeVier K. M. Using thiocyanate as lixiviant for gold recovery in acidic environment. 5^th International Hydrometallurgy Conference. Vol 1: Leaching and Solution Purification. 2003. pp. 105–121.
10. Zhuchkov I. A., Mineev G. G., Aksenov A. V. Sulphur containing solvents for precious metals used in geochemical and metallurgical processes. Irkutsk : Izdatelstvo IrGTU, 2010. 388 p.
11. Barbosa-Filho O., Monhemius A. J. Leaching of gold in thiocyanate solutions. Part 2: redox processes in iron (III) – thiocyanate solutions. Transactions of the Institutions of Mining and Metallurgy: Section C: Mineral Processing and Extractive Metallurgy. 1994. No. 103. pp. 111–116.
12. Barbosa-Filho O., Monhemius A. J. Leaching of gold in thiocyanate solutions. Part 3: rates and mechanism of gold dissolution. Transactions of the Institutions of Mining and Metallurgy: Section C: Mineral Processing and Extractive Metallurgy. 1994. No. 103. pp. 117–125.
13. Fleming C. A. A process for the simultaneous recovery of gold and uranium from South African ores, in Vol 2. Proceedings Gold 100 Conference, Johannesburg, South Africa. 1986. pp. 301–319.
14. Nabiulin R. N., Bogorodskiy A. V., Balikov S. V. Studies on processing of fine gold-copper flotation concentrate by sulphuric acid atmospheric oxidation. Vestnik Irkutskogo gosudarstvennogo tekhnicheskogo universiteta. 2020. Vol. 24, No. 4. pp. 887–895. DOI: 10.21285/1814-3520-2020-4-887-895.
15. Hourn M. M., Turner D. W., Holzberger I. R. Atmospheric mineral leaching process. Patent 9629439 WO. 1995.
16. Epiforov A. V., Kozlov A. A., Nemchinova N. V., Seleznev A. N. The carbon adsorption of gold from thiocyanate containing sulfuric acid solutions of gold-copper float concentrates atmospheric leaching. Tsvetnye Metally. 2020. No. 1. pp. 38–44. DOI: 10.17580/tsm.2020.01.06.
17. Lebedev K. B., Kazantsev E. I., Rozmanov V. M. Ion exchangers in nonferrous metallurgy. Moscow : Metallurg, 1975. 237 p.
18. Oliveira A. M., Leao V. A., da Silva C. A. A proposed mechanism for nitrate and thiocyanate elution of strong-base ion exchange resins loaded with copper and gold cyanocomplexes. Reactive and Func tional Polymers. 2008. Vol. 68, Iss. 1. pp. 141–152.
19. Krinitsyn D. O. The equilibrium and kinetics in the adsorption of gold(I) thiocyanates with certain anionites: PhD dissertation. Krasnoyarsk, 2009. 150 p.