“Science-Research Center “Gidrometallurgiya” LLC, Saint Petersburg, Russia:

G. A. Bitkov, Researcher, e-mail: gbitkov@gidrometall.ru
A. Yu. Lapin, Technical Officer
Ya. M. Shneerson, Chief Executive Officer

This article gives the results of development of technology of two-stage low-temperature autoclave oxidation of refractory gold-containing sulphide ores. Flotation concentrates of several Russian Far Eastern deposits became the objects of this research. The first stage of research demonstrated the effect of source material size, temperature and oxygen partial pressure on the process performance indicators. Low temperature leaching has the following optimal conditions: temperature is 130 ^оC; oxygen partial pressure is 1.0 MPa and leaching time is 1.5–2 hours. Grinding of concentrates before leaching to 80% of 10–15 μm of the grain size fraction is necessary to be carried out together with acid processing for carbonates' destruction. Autoclave and non-autoclave options of dissolving of elemental sulphur were tested. Concentration of unsaturated sulphur species during non-autoclave dissolving is too high. Decreasing of gold extraction values is the result of gold and saturated sulphur species contact. According to this, necessity of unsaturated sulphur species pressure oxidation is proved. The following optimal parameters of the process were defined during the research of autoclave oxidation of unsaturated sulphur species: lime consumption is 150% of stoichiometric ratio; temperature is 130 ^оC and oxidation time is 1.5–2 hours. The dissolution kinetics of elemental sulphur and autoclave oxidation kinetics of unsaturated sulphur species were determined. There are presented the results of recirculation of solutions with unsaturated sulphur species to the studies of different stages. Recirculation of solutions with unsaturated sulphur species to the first stage reduces the extraction of gold in the subsequent cyanidation. Recirculation of solutions with unsaturated sulphur species to the second stage does not reduce the extraction of gold. In some cases, the duration of second stage can be reduced by 1.5 to 2 times by recycling solutions with unsaturated sulphur species.

1. Lapin A. Yu., Bitkov G. A., Shneerson Ya. M. Tsvetnye Metally — Non-ferrous metals. 2011. No. 12. pp. 39–44.
2. Ya. M. Shneerson, A. Yu. Lapin, L. V. Chugaev, G. A. Bitkov. Sposob pererabotki upornogo sulfidnogo zolotosoderzhashchego syrya (Method of processing of refractory sulphide gold-containing raw materials). Patent RF, No. 2434064. MPK С 22 В 11/08. Applied: July 26, 2010. Published: November 20, 2011.
3. Bolobov V. I., Shneerson Ya. M., Lapin A. Yu., Bitkov G. A. Tsvetnye Metally — Non-ferrous metals. 2013. No. 2. pp. 76–81.
4. Papangelakis V. G., Demopulos G. P. Acid pressure oxidation of pyrite: reaction kinetics. Hydrometallurgy. 1991. No. 26. pp. 309–325.
5. Gerlach J., Hahne H., Pawlek F. Zur Kinetic der Drucklaugung von Pyrite. Z Erzberg Metall Huttenw. 1966. Vol. 1, No. 19. pp. 66–74.
6. Sizyakov V. M., Ivanik S. A., Boginskaya A. S., Bitkov G. A. Estestvennye i tekhnicheskie nauki — Natural and engineering sciences. 2012. No. 1. pp. 369–375.
7. Fokina S. B., Sizyakov V. M., Markelov A. V., Ivanik S. A. Estestvennye i tekhnicheskie nauki — Natural and engineering sciences. 2012. No. 1. pp. 376–381.
8. Laptev Yu. V., Sirkis A. L., Kolonin G. R. Sera i sulfidoobrazovanie v gidrometallurgicheskikh protsessakh (Sulphur and sulphide-formation in hydrometallurgical processes). Novosibirsk : Nauka, 1987. 159 p.
9. Mikhnev A. D., Serikov A. P. et al. Izvestiya vuzov. Tsvetnaya metallurgiya — Russian Journal of Non-ferrous Metals. 1980. No. 1. pp. 127–128.

10. Anderson C. G. Alkaline sulphide recovery of gold utilizing nitrogen species catalyzed pressure leaching. Center for Advanced Mineral & Metallurgical Processing. Available at: http://www.camp-montanatech.net/_Documents/Published/Articles_Papers/Article_1.pdf.
11. Bitkov G. A., Lapin A. Yu., Shneerson Ya. M. Dvukhstadialnoe avtoklavnoe okislenie upornykh zolotosoderzhashchikh sulfidnykh kontsentratov pri umerennykh temperaturakh (Two-stage autoclave oxidation of refractory gold-containing sulphide concentrates at moderate temperatures). Sbornik dokladov VI Mezhdunarodnogo kongressa “Tsvetnye metally — 2012” (Collection of reports of the VI International Congress
«Non-ferrous metals-2012»). Krasnoyarsk : Verso, 2012. pp. 568–575.
12. Zhuchkov I. A., Mineev G. G., Aksenov A. V. Serosoderzhashchie rastvoriteli blagorodnykh metallov v geokhimicheskikh i metallurgicheskikh protsessakh (Sulphur-containing dissolvents of noble metals at geochemical and metallurgical processes). Irkutsk : Publishing House of Irkutsk State Technical University, 2010. 388 p.
13. Jeffrey M., Heath J., Hewitt D., Brunt S., Xianwen Dai. A thiosulfate process for recovering gold from refractory ores which encompasses pressure oxidation, leaching, resin adsorption, elution and electrowinning. Proceedings of the Sixth International Symposium “Hydrometallurgy 2008”. Englevood : SME, 2008. pp. 791–800.
14. Muir D. M., Aylmore M. G. Thiosulphate as an alternative to cyanide for gold processing — issues and impediments. Mineral Processing and Extractive Metallurgy. 2004. Vol. 113.
15. Semenchenko G. V., Mukusheva A. S., Osipovskaya L. L. Pryamoe vyshchelachivanie blagorodnykh metallov iz upornykh rud Kazakhstanskikh mestorozhdeniy (Direct lecahing of noble metals from refractory ores of Kazakhstan deposits). Vtoroy mezhdunarodnyy kongress “Tsvetnye metally – 2010” (Second International congress “Non-ferrous metals-2010”). Krasnoyarsk, 2010. pp. 288–291.