Irkutsk National Research Technical University, Irkutsk, Russia:

V. V. Zhmurova, Assistant Professor of a Chair of Non-ferrous Metals Metallurgy, e-mail: v_pichugina@list.ru
N. V. Nemchinova, Head of a Chair of Non-ferrous Metals Metallurgy, e-mail: ninavn@yandex.ru
G. G. Mineev, Professor of a Chair of Non-ferrous Metals Metallurgy

Cathode sediments (KS), obtained as a result of industrial processing of complex gold-polymetallic raw materials, contain a considerable amount of impurity metals (copper, lead, zinc, iron, cobalt and others), which significantly increases the costs of the subsequent refining of materials. We carried out the experimental works on the preliminary acid treatment of KS with the aim of leaching the impurities and increasing the precious metals proportion. The investigation objects were cathode sediments that contained copper and nickel in the amount of 22.68 and 2.11% (by mass), respectively. Hydrochloric and nitric acids were tested as a solvent in our laboratory studies. For the selection of optimal leaching parameters, studies were carried out with different concentrations of the reagent (from 50 to 350 kg/m³) and the ratio of L:S = (3–7):1. The duration of the experiments was 2 hours; the experiments were carried out with intensive agitation and standard ambient temperature (25 °C). The leaching residue was washed with water and dried. The processing of the obtained experimental data was carried out with the help of the computer program STATISTICA 6.0. We chose the following factors of variation: acid concentration, solution temperature, ratio of liquid and solid phases. It was established that nitric acid purifies KS more effectively. After preliminary acid purification, the precious metals content in the leach residue increased, so SK corresponded to the Technical Requirements TU 117-2-3–78. As a result of semi-industrial tests on smelting of gold ligature ingots from KS samples (without and after their preliminary acid treatment), the losses of gold and silver with slags were reduced and ingots with a uniform structure were obtained. The mass fraction of precious metals in ingots increased by 2, which can significantly reduce the costs of their ensuing refining.

1. Kotlyar Yu. A., Meretukov M. A., Strizhko L. S. Metallurgy of noble metals : tutorial. In two volumes. Volume 1. Moscow : “Ore and Metals” Publishing House, 2005. 432 p.
2. Mikhaylova A. N., Fayberg A. A., Dementev V. E., Mineev G. G., Bonch-Osmolovskaya E. A. Biogenic hydrogen sulfide production. Vestnik IrGTU. 2015. No. 1. pp. 124–128.
3. Canda L., Heput T., Ardelean E. Methods for recovering precious metals from industrial waste. IOP Conference Series: Materials Science and Engineering. 2016. Vol. 106, No. 1. pp. 12–20.
4. Syed S. Recovery of gold from secondary sources – A review. Hydrometallurgy. 2012. Vol. 115–116. pp. 30–51.
5. Hussin A. M. Ahmed, Ayman A. El-Midany. Statistical optimization of gold recovery from difficult leachable sulphide minerals using bacteria. Materials Testing. 2012. Vol. 54, No. 5. pp. 351–357.
6. Khmelnitskaya О., Voiloshnikov G., Lodeischikov V. Pilot-Plant testing of ammonical cyanidation for gold recovery from copper gold-bearing ore. XXV International mineral processing congress 2010. Brisbane, Australia, 6–10 September 2010. pp. 345–355.
7. Petrov S., Voyloshnikov G. Carbonaceous matter removal from goldbearing ores. XXVII International mineral processing congress – IMPC 2014. Santiago, Chile, 2014. pp. 475–479.
8. Karpukhin A. I., Stelkina I. I., Medvedeva L. A., Dementev V. E. Method of processing of ligature gold alloy. Patent RF, No. 2151210. Applied: 24.11.1998. Published: 20.06.2000. Bulletin No.17.
9. Technical Requirements TU 117-2-3–78. Cathode gold on coal-graphite basis. Introduced: 1978–01–03.
10. State Standard GOST 857–95. Synthetic hydrochloric acid for industrial use. Specifications. Introduced: 1997–01–01.
11. Zhmurova V. V. Developmnent of method of obtaining of noble metal alloys with minimal impurities. Collection of reports of the II International congress “Non-Ferrous Metals-2010”. Krasnoyarsk : Verso, 2010. pp. 325–332.
12. Zhmurova V. V., Karpukhin A. I. Researches on quality improvement of a cathodic sediments during the processing of gold-polymetallic raw materials. Tsvetnye Metally. 2012. No. 9. pp. 37–40.
13. Kozlov A. Yu., Mkhitaryan V. S., Shishov V. F. Statistical analysis of data using MS Excel : tutorial. Moscow : Infra, 2014. 319 p.
14. Balikov S. V. Dementev V. E. Smelting of gold-bearing concentrates. Irkutsk : Irgiredmet, 2002. 368 p.