Ural Federal University Named after the First President of Russia B. N. Yeltsin, Yekaterinburg, Russia:

D. A. Rogozhnikov, Senior Researcher at the Department of Non-Ferrous Metals, e-mail: darogozhnikov@yandex.ru
R. E. Rusalev, Postgraduate Student, Researcher at the Department of Non-Ferrous Metals
О. А. Dizer, Postgraduate Student, Researcher at the Department of Non-Ferrous Metals
S. S. Naboychenko, Visiting Professor at the Department of Non-Ferrous Metals

This paper examines the most popular techniques of processing rebellious goldcontaining materials that cannot be cyanided using conventional techniques due to gold nanoparticles disseminated in the sulfide minerals. To loosen such rebellious concentrates, it is proposed to use nitric acid, which is an effective oxidizer and leaching agent. A gold sulphide concentrate from the Udereysk deposit was used in the study, which had been subjected to selective separation of antimony in alkaline sulphide solutions. The main gold-containing minerals in the concentrate include pyrite and arsenopyrite. The paper looks at the standard reactions between these minerals and nitric acid. The authors found a rather high thermodynamic probability of these reactions within a broad temperature range. Through building Pourbaix diagrams for arsenic and iron compounds in the considered heterogeneous systems, the authors demonstrate that in order to obtain the desired products from the interactions in view, the oxidation potential of the system should be maintained at the minimum level of 0.6 V. With the help of the mathematical methods of experiment design, the authors selected the nitric acid leaching parameters applicable to the test material: liquid-to-solid ratio = 8:1; nitric acid concentration — 6 mol/dm³; process duration — 75 minutes. The adequacy of the obtained data is confirmed by the calculated values of the determination coefficients, which were close to 100%. The extraction of iron and arsenic into the solution was around 97 and 92%, respectively. The obtained solid leaching residues, in which the concentration of gold can reach 100 g/t, are then sent to further extraction by conventional techniques. The leaching solutions containing iron and arsenic are neutralized and precipitate as low-solubility compounds.

This research was funded by the Russian Science Foundation (Project No. 18-19- 00186). The study of the thermodynamics of the processes under consideration was funded under the Governmental Assignment No. 11.4797.2017/8.9.

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