Irkutsk National Research Technical University, Irkutsk, Russia:

V. V. Zhmurova, Senior Lecturer at the Department of Non-Ferrous Metallurgy, e-mail: v_pichugina@list.ru
N. V. Nemchinova, Head of the Department of Non-Ferrous Metallurgy, Professor, e-mail: ninavn@yandex.ru
А. А. Vasiliev, Associate Professor at the Department of Non-Ferrous Metallurgy

Because high-grade precious metal ores had been depleted, the industry started to use gold containing polymetallic ores which also have high concentrations of heavy non-ferrous metals, such as Cu, Pb, Zn, Ni and others. Application of coal sorption process to such ores results in cathode deposits that contain less Au and Ag and more impurities. All this leads to higher refining costs due to uneven distribution of precious metals in the ingot, a discrepancy between the results of sample analysis by suppliers versus refineries, and a need for verification of base gold, etc. In connection with the above, the work aimed at improving the quality of cathode deposits is of relevance. This paper describes the process of acid leaching of impurities contained in cathode deposits which are obtained through desorption and electrolysis of high-concentration gold solutions at the Berezitovy mine in the Amur region. The chemical composition of the cathode deposits was analysed with the help of atomic adsorption and X-ray phase analyses and electron probe microanalysis; assay tests were carried out to identify precious metals. X-ray fluorescence spectrometry was applied to determine the chemical composition of base gold. The results of the laboratory study helped determine conditions for hydrochloric acid treatment of cathode deposits: solvent concentration — 371.0 kg/m3, tempera ture — 25 ^oC, duration — 2 h, liquid-to-solid ratio = 3:1. The average recovery of copper in the above conditions was 69.0%, and it was 93.9% for lead. A series of pilot tests was conducted for the proposed process, which resulted in the production of base gold (produced from cathode deposits after hydrochemical treatment), in which the concentration of Au increased on average by 20% and the concentration of lead decreased by 6.6%. Due to increased fraction of the precious metal in the alloys, the calculated reduction in the refining costs amounted to 1.5 rubles per 1 g gold. When the chemical composition of the alloy is brought to conformance with TU 117-2-7–75 in terms of lead concentration, the refining costs can be reduced by 5%.

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