Institute of Mining, Far East Branch, Russian Academy of Sciences, Khabarovsk, Russia:

K. V. Prokhorov, Senior Researcher, Candidate of Engineering Sciences, sciencecat86@gmail.com

Irkutsk National Research Technical University, Irkutsk, Russia:

A. E. Burdonov, Associate Professor, Candidate of Engineering Sciences

An alternative non-cyanide method of gold leaching from oxidized ores of the Malmyzh field (Khabarovsk Territory) was investigated in the present work. The mineralogical studies showed the main components of quartz, hematite, goethite, kaolinite and muscovite. Pyrite is contained in its pure form and in intergrowths with chalcopyrite, azurite and malachite. Sphalerite, galena and arsenopyrite are observed in small amounts. Visible gold is not detected; gold is present in ultrathin dispersed form and in association with sulfi des. The initial gold content of ore is 0.8–0.95 g/t. Extraction of gold was carried out using freshly primed chloride–hypochloride solution The solution was prepared by electrolysis of a sodium chloride solution (NaCl) at a concentration of 20 g/dm3 with the addition of 0.1 N hydrochloric acid (HCl). Optimal conditions for obtaining a solution with the maximum concentration of active chlorine necessary for leaching of gold are determined. The scope of the study embraced gold extraction by agitation with preliminary exposure to pulp by preoxidation and cavitations (using ultrasound). The gold analysis was carried out by atomic absorption spectroscopy (AAC). Direct hypochlorite leaching resulted in gold recovery of 23.0 % in 4 hours and 72.7 % in 24 hours. After pre-oxidation and subsequent leaching with hypochlorite, the recovery was 80.2 % and 98.8 % in 4 and 24 hours, respectively. After ultrasonic treatment, the gold extraction was 36.7–66.5 % in 4 hours of agitation. The process of re-precipitation of recovered gold in solid phase and reduction in its extraction during prolonged agitation after preliminary ultrasonic treatment, both initial hypochlorite and pulp, is revealed. Re-precipitation occurs as a result of pH transition of the medium to the neutral range. Consequently, extraction of gold from the chloride–hypochlorite solution should be carried out in an acidic medium.

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