Saint Petersburg Mining University (Saint Petersburg, Russia)

Gordeev D. V., Postgraduate Student, danya.gordeev.2014@mail.ru

Petrov G. V., Professor, Doctor of Engineering Sciences, Associate Professor

Nietz Technologies (Saint Petersburg, Russia)
Fomenko I. V., CEO, PhD in Engineering Sciences
Shneerson Ya. M., Science and Development Director, Doctor of Engineering Sciences, Professor

This article describes the development of a method for reducing the sorption activity of carbonaceous matter (CM), which consists in stimulating oxidation and surface passivation during autoclave oxidation (AO) when exposed to a secondary oxidizer. A study was conducted to assess the fundamental usability of nitric acid as a secondary oxidizer in AO of double refractory gold-containing concentrates. Five refractory concentrates from various deposits with organic carbon contents of 0.5 to 3.6 wt% were tested; gold recovery during standard autoclave oxidation for these varied between 70 and 90 %. The addition of nitric acid has a predominantly positive effect on the main AO performance indicators. At the addition rate of 25 kg/t, the gold recovery increased by 10–15 %; at 100 kg/t, a more significant effect was observed with the recovery growing by up to 20 % as compared to the baseline level. The gold content in cyanidation tailings dropped several times: by a factor of 2–3 for low-carbon materials and by a factor of 5–17 for high-carbon materials. The degree of CM oxidation (removal) when adding 100 kg/t HNO₃ reached 85 % (with a baseline value of approx. 10 %). It has been shown that gold recovery is directly proportional to the organic carbon content. The results obtained confirm the potential of using nitric acid as a CM surface oxidizer/passivator. This method minimizes gold losses associated with autoclave and cyanide preg-robbing. The technology proposed may be successfully introduced at existing autoclave enterprises without significant capital costs.

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