Baikal Institute of Nature Management, Siberian Branch of the Russian Academy of Sciences, Ulan-Ude, Russia:

P. A. Gulyashinov, Junior Researcher, e-mail: gulpasha@mail.ru
P. L. Paleev, Research Fellow
A. K. Subanakov, Senior Researcher
A. N. Gulyashinov, Lead Engineer

In modern conditions, due to the depletion of high-grade ore and placer gold deposits, both domestic and global gold mining industries have to deal with rebellious ores, the extraction of valuable components from which by direct cyanidation is difficult or extremely unprofitable. The most common types of rebellious ores include sulphide ores and sulphide concentrates. A variety of techniques have been developed and widely used to process such materials, including autoclave oxidation, bacterial leaching, etc. However, there is another type of rebellious ores – oxidized ores. Arsenopyrite and scorodite concentrates characterized with a high arsenic concentration, can be classified as a special type of rebellious gold ores. This research was aimed at collecting new data about the behaviour of gold concentrates with high arsenic concentrations under thermal decomposition conditions. Netzsch STA 449 F1 Jupiter was used for differential thermal analysis, which was conducted in an alumina crucible in the argon atmosphere under linear heat of up to 850 ^оС. The paper describes the results of the thermal analysis carried out for specimens of the monomineral scorodite FeAsO₄ and arsenopyrite FeAsS, as well as for their 1:1 combination. The authors found that the thermal breakdown of scorodite includes three stages. They also determined the temperature ranges and heat effects of these reactions. A study of the thermal decomposition of arsenopyrite showed that pyrite would break down into pyrrhotines in one stage. Experiments confirmed that the mixture of scorodite and arsenopyrite concentrates would break down in three stages. The X-ray phase analysis data show that the final roasted products include hematite Fe₂O₃, quartz SiO₂, and potassium aluminium silicate KAl₃Si₃O₁₁. It was also confirmed that up to 99.9% of arsenic goes into the gas phase.

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