“Scientific-Engineering Center “Gidrometallurgiya” JSC, Saint Petersburg, Russia:

Zaytsev P. V., Researcher
Fomenko I. V., Researcher, phone: 8(812) 600-77-45
Pleshkov M. A., Leading Researcher
Chugaev L. V., Leading Researcher
Shneerson Ya. M., Chief Executive Officer

Certain conditions of the pressure oxidation (POX) process, such as high temperature and pressure, make possible to carry out an intensive oxidation of sulfides in refractory gold ores and concentrates. However, there was made a definition that in case of processing of some materials, the POX method leads to irreversible gold losses. Investigation of this phenomenon revealed that the reasons of gold losses are connected with combined presence of carbonaceous substance in the material and chlorideion in the POX solution. This is confirmed by the thermodynamic calculations, which also show the possible ways of this problem solving. This article demonstrates the combined negative effect of organic carbon (contained in the material) and chloride-ion (dissolved in the POX solution) on gold recovery from refractory gold concentrates of Malomyr deposit. There was studied the effect of partial sulfur oxidation on the POX indicators. Obviously, sulfides' oxidation was increased together with increasing of amount of gold, exposed to cyanide leaching. There was observed that relationship between gold recovery and sulfides' oxidation has an extreme behavior, which is more shown under high chloride concentrations in the POX solution. The controlled partial oxidation of sulfides allows to avoid the significant gold losses, formed during POX process. According to this, increasing of gold recovery by 10% and more becomes possible. There was studied the addition of carbonates to the POX feed slurry, which makes possible to control the POX slurry acidity, which – in turn – affects the gold recovery. Decreasing of POX solution acidity leads to an elevated gold recovery level, even when the chloride concentration is relatively low. There were carried out the pilot tests of the continuous POX technology, which confirmed the key relationships, obtained in the laboratory. The experimental data was compared to results of thermodynamic calculations.

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