Phase composition of autoclave oxidation products and its effect on gold coating

This paper describes the mineralogical studies of the solid products of autoclave oxidation. These products were obtained during autoclave pilot tests at a temperature of 225 oС and total pressure 3.25 МPa. Autoclave tests were carried out on the samples of sulfide gold-bearing concentrate of the Malomyr deposit. Mineralogical studies were provided using Mossbauer spectrometry, scanning electron microscope, X-ray fluorescence and X-ray diffraction analysis. It was found that the solid autoclave residues consist of basic ferric arsenate sulfate (Fe(AsO4)x(SO4)y(OH)z·wH2O), sodium jarosite (KFe3(SO4)2(OH)6), basic ferric sulfate (Fe(OH)SO4) and gangue minerals (muscovite, quartz, feldspars and others). The main relationships of the phase transformations in the autoclave oxidation process were described. Data obtained during these studies shows that some part of the gold may be associated with a secondary arsenic-containing phase formed in the autoclave oxidation process. This gold may be isolated from cyanidation solution and remain in the tailings. It was considered to subject the autoclave slurry to an additional treatment — Hot Cure process. This can minimize the loss of the precious metal during autoclave aftertreatment. As a result, a part of the secondary soluble phases (up to 10–50%) decomposes and dissolves. After that gold becomes accessible to the cyanide solution during sorption cyanidation. The increase in precious metal recovery is 2–5% for various samples.

The influence of temperature and partial pressure of oxygen on the extent of autoclave oxidation of active carbon in the model mixtures, simulating refractory gold-containing concentrate.

The article considers the effect of partial pressure of oxygen and temperature on autoclave oxidation of active carbon of various sizes. Carbon is the main natural organic sorbent in gold-sulfide ores, which is involved in the preg-robbing process. In order to overcome preg-robbing, we developed an experiment plan of removing carbon from the reaction mixture. The results of this work are presented in the article.

Flotation extraction of elemental sulfur from gold-bearing cakes

Currently, in the development of the raw materials base of the gold mining industry, there is a tendency to reduce the quality of the initial mineral raw materials due to the depletion of reserves of rich gold-bearing ores. The article discusses the technology of extraction of refractory gold-bearing concentrates based on low-temperature leaching of pyrite concentrate. A decrease in the parameters of the autoclave oxidation of sulfide minerals, such as pyrite and arsenopyrite, leads to the incomplete extraction of gold into the solution and, consequently, its losses during subsequent cyanidation. As a possible option for a more complete extraction of gold using low-temperature oxidation technology, a method of flotation separation of elemental sulfur from leaching cakes is proposed. According to the basic process flow chart, the flotation process designed for gold extraction is carried out after autoclave oxidation, but before cyanidation. A series of experiments were carried out with varying reagent conditions and the dependence of gold losses on the extraction of elemental sulfur in the flotation tailings was established. As determining factors, pH and solid content in the initial pulp were considered. The paper justifies the separation of elemental sulfur from autoclave cake to enriched sulfur concentrate. The cake flotation modes after autoclave oxidative leaching of pyrite concentrate are investigated. The distribution of elemental sulfur and gold by flotation products makes it possible to conduct the tailings cyanidation process with acceptable indicators.

Arsenic Precipitation from Solutions in Autoclave-Hydrometallurgical Technology of Processing Sulphide Concentrates

Currently, the share of gold extracted from technologically simple gold ores is steadily decreasing, which determines the involvement in the processing of refractory gold ores containing finely disseminated gold and silver in sulfides, mainly in pyrites and arsenopyrites. Autoclave oxidation is a promising method of pretreatment of the refractory sulfide-arsenic gold-bearing raw materials before cyanidation. A serious problem of auriferous ores autoclave-hydrometallurgical processing is the removal of contained arsenic into relatively harmless and capable of being kept forms. This article shows the results of behavior of arsenic during the neutralization of solid after autoclave oxidative leaching of refractory gold-containing materials.

Arsenic behavior in the autoclave-hydrometallurgical processing of refractory sulfide gold-platinum-bearing products

Among various types of gold-bearing ores a special place belongs to the ores, which contain gold finely-dispersed in sulphide minerals, mostly in arseno-pyrite and pyrite. Autoclave-hydrometallurgical processing technologies for such raw materials seem to be of a particular interest for study. However, autoclave oxidation of sulfide-arsenic material results in significant amounts of technological solutions with high concentrations of arsenic, iron and sulfuric acid.This article represents the studies of how arsenic behaves in autoclave oxidative leaching of a refractory sulphide gold-platinum-bearing concentrate. We studied how the composition of arsenic-bearing solutions in autoclave leaching (acidity, concentration of iron and arsenic) influences the depth of arsenic precipitation when neutralized with calcium-containing reagents, which allows converting the maximum amount of arsenic together with iron in the form of iron arsenate into a stable long-term storable precipitation.