Gold and silver recovery from a refractory gold-containing arsenic flotation concentrate obtained at the Ikkijelon deposit with the addition of sodium chloride in the process of autoclave oxidation

This work was aimed at developing an effective method for processing a refractory gold-arsenic flotation concentrate using an autoclave-chloride technology followed by cyanidation to recover precious metals. The research object was a flotation concentrate obtained from mixed ores mined at the Ikkizhelon deposit (Northern Tajikistan), the main valuable components of which are gold and silver. In the concentrate, the main mass of gold is associated with iron sulfide minerals (total Fe content - 81.90%), among which pyrite and arsenopyrite predominate (total As content - 90.85%). Experiments on sulfuric acid autoclave oxidation of the flotation concentrate in the presence of NaCl were carried out in a Parr series 4532 laboratory autoclave at a temperature of 220 °C for 60 minutes. Cyanidation of the as-obtained cakes was carried out for 24 hours at a concentration of 0.2% NaCN. To determine the concentration of elements in the solution and the content of solid phase components, the method of optical emission spectrometry with inductively coupled plasma by a Varian 730-ES Axial Eur (Australia) instrument was used. It was found that, following sulfuric acid autoclave (with the addition of sodium chloride) oxidation of the flotation concentrate, precious metals were practically absent in the solution. The total recovery of gold and silver from the flotation concentrate to the cake was ~ 99.9% and 99.3%, respectively. The recovery of Au by cyanidation of the obtained oxidized cakes in all experiments was 96.5-98.13%. It is shown that, the addition of sodium chloride in the process of autoclave oxidation of the studied material increased the extraction of Ag to 54.9-62.1% during cyanidation and reduced the consumption of NaCN by 24.69%. The addition of NaCl to the process of sulfuric acid autoclave oxidation of the gold-containing arsenic flotation concentrate obtained from ores mined at the Ikkizhelon deposit reduces (in comparison with the conventional processing scheme) the formation of argentojarosite AgFe₃(SO₄)₂(OH)₆ due to the formation of silver chloride forms. As a result, a high level of metal recovery is achieved during the subsequent cyanidation of the solid product of autoclave oxidation under reduced reagent consumption.

Ikkijelon deposit, refractory arsenic gold-containing flotation concentrate, autoclave oxidation, cyanidation, argentojarosite, sodium chloride, leaching