Intensification of copper leaching from heaps using biological oxidation

The article presents the results of experiments intended to leach copper from ore heaps of complex mineral composition biochemically. The processing of such heaps is complicated due to the presence of oxidized copper minerals among significant fragments of sulfide minerals and iron-calcium silicates. This factor does not allow to perform standard sulfuric acid leaching effectively without the use of additional oxidation catalysts, or to apply beneficiation methods for that kind of raw materials. Use of A. Ferrooxidans bacteria adapted to the composition of the copper dump, as a bio-catalytic agent, significantly accelerates the leaching process and increases the copper recovery degree into the productive solution

Intensification of copper leaching from heaps using biological oxidation

The article presents the results of experiments intended to leach copper from ore heaps of complex mineral composition biochemically. The processing of such heaps is complicated due to the presence of oxidized copper minerals among significant fragments of sulfide minerals and iron-calcium silicates. This factor does not allow to perform standard sulfuric acid leaching effectively without the use of additional oxidation catalysts, or to apply beneficiation methods for that kind of raw materials. Use of A. Ferrooxidans bacteria adapted to the composition of the copper dump, as a bio-catalytic agent, significantly accelerates the leaching process and increases the copper recovery degree into the productive solution

A study of the biohydrometallurgical method for extracting gold from flotation tailings

This paper shows the results of the comparative study of efficiency of gold extraction methods from technogenic flotation tails by agitation cyanidation and biooxidation followed by leaching. A representative sample of flotation tails was taken at gold extraction plant of Altyntau Kokshetau LLP. Experimentally, an increase in the efficiency of leaching gold from flotation tails during preliminary bacterial oxidation was found. By biochemical leaching, 72 % was extracted, which is 7 % more than using expensive sodium peroxide and 10 % more than using the traditional method of cyanidation

Research of biochemical gold recovery method using high-arsenic raw materials

This article contains the results of experiments to recover gold from complex mineral raw materials containing more than 15 % arsenic. Laboratory tests showed that standard cyanidation recovers only 26,4 % of gold into the solution. Additional oxidizing reagents used increase the leaching efficiency and enable to recover more than 40 % of gold during subsequent cyanidation. The efficiency has been established for replacement of cyanide with thiourea and thiosulfate solutions. 79,5 %, i.e. the maximum recovery rate, was found in the experiment with preliminary oxidation with T. Ferrooxidans, a bacterial culture, followed by leaching with a thiourea solution

Redox processes in sulfide minerals biochemical solutions reactions

Rebellious gold-bearing ores contains among the most abundant minerals as arsenopyrite and pyrites, such natural minerals as chalcopyrite (CuFeS2) and sphalerite (ZnS) impacting the redox processes behavior in these ores leaching. The anodic current maximum (peak) was identified on the sphalerite polarization curve that evidently proves a single-stage process. Curves within –1.5–0 V potentials range are not tending to reach an ultimate current with increasing potentials. Only a log-linear increasing of anodic current with increased values of potentials density defining redox process rate was found. The effects of sphalerite bacterial pretreatment on its oxidation were identified. Sphalerite was treated through 80 days exposure to alkali solution (рН = 9–9.5) containing 108–1010 cells/cm3 of Pseudomonas aureofaciеns bacteria. Polarization current density at anodic oxidation of sphalerite treated with solution of рН = 9 within 0.3–2.0 V potentials range increased by 20 % as compared to an untreated sphalerite. Temperature effects on sphalerite electrochemical oxidation with solution of рН = 9 were studied for 25–55°С temperatures. Sphalerite oxidation rates substantially increased at 0.5–2.0 V (by 1.7–2.3 times) with temperature increasing from 25°С to 55°С. Values of effective energy of anodic sphalerite oxidation process activation were determined by temperature-kinetic method (through lni –1/Т dependence) at рН=9. Study data proved that the oxidation process rates within 0.6–2.0 V potentials range are limited by electrochemical reaction rates (49.0–52.8 kJ/mole). Oxidation proceeded at diffusion-kinetic conditions (20.9–32.4 kJ/mole) within 0.4–0.5 V potentials range. Thus, increased chalcopyrite and sphalerite oxidation rates were identified for alkali-cyanide solutions through pretreatment with Pseudomonas aureofaciеns bacterial solution

Determination of optimal pressure parameters for the system of pulp microaeration dispersants in column flotation

The article presents the results of experiments intended to beneficiate gold-bearing mineral raw materials by column flotation with the use of micro aeration of pulp through a dispersant system. The influence of the pressure level in the pressure system of dispersants within the range from 202,65 to 1013,25 KPa was studied during the experiments. It was found that the parameter of 607,95 KPa enables to achieve the optimal balance of the precious metal mass yield and the content in the concentrate, with a final gold recovery of 87 %