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Microbial pre-treatment of double refractory gold ores

a biological process and gold ores technology, applied in the field of biological processes for recovering, can solve the problems of reducing the adsorption capacity of ores, reducing the quantity of gold, and the technique not working for ores, so as to reduce the selective activity or function

Inactive Publication Date: 2009-06-25
BARRICK GOLD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

[0015]In a first embodiment, a method is provided for treating refractory and double refractory gold-containing materials containing preg robbing carbon-containing components using a fungal agent to deactivate the preg robbing components. The fungal agent can be any suitable fungus, including a white rot fungus, with any Coriolaceae cellular organism being preferred and any Trametes cellular organism, such as Trametes versicolor (formerly Coriolus versicolor), being even more preferred. Before or after inoculation by the fungal agent, any refractory sulfide sulfur may be oxidized by a suitable technique, including roasting, atmospheric oxidation, pressure oxidation, and bio-oxidation. This embodiment can provide an economical and practical method to treat not only refractory but also double refractory ores.
[0018]The second and third embodiments can oxidize sulfidic sulfur at an alkaline pH, thereby reducing base consumption compared to bacterial oxidation of sulfidic sulfur.

Problems solved by technology

An additional problem in recovering gold from highly carbonaceous ores is that a significant quantity of the gold may have been adsorbed onto carbon during formation of the mineral deposit.
This technique, however, does not work for ores in which considerable quantities of gold are associated with the carbonaceous component.
Fuel oils exhibit a high affinity for carbonaceous material, particularly graphitic carbon, and adhere to hydrophobic surfaces of carbonaceous matter, thereby reducing its adsorptive capacity.
Because fuel oil is lighter than water it will not separate readily from the ore solids in the slurry after leaching.
This entrainment causes problems in subsequent operations, particularly liquid solid separation.
This process is generally, but not always, successful and depends upon the temperature of roasting.
Roasting may not be suitable or economical for ores that contain low levels of sulfide and high levels of carbonates, because the roasting is not autogenous
This process is not effective when the ore contains large amounts of carbonaceous matter.
Although pressure oxidation can partially deactivate the indigenous carbon, it is often unable to deactivate the preg robbing carbon in highly preg robbing ores.
The disadvantage of this patent is that the deactivation of preg robbing carbon is facilitated by addition of a chelating agent at very high dosages.
The preferred dosage range quoted, 0.5 g to 5 g EDTA / 20 g of ore or 25-250 kg EDTA per tonne of ore, is likely to be economically prohibitive.

Method used

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  • Microbial pre-treatment of double refractory gold ores

Examples

Experimental program
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Effect test

example 1

Baseline Cyanidation

[0066]Three different ore samples were employed to investigate the two stage bio-oxidation-bio-treatment process. The analysis is shown in Table 1. Sample A is a flotation concentrate. Samples B and C are run-of-mine ore samples.

TABLE 1Analysis of Ore SamplesAuAgCPreg-Sampleg / tg / t(graphitic) %S %Fe %As %Robbing %A76.16.007.0313.3015.301.1251.8B4.800.243.000.692.250.6268.9C2.910.102.363.796.361.4980.3

[0067]Conventional bottle roll cyanidation tests were conducted using (75% minus 75 micron ore), 0.5 g / l NaCN, at a pH of 10.5, for 24 hours. The results presented in Table 2 show that gold extractions for each sample were less than 22%. The sulfide and inorganic carbon contents of the ore and the low gold recovery by cyanidation indicate the samples are double refractory ores.

TABLE 2Results of Straight CyanidationSample% AuResidueConsumption, kg / tNo.Extractiong / t, AuNaCNCaOA21.559.745.623.85B17.73.951.841.42C15.02.471.741.37

example 2

Bio-Oxidation

[0068]The same feed samples employed in Example 1 were pre-treated using microbial bio-oxidation for the treatment of the refractory sulfidic component of the ore. The pretreatment consisted of grinding the ores to 90% minus 200 mesh (74 μm) and forming a slurry of about 20% solids in a 2 liter Erlenmeyer flask. The pH's of the slurries were adjusted to about pH 1.5 with sulfuric acid. The chemolithotrophic bacteria used for sulfide oxidation was a mixture of equal parts Acidithiobacillus ferrooxidans, Acidithiobacillus thiooxidans and Leptospirillum ferrooxidans. These chemolithotrophes were grown together to form a mixed culture and maintained in a medium containing about 0.5 g / l of (NH4)2SO4, K2HPO4, MgSO4.7H2O, 0.1 g / l KCl and 0.01 g / l CaNO3, 15.0 g / l FeSO4.7H2O, 1.0 g / l sulfur and 0.25 ml / l of Wolfe's solution. A 10% v / v microbial culture was added into the flask containing the pH adjusted slurry, and was agitated using an orbital shaker at 180 rpm for 14 days. At ...

example 3

Bio-Treatment of Carbonaceous Preg Robbing Material

[0070]The same feed samples used in Examples 1 and 2 were pre-treated with one stage microbial oxidation for treatment of preg robbing carbonaceous materials, followed by the conventional bottle roll cyanidation as described in Example 1. White rot fungus was used for deactivation of the carbonaceous material.

[0071]The white rot fungus, Trametes versicolor, was cultured in a medium containing Kirk's medium, agar and malt extract. The 1,000 ml Kirk's solution contained about 10.1 grams glucose, 0.44˜0.80 grams ammonium tartrate, 0.05 gram MnSO4.7H2O, 0.01 gram CaCl2.2H2O, 10 μml thiamine, 100 μml trace minerals and 2.92 gram 2.2 dimethylsucicinate supplement.

[0072]Pretreatment of the samples included grinding the ore to 90% minus 200 mesh (74 μm) and forming a slurry of 20% solids in a 2 liter Erlenmeyer flask. A 10% v / v microbial culture of Trametes versicolor was added into the flask containing the pH 9.5 slurry, which was agitated...

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Abstract

The present invention is directed to recovery of gold from refractory and double refractory ores using a fungal agent and / or culture media.

Description

CROSS REFERENCE TO RELATED APPLICATION[0001]The present application claims the benefits of U.S. Provisional Application Ser. Nos. 60 / 990,805, filed Nov. 28, 2007, and 61 / 088,928, filed Aug. 14, 2008, both entitled “Microbial Pre-Treatment of Double Refractory Gold Ores”, both of which are incorporated herein by this reference in their entireties.FIELD[0002]The invention relates generally to hydrometallurgical gold recovery processes and particularly to biological processes for recovering gold from refractory and double refractory materials.BACKGROUND[0003]In carbonaceous gold bearing ores, preg robbing occurs when active carbon, indigenous to the ore, complexes with the gold dissolved in cyanide leach solutions, thereby reducing gold recovery. “Preg robbing” is a generic term and can refer to any of several phenomenon related to an ore's Total Carbonaceous Material (TCM). Not only can preg robbing be caused by activated carbon, but also it can be caused either by high molecular weig...

Claims

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Application Information

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Patent Type & Authority Applications(United States)
IPC IPC(8): C22B11/00
CPCC22B1/06C22B1/11C22B11/08C22B3/24C22B11/04C22B3/18Y02P10/20
Inventor YEN, WAN-TAIAMANKWAH, RICHARD KWASICHOI, YEONUK
Owner BARRICK GOLD
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