Recovery of gold from sulfide refractory gold ore: Oxidation roasting pretreatment and gold extraction

Carbonaceous sulfidic gold ores are commonly double refractory and thus require pretreatment before gold extraction. In this paper, the capacity of pre-bio-oxidation can simultaneously decompose sulfides or deactivate carbonaceous matters (CM) from a double refractory gold ore (DRGO) using pure cultures of A. ferrooxidans or L. ferrooxidans, and a mixed culture containing A. ferrooxidans and L. ferrooxidans was investigated. The results showed that direct thiourea leaching of the as-received DRGO yielded only 28.7% gold extraction, which was due to the encapsulation of sulfides on gold and the gold adsorption of CM. After bio-oxidation, thiourea leaching of the DRGO resulted in gold extraction of over 75–80%. Moreover, bio-oxidation can effectively reduce the adsorption of carbon to gold. XRD, SEM-EDS and FTIR analysis showed that many oxygen-containing groups were introduced on the surface of DRGO during bio-oxidation, while the C=C bond was cleaved and the O–C–O and C–N bonds were degraded, causing a decrease in active sites for gold adsorption. Moreover, passivation materials such as jarosite were formed on the surface of DRGO, which might reduce the affinity of CM for gold in solutions. In addition, the cleavage of the S–S band indicated that sulfides were oxidized by bacteria. This work allows us to explain the applicability of pre-bio-oxidation for degrading both sulfides and CM and increasing gold recovery from DRGO in the thiourea system.

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Biooxidation of a Refractory Gold Ore: Implications of Whole-Ore Heap Biooxidation

Solid State Phenomena ◽

10.4028/www.scientific.net/ssp.262.65 ◽

2017 ◽

Vol 262 ◽

pp. 65-69 ◽

Cited By ~ 1

Author(s):

Bo Wei Chen ◽

Jian Zhi Sun ◽

He Shang ◽

Biao Wu ◽

Jian Kang Wen

Keyword(s):

Pulp Density ◽

Tianshan Mountain ◽

Gold Mine ◽

Gold Extraction ◽

Gold Leaching ◽

Gold Ore ◽

Refractory Gold ◽

Gold Reserve ◽

Initial Ph ◽

South Tianshan

The Sawayardun Gold Mine, the first Muruntau type gold mine in China, was located in the south Tianshan Mountain, Xinjiang Province. The gold reserve was 127 t with an average gold grade of 2.36 g/t. Due to the high content of arsenic and antimony, the traditional flotation-roasting-cyanidation process was not suitable. The direct cyanidation gold extraction for the raw ore was 44.70 %. Thus, biooxidation experiments in shaker flasks were conducted for this ore. The optimum conditions were obtained as inoculation volume 10 %, initial pH 1.7, pulp density 15 %, temperature 33 °C, leaching time 10 days, with the arsenic oxidation rate of 75.12 %. Then the biooxidation residues were test for gold leaching using NaCN, green gold leaching agent and thiourea. After 24 h leaching rate at pulp density of 33%, gold leaching agent dosage of 2 kg/t ore, the gold extraction for NaCN, green gold leaching agent and thiourea were 91.50 %, 86.23 % and 91.09 %, respectively. The high gold extraction showed a bright future for the whole-ore heap biooxidation of this refractory gold ore.

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