Enhanced Gold Recovery from Alkaline Pressure Oxidized Refractory Gold Ore After its Mechanical Activation Followed by Thiosulfate Leaching

The use of alkaline pressure oxidation to pretreat refractory gold ore often results in insufficient gold recovery (<60%) in downstream thiosulfate leaching. To improve gold recovery, flotation was considered for the separation of carbonaceous matter (C-matter). In this study, the effect of MIBC on C-matter flotation was investigated to understand the role of the frother in bubble and froth formation and on flotation kinetics. MIBC dosages between 30 and 150 g/t were used in combination with 500 g/t of kerosene as a collector. The results showed that the recovery and selectivity of C-matter were improved with increasing MIBC dosages. Improved selectivity at higher MIBC dosages was attributed to faster C-matter recovery as bubble size decreased to the critical coalescence concentration (CCC) and to changes to the foam structure. Analysis of flotation kinetics showed that the flotation rate increased as the MIBC dosage increased due to the decreasing bubble size and the reduced induction time caused by the interaction between the collector and the frother. The results of this study explain the role of MIBC in C-matter flotation and can be used as a design basis for scavenger-cleaner flotation testing. Overall, the results show the potential for flotation as a means to improve gold recovery in thiosulfate leaching through the removal of C-matter.

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Modelling pyrite oxidation in a refractory gold ore stockpile to estimate the gold recovery via direct cyanide leaching – A case study

Minerals Engineering ◽

10.1016/j.mineng.2021.107177 ◽

2021 ◽

Vol 173 ◽

pp. 107177

Author(s):

Hang Wang ◽

Peter A. Dowd ◽

Chaoshui Xu

Keyword(s):

Pyrite Oxidation ◽

Gold Recovery ◽

Cyanide Leaching ◽

Gold Ore ◽

Refractory Gold

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Bio-Oxidation of a Double Refractory Gold Ore and Investigation of Preg-Robbing of Gold from Thiourea Solution

Metals ◽

10.3390/met10091216 ◽

2020 ◽

Vol 10 (9) ◽

pp. 1216

Author(s):

Rui Xu ◽

Qian Li ◽

Feiyu Meng ◽

Yongbin Yang ◽

Bin Xu ◽

...

Keyword(s):

Mixed Culture ◽

Active Sites ◽

Gold Recovery ◽

Ftir Analysis ◽

Gold Extraction ◽

Gold Ores ◽

Gold Ore ◽

Thiourea Solution ◽

Refractory Gold ◽

Pure Cultures

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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Comparison of gold recovery from refractory gold ore by different processes

Advances in Energy Equipment Science and Engineering ◽

10.1201/b19126-530 ◽

2015 ◽

pp. 2739-2742

Author(s):

Guiying Zhou ◽

Biao Wu ◽

Wenjuan Li ◽

Yongsheng Song

Keyword(s):

Gold Recovery ◽

Gold Ore ◽

Refractory Gold

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Thiosulfate Leaching of Middle-Refractory Gold Ore with Ferricyanide as Oxidant

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.548.309 ◽

2012 ◽

Vol 548 ◽

pp. 309-314

Author(s):

Fu Ting Zi ◽

Xian Zhi Hu ◽

Wen Bin Zhang ◽

Su Qiong He

Keyword(s):

Dissolution Rate ◽

Iron Hydroxide ◽

Pure Gold ◽

Gold Dissolution ◽

Gold Ore ◽

Base Solution ◽

High Dissolution Rate ◽

Refractory Gold ◽

The Stability ◽

Thiosulfate Leaching

In order to decrease the consumption of lixiviant, study on dissolution of pure gold and middle-refractory gold ore using a novel thiosulfate leaching system with ferricyanide as oxidant was carried out. The results showed that the advantage of the novel system is that the thiosulfate consumption is negligible though the potential of ferricyanide is much higher than that of traditional cupric ammine complex. And compared to the ferric oxalate system, novel system could be used at relatively high pH condition which benefit to the stability of thiosulfate because ferricyanide can’t transfer to iron hydroxide in base solution. It is unlikely that very high dissolution rate of gold can be obtained using an air saturated thiosulfate- ferricyanide system without thiourea catalyst. However gold dissolution rate was increased with the increasing of concentration of ferricyanid in 5 mmol/L to 30mmol/L. When 0.1mmol/L thiourea was presented, the dissolution of gold approximately 1.5 times faster than that of in the absence of thiourea. Leaching of middle-refractory gold ore show that both of the consumption of thiosulfate and leaching rate was decreased compare to the traditional copper–ammonia thiosulfate system. Thiourea is not stable in base solution, but it was found that gold dissolution rates can be increased with a little thiourea ,the mechanism is still unclear.

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Study on the Gold Recovery of Double Refractory Gold Ore Concentrate by Biological Oxidation Pretreatment

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.1130.379 ◽

2015 ◽

Vol 1130 ◽

pp. 379-382 ◽

Cited By ~ 4

Author(s):

Wen Jie Luo ◽

Hong Ying Yang ◽

Zhe Nan Jin

Keyword(s):

Oxidation Process ◽

Packing Problem ◽

Gold Recovery ◽

Cyanide Leaching ◽

Bacterial Oxidation ◽

Gold Ore ◽

Leaching Process ◽

Element Carbon ◽

Refractory Gold ◽

Leaching Experiments

In this paper, Bacterial oxidation-cyanide leaching experiments were carried out and the carbonaceous substances composition of carbonaceous gold concentrate was been studied. The elemental composition was 9.73 % iron, 9.66 % sulfur, 4.84 % arsenic and 13.23 % carbon which element carbon and organic carbon was 12.11wt.% and 0.06 wt.% respectively. The main carbonaceous substances were elemental carbon which the morphology was dense and similar to graphite. The removal rates of iron, arsenic and sulfur were achieved to 93.78%, 97.02% and 95.54% respectively by bioleaching, and the gold recovery of oxidation residue reached 92.34% by carbon inhibited cyanide leaching process. The sulfide minerals packing problem could be effectively solved by bacterial oxidation process and greatly increased the gold recovery. So the bacteria oxidation and carbon inhibited leaching process is applicable to the carbonaceous gold ore.

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Significance of Acid Washing after Biooxidation of Sulfides in Sequential Biotreatment of Double Refractory Gold Ore from the Syama Mine, Mali

Minerals ◽

10.3390/min11121316 ◽

2021 ◽

Vol 11 (12) ◽

pp. 1316

Author(s):

Cindy Cindy ◽

Ryotaro Sakai ◽

Diego M. Mendoza ◽

Kojo T. Konadu ◽

Keiko Sasaki

Keyword(s):

Gold Recovery ◽

Carbonaceous Matter ◽

Acid Attack ◽

Gold Ores ◽

Gold Ore ◽

Positive Effects ◽

Acid Washing ◽

Washing Process ◽

Refractory Gold ◽

Mineralogical Compositions

Environmentally friendly pretreatment of double refractory gold ores (DRGO) to improve gold recovery without emitting pollutant gas is challenging. Sequential biotreatment, including iron-oxidizing microorganisms to decompose sulfides, followed by the enzymatic decomposition of carbonaceous matter, was recently developed. The effect of acid washing by 1 M HCl for 24 h between two bioprocesses was evaluated using a real double refractory gold ore from the Syama mines, Mali, which includes 24 g/t of Au and 5.27 wt % of carbon with a relatively higher graphitic degree. The addition of the acid washing process significantly improved gold recovery by cyanidation to yield to 84.9 ± 0.7% from 64.4 ± 9.2% (n = 2). The positive effects of acid washing can be explained by chemical alteration of carbonaceous matter to facilitate the accessibility for lignin peroxidase (LiP) and manganese peroxidase (MnP) in cell-free spent medium (CFSM), although the agglomeration was enhanced by an acid attack to structural Fe(III) in clay minerals. Sequential treatment of DRGO basically consists of the oxidative dissolution of sulfides and the degradation of carbonaceous matter prior to the extraction of gold; however, the details should be modified depending on the elemental and mineralogical compositions and the graphitic degree of carbonaceous matter.

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