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

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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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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Flotation of Carbonaceous Matter from a Double Refractory Gold Ore: The Effect of MIBC on Flotation Performance and Kinetics

Minerals ◽

10.3390/min11091021 ◽

2021 ◽

Vol 11 (9) ◽

pp. 1021

Author(s):

Sugyeong Lee ◽

Charlotte E. Gibson ◽

Ahmad Ghahreman

Keyword(s):

Bubble Size ◽

Gold Recovery ◽

Carbonaceous Matter ◽

Flotation Kinetics ◽

Pressure Oxidation ◽

Gold Ore ◽

Refractory Gold ◽

Flotation Performance ◽

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-Modification of Carbonaceous Matters in Gold Ore: Model Experiments Using Powdered Activated Charcoal and Cell-Free Extracts of Phanerochaete chrysosporium

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.1130.109 ◽

2015 ◽

Vol 1130 ◽

pp. 109-113

Author(s):

Kojo Twum Konadu ◽

Keiko Sasaki ◽

Grace Ofori-Sarpong ◽

Kwadwo Osseo-Asare ◽

Takashi Kaneta

Keyword(s):

Bond Cleavage ◽

High Ratio ◽

Carbonaceous Matter ◽

Gold Ores ◽

Aliphatic Compounds ◽

Model Experiments ◽

Refractory Gold Ores ◽

Refractory Gold ◽

Work Model ◽

C Nmr

The detailed mechanism behind the bio-decomposition of carbonaceous matter in refractroy goold ore byPhanerocheate chrysosporiumto facilitate improved cyanidation of gold is as yet undersdtood. To gain a better understanding of this mechanism, the present work model experiments using powdery activated carbon (PAC) and cell-free extracts ofP.chrysosporiumto simulate and focus on the biotransformation of carbonaceous matters in refractory gold ores. The results of solid characterization using SEM and XRD indicated a more non-uniform surface and smaller crystal sizes for PAC treaded with cell-free extracts for 72 hours. The significant decomposition of aromatic compounds into aliphatic compounds were observed in13C-NMR and FTIR results for the high ratio of cell-free extract volume to mass of PAC. This results support the theory that one of the fundamental mechanisms behind the bio-decomposition process is aromatic bond cleavage by biomolecules produced byP.chrysosporium.

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Pretreatment of Refractory Gold Ores Using Cell-Free Extracts of P. chrysosporium: A Preliminary Study

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.825.427 ◽

2013 ◽

Vol 825 ◽

pp. 427-430 ◽

Cited By ~ 3

Author(s):

Grace Ofori-Sarpong ◽

Kwadwo Osseo-Asare ◽

Ming Tien

Keyword(s):

Gold Recovery ◽

Active Components ◽

Gold Extraction ◽

Promising Alternative ◽

Gold Ores ◽

Refractory Gold Ores ◽

In Vitro Processing ◽

Refractory Gold

The fungus Phanerochaete chrysosporium has been proven to biotransform refractory gold ores, leading to increase in gold recovery. This transformation has been attributed to enzymes secreted by the microbe. This paper reports the findings of preliminary investigations aimed at assessing the use of hydrogen peroxide and cell-free extracts from the fungus, P. chrysosporium, to effect biotransformation of sulphidic refractory gold ores. The investigations show that the total dissolved arsenic, iron and sulphur in solution were up to 5.2 wt%, 0.9 wt% and 6.0 wt% respectively from flotation concentrate after 72 hrs of treatment. Analysis for sulphide sulphur in the residual solids of the gold concentrate indicated about 25 wt% oxidation within 24 hours of treatment. In general, cell-free decomposition of the samples did not increase beyond 24 hours of contact time, possibly due to exhaustion of the active components. Gold extraction by cyanidation increased by 24% after 24-hr treatment with the cell-free extracts. Comparatively, cell-free (in vitro) treatment recorded 66% overall gold recovery as against 61% for whole cell (in vivo) after 72 hours of treatment. These initial results indicate clearly that in vitro processing is a promising alternative to in vivo processing of refractory gold ores using P. chrysosporium.

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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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The Separation of Carbonaceous Matter from Refractory Gold Ore Using Multi-Stage Flotation: A Case Study

Minerals ◽

10.3390/min11121430 ◽

2021 ◽

Vol 11 (12) ◽

pp. 1430

Author(s):

Sugyeong Lee ◽

Charlotte E. Gibson ◽

Ahmad Ghahreman

Keyword(s):

Treatment Method ◽

Single Stage ◽

Carbonaceous Matter ◽

Flotation Concentrate ◽

Gold Ore ◽

Fine Grained ◽

Multi Stage ◽

Refractory Gold ◽

Pre Treatment ◽

Concentrate Grade

As a pre-treatment method of refractory gold ore, carbonaceous matter (C-matter) flotation was investigated with multi-stage flotation by rougher, scavenger, and cleaner stages. Different dosages of kerosene and MIBC (4-Methyl-2-pentanol) were applied and the optimum dosage was selected by testing in each flotation stage. With the combination of each stage, four circuit designs were suggested, which were a single-stage rougher flotation (R), rougher-scavenger flotation (R+S), rougher-scavenger-scavenger cleaner flotation (R+S+SC), and rougher-rougher cleaner-scavenger-scavenger cleaner flotations (R+S+RC+SC). The results indicated that the scavenger flotation increased C-matter recovery but reduced C-matter grade compared with single-stage rougher flotation. Cleaning of the scavenger flotation concentrate improved C-matter grade significantly, but reduced recovery slightly. Cleaning of the rougher flotation concentrate achieved overall improved selectivity in flotation. A combination of rougher-scavenger flotation followed by cleaning of both concentrates (R+S+RC+SC) resulted in 73% C-matter recovery and a combined cleaner concentrate grade of 4%; the final tailings C-matter grade was 0.9%, where the C-matter remaining in the tailings was locked, and fine grained. The results demonstrate the need for the multi-stage flotation of C-matter from refractory gold ore to achieve selective separation and suggested the potential of C-matter flotation as the pre-treatment for efficient gold production.

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