scholarly journals Analysis of the Microbial Community Associated with a Bioprocess System for Bioremediation of Thiocyanate- and Cyanide-Laden Mine Water Effluents

2015 ◽  
Vol 1130 ◽  
pp. 614-617 ◽  
Author(s):  
Robert J. Huddy ◽  
Rose Kantor ◽  
Wynand van Zyl ◽  
Robert P. van Hille ◽  
Jillian F. Banfield ◽  
...  
Keyword(s):  
Microbial Culture ◽  
Process Optimisation ◽  
Gold Extraction ◽  
Mixed Microbial Culture ◽  
Metabolic Potential ◽  
Gold Ores ◽  
Refractory Gold Ores ◽  
Refractory Gold ◽  
Key Microorganisms ◽  
Activated Sludge Processes

Gold extraction by cyanidation from refractory gold ores results in the formation of thiocyanate-and cyanide-contaminated wastewater effluents that must be treated before recycle or discard. Activated sludge processes, such as ASTERTM, can be used for biodegradation of these effluent streams. The destruction of these compounds is catalyzed by a mixed microbial culture, however, very little is known about the community composition and metabolic potential of the thiocyanate-and cyanide-degrading microorganisms within the community. Here we describe our on-going attempts to better understand the key microorganisms, within the ASTERTM bioprocess, that contribute to the destruction of thiocyanate and cyanide, and how this knowledge relates to further process optimisation.

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

2013 ◽  
Vol 825 ◽  
pp. 427-430 ◽  
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.

scholarly journals Analysis of Microbial Communities Associated with Bioremediation Systems for Thiocyanate-Laden Mine Water Effluents

2017 ◽  
Vol 262 ◽  
pp. 601-604
Author(s):  
Robert J. Huddy ◽  
Fadzai Kadzinga ◽  
Sumayah F. Rahman ◽  
Rose Kantor ◽  
Jillian F. Banfield ◽  
...  
Keyword(s):  
Effluent Water ◽  
Community Members ◽  
Gold Ores ◽  
Rational Development ◽  
Refractory Gold Ores ◽  
Refractory Gold ◽  
Key Microorganisms ◽  
Sulphur Species

During the processing of refractory gold ores, cyanide (CN-) and residual sulphur species react to form an effluent stream containing thiocyanate (SCN-) and residual CN-. The release of SCN- and CN- containing effluent water to the environment is prohibited, necessitating effective treatment prior to discharge and/or reuse of contaminated plant water. Biologically mediated effluent remediation processes have been developed for commercial use, to remediate SCN- containing effluents, with the aim of enabling recycling of process water and improving the quality of effluent water prior to disposal. Bioremediation processes to treat these effluents rely on a complex consortium of microorganisms to metabolise the SCN- resulting in the production of ammonium that is in turn removed by conversion to nitrite and subsequent denitrification. Increasingly, genomic methods are being used to investigate processes in wastewater treatment to identify key microbial species and, thereby, inform the rationale design and operation of these bioremediation systems. The microbial ecology of laboratory-based SCN- degrading bioprocesses have been investigated, using genome resolved metagenomics, to provide detailed information on the community composition and metabolic profile of abundant microbial community members. Our on-going research is focused on developing a greater understanding of the heterotrophic and autotrophic populations of microorganisms within the SCN- degrading community as well as the role of the component members in SCN- destruction. We are interested in the formation of microbial biofilm and the spatial distribution of key microorganisms within the resulting biofilm communities. This information is being used to inform further rational development of SCN- degradation processes for treatment of contaminated wastewater effluents.

Biooxidation of High-Sulfur Refractory Gold Concentrate by Ferroplasma acidiphilum

2014 ◽  
Vol 997 ◽  
pp. 642-645 ◽  
Author(s):  
He Shang ◽  
Jian Kang Wen ◽  
Biao Wu
Keyword(s):  
Pulp Density ◽  
Cyanide Leaching ◽  
Gold Extraction ◽  
Pressure Oxidation ◽  
Gold Ores ◽  
Refractory Gold Ores ◽  
Refractory Gold ◽  
Initial Ph ◽  
Pre Treatment ◽  
Number Of Bacteria

Gold ores can be categorized into two types-free milling and refractory. Free milling ores are easy to treat. Gold in such ores is recovered by gravity separating techniques or direct cyanidation. Refractory gold ores, on the contrary, are difficult to treat and require pre-treatment prior to cyanidation, such as roasting, pressure oxidation, fine grinding and biooxidation. A number of bacteria are used in biomining but the prominent ones that are known to be involved in the oxidation of sulfide ores include Thiobacillusferrooxidans, Thiobacillus thiooxidans and Leptospirillum ferrooxidans. In this study, the gold concentrate was biooxidized in a reactor at 45°C over a period of 10 days at a pulp density of 15% solids using a culture of already grown Ferroplasma acidiphilum. The initial pH was adjusted to 1.5 with sulfuric acid, resulted in 85.39 % oxidation of sulfur from initial grade of 33.83 %, and the slag rate was 68.52 %. The products of sulfide biooxidation were leached at a pulp density of 20 %(v/w) for 24 h at pH 11. The pH was adjusted using CaO and cyanide strength was 10 kg/t, we got a gold extraction of 90.71 %, which ncreaseed 80.09 % compared with the direct cyanide leaching.

scholarly journals Refractory gold ores and concentrates part 1: mineralogical and physico-chemical characteristics

2019 ◽  
pp. 1-13 ◽  
Author(s):  
Richmond K. Asamoah ◽  
Massimiliano Zanin ◽  
Jason Gascooke ◽  
William Skinner ◽  
Jonas Addai-Mensah
Keyword(s):  
Chemical Characteristics ◽  
Gold Ores ◽  
Refractory Gold Ores ◽  
Physico Chemical ◽  
Refractory Gold

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

Metals ◽  
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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