Bioleaching Potential of Indigenous Bacterial Consortia from Gold-Bearing Sulfide Ore of Ta Nang Mine in Vietnam

Abstract

To date, bioleaching using bacterial consortia is widely regarded as an eco-friendly alternative to the traditional mining approaches due to its cost-effectiveness, feasibility, and sustainability.In the present study, for the first time, gold-bearing sulfide ore collected at Ta Nang mine, Vietnam was mineralogically characterized and subjected to bioleaching trial using indigenous bacterial consortia. The ore contains arsenopyrite, pyrite, galena, sphalerite, and chalcopyrite, of which the major metals were iron (4.78%), arsenic (1.73%), lead (0.43), and zinc (0.33%). After enrichment, a total of 19 ironand sulfur-oxidizing bacteria were isolated and classified into six distinct genera including three previously described Bacillus, Pseudomonas, Acidithiobacillus, and three firstly reported heterotrophic Glutamicibacter, Providencia, and Stenotrophomonas from gold ore origin. Moreover, an autotrophic Acidithiobacillus sp. TNG6.3, sharing a 16S rRNA sequence of 95.1% identity with the closest sequence of the type strain A. caldus KU, represented a novel candidate species. The establishment of bioleaching utilizing enriched bacteria from gold ore consequently led to the removal of Ag (99.1%), Zn (37.9%), As (37.0%), and Fe (32.2%) from ore after 21 days of treatment, respectively. The present findings highlighted the potential of acidophilic bacteria originated from gold ores for extending applications in bioleaching of metals in Vietnam.

Acidithiobacillus ferrooxidans Leaching of Silica-Sulfide Gold Ores from May-Hibey Deposits, Tigray, Ethiopia

“…pH values for leaching efects were performed in the presence of A. ferrooxidans to study the change in pH during the leaching of metal ions of iron and gold from the sulfde ore. Bacterial bioleaching takes place in an acidic environment with pH values of 1.5-2.0 where most metal ions remain in solution. Lowering the pH value rapidly decomposes the gold ore as a sulfate solution [5,21,[23][24][25]. A. ferrooxidans iron oxidants efectively oxidize sulfur and sulfdes but grow at high pH values where metal ions are not retained in solution [5,16,21,[23][24][25].…”

“…Bioleaching is typically a pretreatment process that involves the mobilization of metal cations from sulfde ores through biological processes including acidifcation, oxidation, and complexation, in addition, to mainly being used for the extraction of copper, cobalt, nickel, zinc, uranium, and gold ores from its sulfde ores [1][2][3]. Recently, precious metal mining production has increased signifcantly due to the development of advanced technology and global demands [1,2], and new approaches will be needed to recover metals from low-grade ore deposits and mine tailings as a part of economic circular before further chemical treatment [4,5]. Te processes of mining gold, one of the most valuable and economical metals, produce large amounts of waste that still contain large amounts of valuable substances and in some cases, the toxic chemicals cyanide and thiocyanide, often buried as landfll or waste near the mining areas [5].…”

“…Recently, precious metal mining production has increased signifcantly due to the development of advanced technology and global demands [1,2], and new approaches will be needed to recover metals from low-grade ore deposits and mine tailings as a part of economic circular before further chemical treatment [4,5]. Te processes of mining gold, one of the most valuable and economical metals, produce large amounts of waste that still contain large amounts of valuable substances and in some cases, the toxic chemicals cyanide and thiocyanide, often buried as landfll or waste near the mining areas [5]. It is important to develop better methods to avoid the use of these chemicals when extracting gold from its ores [6,7].…”

“…Te environmental conditions of bioleaching are characterized by low pH values and high concentrations of reduced sulfur and iron compounds; in these ores, rocks and acid drainage waters from the mine represent prime places of iron-oxidizing Acidithiobacillus species [4,7,[9][10][11]. Bioleaching is a promising and revolutionary method that uses environmentally friendly technologies, which are useful for the mining industry as well as for environmental detoxifcation [1][2][3][4][5]. Bacterial leaching may be enhanced by an increase in bacterial population.…”

“…Te best-studied leaching bacteria are the genus Acidithiobacillus, which includes sulfur-oxidizing species and sulfur-and ferrous-oxidizing bacteria and which are common inhabitants of extremely acidic ecological sites, rich metals, has been extensively used in the bioleaching of concentrates, sludge, and metal-sulfde ores [13,14]. Despite its high bioleaching efciency, the genus Acidithiobacillus is often found at low densities in indigenous microbial consortia, which is still not fully understood and, conversely, Acidithiobacillus ferrooxidans bacterium is most commonly found in bioleaching [2,3,5]. Iron-and sulfur-oxidizing Acidithiobacillus ferrooxidans bacterium is capable of oxidizing the sulfur matrix before extracting cyanide, which contains gold particles encapsulated in gold-bearing sulfde ore [13,14].…”