Limited role of sessile acidophiles in pyrite oxidation below redox potential of 650 mV

Liu, Chang; Jia, Yan; Sun, Hanwen; Tan, Qiaoyi; Niu, Xiaopeng; Leng, Xuekun

doi:10.1038/s41598-017-04420-2

Cited by 14 publications

(11 citation statements)

References 42 publications

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“…With the reduction of Fe 3+ to Fe 2+ and SO 4 2− to S 2− , the Eh decreased significantly, while the control and lime addition treatments were quite stable, suggested the lesser reducing reaction. It was reported that below the Eh of about 450 mV (vs. Ag/AgCl), pyrite oxidation was negligible even it was fully covered by bioleaching microbes on the surface [31]. So, in all the four treatments, the pyrite oxidation was very slow as their Eh were all lower than 450 mV; thus the pH in the column was not decreased, showing the effectiveness of the anaerobic condition to inhibition the pyrite oxidation.…”

Section: Physiochemical Properties In Different Treatmentsmentioning

confidence: 88%

Competitive Growth of Sulfate-Reducing Bacteria with Bioleaching Acidophiles for Bioremediation of Heap Bioleaching Residue

Phyo

Jia

Tan

et al. 2020

IJERPH

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Mining waste rocks containing sulfide minerals naturally provide the habitat for ironand sulfur-oxidizing microbes, and they accelerate the generation of acid mine drainage (AMD) by promoting the oxidation of sulfide minerals. Sulfate-reducing bacteria (SRB) are sometimes employed to treat the AMD solution by microbial-induced metal sulfide precipitation. It was attempted for the first time to grow SRB directly in the pyritic heap bioleaching residue to compete with the local ironand sulfur-oxidizing microbes. The acidic SRB and iron-reducing microbes were cultured at pH 2.0 and 3.0. After it was applied to the acidic heap bioleaching residue, it showed that the elevated pH and the organic matter was important for them to compete with the local bioleaching acidophiles. The incubation with the addition of organic matter promoted the growth of SRB and iron-reducing microbes to inhibit the iron-and sulfur-oxidizing microbes, especially organic matter together with some lime. Under the growth of the SRB and iron-reducing microbes, pH increased from acidic to nearly neutral, the Eh also decreased, and the metal, precipitated together with the microbial-generated sulfide, resulted in very low Cu in the residue pore solution. These results prove the inhibition of acid mine drainage directly in situ of the pyritic waste rocks by the promotion of the growth of SRB and iron-reducing microbes to compete with local iron and sulfur-oxidizing microbes, which can be used for the source control of AMD from the sulfidic waste rocks and the final remediation. drainage (AMD) through oxidation [1][2][3]. Drainage from mining activities is often acidic and also frequently associated with high concentrations of heavy metals and metalloids. It is considered to be one of the most important sources for heavy metal contamination in the environment [4].When exposed to the atmosphere, sulfide minerals in the waste rocks are oxidized under water and oxygen, and then generate acid, make the environment of the waste rock acidified. The dissolution of sulfide minerals relies to a large extent on the chemical and microbiological processes caused by the reaction of the oxidant Fe 3+ and the activity of natural iron-and sulfur-oxidizing microorganisms [5]. The Fe 3+ is more aggressive and effective than O 2 for pyrite oxidation in acidic conditions [6][7][8][9]. Iron sulfide minerals such as pyrite usually provide the source of oxidant Fe 3+ . Pyrite usually acts as the most important source of AMD, since it is the most abundant sulfide minerals on earth [10].SRB bacteria are usually employed to treat an AMD solution by growing SRB in the AMD solution, through the microbial process of metal-and sulfate-reducing, and producing alkalinity, and attenuating the movement of metals by the precipitation of sulfide minerals [11,12]. These processes are exploited in ex situ treatment of AMD after it comes out from the rocks [13][14][15]. However, a few researchers have used the SRB directly to treat the acid-generating waste rocks in situ to inhibit the ox...

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Section: Physiochemical Properties In Different Treatmentsmentioning

confidence: 88%

Competitive Growth of Sulfate-Reducing Bacteria with Bioleaching Acidophiles for Bioremediation of Heap Bioleaching Residue

Phyo

Jia

Tan

et al. 2020

IJERPH

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“…Our experimental conditions included high redox potential due to the high ratio of the predominant redox couple Fe 3+ /Fe 2+ as the result of sustained bacterial activity. Liu et al (2017) noted the importance of the difference between the redox and rest potentials for pyrite dissolution to soluble iron and sulfate. Our data showed how the different redox conditions established with the Eh and Es values at the same initial pH resulted in sulfate formation in the presence of bacteria or elemental sulfur formation in the abiotic control without bacteria.…”

Section: Discussionmentioning

confidence: 99%

“…Electrochemical study of the oxidation of a crystal pyrite electrode detected sulfate formation, together with S 8 , at the electrode potential at 0.7–0.8 V and pH 2 (Tu et al, 2017b). Liu et al (2017) studied the oxidation of pyrite electrode by sessile acidophiles. The bacteria had limited impact on pyrite dissolution at and below the redox potential of 650 mV (near the rest potential), but an increasing redox potential (e.g., spontaneously at the uncontrolled potential) resulted in pyrite dissolution.…”

Section: Introductionmentioning

confidence: 99%

Can Sulfate Be the First Dominant Aqueous Sulfur Species Formed in the Oxidation of Pyrite by Acidithiobacillus ferrooxidans?

et al. 2018

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According to the literature, pyrite (FeS2) oxidation has been previously determined to involve thiosulfate as the first aqueous intermediate sulfur product, which is further oxidized to sulfate. In the present study, pyrite oxidation by Acidithiobacillus ferrooxidans was studied using electrochemical and metabolic approaches in an effort to extend existing knowledge on the oxidation mechanism. Due to the small surface area, the reaction rate of a compact pyrite electrode in the form of polycrystalline pyrite aggregate in A. ferrooxidans suspension was very slow at a spontaneously formed high redox potential. The slow rate made it possible to investigate the oxidation process in detail over a term of 100 days. Using electrochemical parameters from polarization curves and levels of released iron, the number of exchanged electrons per pyrite molecule was estimated. The values close to 14 and 2 electrons were determined for the oxidation with and without bacteria, respectively. These results indicated that sulfate was the dominant first aqueous sulfur species formed in the presence of bacteria and elemental sulfur was predominantly formed without bacteria. The stoichiometric calculations are consistent with high iron-oxidizing activities of bacteria that continually keep the released iron in the ferric form, resulting in a high redox potential. The sulfur entity of pyrite was oxidized to sulfate by Fe3+ without intermediate thiosulfate under these conditions. Cell attachment on the corroded pyrite electrode surface was documented although pyrite surface corrosion by Fe3+ was evident without bacterial participation. Attached cells may be important in initiating the oxidation of the pyrite surface to release iron from the mineral. During the active phase of oxidation of a pyrite concentrate sample, the ATP levels in attached and planktonic bacteria were consistent with previously established ATP content of iron-oxidizing cells. No significant upregulation of three essential genes involved in energy metabolism of sulfur compounds was observed in the planktonic cells, which represented the dominant biomass in the pyrite culture. The study demonstrated the formation of sulfate as the first dissolved sulfur species with iron-oxidizing bacteria under high redox potential conditions. Minor aqueous sulfur intermediates may be formed but as a result of side reactions.

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“…Among the factors that affect pyrite dissolution, the solution Eh is the most critical and is directly correlated with rate. Below the redox potential of 650 mV (vs. SHE), pyrite is barely oxidized, even though microbes adhere on the pyrite surface [31,32]. It was reported that the pyrite oxidation was 5 times faster with the elevation of redox potential by 100 mV [33].…”

Section: Microbial Community and Activitymentioning

confidence: 99%

Industrial Heap Bioleaching of Copper Sulfide Ore Started with Only Water Irrigation

et al. 2021

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Sulfuric acid solution containing ferric iron is the extractant for industrial heap bioleaching of copper sulfides. To start a heap bioleaching plant, sulfuric acid is usually added to the irrigation solution to maintain adequate acidity (pH 1.0–2.0) for copper dissolution. An industrial practice of heap bioleaching of secondary copper sulfide ore that began with only water irrigation without the addition of sulfuric acid was successfully implemented and introduced in this manuscript. The mineral composition and their behavior related to the production and consumption of sulfuric acid during the bioleaching in heaps was analyzed. This indicated the possibility of self-generating of sulfuric acid in heaps without exogenous addition. After proving by batches of laboratory tests, industrial measures were implemented to promote the sulfide mineral oxidation in heaps throughout the acidifying stages, from a pH of 7.0 to 1.0, thus sulfuric acid and iron was produced especially by pyrite oxidation. After acidifying of the heaps, adapted microbial consortium was inoculated and established in a leaching system. The launch of the bioleaching heap and finally the production expansion were realized without the addition of sulfuric acid, showing great efficiency under low operation costs.

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Limited role of sessile acidophiles in pyrite oxidation below redox potential of 650 mV

Cited by 14 publications

References 42 publications

Competitive Growth of Sulfate-Reducing Bacteria with Bioleaching Acidophiles for Bioremediation of Heap Bioleaching Residue

Competitive Growth of Sulfate-Reducing Bacteria with Bioleaching Acidophiles for Bioremediation of Heap Bioleaching Residue

Can Sulfate Be the First Dominant Aqueous Sulfur Species Formed in the Oxidation of Pyrite by Acidithiobacillus ferrooxidans?

Industrial Heap Bioleaching of Copper Sulfide Ore Started with Only Water Irrigation

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