Untitled

Lin, Hsiu-Li; Say, Wen C.

doi:10.1023/a:1003578728263

Cited by 42 publications

(20 citation statements)

References 9 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…All of the above is in agreement with previous studies of pyrite oxidation under acidic conditions, proposing as an initial oxidation process the transformation of pyrite to sulfur-rich or metal deficient layers (e.g., Fe 1−x S 2 , with S n 2− ), which precedes the formation of S 0 and soluble sulfur species (e.g., S 2 O 3 2− , SO 4 2− ), and in most cases, iron precipitates (e.g., FeOOH) (Hamilton and Woods 1981;Mycroft et al 1990;Kelshall et al 1999;Lin and Say 1999;Cruz et al 2001;Todd et al 2003). However, the reactivity of S n 2− and S 0 species on pyrite and other MS has been rarely investigated (Mikhlin et al 1998;Thomas et al 1998;Schaufuss et al 1998;Nava et al 2008;Meléndez et al 2010).…”

Section: Electrochemical Oxidation Of Unmodified Pyrite Surfacesmentioning

confidence: 99%

Influence of the sulfur species reactivity on biofilm conformation during pyrite colonization by Acidithiobacillus thiooxidans

Lara

García‐Meza

Cruz

et al. 2011

Appl Microbiol Biotechnol

View full text Add to dashboard Cite

Massive pyrite (FeS₂) electrodes were potentiostatically modified by means of variable oxidation pulse to induce formation of diverse surface sulfur species (S(n)²⁻, S⁰). The evolution of reactivity of the resulting surfaces considers transition from passive (e.g., Fe(1-x )S₂) to active sulfur species (e.g., Fe(1-x )S(2-y ), S⁰). Selected modified pyrite surfaces were incubated with cells of sulfur-oxidizing Acidithiobacillus thiooxidans for 24 h in a specific culture medium (pH 2). Abiotic control experiments were also performed to compare chemical and biological oxidation. After incubation, the attached cells density and their exopolysaccharides were analyzed by confocal laser scanning microscopy (CLMS) and atomic force microscopy (AFM) on bio-oxidized surfaces; additionally, S(n)²⁻/S⁰ speciation was carried out on bio-oxidized and abiotic pyrite surfaces using Raman spectroscopy. Our results indicate an important correlation between the evolution of S(n)²⁻/S⁰ surface species ratio and biofilm formation. Hence, pyrite surfaces with mainly passive-sulfur species were less colonized by A. thiooxidans as compared to surfaces with active sulfur species. These results provide knowledge that may contribute to establishing interfacial conditions that enhance or delay metal sulfide (MS) dissolution, as a function of the biofilm formed by sulfur-oxidizing bacteria.

show abstract

Section: Electrochemical Oxidation Of Unmodified Pyrite Surfacesmentioning

confidence: 99%

Influence of the sulfur species reactivity on biofilm conformation during pyrite colonization by Acidithiobacillus thiooxidans

Lara

García‐Meza

Cruz

et al. 2011

Appl Microbiol Biotechnol

View full text Add to dashboard Cite

show abstract

“…Figure shows the cyclic voltammetry (CV) profiles of pyrites at different pHs. Similar peaks detected under different experimental conditions indicate analogous reaction pathways . The peaks of A 1 , A 2 , A 3 , C 1 , and C 2 associated with redox reactions of pyrites are listed in Table S4.…”

Section: Results and Discussionmentioning

confidence: 55%

“… The CV curves under pH-neutral condition are different from those under acidic condition. At pH 7.0, a two-step oxidation model has been proposed by Lin and Say: (1) oxidation of FeS 2 to Fe 2+ and the passive layer (S 0 , FeS n , and Fe 1– x S 2 ) (eq S2) at the A 2 peak (0.1 V) triggers passivation of the pyrite electrode; and (2) further oxidation of S 0 and S 2 2– to SO 4 2– via eqs S3 and S4 at the A 3 peak (0.6–0.8 V). , As the passive layer is broken through (>0.3 V) with increasing potentials, the current densities (I) increase. It is also noted that the current densities under pH-neutral condition are apparently lower than those under acidic condition in the potential region of −0.6 to 0.8 V, suggesting the slower oxidation rates under pH-neutral condition (Figure b).…”

Section: Results and Discussionmentioning

confidence: 99%

See 1 more Smart Citation

Reactivity Comparison of Different Ni(II)-Pyrites during Oxidative Dissolution under Acidic and pH-Neutral Conditions

Liang

Song

Liu

et al. 2019

ACS Earth Space Chem.

View full text Add to dashboard Cite

Natural pyrite has a strong ability to immobilize Ni(II) impurities. However, the differences in the oxidation reactivity between Ni(II)-adsorbed pyrites [Py*-Ni(II)] and Ni(II)-structurally incorporated pyrites [Py-Ni(II)] are still not clearly understood. In this study, Ni(II)-free pyrite (Py-free), Py*-Ni(II), and Py-Ni(II) were prepared, and their oxidation reactivity were compared. Our results show that Ni(II) can be successfully incorporated into the crystalline structure of Py-Ni(II) by replacing structural Fe(II) with the formation of sulfur defects on the surface of Py-Ni(II). The oxidation reactivity of different pyrites depends on how Ni(II) is immobilized in pyrite and follows the order of Py-0.08 > Py-0.02 > Py-free > Py*-Ni(II) [Py-0.02 and Py-0.08 are named according to the Ni(II):Fe(II) molar ratios in the starting material for the synthesis of Py-Ni(II)], indicating that structurally incorporated Ni(II) enhances the oxidation rate of pyrite, whereas adsorbed Ni(II) does the opposite. Differences in the electrochemical properties also indicate that structurally incorporated Ni(II) enhances the electron-transfer rates at the Py-Ni(II) surface, thus increasing the oxidation rates of pyrite. Variations in H 2 O 2 concentrations confirm that the high electron-transfer rates induced by structurally incorporated Ni(II) enhance the reaction rates between dissolved oxygen and the pyrite surface, producing H 2 O 2 at pHs 2.5 and 7.0. The presence of Fe(III)-S(-II) defects also significantly contributes to the production of H 2 O 2 . Variations of cumulative •OH indicate that structurally incorporated Ni(II) improves the production of •OH at pHs 2.5 and 7.0. The significantly higher concentrations of •OH than those of H 2 O 2 at pH 2.5 indicate that •OH plays an important role in pyrite oxidation under acidic condition. The comparable concentrations of H 2 O 2 and •OH at pH 7.0 suggest that H 2 O 2 , •OH, and even Fe(IV) formed between pyrite and H 2 O 2 contribute to pyrite oxidation under pH-neutral condition.

show abstract

“…MAE surfaces were oxidized by applying anodic potential pulses (E a ) ranging from 0.615 to 1.215 V vs. SHE during 3600 s in neutral-alkaline solutions (refer to "Solution to simulate weathering process" section). Selected potentials were chosen according to voltammetric results presented in "Electrochemical study of pristine arsenopyrite" section, to monitor complete and selective oxidation processes covering low and highly active electrochemical responses for SM (e.g., Lin and Say 1999;Kelsall et al 1999;Almeida and Giannetti 2003). Electrochemical oxidation consists of applying multiple energetic conditions which favor the formation of different arsenopyrite species on the electrode surface.…”

Section: Electrochemical Studymentioning

confidence: 99%

Arsenopyrite weathering under conditions of simulated calcareous soil

Lara¹,

Velázquez²,

Vazquez‐Arenas³

et al. 2015

Environ Sci Pollut Res

View full text Add to dashboard Cite

Mining activities release arsenopyrite into calcareous soils where it undergoes weathering generating toxic compounds. The research evaluates the environmental impacts of these processes under semi-alkaline carbonated conditions. Electrochemical (cyclic voltammetry, chronoamperometry, EIS), spectroscopic (Raman, XPS), and microscopic (SEM, AFM, TEM) techniques are combined along with chemical analyses of leachates collected from simulated arsenopyrite weathering to comprehensively examine the interfacial mechanisms. Early oxidation stages enhance mineral reactivity through the formation of surface sulfur phases (e.g., S n (2-)/S(0)) with semiconductor properties, leading to oscillatory mineral reactivity. Subsequent steps entail the generation of intermediate siderite (FeCO3)-like, followed by the formation of low-compact mass sub-micro ferric oxyhydroxides (α, γ-FeOOH) with adsorbed arsenic (mainly As(III), and lower amounts of As(V)). In addition, weathering reactions can be influenced by accessible arsenic resulting in the formation of a symplesite (Fe3(AsO4)3)-like compound which is dependent on the amount of accessible arsenic in the system. It is proposed that arsenic release occurs via diffusion across secondary α, γ-FeOOH structures during arsenopyrite weathering. We suggest weathering mechanisms of arsenopyrite in calcareous soil and environmental implications based on experimental data.

show abstract

Untitled

Cited by 42 publications

References 9 publications

Influence of the sulfur species reactivity on biofilm conformation during pyrite colonization by Acidithiobacillus thiooxidans

Influence of the sulfur species reactivity on biofilm conformation during pyrite colonization by Acidithiobacillus thiooxidans

Reactivity Comparison of Different Ni(II)-Pyrites during Oxidative Dissolution under Acidic and pH-Neutral Conditions

Arsenopyrite weathering under conditions of simulated calcareous soil

Contact Info

Product

Resources

About