FeS2 Research Articles

Synergistic effect between sulfate-reducing bacteria and Shewanella algae on corrosion behavior of 321 stainless steel

Microbiologically influenced corrosion (MIC) caused by mixed microorganisms limits the application of 321 stainless steel (SS) in the field of ocean engineering. Therefore, in this paper, the synergistic effect of sulfate-reducing bacteria (SRB) and Shewanella algae (S. algae) on the corrosion behavior of 321 SS was studied by surface analysis and electrochemical measurements. The results revealed that riboflavin secreted by S. algae promoted the electron transfer between SRB and 321 SS by obtaining the electrons generated by the dissolution of metallic iron on the surface of SS and then transferring them to SRB, thus accelerating the MIC of 321 SS. Meanwhile, SRB gained electrons and reacted with SO42− to form HS−, which reacted with iron oxides in the Cr-rich passive film on the surface of SS to generate iron sulfides, providing thermodynamic and kinetic conditions for the formation of Cr6+. The formation of thermodynamically unstable Cr6+ destructed the passive film on the SS surface and promoted the development of pitting corrosion. The outcome provided a new perspective for studying the corrosion mechanism of extracellular electron transfer (EET)-MIC.

Visualization of nanoscale magnetic domain states in the asteroid Ryugu

In the samples collected from the asteroid Ryugu, magnetite displays natural remanent magnetization due to nebular magnetic field, whereas contemporaneously grown iron sulfide does not display stable remanent magnetization. To clarify this counterintuitive feature, we observed their nanoscale magnetic domain structures using electron holography and found that framboidal magnetites have an external magnetic field of 300 A m−1, similar to the bulk value, and its magnetic stability was enhanced by interactions with neighboring magnetites, permitting a disk magnetic field to be recorded. Micrometer-sized pyrrhotite showed a multidomain magnetic structure that was unable to retain natural remanent magnetization over a long time due to short relaxation time of magnetic-domain-wall movement, whereas submicron-sized sulfides formed a nonmagnetic phase. These results show that both magnetite and sulfide could have formed simultaneously during the aqueous alteration in the parent body of the asteroid Ryugu.

Optical Properties of Sputtered Iron Sulfide for Photonic Device Applications

Iron Pyrite is an earth-abundant, non-toxic, low-cost material commonly referred to as fool’s gold due to its golden-yellow appearance. It belongs to the family of transition metal dichalcogenides (TMDs) and gained fame as a potential solar material during the 70s and 80s. The reason was its suitable band gap and excellent absorption coefficient. However, the performance of pyrite never achieved a beneficial place among other materials and remained a mysterious path of research so far. With advanced technology and better characterization techniques and equipment available, the focus is again shifting towards exploring pyrite as a potential photovoltaic material which can compete with other materials, such as silicon, primarily in terms of cost. However, the true nature of pyrite and its application in photovoltaics cannot be adequately defined without looking deeply into its optical properties and interaction with light [1-3].Here in this work, we explored the photosensitivity of pyrite thin films at different thicknesses. These thin films were fabricated using an RF-powered sputtering method using a 99.9% FeS2 target. P-doped silicon and fused silica were used as substrates. The pressure and RF power were kept at 03 mTorrs and 70 watts, respectively, and the procedure took place at room temperature with an argon gas flow rate of ~24 cm3/min. The thickness was controlled by varying the sputtering time from 20 to 90 mins. As-prepared pyrite films were characterized through variable angle spectroscopic ellipsometry (VASE) and UV-vis spectrophotometer. An optical model was first developed for VASE in which the thin pyrite film showed light-absorbing characteristics (B-spline). Based on that model, the film thickness was determined. It was observed that the thickness of pyrite increased linearly with time, having grown to ~100 nm after 90 minutes of sputtering.UV-vis spectrophotometry was used to collect the transmission, reflectance and absorbance data for the films deposited onto a fused silica substrate. It was observed that the films showed very high absorbance in the UV range, and the absorbance tended to increase with the increase in thickness. The direct band gap was then calculated using absorbance data and building Tauc’s plot, which was observed to be around 2.25 eV.In conclusion, owing to its suitable properties and optical characteristics, iron pyrite opens many paths to scientists and researchers to explore its utilization not only in photovoltaics but also in other opto-electronic fields. However, further studies are also required to deeply understand its mechanism and capability. Nonetheless, high absorption of light in UV and visible range at very thin layers, suitable band gap and easy accessibility could be breakthrough parameters in near future for pyrite.

Freestanding Carbon Lattice-Based Composites for Lithium-Ion Batteries and Beyond

Advancements in technology in conjunction with rising concerns of global warming have led researchers to search for sustainable and environmentally friendly energy sources. Wind and solar are promising alternatives to fossil fuels; however, storage of these renewable energy sources poses a significant threat to their viability. Lithium-ion batteries (LIBs) are ideal candidates to offset their intermittent nature, functioning as an excellent storage medium. In addition, LIBs have been playing a key role in personal electronics (computers, cellphones, etc.) and are ubiquitous. LIBs in electric vehicles (EVs) are also rising exponentially. However, lithium-ion batteries still face many challenges. Their electrodes are currently made based on the conventional wet film coating fabrication process that utilizes a slurry containing active material coated onto current collectors. This slurry coating technology challenges the production of thicker electrodes with less inactive components. Directly increasing electrode mass loading using the traditional slurry coating fabrication process introduces unavoidable issues such as slowed kinetics and binder degradation. Freestanding electrodes are a great alternative as they eliminate the need for inactive components (i.e., binder, additive carbon, and current collector) and shorten the fabrication process. In addition, it preserves the microstructures of the electrodes and alleviates agglomeration. In this work, carbon microlattice templates are designed and fabricated through the use of 3D stereolithography, which allows for design flexibility of any shape or geometry, followed by pyrolysis to create hard carbon. These hard-carbon templates are then subjected to grow iron sulfide that serves as active material, which has a theoretical specific capacity higher than that of commercial graphite. The design utilizes controlled microchannels that facilitate ion transport through charging and discharging cycles and carbon networks for fast electron transfer. The composites show much improved electrochemical performance. These results demonstrate the potential for advancing the development of composite electrodes and shed light on the enormous potential for developing high-energy density batteries using 3D printing.

Characterizing and modeling hydrogen sulfide production in anaerobic digestion of livestock manure, agro‐industrial wastes, and wastewater sludge

AbstractHydrogen sulfide (H2S) is the most undesirable inorganic gas in biogas from anaerobic digestion (AD). However, H2S production in AD is complex and understanding of its processes is still limited. This study performed six controlled batch anaerobic co‐digestion experiments to investigate H2S production. Materials were obtained from four field anaerobic digester systems and co‐digestion feedstocks from agroindustry. An additional precipitation experiment was conducted to further examine H2S production dynamics. Digesters containing highly soluble, carbohydrate‐based wastes had a high H2S final specific production (FSP) value. Additionally, the FSP values were negatively correlated with the initial Fe(II):S ratios in the digester liquid of the batch tests. The precipitation experiment indicated that iron sulfide precipitation was preferred in the presence of an anaerobic community. The H2S production as a time series was successfully modeled using a generalized additive model (R2 > 0.82). This study revealed that sulfate, phosphorus, and iron concentrations are important predictors and potential inhibitors of H2S production in AD. Further examination of real‐time H2S modeling in AD is warranted.

Improvement of hydrogen permeation barrier performance by iron sulphide surface films

Improvement of hydrogen permeation barrier performance by iron sulphide surface films

Reduction and Adsorption of Hexavalent Chromium by Iron Sulfide Loaded Biochar: Isotherms, Kinetics and Thermodynamics

AbstractThe removal of noxious Cr(VI) from water has gained worldwide attention. In this study, biochar derived from macadamia nut shells (MHP) was embedded with iron sulfide (FeS) nanoparticles produced through a solid‐phase reduction of pyrite. The MHP‐FeS composite was evaluated for the adsorption of Cr(VI) and its subsequent reduction to Cr(III). The scanning electron microscope images revealed that the particles were of irregular shape, while the energy dispersive spectroscopy results showed the existence of Fe, S, O, and C atoms. X‐ray diffraction peaks at 2=29.8°, 33.7°, 43.7°, and 53.1° were characteristic of the formation of FeS nanoparticles. A maximum Cr(VI) adsorption capacity of 4.95 mg/g was obtained at pH 3, 60 min, and 25 °C. The higher correlation coefficient (R2>0.873) and lower residual standard error (RSE=1.43) values pointed to the adsorption process favoring Langmuir and pseudo‐second‐order models. As per thermodynamic reaction calculations, the remediation process was spontaneous and endothermic. With further optimization, this material could be a potential adsorbent and reductant for Cr(VI) in water.

Mackinawite nanozymes as reactive oxygen species scavengers for acute kidney injury alleviation

BackgroundIron sulfide nanomaterials have been successfully employed as therapeutic agents for bacterial infection therapy and catalytic-ferroptosis synergistic tumor therapy due to their unique structures, physiochemical properties, and biocompatibility. However, biomedical research and understanding of the biological functions of iron sulfides are insufficient, and how iron sulfide nanomaterials affect reactive oxygen species (ROS) in diseases remains unknown. Acute kidney injury (AKI) is associated with high levels of ROS, and therefore nanomedicine-mediated antioxidant therapy has emerged as a novel strategy for its alleviation.ResultsHere, mackinawite nanozymes were synthesized from glutathione (GSH) and iron ions (Fe3+) (denoted as GFeSNs) using a hydrothermal method, and then evaluated as ROS scavengers for ROS-related AKI treatment. GFeSNs showed broad-spectrum ROS scavenging ability through synergistic interactions of multiple enzymes-like and hydrogen polysulfide-releasing properties. Furthermore, both in vitro and in vivo experiments demonstrated that GFeSNs exhibited outstanding cytoprotective effects against ROS-induced damage at extremely low doses and significantly improved treatment outcomes in AKI.ConclusionsGiven the synergetic antioxidant properties and high biocompatibility, GFeSNs exhibit great potential for the treatment of AKI and other ROS-associated diseases.Graphical

Peroxymonosulfate Activation by Iron Sulfide Minerals for Degradation of Various Thiol Collectors in Mineral Processing Wastewater: Performance, Mechanism, and Structure–Activity Relationship

Peroxymonosulfate Activation by Iron Sulfide Minerals for Degradation of Various Thiol Collectors in Mineral Processing Wastewater: Performance, Mechanism, and Structure–Activity Relationship

Phase Control in the Synthesis of Iron Sulfides.

The identity and repeating arrangement of atoms determine the properties of all solids. Even combinations of two atoms can have multiple crystal structures of varying stoichiometries and symmetries with vastly different electronic and chemical behaviors. The conditions of existing bottom-up routes for achieving one phase over another are serendipitous, and the links among precursor reactivity, decomposition mechanism, temperature, and time are elusive. Our studies take a systematic approach to understanding the role that the precursor kinetic decomposition has in the synthesis of iron sulfides, isolating it from other mechanistic factors. The data suggest that phase determination in binary solids can be logically predicted through the consideration of the anion stacking and thermodynamic relationships between phases. Mapping these relationships allows for the rational synthetic targeting of metastable crystalline phases.

Multiple Sulfur Isotopes of Iron Sulfides From Thick Greigite‐Bearing Sediments Indicate Anaerobic Oxidation and Possible Leakages of Coastal Methane

AbstractMagnetic greigite may be a valuable indicator for methane emissions in the geological past, if its formation pathway and diagenetic environment can be unambiguously defined. Here, we investigate sulfur isotopic compositions of iron sulfides and ferrous iron concentrations of thick greigite‐bearing sediments (TGBSs) in the South Yellow Sea, a shallow marginal sea with strong methane emissions. For the first time, isotopically heavy iron sulfides (up to 28.7‰ in δ34S and 0.19‰ in Δ33S) and enrichments of ferrous iron in the TGBSs are observed. We interpret the data as indicating synchronic occurrences of anaerobic oxidation of methane coupled to sulfate and iron reductions, which occur in coastal methanic zones with limited sulfate availability and therefore probably imply leakages of methane. Consequently, we suggest that greigite is a promising geological indicator for tracing methane liberated from coastal sediments, accounting for ∼60% of the currently rising global marine methane budget.

Thermal Conversion of Nanocrystalline Metal Hydroxide Salts to Metal Carbides, Pnictides, Chalcogenides, and Halides.

A general procedure for synthesizing various inorganic compounds in a similar manner is required in the field of material chemistry. The use of solid-state reactive agents with inorganic precursors is a successful approach in this direction. In this study, organic-inorganic hybrid metal hydroxide salts (MHSs) were utilized to synthesize various inorganic compounds by a simple heat treatment method because they can be assumed to be "premixed" inorganic precursors and solid-state reactive agents. Comparative studies revealed that the nanocrystalline characteristics and coordination of the carboxylate of the synthesized MHSs enabled simultaneous dehydration of hydroxides and decomposition of carboxylates and subsequent formation of metals and metal sulfides. Manganese, iron, cobalt, nickel, and zinc sulfides, as well as nickel carbides, pnictides, chalcogenides, and halides were obtained using the same procedure. We believe that using nanocrystalline organic-inorganic hybrid MHSs as both inorganic precursors and organic reactive agents will be a simple and versatile way to prepare a wide variety of inorganic complex compounds.

Nitrate removal in iron sulfide-driven autotrophic denitrification biofilter: Biochemical and chemical transformation pathways and its underlying microbial mechanism

Iron sulfides-based autotrophic denitrification (IAD) is effective for treating nitrate-contaminated wastewater. However, the complex nitrate transformation pathways coupled with sulfur and iron cycles in IADs are still unclear. In this study, two columns (abiotic vs biotic) with iron sulfides (FeS) as the packing materials were constructed and operated continuously. In the abiotic column, FeS chemically reduced nitrate to ammonium under the ambient condition; this chemical reduction reaction pathway was spontaneous and has been overlooked in IAD reactors. In the biotic column (IAD biofilter), the complex nitrogen-transformation network was composed of chemical reduction, autotrophic denitrification, dissimilatory nitrate reduction to ammonium (DNRA) and sulfate reducing ammonium oxidation (Sulfammox). Metagenomic analysis and XPS characterization of the IAD biofilter further validated the roles of functional microbial communities (e.g., Acidovorax, Diaphorobacter, Desulfuromonas) in nitrate reduction process coupled with iron and sulfur cycles. This study gives an in-depth insight into the nitrogen transformations in IAD system and provides fundamental evidence about the underlying microbial mechanism for its further application in biological nitrogen removal.

Influence of magnetic stirrer speed on the properties of chemical bath deposited FeSxOy thin films

Iron sulfide has a high potential to replace existing solar cell materials due to its cost-effectiveness and non-toxic. Nonetheless, the reported efficiency is still low, attributed to quality issues of interface/bulk single film. Thus, it is essential to overcome those quality issues by focusing on material synthesis. To date, no reported works on the effects of magnetic stirrer speed in the chemical bath deposition (CBD) of iron sulfide film. Hence, this work elucidates the influence of magnetic stirrer speed (100–700 revolutions per minute-RPM) in the CBD on the properties of iron sulfide (iron-sulfide-oxide: FeSxOy) films. The magnetic stirrer speed was limited to below 1000 RPM because the high stirring speed contributed to weak molecule interaction between the FeSxOy cluster and the grown FeSxOy film. As a result, the solution's fast motion could easily break the molecule interaction between them (poor film adherence). The Scanning Electron Microscopy (SEM)-Energy Dispersive X-Ray Spectroscopy (EDX) showed the number/size of agglomerations relatively increased (reduction in uniformity) and the oxygen increased/sulfur decreased with an increase in the speed. The X-ray diffraction (XRD) patterns revealed that the pyrite transformed to goethite/hematite at a magnetic stirrer speed > 300 RPM. The film with 100 RPM produced a larger crystallite size. The Raman spectra exhibited no FeSxOy and pyrite phases for the film deposited at 700 RPM. The Hall Effect displayed that film at 100 RPM yields the highest carrier density of electrons (n-type). Films with 100 and 300 RPM showed absorption edges at a wavelength of around 400 nm, and their estimated bandgaps via the Tauc plot are 3.35–3.44 eV. Furthermore, a film with 100 RPM showed better quality and was suitable to be applied as a window layer (n-type) in thin film solar cells.

Association of Siderite with Iron Sulfides and Silicates in Rocks of the Mikheevskoe Cu(Mo,Au) Porphyry Deposit (Southern Urals)

Association of Siderite with Iron Sulfides and Silicates in Rocks of the Mikheevskoe Cu(Mo,Au) Porphyry Deposit (Southern Urals)

Difunctional Fluorescent Probes for Iron and Hydrogen Sulfide Detection Based on Diphenyl Derivative.

In order to better monitor the content of Fe3+ and H2S in the biological environment, two new fluorescent probes were designed and synthesized. With the addition of Fe3+, the strong fluorescence emission of two probes was significantly quenched due to the paramagnetic effect of Fe3+. With the further addition of S2-, the fluorescence intensity was quickly restored. Two probes showed high selectivity and strong sensitivity for the detection of Fe3+ and S2-, and the fluorescence intensity "ON-OFF-ON" was accompanied with the interaction process. At the same time, two probes displayed good anti-interference ability which was not interfered by the existence of other ions. In addition, two probes illustrated fast response time to Fe3+, S2- and small cytotoxicity to cells. Therefore, two probes can provide a potential ideal tool for detecting Fe3+ and H2S in organisms and the environment.

Utilizing biochar to decorate nanoscale FeS for the highly effective decontamination of Se(IV) from simulated wastewater

Selenium (Se) as an essential nutrient for human beings at trace concentrations, the allowable concentration for the human is only 40 μg/L. Iron sulfide (FeS) nanoparticles have been applied for excessive of selenium (Se) remediation in surface water and groundwater. In this study, FeS nanoparticles were anchored onto biochar (BC) to reduce agglomeration of FeS and prepared into the composite of FeS-BC by pyrolysis to economically and efficiently remove Se(IV) from simulated wastewater based on the excellent performance of FeS and the low cost of BC. Characterizations presented the uniform anchorage of FeS on the BC surface to prevent agglomeration. The results of batch experiments revealed that the removal of Se(IV) by FeS-BC nanomaterials significantly depended on the pH value, with the maximum removal of ∼174.96 mg/g at pH 3.0. A pseudo-second-order kinetic model well reflected the kinetic removal of Se(IV) in pure Se(IV) solution with different concentration, as well as the coexistence of K+, Ca2+, Cl-, and SO42- ions. The presence of K+ ions significantly inhibited the removal of Se(IV) with the increase of K+ ion concentration compared with the effect of the other three ions. SEM-EDS and XPS analyses indicated that the removal process was achieved through adsorption by surface complexation, and reductive precipitation of Se(IV) into Se0 with the electron donor of Fe(II) and S(-II) ions. The FeS-BC nanomaterial exhibited an excellent application prospect in the remediation of Se(IV).

Structural characterisation of iron sulfide tribofilms formed on carbon and stainless steels

AbstractThis study investigated tribofilm layers formed under boundary lubrication using a polysulfide additive on S45C and SUS304 steel surfaces. In the tribotests, the friction coefficient of the SUS304 disc fluctuated and increased more gradually in comparison to that of the S45C disc. The tribofilm on the S45C disc comprised the outermost and inner layers of FeS2 (pyrite) and FeS (troilite), respectively. Notably, all the tribofilm layers on the SUS304 disc surface contained pyrite. The tribofilm on the SUS304 disc was weakly crystalline in the outermost layer and thinner than that on the S45C disc. The poor formation of the tribofilm on the SUS304 disc was potentially caused by the unstable friction coefficient and scuffing.

Activation behavior of Cu0/FeS/N-graphene derived from waste soybean residue for peroxymonosulfate: Performance and mechanism

Nitrogen-enriched graphene grown on zero valent copper (Cu0) and loaded with iron sulfide (FeS) was prepared through a pyrolysis-liquid phase exfoliation process using waste soybean residue as the precursor biomass. Graphene-based catalyst (GBC) exhibits exceptional proficiency as a peroxymonosulfate activator, displaying a remarkable removal surpassing 90% of total petroleum hydrocarbons (TPHs) in 180 min. Reactive oxygen species were identified through masking experiments and electron paramagnetic resonance analysis in the Cu0/FeS/BC-900/PMS system. S(II) was the source of power for the conversion of Fe(III) to Fe(II), and it was also the reason for the continuous generation of SO4•− in the system. Density functional theory calculations revealed the active sites for adsorption and reaction. The presence of SO4•−, O2•−, and 1O2 species was attributed to the elongation of S–O and O–O bonds, as well as enhancement of electrons in sulfur and sp2 hybrid carbon atoms, respectively. The degradation of TPHs was ascribed to various radical and non-radical pathways of ROSs, with SO4•− serving as the primary oxidizing species. It was fascinating that the Cu0/FeS/BC-900/PMS system exhibited good resistance to inorganic anions and surfactants, and the treatment effect on real oilfield produced wastewater was satisfactory.

Detection of Iron Disulfide Materials in Geological Porous Media Using Spectral Induced Polarization Method

Summary Iron sulfide (FeS) scale is a known problem that can significantly impact oil and gas (O&G) production. However, current monitoring methods cannot detect the problem at early stages, not until it is too late for any meaningful remedial action. Spectral induced polarization (SIP) is an established geophysical method increasingly used in near-surface environmental applications. The unique characteristics of the SIP method, mainly the sensitivity to both bulk and interfacial properties of the medium, allow for the potential use as a characterization and monitoring tool. SIP is particularly sensitive to metallic targets, such as FeS, with direct implications for the detection, characterization, and quantification of FeS scale. In a column setup, various concentrations of pyrite (FeS2), a common form of FeS scale, within calcite were tested to examine the SIP sensitivity and establish qualitative and quantitative relationships between SIP signals and FeS2 properties. The concentration of FeS2 in the samples directly impacts the SIP signals; the higher the concentration, the higher the magnitude of SIP parameters. Specifically, the SIP method detected the FeS2 presence as low as 0.25% in the bulk volume of the tested sample. This study supports the potential use of SIP as a detection method of FeS2 presence. Furthermore, it paves the way for upcoming studies utilizing SIP as a reliable and robust FeS scale characterization and monitoring method.