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Understanding the Surfaces and Crystal Growth of Pyrite FeS2
Abstract and Figures
Pyrite is a common sulfide mineral, which has arisen early interest by its euhedral shape and by its metallic glow similar to gold. However, it is only in our century that we began to understand pyrite crystal growth, considering the thermodynamic and kinetic aspects of crystal formation as a function of temperature and concentration of the elements present in the medium. This article reports an analysis by molecular mechanics of 11 surfaces associated to observed morphologies in order to explain the growth of natural and synthesized minerals. The lowest surface and attachment energies (respectively 1.04 J/m² and -20.3 kJ/mol) were obtained for the (001) plane, indicating that it is the most stable surface and that kinetic growth also preferentially occurs on this plane. Less known properties, such as crystal striations along the <100> directions, are also discussed. © 2018 Universidade Federal de Sao Carlos. All rights reserved.
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... 较大争议。Hung [6] 、Corinne [23] 等分析认为黄铁矿(110)面表面能大于(111)面；然而，Xian [17] 、 Leeuw等 [24] 、Wen [25] 等学者的研究结果显示，黄铁矿的 (110) [26,27] ，并将其与本文计算结果进行对比，如图5b所示。 ...
... Pyrites occurred mainly as framboids and isolated crystals, consistent with the results found in other reducing marine environments [33,58,60], with crystals showing a mainly octahedral habit and generally being found in soils with high sulfur contents [61]. Crystals of a cubic habit were only observed in IM, which could be associated with the higher Fe content in soils of this area [62]. ...
Soil properties and components in mangrove ecosystems influence their geochemical processes and services. Despite the extensive mangrove areas present in Brazil, few studies focusing on these themes are under development. In this sense, this work aimed to investigate the spatial variability in soil attributes and composition, the geochemistry of Fe, and the isotopic characteristics of organic matter in mangroves in Baía de Todos os Santos (Cacha Prego, Ponta Grossa, Ilha de Maré, Pitinga), which constitutes Brazil’s second largest bay. The soils investigated showed spatial and temporal changes affecting their properties (pH, Eh) and composition (TOC, Fe fractions), as well as clear spatial changes in the redox potential values (+30–+188 mV), with higher values in PT. Soil textures ranged from predominantly sandy (CP, PT, PG: sand, >70%) to a finer granulometry (IM: sand, 33–64%). These characteristics influenced Fe partitioning and organic matter content, with higher TOC and pyrite values observed in IM (FeS2: 2720–9233 mg kg−1; TOC: 4.4–6.6%) and lower sulfide values found in PT, mainly in the dry season (FeS2: 85–235 mg kg−1). The soil δ13C and N/C ratios seem to suggest a mixed origin of organic matter.
We study the local electronic structure of an equimolar-multimetal solid solution of high-entropy metal disulfide (Fe,Co,Ni,Cu)S2 and its parent compounds MS2 (M=Fe, Co, Ni, and Cu) using x-ray absorption spectroscopy (XAS). The Fe, Co, and Ni L2,3-edge absorption spectra indicate a divalent metal state both in (Fe, Co, Ni, Cu)S2 and its parent compounds, except for the Cu L2,3-edge absorption spectra. The Cu L2,3-edge spectra of CuS2 and (Fe,Co,Ni,Cu)S2 show satellites, which rule out the divalent Cu but can be analyzed as a combination of monovalent and trivalent copper states. The L2,3-edge XAS spectral analysis with charge-transfer multiplet cluster model calculations was carried out for (Fe,Co,Ni,Cu)S2 and its parent compounds. The estimated electronic parameters indicate a negative charge-transfer energy for the parent compounds and high-entropy compound (with the Ni L edge in the high-entropy compound being an exception), which corresponds to a p-p type lowest energy excitation in the extended Zaanen-Sawatzky-Allen phase diagram. The analysis shows that the charge-transfer energy Δ decreases and the on-site Coulomb energy Udd increases systematically from Fe to Cu. The results suggest that in the high-entropy compound compared to the parent compounds, the hybridization strengths are weaker for Fe 3d−S 3p and Co 3d−S 3p and stronger for Ni 3d−S 3p and Cu 3d−S 3p bonds. This behavior is consistent with the longer Fe-S and Co-S bond distances and shorter Ni-S and Cu-S bond distances in the high-entropy compound compared to the parent compounds. The results indicate modifications in the structural lattice parameters of the high-entropy compound are reflected in the electronic structure and provides evidence for the so-called cocktail effect in the high-entropy compound.
This research relies on microscopy and digital microscopy observations and spectral analysis techniques: Raman spectroscopy, laser-induced breakdown spectroscopy (LIBS) and particle-induced X-ray emission (PIXE), to recover part of the lost identity of two pyrite (FeS 2) cones. Conserved in Paris, at the Muséum National d'Histoire Naturelle (MNHN), the first one is registered MIN000-3519 in the collection of the mineralogist René-Just Haüy, the second one, registered 105.504, is a stray object. All information related to its origin would have been lost during the move (1837-1841) of the collections from the former Cabinet du Jardin du Roy to the new earth science gallery of the MNHN. Our historical research (Gendron, 2022) revealed that the first one, described as an "Inca mirror", was shipped from Peru around 1760 by the botanist Joseph de Jussieu to his brothers Antoine and Bernard. They also confirmed that these two pyrite cones are archaeological objects of the Ecuadorian Cañari culture (500-1500 AD). Raman analyses conducted on the MIN000-3519 specimen confirm that it was developed on a quartz para-genesis. While the faces observation of no.105.504 reveals that the crystal used for its cut was triglyph twinned, a crystal which must have been cubic or dodecahedral pentagonal. The observation of the technical traces in digital microscopy makes it possible to reconstruct a process of similar cut for the two "mirrors" and help to discover red mineral clusters in the bottom of the crystalline gaps. LIBS analyses were also applied to get complementary information on in-depth element distribution, such as Fe and Al, in order to understand the stratigraphy inside the cracks. Finally, PIXE measurements do not confirm that these two pyrites come from the same deposit. But, this analytical technique is hampered by the nature of the element Fe which offers multiple and random bonding possibilities during the crystallization of iron minerals and by the lack of a comparative sample in the Parisian mineralogic collections.
Different types of iron ore and pyrite were used to craft a wide variety of reflective artifacts in pre-Columbian Mesoamerica, including “mirrors,” pectorals, necklaces, and dental inlays, among others. In the Maya region, most of these have only been visually assessed, without using analytical techniques. Consequently, our understanding of the diversity of raw materials used in artifact production has been limited. This article presents preliminary results from a pilot study aiming to identify the raw materials used in the manufacture of different reflective objects from a small sample of finds from the sites of La Corona and Cancuen, located in Guatemala, through the use of scanning electron microscopy with EDS detectors (SEM-EDS), energy-dispersive X-ray fluorescence (EDXRF), X-ray diffraction (XRD), and Raman spectroscopy. Although further analyses are needed to confirm the representativeness of the sample, these results indicate the use of hematite and goethite (iron oxides), but not pyrite (iron sulfide). This study also shows how improved knowledge of raw material use can elicit previously unknown patterns of distribution and exchange, and highlight patterns of inter- and intrasite variability in the production, use, and exchange of reflective objects over time in the Maya region throughout the Classic period.
Paragenetic interpretation, defined as the process of constraining the order in which the phases (minerals) comprising a rock formed, are fundamental in all disciplines requiring a detailed mapping of the genetic relationships between the investigated crystal(s) and their surrounding phases. Ore geology, geochronology, petrological and fluid inclusion studies are underpinned by a robust interpretation of the paragenesis. Without this understanding, the interpretation of the analytical data will be greatly restricted and potentially wrong. Textural mapping is particularly useful for studying phases precipitated into hydrothermal veins because the host many metallic ore deposits. Understanding the paragenesis and the association of ore minerals feeds directly into the approach taken towards exploration, mining operation and ore processing. Apart from ore deposits, precipitation of hydrothermal phases occurs in any setting where hot fluids interact with rock or sediment (e.g. CCS storage; geothermal facilities). This paper summarises the principles for developing a robust paragenetic interpretation, including demonstrating the practical workflow via a case study from a sulphide-bearing vein near Loch Tay, Scotland. The principles and the workflow outlined in this paper are applicable to any discipline and route of investigation that necessitates a robust understanding of the relationships of the phases in a rock.
In the paper, the pyrite FeS2 with novel nanostructures had been obtained via ethanolamine (ETA)/water binary system. This method provided a uniform and homogenous environment for the nucleation and growth of the FeS2. When only pure water was used as the reaction solvent, the marcasite FeS2 with hollow sphere structure was achieved, and then transformed into pyrite phase with rod-like structure piled up by nanoparticles with the increase of reaction time. Moreover, cubic, flake-like, and two kinds of tetrakaidecahedron structures were obtained via the adjustment of volume ratio of ETA and H2O. The formation mechanism from flower-like amorphous to kinds of morphologies of pyrite FeS2 crystals was analyzed through the time-dependent controlled experiments. The Raman spectra of samples with different morphologies were investigated, which were consistent with the XRD analysis. The studies of optical properties indicated that the morphologies had a great influence on the absorption properties. This paper provided a very simple and low cost method to control the morphologies of FeS2 crystals, which would be of great potential for the synthesis of other metal chalcogenides and lay the foundation for the development of the solar cell.
It is desirable to develop electrode materials for advanced rechargeable batteries with low cost, long life, and high-rate capability. Pyrite FeS2 as an easy-obtained natural mineral has been already commercialized in primary lithium batteries, but encountered problems in rechargeable batteries with carbonate-based electrolytes due to the limited cycle life caused by the conversion-type reaction (FeS2 + 4M → Fe + 2M2S (M=Li or Na)). Herein, we demonstrate that FeS2 microspheres can be applied in room-temperature rechargeable sodium batteries with only intercalation reaction by simultaneously selecting compatible NaSO3CF3/diglyme electrolyte and tuning the cut-off voltage to 0.8 V. A surprising high-rate capability (170 mAh•g1 at 20 A•g1) and unprecedented long-term cyclability (~90% capacity retention for 20000 cycles) has been obtained. We suggest that a stable electrically conductive layer-structured NaxFeS2 was formed during cycling, which enables the highly reversible sodium intercalation and deintercalation. Moreover, 18650-type sodium batteries were constructed exhibiting a high capacity of ~4200 mAh (corresponding to 126 Wh•kg−1 and 382 Wh•L−1) and a capacity retention of 97% after an initial 200 cycles at 4 A during charge/discharge. This shows that the production of rechargeable sodium batteries with FeS2 microspheres is viable for commercial utilization.
Earth-abundant iron pyrite (FeS2) shows great potential as a light absorber for solar cells and photodetectors due to their high absorption coefficient (>10(5) cm(-1)). In this paper, high-quality phase-pure and single crystalline pyrite nanocrystals were synthesized via facile, low-cost, and environment friendly hydrothermal method. The molar ratio of sulphur to iron and the reaction time play a crucial role in determining the quality and morphology of FeS2 nanocrystals. X-ray diffraction and high-resolution transmission electron microscopy confirm that phase-pure and single crystalline pyrite nanocrystals can be synthesized with high sulphur to iron molar ratio and sufficient reaction time. For the first time, a crystalline nanogap pyrite photodetector with promising photocurrent and UV-visible photoresponse has been fabricated. This work further demonstrates a facile route to synthesize high-quality FeS2 nanomaterials and their potential in optoelectronic applications.
Pyrite (FeS2) material is attractive for applications in solar cells, lithium batteries and hydrogen production because of its abundant, non-toxic features as well as the extraordinary electrical and optical properties. Pyrite (FeS2) nanocrystals (NCs) were synthesized via hot injection method and the crystalline structure and morphologic evolution of pyrite NCs were investigated. We found that pyrite (FeS2) NCs were generated from mackinawite FeS0.94 nanosheets template. The initial anisotropic growth of NCs was dominated by oriented attachment mechanism. Ostwald ripening growth become obvious as time progressed, resulting in facetted NCs. In accordance to the analysis of high-resolution transmission electron microscopy (HRTEM) images and surface free energies, we found that the attachment occur between the opposite facets with high surface free energies including (210)-Fe and (210)-2S as well as (001)-Fe and (001)-2S. The attachment could also happen through a “point-contact” followed by inter-particle growth. This study sheds the light to better understand the growth mechanism of anisotropic pyrite FeS2 NCs and provides a mean to rationally manipulate the morphology of pyrite FeS2 NCs in order to achieve desired physical properties for efficient photovoltaic conversions.
Electronic waste (e-waste) contains a wide range of elements, many of which are highly toxic to environmental and human health. On the other hand e-waste represents a significant potential source of valuable metals. This study used microbial oxidation of pyrite to generate a biolixiviant. Its efficiency in the dissolution of metals from printed circuit boards (PCBs) was evaluated as well as the effects of metals and PCB concentrations on microbial activity. The addition of elemental metals (Cu, Cr, Ni, Sn, Zn) had an immediate inhibitory effect on pyrite oxidation, though leaching recovered after a period of adaptation. Bioleaching was inhibited initially by the addition of 1 % (w/v) ground PCB, but recovered rapidly, whereas pulp densities of ≥ 5 % had sustained negative impacts on culture activity and viability. The loss of culture viability meant that only abiotic copper dissolution occurred at ≥ 5 % PCB. Final copper recoveries declined with increasing PCB pulp density. The relatively high content of elemental iron caused a lag period in copper solubilisation possibly due to displacement reactions. Leptospirillum ferriphilum was primarily responsible for pyrite oxidation, and most affected by both the pure metals (particularly Ni and Cu) and PCB.
Iron pyrite is an earth-abundant and inexpensive material that has long been interesting for electrochemical energy storage and solar energy conversion. A large-scale conversion synthesis of phase-pure pyrite nanowires has been developed for the first time. Nano-pyrite cathodes exhibited high Li-storage capacity and excellent capacity retention in Li/pyrite batteries using a liquid electrolyte, which retained a discharge capacity of 350 mAh g(-1) and a discharge energy density of 534 Wh kg(-1) after 50 cycles at 0.1 C rate.