Pentlandite Research Articles

Occurrence and enrichment mechanism of Co in Fe-Ti oxide deposits: A case study of the world-class Panzhihua deposit in SW China

The Panzhihua deposit is the one of the largest Fe-Ti oxide deposits in the world and holds 10,000 to 20,000 tons of Co resource with grades varying from 0.01 % to 0.02 %. Detailed field geological investigations and major and trace element analyses, were conducted to reveal occurrence of Co and Ni and their enrichment mechanism. Co and Ni are predominantly enriched in massive magnetite ores (average 277 ppm Co, 281 ppm Ni) of the Lower zone in the Panzhihua intrusion. Co occurs as three types:(1) independent minerals such as cobalt pentlandite (Co3.96-6.98Ni0.85-2.62Fe1.36-2.53S8) and linnaeite (Co1.65-1.88Ni0.99-1.05Fe0.15-0.37S4); (2) isomorphic state substituting for Fe, Ni and/or Mg in pentlandite (Co0.53-0.55Ni4.57-4.65Fe3.80-3.83S8), Co-bearing pyrite (Co0.09-0.12Fe0.89-0.93S2), pyrrhotite (Co 111–1964 ppm), olivine (Co 161–184 ppm), pyrite (Co 3–272 ppm), titanomagnetite (Co 57–181 ppm), ilmenite (Co 57–110 ppm), clinopyroxeneclinopyroxene (Co 34–40 ppm); (3) microscopic sulfide inclusions in chalcopyrite. Sulfide segregation and crystallization are principal mechanisms of Co enrichment. The results offers valuable insights into understanding Co mineralization, resource assessment, and comprehensive utilization in magmatic Fe-Ti oxide deposits.

Rational Phase Control in the Synthesis of Cobalt Sulfides.

A library of substituted thioureas was used as sulfur reagents in the synthesis of cobalt sulfides. The substitution pattern of the thioureas controls the decomposition rate of precursors into sulfur monomers and thereby aids in the exploration of decomposition kinetics on cobalt sulfide-phase formation, including phase-pure jaipurite (CoS), cobalt pentlandite (Co8S9), linnaeite (Co3S4), and cattierite (CoS2). We hypothesize that the available transformation pathways between phases during synthesis are dictated by the approximate ccp or hcp stacking of the sulfur lattice. Through gaining a complex understanding of the cobalt sulfide crystal system, phase-pure syntheses of all four naturally occurring crystalline structures in the cobalt sulfide system were achieved.

Internal and External Cultivation Strategy toward Efficient Electrochemical Oxygen Evolution in Cobalt Pentlandite

Internal and External Cultivation Strategy toward Efficient Electrochemical Oxygen Evolution in Cobalt Pentlandite

Synergistic effect customized for cobalt pentlandite (Co,Ni,Fe)9S8 accelerated charge transfer toward highly efficient oxygen evolution reaction

The oxygen evolution reaction (OER) is one of the core reaction modules of important renewable energy technologies with applications in water splitting, metal-air (oxygen) cells and regenerative fuel cells. However, OER catalysts are forced to operate with a significant intrinsic overpotential and inefficient charge transfer due to the adsorption energy scaling balance between the reaction intermediates. It is critical to develop an understanding of structure-activity relationship of catalysts, determine the speed control steps and improve catalytic activity. In this work, cobalt pentlandite (Co,Ni,Fe)9S8 (CNFS) electrocatalysts were successfully prepared by combining the earth-abundant transition metal elements Co, Ni and Fe into a single structure. Benefiting from the structure, nanoflower morphology, and the synergistic effect among the three elements, the optimized sample requires an overpotential of only 335 mV to drive a current density of 50 mA cm–2 under alkaline conditions. The experimental results establish a composition-structure-function relationship, and the density functional theory results further indicate that the Fe sites bind more moderately to the intermediates and the electron synergistic effect occurs dynamically during the OER cycle reaction. This work not only provides a very promising catalyst candidate for efficient OER processes but also highlights the superiority of the cobalt pentlandite structure in the rational design of efficient OER electrocatalysts.

Influence of Co:Fe:Ni ratio on cobalt Pentlandite’s electronic structure and surface speciation

X-ray photoemission spectroscopy (XPS) was used to investigate the electronic structure and oxidation state of transition metals in synthetic cobalt pentlandites (Fe,Co,Ni)9S8 with measured stoichiometries of Fe4.85Ni4.64S8, Co0.13Fe4.68Ni4.71S8, Co2.73Fe3.18Ni3.16S8, Co5.80Fe1.63Ni1.59S8 and Co8.70S8. The addition of cobalt was found to decrease the bond length and hence decrease the unit cell dimensions of the cobalt pentlandite crystal structure by up to 0.18 Å. High resolution XPS S 2p spectra show increases in the binding energies of bulk 5-coordinated (162.1 eV) and surface 3-coordinated (160.9 eV) sulfur (≈0.2 eV) with increasing Co concentration and decreasing bond lengths. As the Co concentration increases, variation in metal site occupation decreases, resulting in smaller S 2p FWHMs due to a dominant single Co-S state rather than mixed Fe-S, Ni-S and Co-S states with similar binding energies. The S 2p high binding energy tail, previously identified as a S 3p- Fe 3d ligand to metal transfer in Fe chalcogenides, shows a marked decrease in intensity as the concentration of Co increases, that is attributed to a decreased probability of ligand-to-metal charge transfer as the eg orbitals are filled. The transition metal XPS 2p spectra were modelled using CTM4XAS to investigate metal site occupation and ligand-to-metal charge transfer. Fe, Co, and Ni were all best simulated using a tetrahedral symmetry and 2+ oxidation state, their 2p3/2 and 2p1/2 peaks occurred at 706.9 and 719.9 eV, 778.2 and 793.1 eV, and 852.8 and 870.0 eV, respectively. A negative charge transfer energy confirms the high binding energy tail results from S3p-Fe3d ligand to metal charge transfer. This increased understanding of the pentlandite electronic structure will provide a basis for the refinement of mineral processing techniques and allow for a reduced environmental impact from limited efficiency.

Cobalt pentlandite structured (Fe,Co,Ni)9S8: Fundamental insight and evaluation of hybrid supercapacitor

From the perspective of improving energy density, research efforts to design electrode materials that can be used in supercapacitors based on mature transition metal sulfides are already so common and efficient but insufficient. So it is a nice approach to empower the traditional transition metal sulfides with new vitality by composite structures to enrich the family of metal sulfides. In this study, we synthesized a kind of cobalt pentlandite structured (Fe,Co,Ni)9S8 originally existed only in natural ores by relatively mild means, and found that such structured materials have good potential for use in supercapacitors. The optimized (Fe,Co,Ni)9S8 sample presents a remarkably high specific capacity of 135 mAh/g at 1 A/g as well as favorable cycling stability. Density functional theory simulations confirmed the metallic properties of such sample, and Co sites are more favorable for the adsorption of OH–. Moreover, a button-type hybrid supercapacitor was fabricated utilizing our designed electrode material, presenting a relatively high energy density of 50 Wh kg−1 at 1353 W kg−1 and good cyclic stability. Moreover, two such hybrid supercapacitors can power a red LED for 22 min, which has shown its attractive and promising possibilities for practical energy storage devices.

Atomic modulation of Fe-Co pentlandite coupled with nitrogen-doped carbon sphere for boosting oxygen catalysis

Reversible oxygen reaction plays a crucial role in rechargeable battery systems, but it is limited by the slow reaction kinetics. Herein, the ionic modulation of cobalt pentlandite coupled with nitrogen-doped bowl-like hollow carbon sphere is well designed on octahedral and tetrahedral sites. The robust FexCo9–xS8-NHCS-V with iron replacing at the octahedron possesses prolonged metal sulfur bond and exhibits excellent bifunctional electrocatalytic performance towards oxygen reduction reaction (ORR, E1/2 = 0.80 V vs. RHE) and excellent oxygen evolution reaction (OER, Ej= 10 = 1.53 V vs. RHE) in 0.1 mol/L KOH. Accordingly, a rechargeable Zn-air battery of FexCo9–xS8-NHCS-V cathode endows high energy efficiency (102 mW cm−2), and a microbial fuel cell achieves a high-power density (791 ± 42 mW m−2), outperforming the benchmark Pt/C catalyst.

Enhanced alkaline bifunctional electrocatalytic water splitting achieved through N and S dual-doped carbon shell reinforced Co9S8microplates

Overall alkaline water splitting by carbon-coated cobalt pentlandite (Co9S8@NSC) microplates electrocatalyst.

Determinants of crystal structure transformation of ionic nanocrystals in cation exchange reactions.

Changes in the crystal system of an ionic nanocrystal during a cation exchange reaction are unusual yet remain to be systematically investigated. In this study, chemical synthesis and computational modeling demonstrated that the height of hexagonal-prism roxbyite (Cu1.8S) nanocrystals with a distorted hexagonal close-packed sulfide anion (S2-) sublattice determines the final crystal phase of the cation-exchanged products with Co2+ [wurtzite cobalt sulfide (CoS) with hexagonal close-packed S2- and/or cobalt pentlandite (Co9S8) with cubic close-packed S2-]. Thermodynamic instability of exposed planes drives reconstruction of anion frameworks under mild reaction conditions. Other incoming cations (Mn2+, Zn2+, and Ni2+) modulate crystal structure transformation during cation exchange reactions by various means, such as volume, thermodynamic stability, and coordination environment.

Fe/Co and Ni/Co-pentlandite type electrocatalysts for the hydrogen evolution reaction

Metal-rich transition metal sulfides recently gained increasing attention as electrocatalysts for the hydrogen evolution reaction (HER), as they are capable to overcome major challenges faced by sulfide-rich metal catalysts such as limited conductivity and the necessity of nanostructuring. Herein, we present the synthesis, characterization and electrocatalytic investigation of ternary metal-rich sulfide composites FexCo9–xS8 as well as NiyCo9–yS8 (x = y = 0–4.5), which possess pentlandite-type structures. In this study, we show a stepwise alteration of the binary cobalt pentlandite Co9S8 and report on the replacement of cobalt with up to 4.5 equivalents of either iron or nickel. These altered pentlandite composites facilitate the proton reduction in acidic media at different temperatures. We furthermore show that the stoichiometric variation has a decisive influence on the electrochemical activation/deactivation behavior of the catalysts under reductive electrocatalytic conditions. Here, Co-deficient composites display an improved HER performance in contrast to Co9S8. Notably, Ni/Co compounds generally tend to show higher catalytic activities towards HER than their respective Fe/Co compounds.

Insights into the Biogeochemical Cycling of Cobalt: Precipitation and Transformation of Cobalt Sulfide Nanoparticles under Low-Temperature Aqueous Conditions.

Cobalt sulfide precipitates, key phases in the natural biogeochemistry of cobalt and in relevant remediation and resource recovery processes, are poorly defined under low-temperature aqueous conditions. Here, we systematically studied Co (Fe) sulfides precipitated and aged in environmentally relevant solutions, defined by different combinations of pH, initial cobalt to iron ratios ([Co]aq/[Fe]aq), with/without S0, and the presence/absence of sulfate-reducing bacteria. The initial abiogenic precipitates were composed exclusively of amorphous Co sulfide nanoparticles (CoS·xH2O) that were stable in anoxic solution for 2 months, with estimated log K* values 1-5 orders of magnitude higher than that previously reported for Co sulfides. The addition of S0, in combination with acidic pH and elevated temperature (60 °C), resulted in recrystallization of the amorphous precipitates into nanocrystalline jaipurite (hexagonal CoS) within 1 month. In the presence of Fe(II)aq, the abiogenic precipitates were composed of more crystalline Co sulfides and/or Co-rich mackinawite, the exact phase being dependent on the [Co]aq/[Fe]aq value. The biogenic precipitates displayed higher crystallinity for Co sulfides (up to the formation of nanocrystalline cobalt pentlandite, Co9S8) and lower crystallinity for Co-rich mackinawite, suggestive of mineral-specific bacterial interaction. The revealed precipitation and transformation pathways of Co (Fe) sulfides in this study allows for a better constraint of Co biogeochemistry in various natural and engineered environments.

Cobalt enrichment at the Juomasuo and Hangaslampi polymetallic deposits, Kuusamo Schist Belt, Finland: a role for an orogenic gold fluid?

The Juomasuo (Co-Au) and Hangaslampi (Au-Co) deposits are located in the Kuusamo Schist Belt, part of the 1.9–1.8 Ga Svecokarelian Orogenic Belt, central Finland. The deposits are hosted by metasedimentary and mafic rocks, and structurally controlled by the F2 Kayla-Konttiaho Antiform. Hydrothermal alteration is spatially zoned, from early albite through biotite and then chlorite and late muscovite alteration. Pipe-like chlorite-quartz-pyrrhotite bodies plunge parallel to the F2 fold axis and are cut by tabular quartz-muscovite-pyrite gold lodes in the S2 axial plane orientation. The chlorite alteration zone contains 10–40 vol.% pyrrhotite containing approximately 0.25 wt% Co but whole-rock Co grades are enhanced by the late-stage and heterogeneous enrichment of minor pyrite (up to 3% Co) and introduction of cobaltian pyrite and cobalt pentlandite. Cobaltite formed where muscovite replaces chlorite within metres of the gold lodes. Cobaltite and Co-enriched pyrite formed because Co and S were mobilized from pyrrhotite in relatively S-poor gold lodes by an As-rich gold ore fluid, during late-D2. Potassium, cobalt, sulfur and arsenic were transported into the mainly chlorite-rich wallrocks, via veinlets and fractures, by the now depleted gold ore fluid. Approximately 5 vol.% pyrite in the gold lodes displays extremely variable cobalt contents, which is interpreted to reflect mobility of Co during formation of the gold lodes. The origin of the gold ore fluid is enigmatic but is most plausibly an orogenic gold fluid, despite the paucity of carbonate minerals in the gold lodes.

Pseudocapacitive Co9S8/graphene electrode for high-rate hybrid supercapacitors

Cobalt pentlandite (Co9S8) has recently emerged as a promising electrode material for energy storage devices. Herein, Co9S8/graphene hybrid is rationally synthesized through a facile hydrothermal method. Minor-sized Co9S8 flakes is finely-deposited on the surface of graphene sheet and an interconnected Co9S8/graphene architecture structure is obtained. The electrochemical test results show that Co9S8/graphene electrode delivers a remarkable charge capacity of 540 C g−1 within 1 min and 74.5% capacitance is retained within a discharge time of 14 s. A hybrid supercapacitor assembled with Co9S8-involved electrode delivers a high energy density of 37 Wh kg−1 at a power density of 170 W kg−1, and 15.3 Wh kg−1 can be maintained even at a high power density of 12 kW kg−1. The excellent electrochemical performance should be attributed to abundant active sites, enhanced charge-transfer characters and maximized capacitive contribution of Co9S8/graphene electrode.

First occurrences of Ni-V-Co phosphides in chromitite from the Agios Stefanos Mine, Othrys Ophiolite, Greece

Phosphide minerals, generally less than 20 μm in size, are mainly made of Ni-V-Co-Mo constituents, discovered in concentrates obtained from chromitite samples from the Agios Stefanos mine, Othrys ophiolite, Greece. Spinel from the chromitite is rich in Fe2O3and very similar to chromites from podiform chromitites. Its Cr/(Cr+Al) ratios are lower than those of chromites with a boninitic affinity. On the basis of their chemical compositions, the following phosphide minerals have been identified: melliniite, nickelphosphide and two phases that can be classified as (i) either Ni-allabogdanite or Ni-barringerite, and (ii) either V-allabogdanite or V-barringerite. Under reflected-light microscope, all the inspected phosphide minerals display similar reflectance and a creamy-yellowish color, despite their different compositions. Melliniite is isotropic, while nickelphosphide shows a weak anisotropism. The Ni-allabogdanite or Ni-barringerite and V-allabogdanite or V-barringerite display a strong anisotropism. They occur associated with awaruite, pentlandite, native vanadium, vanadium sulfides, Mo-Ni-V-Co alloy (probably hexamolybdenum), Hg selenide (possible tiemmanite) and several minerals composed of Ni, As and Sb. A few of them were in contact with chromite, chlorite, quartz and glass. This mineralogical assemblage suggests that the discovered minerals are natural in origin and they do not represent an artefact related to the sample preparation. Furthermore, it is suggested that the investigated minerals have been crystallized in a local reducing geochemical environment. During the serpentinization of peridotites, reducing fluids containing dissolved H2 are released from the reduction of H2O. Therefore, these phosphides and the associated minerals may have precipitated during the serpentinization process at low temperature. Nickel and cobalt may have been released during alteration of olivine or they were originally hosted in magmatic sulfides that were altered during the serpentinization. Phosphorous may represent an alteration product of apatite and olivine. Vanadium was probably released during the alteration of the host chromite. We speculate that Mo was originally hosted in sulfides or oxides and after its remobilization it was incorporated into the crystal lattice of the Mo-rich phases. Alternatively, the high reducing minerals of the Othrys may have formed because of the interaction of their host rock with a lightning. The stoichiometry of the analyzed phosphide minerals indicates that some grains found in the Othrys chromitites may represent new mineral species, such as Ni-allabogdanite or Ni-barringerite, as well as V-allabogdanite or V-barringerite. However, their small size and complex micro-intergrowths with other minerals inhibit the elaboration of an X-ray diffraction study, which would unequivocally determine their nature. To the best of our knowledge, melliniite and nickelphosphide in the Othrys chromitite represent the first finding of these rare minerals in terrestrial samples.

Textures and compositions of cobalt pentlandite and cobaltian mackinawite from the Madan-Kudan copper deposit, Khetri Copper Belt, Rajasthan, India

The Khetri Copper Belt (KCB), a part of the Proterozoic Delhi–Aravalli fold belt in western India, hosts several Cu deposits, which are known to contain considerable Au, Ag, Co and Ni. Although many Co-bearing phases have been reported from the KCB and adjacent areas, detailed textural and geochemical data are either unavailable or scant except for mackinawite. In this study, we describe the textures and compositions (determined by EPMA) of two very rare Co-rich phases, namely cobaltian mackinawite (containing up to 12.68 wt.% Co, 1.90 wt.% Ni and 2.52 wt.% Cu) and cobalt-pentlandite (containing up to 49.30 wt.% Co and 10.19 wt.% Ni), identified based on composition, from the Madan-Kudan deposit. To the best of our knowledge, neither cobalt-pentlandite nor such highly Co-rich mackinawite have previously been reported from this area. The common sulphide minerals viz. chalcopyrite, pyrrhotite and rare pyrite occur in chalcopyrite-pyrrhotite ± pyrite-magnetite-chlorite-blue amphibole (Cl-rich hastingsite-pargasite-sadanagaite) ± marialitic scapolite ± allanite ± uraninite veins in amphibole-bearing feldspathic quartzite and garnetiferous chlorite schist. Cobaltian mackinawite is invariably associated with chalcopyrite and occurs as exsolution and inclusion within chalcopyrite or outside, but at the contact of chalcopyrite. On the other hand, cobalt-pentlandite is invariably associated with pyrrhotite and shows similar textural relation with pyrrhotite as that of mackinawite with chalcopyrite. Mineralogically diverse undeformed sulphide veins comprising Cl-rich amphibole and locally Cl-rich marialitic scapolite suggests epigenetic hydrothermal mineralization involving Cl-rich saline fluid in the Madan-Kudan deposit. Transport of metals, derived from a mafic source rock with high intrinsic Ni:Co ratio, by Cl-rich fluid can suitably explain the high Co:Ni ratio of the studied ore minerals. Presence of such highly Co-rich phases and other circumstantial evidences, enumerated in this work, are consistent with variants of Fe oxide (–Cu–Au) (IOCG) style mineralization, at least for some stages of mineralization in the Madan-Kudan deposit.

Facile Synthesis of Co9S8 Hollow Spheres as a High-Performance Electrocatalyst for the Oxygen Evolution Reaction

Cobalt pentlandite (Co9S8) has recently attracted great attention as a highly efficient and stable earth-abundant catalyst for the oxygen evolution reaction (OER) because of its electronic properties and intrinsic structure. However, the rational design and synthesis of OER catalysts to further enhance the electrochemical activity and durability remain major challenges. Herein, novel Co9S8 hollow spheres were successfully obtained through a template- and surfactant-free method, and they exhibit impressive electrocatalytic properties for the OER. Notably, the as-prepared material has superior OER performance with a low overpotential of 285 mV reached at 10 mA cm–2, a Tafel slope of 58 mV decade–1, and improved stability in 1 M aqueous solution KOH. Impressively, the unique hollow structure of Co9S8 hollow spheres imparts large surface area and abundant active sites, resulting in the superior catalytic activity. Thus, this work provides promising alternative cobalt sulfide-based oxygen evolution electrocata...

Behavior of cobalt-containing phases in hydrochloride decomposition of sulfide Cu–Ni materials

Effect of the solution redox potential on the behavior of cobalt-containing phase components of sulfide copper-nickel concentrates in the Cu(II)/Fe(III)–Cl––HCl–Cl2 system was studied. It was shown that, at solution redox potentials in the range 350–650 mV, phases based on heazlewoodite, pentlandite, cobaltous pentlandite, and cobalt pentlandite are transformed to thiospinels from the linneite group (M3S4, where M = Ni, Fe, Co). The resulting thiospinels are dissolved, with the exception of Co3S4, at solution redox potentials of 450 mV and less. The Co3S4 thiospinel is a stable compound in concentrated chloride solutions up to 650 mV, which, in the system under study, may be a reason for the poor cobalt recovery from sulfide concentrates.

Hydrothermal impregnation synthesis of cobalt pentlandite as anode material of H2S SOFC

In the present work, cobalt pentlandite (Co9S8) is studied as a solid oxide fuel cells (SOFC) anode material which is stable in H2S-containing fuels and is promising in coal-based SOFCs. Co9S8 is synthesized via a simple hydrothermal method. Uniform and fine Co9S8 particles are deposited on to the YSZ skeleton directly by using hydrothermal impregnation method and adhered to the skeleton closely after heat treating in N2. The symmetrical cells are measured in the presence of 50 ppm H2S–H2 to determine the electrochemical performance at intermediate temperatures. The polarization resistance is only 0.3385 Ω cm2 at 650 °C. It is concluded that Co9S8 exhibits a combination of good electronic conductivity and catalytic activity and has the potential to be used as a sulfur-tolerant anode material of SOFCs.

One-step solid phase synthesis of a highly efficient and robust cobalt pentlandite electrocatalyst for the oxygen evolution reaction

One-step concurrent growth of a Co9S8/carbon nanosheet composite as an efficient and robust oxygen evolution electrocatalyst.

Geochemistry of the Unusual Mafic Intrusions in Betul Fold Belt, Central India: Implications for Ni-Cu-Au-PGE Metallogeny

We report here the recent occurrence of native gold and platinoids, associated with Fe-Ni-Cu-Pb-Zn sulphides and tungsten-bearing phases in the gabbroic intrusions emplaced in the Betul-Chhindwara Belt in the Central Indian Tectonic Zone (CITZ). The ore minerals are represented mainly by native gold, pentlandite, chalcopyrite, pyrite, bowieite and rare phases of tungsten, cadmium and palladium, which were identified by scanning electron microscopy. The whole rock geochemistry shows anomalous Ni-Cu and platinum group elements (PGE) in which palladium is always higher in concentration than in platinum. The inter-element relationships of PGE such as Pd versus Ir and Pt versus Ir indicate their fractionation by a sulphide phase and also suggest that the parental magmas are primitive in nature having high-Mg, low- Ti characteristics, which indicate the boninitic/picritic nature of magmas. A thorough investigation is essential for exploring the Betul mafic-ultramafic intrusions for proving their potential as the host rocks for Au and Ni-Cu-PGE ores.